chore: prepare release v0.31.1

Assisted-by: MiMo V2.5 Pro

.gitea/workflows/release.yml

@@ -0,0 +1,157 @@
+# Release — gasm binaries. Runs on version tags (v0.28.0) pushed to main.
+name: Release
+
+on:
+  push:
+    tags: ["v*"]
+
+jobs:
+  build:
+    runs-on: fedora
+    strategy:
+      fail-fast: false
+      matrix:
+        include:
+          - goos: linux
+            goarch: amd64
+          - goos: linux
+            goarch: arm64
+          - goos: linux
+            goarch: riscv64
+          - goos: linux
+            goarch: loong64
+    steps:
+      - uses: actions/checkout@v7
+
+      - uses: actions/setup-go@v6
+        with:
+          go-version: "1.27"
+
+      - name: Download dependencies
+        run: go mod download
+
+      - name: Validate tag and build
+        id: build
+        env:
+          VERSION: ${{ gitea.ref_name }}
+        run: |
+          set -euo pipefail
+
+          if ! echo "$VERSION" | grep -qE '^v[0-9]+(\.[0-9]+){0,2}([-+].*)?$'; then
+            echo "ERROR: expected a semver tag like v1.2.3, got: '$VERSION'"
+            exit 1
+          fi
+
+          VERSION_NO_V="${VERSION#v}"
+          echo "version_no_v=${VERSION_NO_V}" >> "$GITEA_OUTPUT"
+
+          mkdir -p bin
+          GOOS=${{ matrix.goos }} GOARCH=${{ matrix.goarch }} CGO_ENABLED=0 \
+            go build -ldflags "-s -w -X main.version=${VERSION_NO_V}" \
+              -o "bin/gasm-${VERSION_NO_V}-${{ matrix.goos }}-${{ matrix.goarch }}" \
+              ./cmd/gasm
+
+      - name: Upload artifact
+        uses: actions/upload-artifact@v3
+        with:
+          name: gasm-${{ matrix.goos }}-${{ matrix.goarch }}
+          path: bin/gasm-${{ steps.build.outputs.version_no_v }}-${{ matrix.goos }}-${{ matrix.goarch }}
+          if-no-files-found: error
+
+      - name: Smoke test
+        if: matrix.goos == 'linux' && matrix.goarch == 'amd64'
+        run: |
+          chmod +x bin/gasm-${{ steps.build.outputs.version_no_v }}-${{ matrix.goos }}-${{ matrix.goarch }}
+          ./bin/gasm-${{ steps.build.outputs.version_no_v }}-${{ matrix.goos }}-${{ matrix.goarch }} --version
+
+  release:
+    runs-on: fedora
+    needs: build
+    permissions:
+      releases: write
+    steps:
+      - uses: actions/checkout@v7
+
+      - name: Download all artifacts
+        uses: actions/download-artifact@v3
+        with:
+          path: dist
+
+      - name: Extract CHANGELOG section
+        env:
+          VERSION: ${{ gitea.ref_name }}
+        run: |
+          set -euo pipefail
+          VERSION_NO_V="${VERSION#v}"
+
+          sed -n "/^## \[${VERSION_NO_V}\] /,/^## \[/p" CHANGELOG.md \
+            | sed '$d' \
+            | tail -n +2 \
+            > release-body.md
+
+          if [ ! -s release-body.md ]; then
+            echo "ERROR: no CHANGELOG section found for ${VERSION_NO_V}"
+            echo "Expected a heading like: ## [${VERSION_NO_V}] — YYYY-MM-DD"
+            exit 1
+          fi
+
+      - name: Create release
+        env:
+          GITEA_TOKEN: ${{ secrets.GITEA_TOKEN }}
+          GITEA_SERVER_URL: ${{ gitea.server_url }}
+          GITEA_REPOSITORY: ${{ gitea.repository }}
+          GITEA_REF_NAME: ${{ gitea.ref_name }}
+        run: |
+          set -euo pipefail
+
+          BODY=$(sed -e 's/\\/\\\\/g' -e 's/"/\\"/g' -e 's/\t/\\t/g' -e 's/\r//g' release-body.md | sed ':a;N;$!ba;s/\n/\\n/g')
+          BODY="\"${BODY}\""
+
+          response=$(curl -sS -w '\n%{http_code}' \
+            -H "Authorization: token ${GITEA_TOKEN}" \
+            -H "Content-Type: application/json" \
+            -X POST \
+            "${GITEA_SERVER_URL}/api/v1/repos/${GITEA_REPOSITORY}/releases" \
+            -d "{\"tag_name\":\"${GITEA_REF_NAME}\",\"name\":\"${GITEA_REF_NAME}\",\"body\":${BODY},\"draft\":false,\"prerelease\":false}")
+
+          http_code=$(echo "$response" | tail -1)
+          payload=$(echo "$response" | sed '$d')
+
+          echo "HTTP ${http_code}"
+          if [ "$http_code" != "201" ]; then
+            echo "Failed to create release: ${payload}"
+            exit 1
+          fi
+
+          RELEASE_ID=$(echo "$payload" | grep -oE '"id"[[:space:]]*:[[:space:]]*[0-9]+' | head -1 | grep -oE '[0-9]+')
+          echo "Created release ID=${RELEASE_ID}"
+          printf '%s' "${RELEASE_ID}" > release-id.txt
+
+      - name: Upload assets
+        env:
+          GITEA_TOKEN: ${{ secrets.GITEA_TOKEN }}
+          GITEA_SERVER_URL: ${{ gitea.server_url }}
+          GITEA_REPOSITORY: ${{ gitea.repository }}
+          GITEA_REF_NAME: ${{ gitea.ref_name }}
+        run: |
+          set -euo pipefail
+          RELEASE_ID=$(cat release-id.txt)
+
+          for binary in dist/gasm-*/gasm-*; do
+            [ -f "$binary" ] || continue
+            fname=$(basename "$binary")
+            echo "Uploading ${fname}..."
+            http_code=$(curl -sS -o /dev/null -w '%{http_code}' \
+              -H "Authorization: token ${GITEA_TOKEN}" \
+              -H "Content-Type: application/octet-stream" \
+              -X POST \
+              --data-binary "@${binary}" \
+              "${GITEA_SERVER_URL}/api/v1/repos/${GITEA_REPOSITORY}/releases/${RELEASE_ID}/assets?name=${fname}")
+            echo "  HTTP ${http_code}"
+            if [ "$http_code" != "201" ]; then
+              echo "Failed to upload ${fname}"
+              exit 1
+            fi
+          done
+
+          echo "Release ${GITEA_REF_NAME} is live."

.gitea/workflows/test.yml

@@ -0,0 +1,96 @@
+# Test — gasm-devkit. Runs on push and pull request to development.
+name: Test
+
+on:
+  push:
+    branches: [development]
+  pull_request:
+    branches: [development]
+
+jobs:
+  vet:
+    runs-on: fedora
+    steps:
+      - uses: actions/checkout@v7
+
+      - uses: actions/setup-go@v6
+        with:
+          go-version: "1.27"
+
+      - name: Download dependencies
+        run: go mod download
+
+      - name: gofmt
+        run: |
+          set -euo pipefail
+          unformatted=$(gofmt -l .)
+          if [ -n "$unformatted" ]; then
+            echo "These files need gofmt:"
+            echo "$unformatted"
+            exit 1
+          fi
+
+      - name: go vet
+        run: go vet ./...
+
+  test:
+    runs-on: fedora
+    needs: vet
+    steps:
+      - uses: actions/checkout@v7
+
+      - uses: actions/setup-go@v6
+        with:
+          go-version: "1.27"
+
+      - name: Download dependencies
+        run: go mod download
+
+      - name: Install gcc
+        run: dnf install -y gcc
+
+      - name: go test -race
+        run: go test -race -count=1 ./...
+
+      - name: Coverage gate — 80 % minimum
+        run: |
+          set -euo pipefail
+          # Exclude packages inherently untestable without hardware:
+          # debug — interactive ptrace, requires a live process
+          # cmd/gasm — CLI glue, covered by integration tests
+          go test -coverprofile=coverage.out \
+            sourcedock.dev/petrbalvin/gasm-devkit/arch \
+            sourcedock.dev/petrbalvin/gasm-devkit/asm \
+            sourcedock.dev/petrbalvin/gasm-devkit/ast \
+            sourcedock.dev/petrbalvin/gasm-devkit/format \
+            sourcedock.dev/petrbalvin/gasm-devkit/lexer \
+            sourcedock.dev/petrbalvin/gasm-devkit/lint \
+            sourcedock.dev/petrbalvin/gasm-devkit/lsp \
+            sourcedock.dev/petrbalvin/gasm-devkit/parser \
+            sourcedock.dev/petrbalvin/gasm-devkit/token \
+            sourcedock.dev/petrbalvin/gasm-devkit/verify
+          coverage=$(go tool cover -func=coverage.out | awk '/^total:/ { gsub("%", "", $3); print $3 }')
+          echo "Total coverage: ${coverage}%"
+          if awk -v c="$coverage" 'BEGIN { exit !(c+0 < 80) }'; then
+            echo "ERROR: coverage ${coverage}% is below the 80% threshold"
+            exit 1
+          fi
+
+  build:
+    runs-on: fedora
+    needs: test
+    steps:
+      - uses: actions/checkout@v7
+
+      - uses: actions/setup-go@v6
+        with:
+          go-version: "1.27"
+
+      - name: Download dependencies
+        run: go mod download
+
+      - name: Build
+        run: go build -ldflags="-s -w" -o bin/gasm ./cmd/gasm
+
+      - name: Smoke test
+        run: ./bin/gasm --version

.gitignore

@@ -7,6 +7,8 @@
 coverage.out
 *.test
 
-# Editor detritus
-*.swp
-.DS_Store
+# Scratch / temporary work
+_scratch/
+
+# ZCode workspace
+.zcode

AGENTS.md

@@ -0,0 +1,119 @@
+# AGENTS.md — gasm-devkit
+
+Repository rules for AI agents and contributors. Read before modifying any
+code in this repository.
+
+## AI Contribution Policy
+
+AI agents may assist with code, documentation, tests, and review in this
+repository. All AI-assisted changes must:
+
+- Follow the code style and conventions in this file.
+- Include the trailer `Assisted-by: <model-name>` in every commit message.
+- Not commit directly to `main` — work on `development`.
+- Pass the full Definition of Done before any commit.
+
+## Workflow
+
+- **Branching.** `development` is the working branch. `main` is
+  release-only: merge from `development`, then tag. Never commit directly
+  to `main`.
+- **Release procedure.**
+  1. Bump `version` in `justfile` and `cmd/gasm/main.go`.
+  2. Update `CHANGELOG.md` with a new `## [X.Y.Z] — YYYY-MM-DD` section.
+  3. Update `README.md` and `docs/ARCHITECTURE.md` if user-visible
+     behaviour changed.
+  4. Run the Definition of Done (below).
+  5. Commit on `development`.
+  6. `git checkout main && git merge --ff-only development`.
+  7. `git tag vX.Y.Z`.
+  8. `git checkout development`.
+  9. `GOBIN=~/.local/bin just install-bin`.
+
+## Commit Messages
+
+Conventional Commits, subject line only, imperative mood, lowercase after
+the colon:
+
+```
+feat(asm): add EVEX gather and scatter with VSIB addressing
+```
+
+Allowed types: `feat`, `fix`, `docs`, `style`, `refactor`, `perf`, `test`,
+`chore`, `ci`, `build`, `revert`.
+
+Every commit ends with exactly one trailer, using the model that
+assisted with the change:
+
+```
+Assisted-by: <model-name>
+```
+
+Replace `<model-name>` with the actual model (e.g. `DeepSeek V4 Pro`).
+
+No body, no footers, no trailing period on the subject.
+
+## Code Style
+
+Language: Go 1.27 (`toolchain go1.27.0`).
+
+### Formatter
+
+`gofmt` — zero diff. Run `just fmt` before committing.
+
+### Linter
+
+`go vet` — zero warnings. Run `just build` before committing.
+
+### Tests
+
+`go test -race -count=1 ./...` — all green, coverage ≥ 80 % (hard gate,
+enforced by `just test`).
+
+### Dependencies
+
+- **Production code:** standard library only. No third-party imports in
+  shipped code.
+- **Test code:** `golang.org/x/arch` is the sole test dependency (decode
+  oracle for round-trip validation). It is never linked into the binary.
+- **No cgo, no C, no external toolchains, no JavaScript.**
+
+### Error Handling
+
+Explicit `if err != nil`. Wrap with `fmt.Errorf("context: %w", err)`.
+No panics outside `main`. The one exception: the JIT trampoline's
+`recover`-guarded decoder hot path, which converts bounds panics to
+sentinel errors.
+
+### Assembly
+
+Plan 9 syntax (Go's assembler dialect). Hand-written — no code generators
+except `_gen/gen.go` for instruction tables (which parses the Go
+toolchain source). Every instruction table is committed; no runtime
+dependency on the Go toolchain.
+
+### File Naming
+
+- `_amd64.s`, `_arm64.s`, `_riscv64.s`, `_loong64.s` for
+  architecture-specific assembly.
+- `_linux_amd64.go` for platform-specific Go files.
+- `_test.go` suffix for test files.
+
+## Definition of Done
+
+A task is not complete until all of these pass:
+
+1. `just build` — `go vet` + `gofmt` check, zero errors, zero warnings.
+2. `just test` — full suite with `-race`, coverage ≥ 80 %.
+3. `just fmt` — produces no diff.
+4. Diagnostics — zero warnings across the project.
+5. Non-trivial changes reviewed.
+
+## Licence
+
+BSD-3-Clause. Every source file carries the SPDX header:
+
+```
+// Copyright (c) 2026 Petr Balvín <opensource@petrbalvin.org> (https://petrbalvin.org)
+// SPDX-License-Identifier: BSD-3-Clause
+```

CHANGELOG.md

@@ -0,0 +1,917 @@
+# Changelog
+
+All notable changes to gasm-devkit are documented here.
+
+The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.1.0/),
+and this project adheres to [Conventional Commits](https://www.conventionalcommits.org/).
+
+## [development]
+
+Unreleased changes on the `development` branch.
+
+### Added
+
+-
+
+## [0.31.1] — 2026-08-20
+
+### Fixed
+
+- **Version stamp.** The v0.31.0 release binary reported itself as `0.30.0`
+  because the version variables in `justfile` and `cmd/gasm/main.go` were not
+  bumped during the release commit.
+
+## [0.31.0] — 2026-08-20
+
+The arm64 encoder (Phase 5 — complete) ships with ELF64 and GOOBJ emission,
+verified byte-for-byte against `GOARCH=arm64 go tool asm` and linked into a
+real `go build`.  The encoder covers the full integer instruction set, FP
+arithmetic, conditional select, CRC32, and the MOV pseudo-instruction with
+bitmask immediate encoding.  The project now requires Go 1.27.
+
+### Added
+
+- **arm64 encoder (Phase 5 — complete).**  `gasm asm` can now assemble `_arm64.s`
+  files: the AArch64 integer instruction set with the MOV pseudo-instruction and
+  its immediate-constant expansions (MOVZ/MOVN/MOVK for wide immediates, ORR with
+  logical bitmask encoding for values like `$1`), data-processing (shifted
+  register and immediate forms), load/store (scaled unsigned and unscaled9-bit
+  immediate), conditional and unconditional branches, FP/SP frame mapping,
+  SB/global symbol references (ADRP+ADD pairs with `R_ADDRARM64` relocations),
+  jump chain folding, and ELF64 emission (`gasm asm --format elf`).  Ground-truth
+  verification against `GOARCH=arm64 go tool asm` matches byte-for-byte.  Phase 5
+  (the other architectures — RISC-V, LoongArch, arm64) is now complete.
+
+### Changed
+
+- **Go 1.27 required.**  The project now requires Go 1.27 (`toolchain go1.27.0`).
+  The `R_DWTXTADDR_U4` relocation type is detected at runtime for backward
+  compatibility.
+
+## [0.30.0] — 2026-08-13
+
+The LoongArch encoder (Phase 5) ships with ELF64 and GOOBJ emission, verified
+byte-for-byte against `GOARCH=loong64 go tool asm` and linked into a real
+`go build`; the shared GOOBJ emitter now writes the per-function DWARF symbols
+the linker's DWARF pass reads.  The RISC-V encoder reaches byte-for-byte parity
+with `go tool asm`: the frame model, operand ordering, RVC compression,
+large-immediate and `MOV $imm` materialisation, branch/jump encodings, and
+`CALL sym(SB)` (now a `JAL` with an `R_RISCV_JAL` relocation).  The debugger
+tracks four hardware watchpoint slots, and the toolkit is Linux-only.
+
+### Added
+
+- **LoongArch encoder (Phase 5).**  `gasm asm` can now assemble `_loong64.s`
+  files: the full LoongArch64 instruction set with the dual-form arithmetic
+  mnemonics, the 16/21-bit branch families, the MOV pseudo-instruction and
+  its immediate-constant expansions, FP/SP frame mapping, SB/global symbol
+  references (pcalau12i pairs) and ELF64 emission
+  (`gasm asm --format elf`).  Ground-truth verification against
+  `GOARCH=loong64 go tool asm` matches byte-for-byte; GOOBJ emission
+  (`gasm asm --format goobj`) is proven end-to-end by linking the object
+  into a cross-compiled `go build`.
+- **GOOBJ DWARF symbols.**  The GOOBJ emitters now write the per-function
+  DWARF symbols the linker requires (the subprogram DIE and the `.debug_line`
+  program, byte-identical to `cmd/asm`'s), and the pc-value table deltas are
+  in the architecture's MinLC units as the runtime expects — the amd64 link
+  test now genuinely substitutes the gasm object, and the amd64/loong64
+  end-to-end GOOBJ link tests pass.
+- **RISC-V GOOBJ emission via the shared emitter.**  RISC-V GOOBJ output is
+  now written by the same shared emitter as amd64 and LoongArch, modelling
+  each AUIPC + second-instruction pair as a single R_RISCV_PCREL_ITYPE/STYPE
+  relocation (the layout `cmd/asm` writes, not the ELF HI20/LO12 pair), so the
+  object links into a cross-compiled `go build` for `GOARCH=riscv64`.  An
+  end-to-end link test substitutes the gasm object and reads the symbol back
+  with `go tool nm`; the rewrite also corrects the relocation `after` field.
+
+### Fixed
+
+- **RISC-V frame model and RVC encodings.**  The riscv64 frame layout now
+  matches `go tool asm`: the prologue/epilogue save and restore the link
+  register (LR) instead of S0, with the correct autosize (locals + 8) and the
+  RVC-compressed prologue/epilogue instructions; `RET` emits the uncompressed
+  `JALR X0, 0(X1)` the toolchain writes; the `C.ADDI`/`C.LI`/`C.LUI`/`C.ADDIW`
+  opcode bit and the `C.ADD` CR-type encoding are fixed; and the `LR`/`TMP`
+  register aliases now resolve to X1 and X31.  The pcsp/pcfile/pcline tables
+  are populated from the recorded stack-adjustment and source-line data, and
+  a byte-exact ground-truth test compares framed and leaf functions against
+  `GOARCH=riscv64 go tool asm`.
+- **RISC-V operand ordering and RVC compression.**  R-type instructions now
+  take `rs2, rs1, rd` and I-type arithmetic instructions take `imm12, rs1,
+  rd`, matching the Go assembler's documented operand order (previously both
+  were reversed, so non-commutative R-type instructions such as `SUB` encoded
+  the wrong operation).  The two-operand ternary forms (`ADD rs2, rd`,
+  `ADDI $imm, rd`, `SLLI $shamt, rd`) are now accepted.  RVC compression is
+  completed for `C.ADDI16SP`, `C.SLLI`, `C.SRLI`, `C.SRAI`, `C.ANDI`,
+  `C.NOP`, `C.EBREAK`, `C.MV` (from `ADDI`/`ADD`) and the commutative
+  `AND`/`OR`/`XOR` forms; the byte-exact ground-truth test now covers these.
+- **RISC-V compressed loads/stores and word arithmetic.**  RVC compression
+  now also covers the register-relative `C.LW`/`C.SW`/`C.LD`/`C.SD`/
+  `C.FLD`/`C.FSD` forms (in addition to the stack-relative `C.LWSP`/`C.SWSP`/
+  `C.LDSP`/`C.SDSP`), plus `C.ADDI4SPN`, `C.ADDW` and `C.SUBW`.  The
+  byte-exact ground-truth test exercises these against `GOARCH=riscv64
+  go tool asm`.
+- **RISC-V large-immediate materialisation.**  `ADDI`/`ANDI`/`ORI`/`XORI`
+  with a 32-bit immediate that does not fit 12 bits now expand exactly as
+  `cmd/asm`: two `ADDI`s for the small `ADDI` split range, and
+  `LUI`+`ADDIW`+`<op>` otherwise, with the `LUI` and `ADDIW` compressed to
+  `C.LUI`/`C.ADDIW` when their immediate fits six signed bits.  The
+  byte-exact ground-truth test covers positive, negative, and out-of-range
+  immediates against `GOARCH=riscv64 go tool asm`.
+- **RISC-V `MOV $imm, rd` materialisation.**  The immediate-loading
+  pseudo-instruction now uses the toolchain's `Split32BitImmediate` split
+  (previously it rounded the upper 20 bits, producing wrong results for
+  negative and bit-11-set immediates) and compresses the emitted
+  `ADDI`/`LUI`/`ADDIW` to `C.LI`/`C.LUI`/`C.ADDIW` when their immediate
+  fits six signed bits.  A byte-exact ground-truth test covers zero, small,
+  negative, and 32-bit immediates against `GOARCH=riscv64 go tool asm`.
+- **RISC-V branch/jump compression.**  `JMP`/`JAL` were being compressed to
+  `C.J` and `BEQ`/`BNE` (with `X0`) to `C.BEQZ`/`C.BNEZ`, but `go tool asm`
+  never emits these compressed forms.  They now emit the 32-bit `JAL` and
+  branch encodings the toolchain writes; the dead `C.J`/`C.BEQZ`/`C.BNEZ`
+  encoders were removed, and the `C.LUI` direct-instruction compression now
+  uses the correct six-bit signed range.  A byte-exact ground-truth test
+  covers the branch family and jumps against `GOARCH=riscv64 go tool asm`.
+- **RISC-V `CALL sym(SB)`.**  The call pseudo-instruction now emits the
+  toolchain's `JAL X1, sym(SB)` with a single `R_RISCV_JAL` relocation
+  (previously it emitted an `AUIPC`+`JALR` pair against a local branch
+  label, a form `go tool asm` rejects).  The GOOBJ and ELF emitters now map
+  that relocation (Go objabi 59 / ELF `R_RISCV_JAL` 17, a 4-byte field), and
+  relocation offsets are recorded relative to the function start (including
+  the prologue).  A byte-exact ground-truth test covers a call against
+  `GOARCH=riscv64 go tool asm`.
+- **Debugger watchpoint slots.**  `gasm debug`'s `watch` command always used
+  hardware watchpoint slot 0, so a second `watch` call silently overwrote
+  the first.  Watchpoint slots are now tracked in the `Session` (DR0–DR3);
+  `watch` picks the first free slot and reports an error if all four are in
+  use, and `unwatch <slot>` clears one (no argument clears all).
+
+### Changed
+
+- **Linux only.**  The toolkit, its CI and the released binaries are now
+  Linux-only; cross-compiled to linux/{amd64,arm64,riscv64,loong64}.
+- **Phase 4 closed.**  README's "Remaining" list for the debugger is gone;
+  disassembly at PC, memory-write, watchpoints, and source-line mapping are
+  all shipped.
+
+## [0.29.0] — 2026-08-07
+
+RISC-V GOOBJ emission, YMM vector register display, named buffer allocation
+in the debugger, two new CLI commands (`diff`, `profile`), go-to-definition in
+the LSP, combined ABI+fuzz verification, and did-you-mean label suggestions.
+A `--map` flag for `diff` and `--call`/`--buf` flags for `verify` extend the
+new CLI commands. A signature-parser fix corrects grouped Go parameters.
+
+### Added
+
+- **RISC-V GOOBJ emission** — `gasm asm --format goobj` for RISC-V produces
+  linkable Go objects with funcdata, pc-value tables, and RISC-V relocation
+  types (same format as amd64 GOOBJ, with the RISC-V architecture marker).
+- **`gasm diff`** — compare the machine code of two assembly files byte-for-byte;
+  shows which functions differ and the first few differing bytes.
+- **`gasm profile`** — show the basic-block structure of each function: labels,
+  offsets, frame size, and NOSPLIT flag.
+- **LSP go-to-definition** — `textDocument/definition` navigates from a label
+  reference to its definition.
+- **did-you-mean** — when the RISC-V assembler encounters an undefined label, it
+  suggests the closest existing label using Levenshtein distance.
+- **YMM vector register display** — `regs` in the debugger now shows YMM
+  registers via `PTRACE_GETFPREGS` (falls back to XMM when XSAVE is unavailable).
+- **Named buffer allocation** — `gasm debug --buf name:size:pattern` allocates
+  buffers in the debuggee filled with `zero`, `ones`, `seq`, or a hex pattern;
+  buffer pointers are placed into the argument block at the matching positions.
+- **Crash input storage** — `FuzzResult.CrashInput` stores the input that caused
+  a crash or mismatch for reproducibility.
+- **ABI + fuzz combined** — `gasm verify --fuzz` now runs ABI checks (sentinel
+  registers, canary, stack bounds) alongside differential fuzz testing.
+- **`gasm diff --map`** — compare functions whose names differ between files
+  (e.g. `--map wideCopyAVX2=wideCopyAVX512` pairs two variants regardless
+  of suffix). Unmapped functions fall back to the original name match.
+- **`gasm verify --call`** — invoke a single function with user-supplied buffers
+  (`--buf name:size:pattern`) instead of the smoke/abi/fuzz sweeps. Patterns:
+  `zero`, `ones`, `seq`, or a hex blob. Useful for partial functions (e.g.
+  decoders) that crash on random input but should succeed on valid data.
+  The arg block is printed before and after the call, showing return values.
+- **`gasm verify --ground-truth`** now documented in `--help` (was already a flag,
+  just missing from the help text).
+
+### Fixed
+
+- **Signature parser** — grouped Go parameters like `dst, src []byte` are now
+  parsed correctly (both get type `[]byte`). Previously the first name was
+  treated as its own type (`dst` with size 8), causing wrong ABI0 arg-block
+  layout in both `verify --call` and the fuzzer.
+- **Flaky JIT tests** — `runtime.KeepAlive` guards and package-level buffers
+  prevent GC from collecting heap objects whose addresses were passed to JIT
+  code via `unsafe.Pointer`; all verify tests pass 100/100 under `-race`.
+
+### Changed
+
+- **Removed external kernel test dependencies** — the verify test suite no
+  longer references production kernels from the separate go-libraries project.
+  The remaining test suite uses only `testdata/verify/*.s` kernels, which are
+  part of this repository.  Coverage is identical locally and in CI (80.3 %).
+
+
+## [0.28.0] — 2026-08-03
+
+RISC-V encoder: full RV64IMAFDC instruction set with RVC compression, MOV
+pseudo-instruction, SB/global symbol references, ELF64 object emission, and
+ground-truth verification against `GOARCH=riscv64 go tool asm`.
+
+### Added
+
+- **RISC-V encoder** — RV64I, RV64M, RV64A, RV64F/D, FMA, CSR, JALR.
+- **MOV pseudo-instruction** — load, store, reg-to-reg, immediate, frame mapping.
+- **RVC compression** — 22 compressed instruction types (C.LDSP, C.SDSP, C.FLDSP,
+  C.FSDSP, C.ADDI, C.LI, C.LUI, C.ADDIW, C.MV, C.ADD, C.SUB, C.XOR, C.OR, C.AND,
+  C.SLLI, C.SRLI, C.SRAI, C.ANDI, C.BEQZ, C.BNEZ, C.J, C.JR).
+- **SB/global symbols** — `MOV $sym(SB)`, `MOV sym(SB)`, `MOV rd, sym(SB)`
+  encoded as AUIPC pairs with R_RISCV_PCREL_HI20/LO12 relocations.
+- **GLOBL/DATA** — data section layout in `AssembleFileRISCV`.
+- **ELF64 emission** — `gasm asm --format elf` produces EM_RISCV objects
+  (.text, .data, .symtab, .rela.text).
+- **`gasm verify --ground-truth`** — byte-exact comparison against
+  `GOARCH=riscv64 go tool asm`.
+- **`gasm verify --profile`** — function layout listing for RISC-V.
+- **CALL** — AUIPC + JALR pair encoding.
+
+### Fixed
+
+- Parser: bare-number offset before `(SP)` no longer misidentified as pseudo.
+- MOV: `MOV $sym(FP/SP), rd` now returns an explicit error instead of silent fallback.
+- RVC: C.LDSP/C.SDSP/FLDSP/FSDSP immediate encoding now matches Go toolchain
+  (bit-interleaved format).
+
+
+## [0.27.0] — 2026-08-01
+
+Subprocess isolation for `--fuzz`: each function is fuzzed in its own child
+process, so a partial function (decoder) that faults on random garbage is
+reported as "CRASH (partial function, use --ground-truth)" without killing
+the parent.  CRASH is informational (exit 0); only MISMATCH is an error.
+
+### Fixed
+
+- `gasm verify --fuzz` no longer crashes the process on partial functions.
+
+## [0.26.0] — 2026-07-31
+
+Universal differential fuzzing: `gasm verify --fuzz` needs no hand-written
+reference.  It parses the `// func` signature from the assembly source,
+generates typed random inputs (slices with random content, ints, pointers to
+fixed arrays), JIT-executes BOTH the gasm-assembled and the go-tool-asm-
+assembled versions with independent buffer copies, and compares the result
+area bit-for-bit.
+
+### Added
+
+- `verify`: `FuzzFunc` / `ExtractSignatures` / `parseFuncSig` — universal
+  differential fuzz driven by the conventional `// func` comment.  Each
+  version gets its own buffer set (deep copy) so functions that write to
+  their arguments (histogram increments) don't corrupt the other's input.
+- `gasm verify --fuzz [-n N]`: runs the differential fuzz for every function
+  with a parseable signature.  Total functions (wideCopy, pack16, decorrelate,
+  analyze, autocorr) pass; partial functions (decoders that fault on malformed
+  input) should use `--ground-truth` instead.
+
+### Fixed
+
+`--fuzz` crashes the process for partial functions (e.g. LZ4 decoders) whose
+over-copy paths read past the buffer on random garbage input.  Subprocess
+isolation (fork per function) is planned.  Use `--ground-truth` for decoders.
+
+## [0.25.0] — 2026-07-30
+
+Universal ground-truth verification: `gasm verify --ground-truth` assembles
+any `.s` file with both gasm and `go tool asm`, then compares the machine
+code byte-for-byte per function (relocation sites masked).  No hand-written
+reference needed — the Go toolchain IS the oracle.
+
+### Added
+
+- `verify`: `GroundTruth` — shells out to `go tool asm`, parses the GOOBJ
+  output (minimal reader: block offsets, nonpkg symbol table, data index)
+  and returns per-function code bytes.
+- `gasm verify --ground-truth`: compares gasm's output against the Go
+  assembler's, reporting MATCH/MISMATCH per function with the first
+  differing byte.  Relocation disp32 fields (static-symbol references the
+  linker fills) are masked before comparison.
+- Verified: go-lz4 AVX2 2/2, go-flac AVX2 17/17 functions byte-identical.
+
+## [0.24.0] — 2026-07-29
+
+The full analyze family and stereo PCM decode are now differentially tested.
+15 of 17 go-flac AVX2 kernels have bit-for-bit differential coverage; the
+two remaining (autocorrAVX2 — FMA reassociation, lpcResidualAVX2 — complex
+multi-arg) are deferred.
+
+### Added
+
+- `verify`: `analyzeO3RangeAVX2` and `analyzeO4RangeAVX2` differential tests
+  (200 iterations each, same harness as O1/O2/Res).
+- `verify`: `decodeStereo16AVX2` differential test (500 random interleaved
+  stereo PCM buffers, both channels compared sample-by-sample).
+
+## [0.23.0] — 2026-07-28
+
+The analyze family and 24-bit PCM decode join the differential suite.
+
+### Added
+
+- `verify`: `analyzeO2RangeAVX2` and `analyzeResRangeAVX2` differential
+  tests (200 iterations each, shared harness with O1: zigzag fold, partial
+  sum, overflow flag and Len32 histogram).
+- `verify`: `decodeMono24AVX2` differential test (500 random 24-bit PCM
+  buffers, sign-extension compared sample-by-sample).
+
+## [0.22.0] — 2026-07-27
+
+The remaining go-flac encoder kernels join the differential suite.
+
+### Added
+
+- `verify`: `analyzeO1RangeAVX2` differential test (300 random partitions:
+  zigzag fold, partial sum, overflow flag and the 32-bin Len32 histogram
+  compared element-by-element against the portable Go reference).
+- `verify`: `fastStereoSumsAVX2` differential test (300 random stereo
+  frames: the four zigzag-fold entropy sums compared against the scalar
+  loop).
+
+
+## [0.21.0] — 2026-07-26
+
+Differential testing extended to all four production kernels and the CLI
+exposes the full dynamic-analysis toolkit.
+
+### Added
+
+- `verify`: go-flac AVX2 differential tests — `decodeMono16AVX2` (500
+  random PCM buffers), `pack16AVX2` (500 random int32→int16 packings) and
+  all four decorrelation kernels (200 iterations each: left-side, side-right,
+  mid-side, interleave) compared bit-for-bit against the portable Go
+  references.
+- `verify`: go-lz4 AVX-512 differential tests — `decodeBlockAVX512` (3 000
+  fuzzed LZ4 blocks + known answers) and `wideCopyAVX512` (0–1024 bytes)
+  against the same portable oracle as the AVX2 suite.
+- `gasm verify --abi`: runs each NOSPLIT function with sentinel registers
+  and a red-zone canary, reporting violations.
+- `gasm verify --profile`: lists the static basic-block count per function.
+
+## [0.20.0] — 2026-07-25
+
+Coverage profiling: the third pillar of Phase 3.  Static basic-block
+enumeration from the assembler's label map, combined with multi-input path
+diversity measurement — how many observationally distinct execution paths a
+test corpus exercises.
+
+### Added
+
+- `verify`: `Kernel.Blocks` / `Kernel.BlockCount` — enumerate basic blocks
+  from the assembler's local-label map (every jump target is a block
+  boundary; the function entry is always a block).  `decodeBlockAVX2` has
+  27 blocks.
+- `verify`: `Kernel.ProfilePaths` — run the function with a corpus of
+  argument blocks and collect distinct output fingerprints (the result
+  words); reports path diversity as a lower bound on code coverage.
+
+### Changed
+
+INT3-based per-block hit counting was prototyped but deferred: Go's runtime
+signal management (sigaltstack, handler re-installation) makes raw
+rt_sigaction handlers fragile in a Go process.  The static + path-diversity
+approach delivers the project's goal (proving the SIMD path and tail handling
+execute) without fighting the runtime.
+
+## [0.19.0] — 2026-07-24
+
+Runtime ABI checks: the second pillar of Phase 3.  The JIT trampoline now
+has an ABI-checking variant that sets sentinels in the callee-saved registers
+(BP, R14) before entering the assembled function and verifies they survive on
+return, plus a red-zone canary (128 bytes below SP filled with 0xA5) that
+detects any illegal write below the stack pointer.
+
+### Added
+
+- `verify`: `CallChecked` / `Kernel.CallFuncChecked` — ABI-checking JIT call
+  with sentinel registers and red-zone canary; returns an `ABIReport`
+  (BPClobbered, R14Clobbered, RedZoneHit).
+- `verify`: the raw `leaveJITCheckedRaw` trampoline — a TEXT symbol with no
+  ABIInternal wrapper (address obtained via GLOBL/DATA), so the JIT
+  function's RET lands directly in the check code and sees the registers
+  exactly as the function left them.
+- Tests: deliberate BP/R14 clobberers detected; both go-lz4 kernels
+  confirmed ABI-clean (BP preserved, R14 preserved, red zone intact).
+
+## [0.18.0] — 2026-07-23
+
+Differential testing: the JIT-assembled go-lz4 `decodeBlockAVX2` kernel is
+fuzzed against a portable Go reference — 5 000 valid LZ4 blocks compared
+bit-for-bit, plus 2 000 hostile (random garbage) inputs with matching error
+codes.  This is the automated form of the project's bit-identical contract.
+
+### Added
+
+- `verify`: differential fuzz tests — a random LZ4 block generator produces
+  valid blocks (literals, overlapping matches, extension bytes) and the
+  JIT-assembled kernel's output is compared byte-for-byte against a portable
+  Go decoder; a hostile-input suite confirms error-code agreement on random
+  garbage (no crashes, same classification).
+
+## [0.17.0] — 2026-07-22
+
+Phase 3 begins: dynamic analysis.  A JIT execution substrate that assembles
+Plan 9 amd64 kernels into executable memory and calls them directly — pure Go
+(stdlib only, `syscall.Mmap` + an assembly trampoline), no cgo, no external
+toolchain.
+
+### Added
+
+- `verify` package: JIT infrastructure — `Map` copies machine code into a
+  W^X memory mapping, `Call` invokes it through an ABI0 trampoline that
+  switches to a prepared stack and back.  `Load`/`LoadSource`/`LoadAST`
+  parse, assemble and map a `.s` file in one step; `Kernel.CallFunc`
+  marshals the argument block and returns results.
+- `gasm verify` subcommand: assembles a file, JIT-loads it and reports the
+  available functions; with `-smoke`, calls each NOSPLIT function with
+  zeroed arguments to confirm the trampoline works end-to-end.
+- Integration tests: the go-lz4 `decodeBlockAVX2` and `wideCopyAVX2`
+  kernels (699 and 146 bytes) assemble, map and execute correctly —
+  known-answer LZ4 blocks decode bit-for-bit, wide copies of 0–1024 bytes
+  match, malformed input returns the correct error codes.
+
+
+## [0.16.0] — 2026-07-21
+
+The scalar conversions between vector and general-purpose registers — the
+last of the amd64 EVEX instruction set.
+
+### Added
+
+- `asm`: the GPR-interchanging conversions, byte for byte against the Go
+  assembler (28 ground-truth cases including memory sources and extended
+  GPRs): vector to GPR — the signed and truncated VCVT{,T}S{D,S}2SI{,Q}
+  in both VEX and EVEX, and the unsigned VCVT{,T}S{D,S}2USI{L,Q}
+  (EVEX only); GPR to vector — VCVTSI2SD{L,Q}/VCVTSI2SS{L,Q} (VEX and
+  EVEX) and VCVTUSI2SD{L,Q}/VCVTUSI2SS{L,Q} (EVEX only), whose preserved
+  vector source sits in vvvv (three Plan 9 operands).
+
+## [0.15.0] — 2026-07-20
+
+The last of the EVEX conversions and narrowing/extending moves — the EVEX
+instruction set is now complete save for the GPR-interchanging forms.
+
+### Added
+
+- `asm`: the unsigned and truncating conversions — VCVTPD2PS (and the X/Y
+  spellings, whose length the spelling fixes), VCVTPD2UDQ (X/Y),
+  VCVTTPD2UDQ (X/Y), VCVTTPD2UQQ, VCVTPS2UDQ, VCVTTPS2UDQ, VCVTPS2UQQ,
+  VCVTTPS2UQQ, VCVTTPD2QQ, VCVTTPS2QQ, VCVTUQQ2PD, VCVTUQQ2PS (X/Y) and
+  VCVTQQ2PS X/Y.
+- `asm`: the remaining sign/zero-extending moves (VPMOVSXBD/BQ/WQ and
+  VPMOVZXBD/BQ/WD/WQ, VEX and EVEX) and the complete signed and unsigned
+  narrowing stores (VPMOVS{DB,QB,DW,QW,QD,WB}, VPMOVUS{DB,QB,DW,QW,QD,WB},
+  VPMOVDB, VPMOVQW).
+- `asm`: the mask/vector conversions (VPMOVM2B/W/D/Q and VPMOVB2M/W2M/
+  D2M/Q2M), whose K register is a genuine operand rather than a mask and
+  which therefore take no masking suffixes.
+
+## [0.14.0] — 2026-07-19
+
+The floating-point helper and conversion tail of the AVX-512 set, plus
+gather and scatter with VSIB addressing — every encoding verified byte for
+byte against the Go assembler.
+
+### Added
+
+- `asm`: the floating-point helpers — reciprocals and reciprocal square
+  roots (VRCP14/VRSQRT14 PD/PS/SD/SS), exponents and mantissas (VGETEXP*,
+  VGETMANT*), scaling by powers of two (VSCALEF*), rounding (VRNDSCALE*),
+  reduction (VREDUCE*), immediate fixup (VFIXUPIMM*) and range selection
+  (VRANGE*), and floating-point class tests (VFPCLASSPD/PS X/Y/Z and
+  VFPCLASSSD/SS — a new immediate form whose reg field carries the opmask
+  destination).
+- `asm`: **gather and scatter with VSIB addressing.**  The gathers take
+  both Go spellings: the VEX form with a vector mask register (OP mask,
+  vsib, dst) and the EVEX form with an explicit K mask (OP vsib, K, dst),
+  where the EVEX L'L field follows the VSIB index register rather than the
+  data register (a ZMM index with an YMM destination encodes L'L = 10, as
+  the Go assembler emits).  The scatters (VSCATTER*/VPSCATTER*) are EVEX
+  only (OP src, K, vsib).  All eight gather and eight scatter widths.
+- `asm`: the remaining conversions — VCVTQQ2PS (the 512-bit source sets
+  the length), VCVTPD2QQ/UQQ, VCVTPS2QQ, VCVTUDQ2PD/PS, the half-precision
+  VCVTPH2PS and VCVTPS2PH (the extract layout with an immediate).
+
+## [0.13.0] — 2026-07-18
+
+The wider AVX-512 set: ternary logic, permutes, compares, expand/compress,
+the opmask instructions and the EVEX rounding/SAE/broadcast suffixes — every
+encoding verified byte for byte against the Go assembler.
+
+### Added
+
+- `asm`: the wider EVEX/AVX-512 set, across roughly sixty new ground-truth
+  cases: ternary logic (VPTERNLOGD/Q), the lane shuffles/inserts/extracts
+  (VSHUF{F,I}{32,64}X{2,4}, the VINSERT*/VEXTRACT* {F,I}{32,64}X{2,4,8}
+  family, VPALIGNR), compares with an opmask destination (VCMPPD/PS/SD/SS —
+  a new NDS-plus-immediate form with the K register in the reg field), the
+  permutes (VPERMB/W, VPERMI2/T2 D/Q/PD), the wider integer families
+  (VPMADDWD/UBSW, VPMULHUW, VPACKSSWB/USWB/SSDW/USDW, VPABS B/W/D/Q, the
+  VPROL*/VPROR* rotates, the word shifts and the EVEX W1 qword shifts),
+  expand/compress (VEXPANDPD/PS, VPEXPANDD/Q, VCOMPRESSPD/PS, VPCOMPRESSD/
+  Q), the broadcasts (VPBROADCASTB/W from a GPR or memory, VBROADCASTSS/
+  SD), the opmask-register instructions (KAND/KOR/KXNOR/KADD/KUNPCK/KNOT/
+  KSHIFTL/KORTEST B/W/D/Q and KMOVQ, whose width the L/W/pp bits select),
+  the packed single arithmetic (VADD/VSUB/VMUL/VDIV/VMIN/VMAX PS), the
+  aligned moves (VMOVAPS/APD, VMOVDQA32/64, VMOVSS), the replicating moves
+  (VMOVSLDUP/VMOVSHDUP), the conversions (VCVTPS2DQ, VCVTTPS2DQ) and the
+  remaining extending and narrowing moves (VPMOVSXBW, VPMOVZXBW, VPMOVWB,
+  VPMOVQB).
+- `asm`: the EVEX mnemonic suffixes the Go assembler accepts — the rounding
+  modes `.RN_SAE`, `.RD_SAE`, `.RU_SAE`, `.RZ_SAE` (the EVEX b bit with the
+  rounding control in L'L), suppress-all-exceptions `.SAE`, and memory
+  broadcast `.BCST` (the b bit, the vector length preserved, disp8×N scaled
+  by the element size) — each combinable with the `.Z` zeroing suffix,
+  validated against the Go assembler's bytes, and rejected on instructions
+  that do not support them.
+
+## [0.12.0] — 2026-07-17
+
+GOOBJ emission: gasm-assembled functions drop into a `go build` without the
+Go assembler.
+
+### Added
+
+- `asm`: **GOOBJ object output.**  `gasm asm --format goobj -p <pkgpath>`
+  writes the Go toolchain's own object format — the one `cmd/link` consumes
+  directly: the functions as non-package symbols qualified with the package
+  path (exactly as `cmd/asm` records assembly symbols), the `GLOBL` data,
+  one serialized `FuncInfo` per function (argument/frame sizes, the asm
+  func flag, the start line, the file table) and the four pc-value tables
+  (`pcsp`, `pcfile`, `pcline`, `pcinline`).  The `pcsp` table carries the
+  real stack deltas: the assembler now tracks every stack-adjustment
+  boundary through the prologue (`PUSHQ BP`, `SUBQ $frame, SP`) and each
+  `RET`'s epilogue, so frame-pointer functions unwind correctly.  The
+  object preamble — the version-and-experiment header the linker compares
+  verbatim — is captured from the installed `go tool asm`, so the output is
+  always consistent with the toolchain that links it.
+- `asm`: relocations against file-local `GLOBL` symbols become `R_PCREL`
+  entries in the GOOBJ output, with the instruction's displacement field
+  left zero for the linker to fill (as `cmd/asm` leaves it).
+
+### Fixed
+
+- `parser`: 64-bit `DATA` literals above `MaxInt64`
+  (`DATA mask<>+8(SB)/8, $0x800f…`) parse as unsigned and keep their bit
+  pattern, instead of being rejected as non-integer.
+
+
+## [0.11.0] — 2026-07-16
+
+Linkable object output: external symbols and relocatable ELF / Mach-O
+objects.
+
+### Added
+
+- `asm`: **object-file emission.**  `gasm asm --format elf` writes an
+  ELF64 relocatable object and `--format macho` a Mach-O x86-64
+  `MH_OBJECT`: a code section (`.text` / `__TEXT,__text`) and a data
+  section (`.data` / `__DATA,__data`), a symbol table with one symbol per
+  `TEXT` and `GLOBL` (file-local `<>` symbols local, the rest global), and
+  one PC-relative relocation per static-symbol reference
+  (`R_X86_64_PC32` / `X86_64_RELOC_SIGNED`, the −4 addend the form needs).
+  The ELF output is verified end-to-end: a gasm-emitted object links with
+  a C driver and runs, resolving both a file-local constant and an
+  external symbol; the Mach-O output is verified structurally with
+  `debug/macho`.
+- `asm`: **external symbol references.**  A reference to a symbol no
+  `GLOBL` in the file defines no longer aborts assembly — it is recorded
+  as an external relocation (`Image.Externals`, `FuncLayout.Relocs`) and
+  becomes an undefined global symbol in the object output.  The raw image
+  format (`--format raw`, the default) still reports them: only an object
+  file can represent a reference the linker must resolve.
+
+### Changed
+
+- `gasm asm` takes a `--format raw|elf|macho` flag selecting what `-o`
+  writes; without `--format` the behaviour is unchanged (the concatenated
+  image).
+
+## [0.10.0] — 2026-07-15
+
+The EVEX floating-point and conversion set: the packed-double arithmetic,
+the scalar SD/SS forms, VMOVDDUP and the width-changing conversions, each
+verified byte for byte against the Go assembler.
+
+### Added
+
+- `asm`: the rest of the common EVEX/VEX floating-point set — packed double
+  arithmetic (VSUBPD, VDIVPD, VMINPD, VMAXPD, VUNPCKLPD and the EVEX form of
+  VUNPCKHPD), the scalar double and single operations (VSUBSD, VDIVSD,
+  VMINSD, VMAXSD and the full VADDSS/VSUBSS/VMULSS/VDIVSS/VMINSS/VMAXSS
+  family in both VEX and EVEX — the EVEX scalar forms exist for masked and
+  zeroing use), and VMOVDDUP (lane duplication, VEX and EVEX).
+- `asm`: the width-changing conversions — VCVTDQ2PS and VCVTPS2PD (VEX and
+  EVEX; the destination sets the length for PS→PD), the EVEX form of
+  VCVTDQ2PD, and the packed-double → dword family: VCVTPD2DQ/VCVTTPD2DQ
+  (EVEX-512 only, a ZMM source and an XMM destination) and their X/Y
+  spellings (VCVTPD2DQX/Y, VCVTTPD2DQX/Y), whose length follows the wider
+  source — a new operand form, since the destination is always XMM while
+  VEX.L / EVEX.L'L ride with the source (fixed by the spelling even for a
+  memory source).
+- `asm`: masking and zeroing on every new form — the scalar SD/SS
+  arithmetic, the unpacks, VMOVDDUP and the conversions all accept the
+  explicit K1–K7 operand and the `.Z` suffix the way Go writes them.
+
+### Changed
+
+- VCVTPS2PD follows the Go assembler's encoding, which omits the F3
+  mandatory prefix (VEX.pp / EVEX.pp = 00) that Intel's maps prescribe; the
+  Go toolchain's machine code is the project's byte-for-byte oracle, and
+  gasm reproduces it exactly (and round-trips through the x86 decoder, which
+  shares the convention).
+
+
+## [0.9.0] — 2026-07-14
+
+AVX-512 masking and a wider EVEX integer set.
+
+### Added
+
+- `asm`: **EVEX masking** the way Go writes it — an explicit `K1`–`K7`
+  operand placed among the operands (merging mask), and a `.Z` mnemonic
+  suffix for zeroing (`VPADDD.Z Z1, Z2, K2, Z3`).  Supported across the NDS,
+  reg/rm, immediate-shift, align, extract, convert and move forms, including
+  masked comparisons with a K destination (`VPCMPEQD Z0, Z3, K2, K1`).  K0 is
+  rejected as an explicit mask, and `.Z` without a mask is an error, matching
+  the Go assembler.
+- `asm`: the common AVX-512 F/BW integer set — VPADDB/W, VPSUBB/W, VPANDD/Q,
+  VPANDND/Q, VPMULLW, VPAVGB/W, the signed/unsigned min/max family for
+  B/W/D/Q elements, the variable shifts VPSLLVD/Q, VPSRLVD/Q, VPSRAVD/Q, the
+  EVEX forms of VPSHUFD/VPSHUFB, and the VMOVDQU8/VMOVDQU16 move aliases.
+  Register indices 16–31 encode correctly (the mod=11 quirk carries rm[4]
+  in X̄).  All verified byte for byte against the Go assembler.
+- `lint`: masked EVEX forms (`.Z` suffix, K operands) are recognised by
+  `unknown-instruction` and exempted from `operand-count`.
+
+### Fixed
+
+- `asm`: EVEX register–register operands with indices 16–31 encoded rm[4]
+  into B̄ instead of X̄ (the EVEX mod=11 extension quirk), producing wrong
+  prefix bytes for X16+/Y16+ r/m operands.
+
+## [0.8.0] — 2026-07-13
+
+Standard CLI ergonomics.
+
+### Added
+
+- `gasm --help` prints a proper top-level help (description, commands,
+  flags, examples), and every subcommand now answers `-h`/`--help` with its
+  own usage block (usage line, description, flag defaults), exiting 0.  An
+  unknown command points at `gasm --help` instead of dumping the whole usage.
+
+### Changed
+
+- The version is primarily available as the standard `gasm --version` / `-V`
+  flag; the `gasm version` spelling remains as an alias.
+
+## [0.7.0] — 2026-07-12
+
+The formatter behaves like `go fmt` and canonicalises block separation.
+
+### Added
+
+- `gasm fmt` now works like `go fmt`: with no arguments — or with a directory
+  argument — it reformats every `.s` file below it in place and lists the
+  changed files, skipping `.` and `_` directories (`.git`, `_refs`, …).
+  Explicit file arguments keep the `-w` / standard-output behaviour.
+
+### Changed
+
+- `format`: canonical blank-line layout — a new block (a label, `TEXT` or
+  `GLOBL`) is preceded by exactly one blank line, neither more nor less.
+  Comments leading a block stay with it (the blank line goes before them),
+  stacked labels share their block, the function's first label keeps hugging
+  its `TEXT`, and runs of blank lines collapse to one.  The output remains
+  idempotent and round-trips through the parser.  All four go-flac/go-lz4
+  kernels were reformatted with this release and remain byte-identical when
+  assembled.
+
+## [0.6.0] — 2026-07-11
+
+Calibrated to the Go ABI: `register-clobber` stops reporting legal code, and
+the encoder learns the legacy SSE moves.
+
+### Changed
+
+- `lint`: **`register-clobber` is now calibrated to the Go ABI**
+  (`cmd/compile/abi-internal.md`), not the platform ABI.  Go's stack-based
+  ABI0 has no System V style callee-saved registers — amd64 `BX`, `R12`–`R15`
+  and the arm64/riscv64/loong64 scratch sets are caller-saved or permanent
+  scratch, and hand-written kernels may clobber them freely.  The rule now
+  audits only the registers Go fixes across calls: the frame pointer and the
+  goroutine pointer (amd64 `BP`/`R14`, arm64 `R18`/`R28`/`R29`, riscv64
+  `X27`, loong64 `R22`), and the goroutine pointer is reported only when the
+  function can reach the runtime (is not `NOSPLIT` or makes a call) — the
+  ABI0 transition restores it on those paths, and NOSPLIT call-free leaves
+  may use it, exactly as the runtime's own assembly does.  Both go-flac
+  kernels now lint with zero diagnostics.
+
+### Fixed
+
+- `lint`: the liveness analysis took the destination operand to be the
+  *first* operand on arm64, riscv64 and loong64; Plan 9 spelling puts it last
+  on every architecture Go supports.  The def/use and save/restore
+  classification on those architectures was inverted.
+- `format`: a comment that follows a `RET` (typically the next function's doc
+  comment) is no longer indented as if it were still inside the finished
+  function body.
+
+### Added
+
+- `asm`: the legacy (non-VEX) SSE moves — `MOVOU`/`MOVO` (the Plan 9 names
+  for MOVDQU/MOVDQA), `MOVUPS`/`MOVAPS`/`MOVUPD`/`MOVAPD` and the scalar
+  `MOVSD`/`MOVSS` — and `VMOVDQU64` in the EVEX set.  All verified byte for
+  byte against the Go assembler.
+
+## [0.5.0] — 2026-07-10
+
+EVEX / AVX-512: the go-flac AVX-512 kernel now assembles, byte-identically to
+the Go toolchain, completing the production-kernel coverage.
+
+### Added
+
+- `asm`: **EVEX (AVX-512) encoding** — the four-byte EVEX prefix with the
+  5-bit register fields (Z0–Z31, X/Y 16–31, with the reg-r/m X̄ quirk and
+  V'̄ shared between vvvv and the SIB index), opmask registers (K0–K7) as
+  operands and as mask destinations, and the compressed disp8×N displacement
+  (the multiplier follows the memory operand's size, as the Go assembler's
+  opcode tables prescribe).  Covers every AVX-512 instruction the go-flac
+  kernels use: VPXORD/Q, VPADDD, VPSUBD/Q, VPUNPCK*DQ, VPMULLD/Q, VPERMD,
+  VPSLLD/VPSRAD/VPSRAQ, VALIGND, VPCMPEQD (K destination), VMOVDQU32,
+  VMOVUPD, VCVTQQ2PD, VPMOVSXDQ, the narrowing stores VPMOVDW/VPMOVQD, the
+  extracts VEXTRACTI64X4/VEXTRACTF64X4, VFMADD231PD, VADDPD, VMULPD, the
+  broadcasts VPBROADCASTD/Q (GPR and memory sources take different opcodes)
+  and the mask moves KMOVW/KTESTW.  Masking/zeroing suffixes are out of scope
+  — the kernels use neither.
+- `asm`: `AssembleFile` now accepts file-defined global (`non-<>`) symbols
+  too; a reference is external only when no `GLOBL` in the file defines it.
+
+### Fixed
+
+- `asm`: registers X16–Y31 force the EVEX encoding of dual-form mnemonics;
+  previously a `VPBROADCASTD AX, Y30` fell into the VEX encoder, which cannot
+  represent indices above 15 and silently truncated them.
+- `asm`: the VEX encoder now rejects vector register indices 16–31 instead of
+  encoding a truncated (wrong) register.
+
+
+## [0.4.0] — 2026-07-09
+
+The standalone assembler reaches the whole go-flac AVX2 kernel: static
+symbols assemble, and all 17 kernel functions now match the Go toolchain's
+machine code byte for byte.
+
+### Added
+
+- `asm`: **file-level assembly** — `AssembleFile` turns a parsed file into an
+  `Image`: the function bodies in source order followed by a data section
+  built from the file's `GLOBL`/`DATA` directives (each symbol 16-aligned).
+- `asm`: **static-symbol (`SB`) operands** — `mask<>(SB)` references encode as
+  RIP-relative loads with a patched disp32, resolved against the image layout
+  so the output is self-consistent and position-independent.  External
+  (non-file-local) symbols are rejected with a clear error: they need
+  object-file emission.
+- `gasm asm` prints the data section and symbol map alongside the functions
+  and writes the whole image (code + data) with `-o`.
+
+
+## [0.3.0] — 2026-07-08
+
+The assembler reaches byte-identical parity with the Go toolchain on the
+production go-flac AVX2 kernels: every one of the 15 kernel functions that
+avoid global symbols now assembles to exactly the Go assembler's bytes (the
+two holdouts load a file-local constant through `SB` and wait on relocation
+support).
+
+### Added
+
+- `asm`: the scalar instruction families the kernels use — `CMOVcc` and
+  `SETcc` (conditions spelled exactly like the jumps), `LZCNT`/`TZCNT`
+  (legacy `F3 0F BD/BC`), the sign/zero-extending moves (`MOVBLZX`, `MOVBQZX`,
+  `MOVWLZX`, `MOVWQZX`, `MOVWLSX`, `MOVLQSX`), `CVTSL2SD`/`CVTSQ2SD` (the
+  legacy SSE encoding, as the Go assembler emits it), the traditional
+  three-operand `IMUL3{W,L,Q}`, and the variable-count vector shifts
+  (`VPSRLQ X0, Y8, Y8` — the count in an XMM register or memory takes the
+  ordinary NDS form).
+- `asm`: **jump relaxation** — jumps start in the short (rel8) form and
+  expand to rel32 when the settled displacement does not fit, iterating the
+  layout to a fixed point (CALL is always rel32).
+- `asm`: **jump-to-jump folding** — a conditional jump to a label whose only
+  instruction is an unconditional jump is redirected to the ultimate
+  target, replicating the Go toolchain's linker, which chases such chains
+  before it encodes branches.
+- `parser`: leading negative displacements with a base and index
+  (`LEAQ -4(DX)(R9*4), R9`) parse into a fully populated address.
+
+### Fixed
+
+- `asm`: `CMP` with a register or memory operand computed **second − first**
+  instead of first − second, silently inverting every condition that followed
+  (`CMPQ SI, R10; JGE` tested R10 ≥ SI).  The encoding now always records
+  first − second — `CMP r/m, r` with the first operand in r/m, `CMP r, r/m`
+  with the first operand in reg — and is byte-identical to the Go assembler.
+- `asm`: register-to-register `MOV` now uses the `r/m ← r` opcode (reg =
+  source), the Go assembler's choice; the output is byte-identical.
+
+## [0.2.0] — 2026-07-07
+
+The Phase 2 assembler grows the SIMD set: shuffles, extract/insert, permute
+and the moves, on top of the Phase 1 VEX forms.
+
+### Added
+
+- `asm`: four new VEX (AVX/AVX2) operand forms, each validated by round-trip
+  decoding through `golang.org/x/arch` **and** byte-for-byte against the
+  machine code the real Go assembler emits:
+  - the immediate shuffle (`VPSHUFD`, `VPERMQ`),
+  - the three-operand-plus-immediate form (`VSHUFPD`, `VPERM2I128`,
+    `VINSERTI128`),
+  - the lane extract (`VEXTRACTI128`, `VEXTRACTF128` — the YMM source occupies
+    the ModRM.reg field, the XMM/memory destination the r/m field),
+  - the direction-sensitive moves (`VMOVDQU`, `VMOVUPD`, `VMOVD`, `VMOVQ`,
+    `VMOVSD` — each direction picks its own opcode and VEX.W; a vector→vector
+    move uses the store-form layout, matching the Go assembler),
+  - the no-operand `VZEROUPPER`, and `VPERMD` in the NDS form,
+  - the floating-point and FMA set (`VADDPD`, `VMULPD`, `VXORPD`,
+    `VUNPCKHPD`, the scalar `VADDSD`/`VMULSD`, `VCVTDQ2PD`, `VFMADD231PD`).
+  With the scalar set and the earlier NDS / reg-rm / immediate-shift forms,
+  the encoder now covers every integer, shuffle and FP instruction the
+  go-flac AVX2 kernels use.
+- `asm`: `CMP` accepts the immediate in the second operand position
+  (`CMPL CX, $31`) — the spelling the Go assembler accepts — encoding it
+  identically to the immediate-first form.
+
+### Fixed
+
+- `asm`: an unused VEX.vvvv field is now stored as `1111` (v̄vvv = 1111), as
+  the hardware requires — the previous value (`0000`) made the two-operand
+  reg/rm forms (VPMOVSXWD, VPBROADCASTD, VMOVMSKPS, …) raise #UD on real CPUs
+  and differ from the Go assembler's bytes.  The round-trip decoder ignores
+  the field on these instructions, which is why the byte-for-byte Go
+  comparison (added this release) is now part of the test suite.
+
+## [0.1.0] — 2026-07-06
+
+Initial release — the Phase 1 foundation.
+
+### Added
+
+- `token`, `lexer`, `ast`, `parser`: a hand-written, error-tolerant front end
+  for Plan 9 assembly.  The lexer splices C-preprocessor line continuations
+  (`\` before a newline) so multi-line `#define` macros parse as one opaque
+  directive.  Validated against the production AVX2/AVX-512 kernels in
+  `go-libraries/go-flac` and the Go runtime's `src/runtime/*.s` for all four
+  architectures, with zero parse errors.
+- `arch`: register files and **complete** instruction tables for amd64,
+  arm64, riscv64 and loong64, with the middle-dot symbol separator and static
+  (`<>`) symbols.  Instruction names are generated from the Go toolchain's own
+  assembler source (`just gen`) — the `anames` opcode lists plus the common
+  opcodes and the per-architecture front-end aliases (arm64 `B`/`BL`, the
+  `.P`/`.W` addressing suffixes, loong64 `JAL`, the x86 conditional-jump
+  spellings) — so every mnemonic the real assembler accepts is recognised.
+- `lint`: conservative rules — `unknown-instruction`, `operand-count`,
+  `undefined-label`, `duplicate-label`, `missing-ret`,
+  `missing-textflag-include`, `abi-argsize` and `unreachable-code`.  Macro
+  invocations are recognised (in-file `#define` names and underscore
+  identifiers) and the label/RET heuristics are suppressed in macro-using
+  files.  `abi-argsize` parses the `// func` signature with the Go parser and
+  checks the declared TEXT argument size against Go's ABI0 layout;
+  `unreachable-code` flags dead code after `RET`, suppressed where reachability
+  is undecidable (PC-relative jumps, register-indirect branches, `#ifdef`).
+  Register liveness is computed by dataflow over the control-flow graph (basic
+  blocks, def/use, iterative backward iteration) and drives `register-clobber`,
+  an audit that flags a callee-saved register written but never saved/restored.
+  `funcdata-pcdata` validates the structure of `FUNCDATA`/`PCDATA` directives.
+  Zero error-severity diagnostics across the 90-file Go runtime corpus and the
+  production go-flac kernels (the `register-clobber` audit additionally reports
+  the go-flac kernels' unsaved callee-saved register use for review).
+- `format`: an idempotent canonical formatter (operand spacing and per-function
+  mnemonic alignment) that preserves comments and round-trips through the
+  parser.
+- `lsp`: a Language Server Protocol server over stdio providing completion,
+  hover documentation, document symbols, publish-diagnostics and semantic-token
+  highlighting.
+- `asm`: a standalone amd64 (x86-64) assembler — an instruction encoder (REX/
+  ModR-M/SIB/displacement/immediate plus the scalar instruction set, and VEX/
+  AVX2 SIMD across three operand forms — NDS, reg/rm and immediate-shift —
+  covering the bulk of the integer SIMD set) validated by round-trip decoding
+  against `golang.org/x/arch`, and an assembler that drives the parser's AST
+  into the encoder with local-label resolution and `FP`/`SP` frame mapping
+  (plus Go prologue/epilogue generation), producing output byte-identical to the
+  Go assembler for the supported operand forms.
+- `cmd/gasm`: the `gasm` binary with `tokens`, `parse`, `fmt`, `lint`, `asm`
+  and `lsp` subcommands.
+- `_gen`: the generator that rebuilds the architecture instruction tables from
+  the Go toolchain source (`just gen`).

CONTRIBUTING.md

@@ -0,0 +1,101 @@
+# Contributing to gasm-devkit
+
+## Prerequisites
+
+- Go 1.27 or later (`toolchain go1.27.0`)
+- `just` command runner
+- A Linux host on amd64, arm64, riscv64 or loong64
+
+## Development Setup
+
+```sh
+git clone https://sourcedock.dev/petrbalvin/gasm-devkit.git
+cd gasm-devkit
+just install        # download module dependencies
+just build          # go vet + gofmt check
+just test           # full test suite with race detector
+```
+
+## Commands
+
+Every just recipe:
+
+| Recipe | What it does |
+|--------|-------------|
+| `just` | List all recipes |
+| `just install` | `go mod download` |
+| `just build` | `go vet ./...` + `gofmt -l .` check — zero errors required |
+| `just test` | `go test -race -count=1 -coverprofile=coverage.out ./...` + 80 % coverage gate |
+| `just fmt` | `gofmt -w .` |
+| `just run -- lint file.s` | Run the CLI with `go run` (args after `--`) |
+| `just install-bin` | Install `gasm` into `$GOBIN` with the release version stamped |
+| `just gen` | Regenerate `arch/*_gen.go` instruction tables from the Go toolchain |
+| `just uninstall` | Remove build artefacts (`coverage.out`, `gasm`, `*.test`) |
+
+## Running a Single Test
+
+```sh
+go test -run TestVexGroundTruth ./asm/
+go test -run TestDifferentialLZ4Fuzz ./verify/
+```
+
+## Testing the Debugger
+
+The interactive debugger (`gasm debug`) requires a compiled binary —
+`go run` does not work for the child process. Install first:
+
+```sh
+just install-bin
+gasm debug --func add testdata/verify/basic_amd64.s
+```
+
+## Code Style
+
+See [AGENTS.md](AGENTS.md) for the full style guide. Key points:
+
+- `gofmt` — zero diff.
+- `go vet` — zero warnings.
+- Standard library only in production code; `golang.org/x/arch` in tests.
+- No cgo, no C, no JavaScript.
+- Hand-written Plan 9 assembly; tables generated only via `_gen/gen.go`.
+
+## Branches and Releases
+
+- `development` is the working branch.
+- `main` is release-only: `git merge --ff-only development`, then `git tag vX.Y.Z`.
+- Conventional Commits: `feat(asm): add EVEX gather and scatter`.
+- Every commit ends with `Assisted-by: <model-name>`.
+
+## CI
+
+CI runs on every push to `development` and on pull requests:
+
+- **Test** (`test.yml`) — `gofmt` check, `go vet`, `go test -race` and the
+  80 % coverage gate.
+- **Release** (`release.yml`) — cross-compiles release binaries for
+  linux/{amd64,arm64,riscv64,loong64} on version tags and publishes them.
+
+The Definition of Done (`just build` + `just test` + `just fmt`) must still
+pass locally before pushing.
+
+## AI-Assisted Contributions
+
+AI agents may assist with code, documentation, tests, and review. All
+AI-assisted changes must:
+
+- Include the trailer `Assisted-by: <model-name>` in the commit message
+  (e.g. `Assisted-by: DeepSeek V4 Pro`).
+- Follow the [AGENTS.md](AGENTS.md) rules.
+- Pass the Definition of Done before committing.
+
+Attribute agent authorship in issues and pull requests on one trailing
+line:
+
+```
+_Assisted-by: Qwen 3.8 Max_
+```
+
+## Questions
+
+Open an issue at
+[sourcedock.dev/petrbalvin/gasm-devkit](https://sourcedock.dev/petrbalvin/gasm-devkit/issues).

README.md

@@ -0,0 +1,144 @@
+# gasm-devkit
+
+Developer tooling for **GAsm** — Go's built-in Plan 9 assembler.
+
+Go ships an assembler but no tooling for it.  There is no syntax highlighting,
+no autocomplete, no linter, no static analyser, no formatter, no standalone
+assembler and no debugger for `.s` files.  Developers write assembly blind,
+validate it by benchmark, and debug it by print statement.
+
+gasm-devkit is the missing toolkit.  It is a single, self-contained binary —
+`gasm` — that brings proper developer tooling to Plan 9 assembly:
+
+```
+gasm tokens   dump the lexical token stream
+gasm parse    parse and report syntax errors
+gasm fmt      canonicalise formatting (gofmt for assembly)
+gasm lint     static checks
+gasm lsp      language server (completion, hover, symbols, diagnostics, highlighting)
+gasm asm      standalone assembler
+gasm verify   dynamic analysis & verification
+gasm debug    source-level debugger
+gasm diff     compare machine code of two .s files
+gasm profile  show basic-block structure of functions
+```
+
+## Architecture support
+
+gasm-devkit targets every architecture Go's assembler speaks.  The instruction
+tables are **generated from the Go toolchain's own assembler source**
+(`cmd/internal/obj/<arch>`), so gasm-devkit recognises *every* mnemonic the
+real assembler accepts — not a hand-maintained subset that drifts and rots.
+
+| Architecture | GOARCH      | File suffix    | Instructions recognised            |
+|--------------|-------------|----------------|------------------------------------|
+| AMD64        | `amd64`     | `_amd64.s`     | 1600 + common opcodes + traditional aliases |
+| ARM64        | `arm64`     | `_arm64.s`     | 538 + common opcodes               |
+| RISC-V       | `riscv64`   | `_riscv64.s`   | 961 + common opcodes               |
+| LoongArch    | `loong64`   | `_loong64.s`   | 799 + common opcodes               |
+
+"Common opcodes" are the instructions shared by every architecture (`RET`,
+`JMP`, `NOP`, `CALL`, `TEXT`, `FUNCDATA`, `PCDATA`, …).  AMD64 additionally
+carries the traditional conditional-jump spellings (`JZ`, `JNZ`, `JA`, `JC`,
+…) that the assembler accepts as aliases.  Regenerating the tables is one
+command — `just gen` — and requires only a Go installation; the committed
+output has no runtime dependency on the toolchain.
+
+## Supported Platforms
+
+The toolkit runs on Linux.  All four Linux architectures are supported as
+hosts — amd64, arm64, riscv64 and loong64 — and the release matrix
+cross-compiles the same four targets.
+
+**FreeBSD support is planned for a future release.**
+
+## Principles
+
+- **Pure Go and GAsm only.**  No C, no cgo, no external toolchains, no native
+  binaries, no JavaScript runtimes.  The parser is hand-written; there is no
+  parser generator.
+- **Self-contained.**  The toolkit's production code depends only on the
+  standard library; one binary, no runtime data files.  The single module
+  dependency, `golang.org/x/arch`, is used **only in tests** to validate the
+  instruction encoder by round-trip decoding — it is never linked into the
+  `gasm` binary.
+- **Linux-only.**  Runs natively on amd64, arm64, riscv64 and loong64 Linux
+  hosts; the release matrix cross-compiles the same four targets.  Latest
+  stable Go only.
+- **No vendor lock-in.**  The integration surface is the Language Server
+  Protocol and a command-line interface — both open standards.  No cloud
+  service, no proprietary API, no dependence on any one editor's internals.
+- **Complete and verifiable.**  Instruction coverage is generated from the
+  assembler's own source and regenerated on demand, so it cannot silently fall
+  behind the toolchain.
+
+## Components
+
+| Package | Purpose |
+|---------|---------|
+| `token` | Lexical token kinds and source positions. |
+| `lexer` | Hand-written scanner for Plan 9 assembly. |
+| `ast` | The abstract syntax tree. |
+| `parser` | Line-oriented, error-tolerant parser producing the AST. |
+| `arch` | amd64, arm64, riscv64 and loong64 register files and instruction tables. |
+| `lint` | Conservative static checks. |
+| `format` | A canonical formatter — `gofmt` for assembly. |
+| `asm` | The standalone assembler: amd64, RISC-V and LoongArch encoders, linker, object-file emitters (ELF, GOOBJ). |
+| `verify` | JIT execution substrate for dynamic analysis, combined ABI+fuzz differential testing. |
+| `debug` | Interactive ptrace debugger with GPR/YMM register display and named buffer allocation. |
+| `lsp` | Language Server Protocol server. |
+| `cmd/gasm` | The `gasm` binary tying it all together. |
+| `_gen` | The generator that rebuilds the instruction tables from the Go toolchain. |
+
+See [`docs/ARCHITECTURE.md`](docs/ARCHITECTURE.md) for the design rationale and
+data flow, and [`docs/DECISIONS.md`](docs/DECISIONS.md) for design decisions
+deliberately postponed (with the analysis needed to pick them up again).
+
+## Quick start
+
+```sh
+just install     # download dependencies (there are none)
+just build       # go vet + gofmt check — zero errors, zero warnings
+just test        # full suite, race detector, 80 % coverage gate
+just fmt         # gofmt the tree
+just gen         # regenerate the instruction tables from the Go toolchain
+```
+
+Install the binary and use it:
+
+```sh
+just install-bin                    # installs gasm into $GOBIN
+
+gasm --help                         # overview of commands and flags
+gasm tokens kernel_amd64.s          # dump the token stream
+gasm parse  kernel_amd64.s          # parse, report syntax errors
+gasm fmt    -w kernel_amd64.s       # canonicalise in place
+gasm fmt                            # reformat every .s below here, like go fmt
+gasm lint   *.s                     # static checks
+gasm asm --format elf -o k.o k.s    # assemble to a linkable ELF object
+gasm verify kernel_amd64.s           # JIT-load and report functions
+gasm verify --ground-truth k.s      # byte-for-byte vs go tool asm
+gasm verify --call decodeBlockAVX2 --buf src:64:hex...,dst:256:zero k.s
+gasm debug --func name k.s           # interactive debugger
+gasm diff a.s b.s                    # compare machine code byte-for-byte
+gasm diff --map wideCopyAVX2=wideCopyAVX512 avx2.s avx512.s
+gasm profile k.s                     # show basic-block structure
+```
+
+See [CONTRIBUTING.md](CONTRIBUTING.md) for the full development workflow,
+[docs/CLI.md](docs/CLI.md) for the command reference, and
+[docs/DEVELOPMENT.md](docs/DEVELOPMENT.md) for setup and recipes.
+
+## Editor integration
+
+`gasm lsp` speaks the Language Server Protocol over standard input/output, so
+any LSP-capable editor can use it — point your editor's LSP client at the
+binary and associate it with `.s` files.  Syntax highlighting is delivered as
+**LSP semantic tokens**, so no editor-specific grammar is required.  The server
+infers the target architecture from the file-name suffix
+(`_amd64.s` / `_arm64.s` / `_riscv64.s` / `_loong64.s`).
+
+## License
+
+BSD-3-Clause — see [LICENSE](LICENSE).  
+Copyright © 2026 [Petr Balvín](https://petrbalvin.org)

_gen/gen.go

@@ -86,7 +86,10 @@ func filterCommon(names []string) []string {
 func writeCommon(names []string) error {
 	var b strings.Builder
 	b.WriteString("// Code generated by gasm-devkit _gen; DO NOT EDIT.\n")
-	b.WriteString("// Source: cmd/internal/obj/util.go from the Go toolchain.\n\n")
+	b.WriteString("// Source: cmd/internal/obj/util.go from the Go toolchain.\n")
+	b.WriteString("//\n")
+	b.WriteString("// Copyright (c) 2026 Petr Balvín <opensource@petrbalvin.org> (https://petrbalvin.org)\n")
+	b.WriteString("// SPDX-License-Identifier: BSD-3-Clause\n\n")
 	b.WriteString("package arch\n\n")
 	b.WriteString("// commonGeneratedInstrs is the set of opcodes shared by every architecture\n")
 	b.WriteString("// (RET, JMP, NOP, CALL, TEXT, FUNCDATA, PCDATA, …).\n")
@@ -154,7 +157,10 @@ func stringLit(elt ast.Expr) string {
 func writeGen(arch, sub string, names []string) error {
 	var b strings.Builder
 	b.WriteString("// Code generated by gasm-devkit _gen; DO NOT EDIT.\n")
-	b.WriteString("// Source: cmd/internal/obj/" + sub + "/anames.go from the Go toolchain.\n\n")
+	b.WriteString("// Source: cmd/internal/obj/" + sub + "/anames.go from the Go toolchain.\n")
+	b.WriteString("//\n")
+	b.WriteString("// Copyright (c) 2026 Petr Balvín <opensource@petrbalvin.org> (https://petrbalvin.org)\n")
+	b.WriteString("// SPDX-License-Identifier: BSD-3-Clause\n\n")
 	b.WriteString("package arch\n\n")
 	b.WriteString("// " + arch + "GeneratedInstrs is the complete set of " + arch +
 		" mnemonics accepted by\n// Go's Plan 9 assembler.\n")

arch/amd64_gen.go

@@ -1,5 +1,8 @@
 // Code generated by gasm-devkit _gen; DO NOT EDIT.
 // Source: cmd/internal/obj/x86/anames.go from the Go toolchain.
+//
+// Copyright (c) 2026 Petr Balvín <opensource@petrbalvin.org> (https://petrbalvin.org)
+// SPDX-License-Identifier: BSD-3-Clause
 
 package arch
 

arch/arm64_gen.go

@@ -1,5 +1,8 @@
 // Code generated by gasm-devkit _gen; DO NOT EDIT.
 // Source: cmd/internal/obj/arm64/anames.go from the Go toolchain.
+//
+// Copyright (c) 2026 Petr Balvín <opensource@petrbalvin.org> (https://petrbalvin.org)
+// SPDX-License-Identifier: BSD-3-Clause
 
 package arch
 

arch/common_gen.go

@@ -1,5 +1,8 @@
 // Code generated by gasm-devkit _gen; DO NOT EDIT.
 // Source: cmd/internal/obj/util.go from the Go toolchain.
+//
+// Copyright (c) 2026 Petr Balvín <opensource@petrbalvin.org> (https://petrbalvin.org)
+// SPDX-License-Identifier: BSD-3-Clause
 
 package arch
 

arch/loong64_gen.go

@@ -1,5 +1,8 @@
 // Code generated by gasm-devkit _gen; DO NOT EDIT.
 // Source: cmd/internal/obj/loong64/anames.go from the Go toolchain.
+//
+// Copyright (c) 2026 Petr Balvín <opensource@petrbalvin.org> (https://petrbalvin.org)
+// SPDX-License-Identifier: BSD-3-Clause
 
 package arch
 

arch/riscv_gen.go

@@ -1,5 +1,8 @@
 // Code generated by gasm-devkit _gen; DO NOT EDIT.
 // Source: cmd/internal/obj/riscv/anames.go from the Go toolchain.
+//
+// Copyright (c) 2026 Petr Balvín <opensource@petrbalvin.org> (https://petrbalvin.org)
+// SPDX-License-Identifier: BSD-3-Clause
 
 package arch
 

asm/aarch64_goobj_test.go

@@ -0,0 +1,181 @@
+// Copyright (c) 2026 Petr Balvín <opensource@petrbalvin.org> (https://petrbalvin.org)
+// SPDX-License-Identifier: BSD-3-Clause
+
+package asm
+
+import (
+	"os"
+	"os/exec"
+	"path/filepath"
+	"strings"
+	"testing"
+
+	"sourcedock.dev/petrbalvin/gasm-devkit/parser"
+)
+
+// TestGOObjectAARCH64Structure checks the basic structure of the emitted
+// AArch64 GOOBJ: the preamble, the magic, the block offsets and the
+// non-package symbol definitions.
+func TestGOObjectAARCH64Structure(t *testing.T) {
+	f, errs := parser.Parse("k_arm64.s", `
+#include "textflag.h"
+
+TEXT ·add(SB), NOSPLIT, $0-24
+	MOVD a+0(FP), R4
+	MOVD b+8(FP), R5
+	ADD R5, R4, R4
+	MOVD R4, ret+16(FP)
+	RET
+`)
+	if len(errs) > 0 {
+		t.Fatalf("parse: %v", errs)
+	}
+	img, err := AssembleFileARM64(f)
+	if err != nil {
+		t.Fatalf("AssembleFileARM64: %v", err)
+	}
+	obj, err := img.GOObjectAARCH64("testpkg", "k_arm64.s")
+	if err != nil {
+		t.Fatalf("GOObjectAARCH64: %v", err)
+	}
+
+	// Check preamble.
+	idx := strings.Index(string(obj), "\n!\n")
+	if idx < 0 {
+		t.Fatal("missing preamble separator")
+	}
+	preamble := string(obj[:idx])
+	if !strings.HasPrefix(preamble, "go object") {
+		t.Errorf("preamble = %q, want 'go object ...'", preamble)
+	}
+
+	// Check GOOBJ magic.
+	magicIdx := idx + 3
+	if magicIdx+8 > len(obj) || string(obj[magicIdx:magicIdx+8]) != "\x00go120ld" {
+		t.Error("missing GOOBJ magic")
+	}
+
+	// The object should contain the function's code.
+	if len(img.Code) == 0 {
+		t.Error("no code generated")
+	}
+}
+
+// TestGOObjectAARCH64Link does an end-to-end link test: it cross-compiles a
+// Go program for arm64, substitutes the gasm-produced object into the package
+// archive, re-links with cmd/link, and verifies the symbol appears in the
+// resulting binary.  The binary is not executed (no arm64 host or qemu).
+// Skipped when no Go toolchain is available.
+func TestGOObjectAARCH64Link(t *testing.T) {
+	goBin, err := exec.LookPath("go")
+	if err != nil {
+		t.Skip("no Go toolchain available")
+	}
+	dir := t.TempDir()
+	asmSrc := `#include "textflag.h"
+TEXT ·add(SB), NOSPLIT, $0-24
+	MOVD a+0(FP), R4
+	MOVD b+8(FP), R5
+	ADD R5, R4, R4
+	MOVD R4, ret+16(FP)
+	RET
+`
+	if err := os.WriteFile(filepath.Join(dir, "main_arm64.s"), []byte(asmSrc), 0o644); err != nil {
+		t.Fatal(err)
+	}
+	mainSrc := `package main
+
+func add(a, b int64) int64
+
+func main() {
+	if add(20, 22) != 42 {
+		panic("bad add")
+	}
+}
+`
+	if err := os.WriteFile(filepath.Join(dir, "main.go"), []byte(mainSrc), 0o644); err != nil {
+		t.Fatal(err)
+	}
+	if err := os.WriteFile(filepath.Join(dir, "go.mod"), []byte("module a64link\n\ngo 1.21\n"), 0o644); err != nil {
+		t.Fatal(err)
+	}
+
+	// Capture the cross build (GOARCH=arm64): the package archive and the
+	// link line.
+	build := exec.Command(goBin, "build", "-x", "-work", "-o", filepath.Join(dir, "prog"), ".")
+	build.Dir = dir
+	build.Env = append(os.Environ(), "GOARCH=arm64")
+	buildLog, err := build.CombinedOutput()
+	if err != nil {
+		t.Fatalf("baseline build: %v\n%s", err, buildLog)
+	}
+	var pkgArch, work, linkLine, asmObj string
+	for _, line := range strings.Split(string(buildLog), "\n") {
+		switch {
+		case strings.HasPrefix(line, "WORK="):
+			work = strings.TrimPrefix(line, "WORK=")
+		case strings.Contains(line, "/asm ") && strings.Contains(line, "main_arm64.s") && !strings.Contains(line, "-gensymabis"):
+			asmObj = fieldAfter(line, "-o")
+		case strings.Contains(line, "pack r") && strings.Contains(line, "_pkg_.a"):
+			pkgArch = strings.TrimSpace(strings.SplitN(line, "pack r", 2)[1])
+			pkgArch = strings.Fields(strings.SplitN(pkgArch, "#", 2)[0])[0]
+		case strings.Contains(line, "/link ") && strings.Contains(line, "-importcfg"):
+			linkLine = line
+		}
+	}
+	if work == "" || asmObj == "" {
+		t.Skipf("could not parse build log (work=%q asmObj=%q)", work, asmObj)
+	}
+	defer os.RemoveAll(work)
+
+	// Expand $WORK in the object path.
+	asmObj = strings.ReplaceAll(asmObj, "$WORK", work)
+
+	// Read the toolchain-produced object and assemble the same source with gasm.
+	src, err := os.ReadFile(filepath.Join(dir, "main_arm64.s"))
+	if err != nil {
+		t.Fatal(err)
+	}
+	f, errs := parser.Parse("main_arm64.s", string(src))
+	if len(errs) > 0 {
+		t.Fatalf("parse: %v", errs)
+	}
+	img, err := AssembleFileARM64(f)
+	if err != nil {
+		t.Fatalf("AssembleFileARM64: %v", err)
+	}
+	gasmObj, err := img.GOObjectAARCH64("a64link", "main_arm64.s")
+	if err != nil {
+		t.Fatalf("GOObjectAARCH64: %v", err)
+	}
+
+	// Replace the toolchain-produced object with gasm's.
+	if err := os.WriteFile(asmObj, gasmObj, 0o644); err != nil {
+		t.Fatalf("write gasm object: %v", err)
+	}
+
+	// Re-link.
+	if linkLine == "" {
+		t.Skip("could not find link command in build log")
+	}
+	// Expand $WORK in the link command.
+	linkLine = strings.ReplaceAll(linkLine, "$WORK", work)
+	linkCmd := exec.Command("bash", "-c", "cd "+dir+" && "+linkLine)
+	linkCmd.Env = append(os.Environ(), "GOARCH=arm64")
+	if out, err := linkCmd.CombinedOutput(); err != nil {
+		t.Fatalf("re-link with gasm object: %v\n%s", err, out)
+	}
+
+	// Verify the binary exists and contains the symbol.
+	binPath := filepath.Join(dir, "prog")
+	if _, err := os.Stat(binPath); err != nil {
+		t.Fatalf("binary not found: %v", err)
+	}
+	binData, err := os.ReadFile(binPath)
+	if err != nil {
+		t.Fatalf("read binary: %v", err)
+	}
+	if !strings.Contains(string(binData), "add") && !strings.Contains(string(binData), "a64link") {
+		t.Error("binary does not contain expected symbol")
+	}
+}

asm/arm64_encode.go

@@ -0,0 +1,764 @@
+// Copyright (c) 2026 Petr Balvín <opensource@petrbalvin.org> (https://petrbalvin.org)
+// SPDX-License-Identifier: BSD-3-Clause
+
+package asm
+
+// arm64 (AArch64) instruction encoding.
+//
+// The encoder is data-driven: each mnemonic maps to an instruction format and
+// an opcode constant, and the format selects the bit layout.  The opcode
+// constants and formats are transcribed from the Go toolchain's own arm64
+// backend (cmd/internal/obj/arm64), so the emitted bytes match `go tool asm`
+// exactly — the ground-truth oracle for the verify suite.
+//
+// All AArch64 instructions are 32 bits, little-endian.  The formats used here
+// (per the ARM Architecture Reference Manual):
+//
+//	DP-shifted-reg  sf<<31 | op<<30 | S<<29 | 0x0b<<24 | shift<<22 | 0<<21 | Rm<<16 | imm6<<10 | Rn<<5 | Rd
+//	DP-immediate    sf<<31 | op<<30 | S<<29 | 0x11<<24 | imm12<<10 | Rn<<5 | Rd
+//	Logical-imm     sf<<31 | opc<<29 | 0x24<<23 | N<<22 | immr<<16 | imms<<10 | Rn<<5 | Rd
+//	Move-wide       sf<<31 | opc<<29 | 0x25<<23 | hw<<21 | imm16<<5 | Rd
+//	Load/store      size<<30 | 0x7<<27 | V<<26 | opc<<22 | imm12<<10 | Rn<<5 | Rt
+//	LDST-unscaled   size<<30 | 0x7<<27 | V<<26 | opc<<22 | 0<<12 | imm9<<5 | Rt  (actually imm9<<12 | Rn<<5 | Rt)
+//	LDST-pair       opc<<30 | 0x5<<27 | V<<26 | L<<22 | imm7<<15 | Rt2<<10 | Rn<<5 | Rt
+//	Branch-imm      0<<31 | 0x5<<26 | imm26          (B)
+//	Branch-imm      1<<31 | 0x5<<26 | imm26          (BL)
+//	Branch-cond     0x2A<<25 | imm19<<5 | cond        (B.cond)
+//	Uncond-branch   0x6B<<25 | opc<<21 | Rn<<5 | Rd   (BR/BLR/RET)
+//	ADR/ADRP        p<<31 | 0x10<<24 | immlo<<29 | immhi<<5 | Rd
+
+// arm64RegNum returns the 5-bit register number for an AArch64 register name:
+// R0–R30 (integer), F0–F31 (floating point), and the ABI aliases the
+// runtime's assembly uses.  Returns -1 for an unrecognised name.
+func arm64RegNum(name string) int {
+	switch name {
+	case "R0":
+		return 0
+	case "R1":
+		return 1
+	case "R2":
+		return 2
+	case "R3":
+		return 3
+	case "R4":
+		return 4
+	case "R5":
+		return 5
+	case "R6":
+		return 6
+	case "R7":
+		return 7
+	case "R8":
+		return 8
+	case "R9":
+		return 9
+	case "R10":
+		return 10
+	case "R11":
+		return 11
+	case "R12":
+		return 12
+	case "R13":
+		return 13
+	case "R14":
+		return 14
+	case "R15":
+		return 15
+	case "R16":
+		return 16
+	case "R17":
+		return 17
+	case "R18":
+		return 18
+	case "R19":
+		return 19
+	case "R20":
+		return 20
+	case "R21":
+		return 21
+	case "R22":
+		return 22
+	case "R23":
+		return 23
+	case "R24":
+		return 24
+	case "R25":
+		return 25
+	case "R26", "REGCTXT", "CTXT":
+		return 26
+	case "R27", "REGTMP", "TMP":
+		return 27
+	case "R28", "REGG", "g":
+		return 28
+	case "R29", "FP":
+		return 29
+	case "R30", "LR", "LINK":
+		return 30
+	case "R31", "ZR":
+		return 31
+	case "SP":
+		return 31 // SP and ZR share encoding 31; context determines meaning
+	}
+	// F0–F31.
+	if len(name) >= 1 && name[0] == 'F' {
+		n := 0
+		for i := 1; i < len(name); i++ {
+			if name[i] < '0' || name[i] > '9' {
+				return -1
+			}
+			n = n*10 + int(name[i]-'0')
+		}
+		if n <= 31 {
+			return n
+		}
+	}
+	return -1
+}
+
+// arm64IsSP reports whether a register operand is the stack pointer (R31/SP),
+// which uses a different encoding path for some instructions.
+func arm64IsSP(name string) bool {
+	return name == "SP"
+}
+
+// ---- format helpers ----
+
+// a64wordLE encodes a uint32 as 4 little-endian bytes.
+func a64wordLE(w uint32) []byte {
+	return []byte{byte(w), byte(w >> 8), byte(w >> 16), byte(w >> 24)}
+}
+
+// a64WordsLE concatenates one or more instruction words as little-endian bytes.
+func a64WordsLE(ws ...uint32) []byte {
+	var out []byte
+	for _, w := range ws {
+		out = append(out, a64wordLE(w)...)
+	}
+	return out
+}
+
+// ---- data-processing (shifted register) ----
+
+// a64DPSR encodes a data-processing (shifted register) instruction:
+// sf<<31 | op<<30 | S<<29 | 0x0b<<24 | shift<<22 | 0<<21 | Rm<<16 | imm6<<10 | Rn<<5 | Rd.
+func a64DPSR(sf, op, S, shift, rm, imm6, rn, rd uint32) uint32 {
+	return sf<<31 | op<<30 | S<<29 | 0x0b<<24 | shift<<22 | rm<<16 | imm6<<10 | rn<<5 | rd
+}
+
+// ---- data-processing (immediate) ----
+
+// a64AddSub encodes an ADD/SUB (immediate) instruction:
+// sf<<31 | op<<30 | S<<29 | 0x11<<24 | sh<<22 | imm12<<10 | Rn<<5 | Rd.
+func a64AddSub(sf, op, S, sh, imm12, rn, rd uint32) uint32 {
+	return sf<<31 | op<<30 | S<<29 | 0x11<<24 | sh<<22 | imm12<<10 | rn<<5 | rd
+}
+
+// ---- logical (immediate) ----
+
+// a64LogicalImm encodes a logical (immediate) instruction:
+// sf<<31 | opc<<29 | 0x24<<23 | N<<22 | immr<<16 | imms<<10 | Rn<<5 | Rd.
+func a64LogicalImm(sf, opc, N, immr, imms, rn, rd uint32) uint32 {
+	return sf<<31 | opc<<29 | 0x24<<23 | N<<22 | immr<<16 | imms<<10 | rn<<5 | rd
+}
+
+// ---- move wide ----
+
+// a64MoveWide encodes a MOVZ/MOVK/MOVN instruction:
+// sf<<31 | opc<<29 | 0x25<<23 | hw<<21 | imm16<<5 | Rd.
+func a64MoveWide(sf, opc, hw, imm16, rd uint32) uint32 {
+	return sf<<31 | opc<<29 | 0x25<<23 | hw<<21 | imm16<<5 | rd
+}
+
+// ---- load/store (unsigned immediate, scaled) ----
+
+// a64LSU encodes a load/store register (unsigned immediate, scaled):
+// size<<30 | 0x39<<24 | V<<26 | opc<<22 | imm12<<10 | Rn<<5 | Rt.
+// (0x39<<24 encodes bits 29:24 = 111001, the scaled unsigned offset form.)
+func a64LSU(size, V, opc, imm12, rn, rt uint32) uint32 {
+	return size<<30 | 0x39<<24 | V<<26 | opc<<22 | imm12<<10 | rn<<5 | rt
+}
+
+// ---- load/store (unscaled immediate) ----
+
+// a64LSUnscaled encodes a load/store register (unscaled immediate, 9-bit signed):
+// size<<30 | 0x7<<27 | V<<26 | opc<<22 | 0<<12 | imm9<<12 | Rn<<5 | Rt.
+// Note: the 0<<24 distinguishes unscaled from the pre/post-index forms.
+func a64LSUnscaled(size, V, opc int, imm9 int32, rn, rt int) uint32 {
+	return uint32(size)<<30 | 7<<27 | uint32(V)<<26 | uint32(opc)<<22 |
+		(uint32(imm9)&0x1FF)<<12 | uint32(rn&31)<<5 | uint32(rt&31)
+}
+
+// ---- load/store pair ----
+
+// a64LSP encodes a load/store pair instruction (signed offset):
+// opc<<30 | 0x5<<27 | V<<26 | 2<<23 | L<<22 | imm7<<15 | Rt2<<10 | Rn<<5 | Rt.
+// opc: 0=32-bit, 1=reserved, 2=64-bit.  V: 0=integer, 1=FP/SIMD.
+// L: 0=store, 1=load.  imm7 is the signed scaled offset (÷8 for 64-bit pairs).
+func a64LSP(opc, V, L uint32, imm7 int32, rt2, rn, rt uint32) uint32 {
+	return opc<<30 | 5<<27 | V<<26 | 2<<23 | L<<22 | (uint32(imm7)&0x7F)<<15 | rt2<<10 | rn<<5 | rt
+}
+
+// ---- load/store pair (pre-index) ----
+
+// a64LSPPre encodes a load/store pair (pre-index):
+// opc<<30 | 0x5<<27 | V<<26 | 0b11<<23 | L<<22 | imm7<<15 | Rt2<<10 | Rn<<5 | Rt.
+func a64LSPPre(opc, V, L uint32, imm7 int32, rt2, rn, rt uint32) uint32 {
+	return opc<<30 | 5<<27 | V<<26 | 3<<23 | L<<22 | (uint32(imm7)&0x7F)<<15 | rt2<<10 | rn<<5 | rt
+}
+
+// ---- load/store pair (post-index) ----
+
+// a64LSPPost encodes a load/store pair (post-index):
+// opc<<30 | 0x5<<27 | V<<26 | 0b01<<23 | L<<22 | imm7<<15 | Rt2<<10 | Rn<<5 | Rt.
+func a64LSPPost(opc, V, L uint32, imm7 int32, rt2, rn, rt uint32) uint32 {
+	return opc<<30 | 5<<27 | V<<26 | 1<<23 | L<<22 | (uint32(imm7)&0x7F)<<15 | rt2<<10 | rn<<5 | rt
+}
+
+// ---- pre-index load/store ----
+
+// a64LSPreIndex encodes a load/store register (pre-index):
+// size<<30 | 0x7<<27 | V<<26 | opc<<22 | 1<<11 | 1<<10 | imm9<<12 | Rn<<5 | Rt.
+func a64LSPreIndex(size, V, opc uint32, imm9 int32, rn, rt uint32) uint32 {
+	return size<<30 | 7<<27 | V<<26 | opc<<22 | 3<<10 | (uint32(imm9)&0x1FF)<<12 | rn<<5 | rt
+}
+
+// ---- post-index load/store ----
+
+// a64LSPostIndex encodes a load/store register (post-index):
+// size<<30 | 0x7<<27 | V<<26 | opc<<22 | 0<<11 | 1<<10 | imm9<<12 | Rn<<5 | Rt.
+func a64LSPostIndex(size, V, opc uint32, imm9 int32, rn, rt uint32) uint32 {
+	return size<<30 | 7<<27 | V<<26 | opc<<22 | 1<<10 | (uint32(imm9)&0x1FF)<<12 | rn<<5 | rt
+}
+
+// ---- branches ----
+
+// a64Branch encodes an unconditional branch (B/BL):
+// op<<31 | 0x5<<26 | imm26.
+func a64Branch(op uint32, imm26 int32) uint32 {
+	return op<<31 | 5<<26 | (uint32(imm26) & 0x03FFFFFF)
+}
+
+// a64BranchCond encodes a conditional branch (B.cond):
+// 0x2A<<25 | imm19<<5 | cond.
+func a64BranchCond(imm19 int32, cond uint32) uint32 {
+	return 0x2A<<25 | (uint32(imm19)&0x7FFFF)<<5 | cond&0xF
+}
+
+// a64UncondBranch encodes an unconditional branch register (BR/BLR/RET):
+// 0x6B<<25 | opc<<21 | 0x1F<<16 | Rn<<5 | Rd.
+// opc: 0=BR, 1=BLR, 2=RET. For RET, Rn defaults to LR(30).
+func a64UncondBranch(opc, rn, rd uint32) uint32 {
+	return 0x6B<<25 | opc<<21 | 0x1F<<16 | rn<<5 | rd
+}
+
+// ---- ADR/ADRP ----
+
+// a64ADR encodes an ADR instruction (p=0) or ADRP instruction (p=1):
+// p<<31 | immlo<<29 | 0x10<<24 | immhi<<5 | Rd.
+func a64ADR(p uint32, immhi int32, immlo uint32, rd uint32) uint32 {
+	return p<<31 | immlo<<29 | 0x10<<24 | (uint32(immhi)&0x7FFFF)<<5 | rd
+}
+
+// ---- EXTR ----
+
+// a64EXTR encodes an EXTR instruction:
+// sf<<31 | 0<<29 | 0x27<<23 | N<<22 | 0<<21 | Rm<<16 | imms<<10 | Rn<<5 | Rd.
+func a64EXTR(sf, N, rm, imms, rn, rd uint32) uint32 {
+	return sf<<31 | 0x27<<23 | N<<22 | rm<<16 | imms<<10 | rn<<5 | rd
+}
+
+// ---- system ----
+
+// a64NOP encodes a NOP: 0xd503201f.
+const a64NOP uint32 = 0xd503201f
+
+// a64BRK encodes a BRK instruction: 0xd4200000 | imm16<<5.
+func a64BRK(imm16 uint32) uint32 {
+	return 0xd4200000 | imm16<<5
+}
+
+// ---- condition codes ----
+
+const (
+	a64CondEQ = 0x0
+	a64CondNE = 0x1
+	a64CondCS = 0x2
+	a64CondHS = 0x2
+	a64CondCC = 0x3
+	a64CondLO = 0x3
+	a64CondMI = 0x4
+	a64CondPL = 0x5
+	a64CondVS = 0x6
+	a64CondVC = 0x7
+	a64CondHI = 0x8
+	a64CondLS = 0x9
+	a64CondGE = 0xa
+	a64CondLT = 0xb
+	a64CondGT = 0xc
+	a64CondLE = 0xd
+	a64CondAL = 0xe
+	a64CondNV = 0xf
+)
+
+// arm64CondMap maps Go assembler condition mnemonics to AArch64 condition codes.
+var arm64CondMap = map[string]uint32{
+	"EQ": a64CondEQ,
+	"NE": a64CondNE,
+	"CS": a64CondCS,
+	"HS": a64CondHS,
+	"CC": a64CondCC,
+	"LO": a64CondLO,
+	"MI": a64CondMI,
+	"PL": a64CondPL,
+	"VS": a64CondVS,
+	"VC": a64CondVC,
+	"HI": a64CondHI,
+	"LS": a64CondLS,
+	"GE": a64CondGE,
+	"LT": a64CondLT,
+	"GT": a64CondGT,
+	"LE": a64CondLE,
+}
+
+// ---- instruction format tags ----
+
+type a64Format uint8
+
+const (
+	a64FDPSR         a64Format = iota // data-processing (shifted register): ADD, SUB, AND, ORR, EOR, etc.
+	a64FDPIR                          // data-processing (immediate): ADD/SUB $imm
+	a64FLogImm                        // logical (immediate): AND/ORR/EOR $imm
+	a64FMovWide                       // move wide: MOVZ, MOVN, MOVK
+	a64FLSU                           // load/store (unsigned immediate, scaled)
+	a64FLSUnscaled                    // load/store (unscaled immediate)
+	a64FLSPair                        // load/store pair
+	a64FBranch                        // unconditional branch (B/BL)
+	a64FBranchCond                    // conditional branch (B.cond)
+	a64FUncondBranch                  // unconditional branch register (BR/BLR/RET)
+	a64FADR                           // ADR/ADRP
+	a64FEXTR                          // EXTR
+	a64FBitfield                      // bitfield: BFI/BFXIL/SBFM/UBFM/BFM
+	a64FSystem                        // system: NOP, BRK, etc.
+	a64FFP3                           // FP 3-operand (Rm, Rn, Rd): FADD, FSUB, FMUL, FDIV, etc.
+	a64FFPUnary                       // FP unary (Rn, Rd): FMOV, FABS, FNEG, FSQRT, FCVT, FRINT*
+	a64FFP4                           // FP 4-operand FMA (Ra, Rm, Rn, Rd): FMADD, FMSUB, etc.
+	a64FFPCmp                         // FP compare (Rm, Rn): FCMP, FCMPE
+	a64FFPCCmp                        // FP conditional compare (Rm, Rn, nzcv, cond): FCCMP, FCCMPE
+	a64FFPCvt                         // FP↔integer conversion: FCVTZS, SCVTF, etc.
+	a64FFPSel                         // FP conditional select (Rm, Rn, Rd, cond): FCSEL
+	a64FFMovGR                        // FMOV between GP and FP registers
+	a64FCRC32                         // CRC32
+	a64FCSEL                          // conditional select: CSEL, CSINC, CSINV, CSNEG
+	a64FExcl                          // exclusive load/store: LDXR, STXR, LDAXR, STLXR
+	a64FLSE                           // LSE atomics: LDADD, CAS, SWP
+	a64FSIMD3                         // SIMD 3-operand: VADD, VSUB, VMUL
+)
+
+// a64Enc is one instruction's encoding: its bit layout (format) and the
+// opcode constant, positioned at its exact bit range.
+type a64Enc struct {
+	format a64Format
+	op     uint32 // the pre-positioned opcode bits
+	size   int    // 4 for most, 8 for DP-imm with shift, etc.
+}
+
+// a64InstrTable maps AArch64 mnemonics (as the Go assembler spells them) to
+// their encoding.  The base integer, memory, floating-point and SIMD
+// instruction sets are covered.
+var a64InstrTable = map[string]a64Enc{}
+
+func init() {
+	// ---- data-processing (shifted register) ----
+	// Format: sf<<31 | op<<30 | S<<29 | 0x0b<<24 | shift<<22 | Rm<<16 | imm6<<10 | Rn<<5 | Rd
+	dpsr := map[string]uint32{
+		// Add/Sub
+		"ADD":   1<<31 | 0<<30 | 0<<29 | 0x0b<<24, // sf=1, op=0, S=0 (64-bit default)
+		"ADDW":  0<<31 | 0<<30 | 0<<29 | 0x0b<<24, // sf=0
+		"ADDS":  1<<31 | 0<<30 | 1<<29 | 0x0b<<24,
+		"ADDSW": 0<<31 | 0<<30 | 1<<29 | 0x0b<<24,
+		"SUB":   1<<31 | 1<<30 | 0<<29 | 0x0b<<24,
+		"SUBW":  0<<31 | 1<<30 | 0<<29 | 0x0b<<24,
+		"SUBS":  1<<31 | 1<<30 | 1<<29 | 0x0b<<24,
+		"SUBSW": 0<<31 | 1<<30 | 1<<29 | 0x0b<<24,
+		// Logical (shifted register)
+		"AND":   1<<31 | 0<<29 | 0x0a<<24,
+		"ANDW":  0<<31 | 0<<29 | 0x0a<<24,
+		"BIC":   1<<31 | 0<<29 | 0x0a<<24 | 1<<21,
+		"BICW":  0<<31 | 0<<29 | 0x0a<<24 | 1<<21,
+		"ORR":   1<<31 | 1<<29 | 0x0a<<24,
+		"ORRW":  0<<31 | 1<<29 | 0x0a<<24,
+		"ORN":   1<<31 | 1<<29 | 0x0a<<24 | 1<<21,
+		"ORNW":  0<<31 | 1<<29 | 0x0a<<24 | 1<<21,
+		"EOR":   1<<31 | 2<<29 | 0x0a<<24,
+		"EORW":  0<<31 | 2<<29 | 0x0a<<24,
+		"EON":   1<<31 | 2<<29 | 0x0a<<24 | 1<<21,
+		"EONW":  0<<31 | 2<<29 | 0x0a<<24 | 1<<21,
+		"ANDS":  1<<31 | 3<<29 | 0x0a<<24,
+		"ANDSW": 0<<31 | 3<<29 | 0x0a<<24,
+		"BICS":  1<<31 | 3<<29 | 0x0a<<24 | 1<<21,
+		"BICSW": 0<<31 | 3<<29 | 0x0a<<24 | 1<<21,
+		// Shift
+		"LSL":  1<<31 | 0<<29 | 0x0a<<24, // alias of UBFM
+		"LSLW": 0<<31 | 0<<29 | 0x0a<<24,
+		"LSR":  1<<31 | 0<<29 | 0x0a<<24,
+		"LSRW": 0<<31 | 0<<29 | 0x0a<<24,
+		"ASR":  1<<31 | 0<<29 | 0x0a<<24,
+		"ASRW": 0<<31 | 0<<29 | 0x0a<<24,
+		"ROR":  1<<31 | 0<<29 | 0x0a<<24,
+		"RORW": 0<<31 | 0<<29 | 0x0a<<24,
+		// Multiply
+		"MADD":  1<<31 | 0<<29 | 0x1b<<24 | 0<<21,
+		"MADDW": 0<<31 | 0<<29 | 0x1b<<24 | 0<<21,
+		"MSUB":  1<<31 | 0<<29 | 0x1b<<24 | 1<<21,
+		"MSUBW": 0<<31 | 0<<29 | 0x1b<<24 | 1<<21,
+		// Divide
+		"SDIV":  1<<31 | 0<<29 | 0x0d<<24,
+		"SDIVW": 0<<31 | 0<<29 | 0x0d<<24,
+		"UDIV":  1<<31 | 0<<29 | 0x0d<<24 | 1<<10,
+		"UDIVW": 0<<31 | 0<<29 | 0x0d<<24 | 1<<10,
+		// CRC
+		"CRC32B": 0<<31 | 0<<29 | 0x1b<<24 | 4<<10,
+		"CRC32H": 0<<31 | 0<<29 | 0x1b<<24 | 5<<10,
+		"CRC32W": 0<<31 | 0<<29 | 0x1b<<24 | 6<<10,
+		"CRC32X": 1<<31 | 0<<29 | 0x1b<<24 | 7<<10,
+		// Conditional select
+		"CSEL":   1<<31 | 0<<29 | 0x1d<<24 | 0<<10,
+		"CSELW":  0<<31 | 0<<29 | 0x1d<<24 | 0<<10,
+		"CSINC":  1<<31 | 0<<29 | 0x1d<<24 | 1<<10,
+		"CSINCW": 0<<31 | 0<<29 | 0x1d<<24 | 1<<10,
+		"CSINV":  1<<31 | 0<<29 | 0x1d<<24 | 2<<10,
+		"CSINVW": 0<<31 | 0<<29 | 0x1d<<24 | 2<<10,
+		"CSNEG":  1<<31 | 0<<29 | 0x1d<<24 | 3<<10,
+		"CSNEGW": 0<<31 | 0<<29 | 0x1d<<24 | 3<<10,
+	}
+	for m, op := range dpsr {
+		a64InstrTable[m] = a64Enc{format: a64FDPSR, op: op}
+	}
+
+	// Aliases that map to the same encoding as their target.
+	a64InstrTable["CMP"] = a64Enc{format: a64FDPSR, op: dpsr["SUBS"]}
+	a64InstrTable["CMPW"] = a64Enc{format: a64FDPSR, op: dpsr["SUBSW"]}
+	a64InstrTable["CMN"] = a64Enc{format: a64FDPSR, op: dpsr["ADDS"]}
+	a64InstrTable["CMNW"] = a64Enc{format: a64FDPSR, op: dpsr["ADDSW"]}
+	a64InstrTable["TST"] = a64Enc{format: a64FDPSR, op: dpsr["ANDS"]}
+	a64InstrTable["TSTW"] = a64Enc{format: a64FDPSR, op: dpsr["ANDSW"]}
+	a64InstrTable["NEG"] = a64Enc{format: a64FDPSR, op: dpsr["SUB"]}
+	a64InstrTable["NEGW"] = a64Enc{format: a64FDPSR, op: dpsr["SUBW"]}
+	a64InstrTable["NEGS"] = a64Enc{format: a64FDPSR, op: dpsr["SUBS"]}
+	a64InstrTable["MVN"] = a64Enc{format: a64FDPSR, op: dpsr["ORN"]}
+	a64InstrTable["MVNW"] = a64Enc{format: a64FDPSR, op: dpsr["ORNW"]}
+	a64InstrTable["MOV"] = a64Enc{format: a64FDPSR, op: dpsr["ORR"]}
+	a64InstrTable["MOVW"] = a64Enc{format: a64FDPSR, op: dpsr["ORRW"]}
+
+	// ---- data-processing (immediate) ----
+	// ADD/SUB $imm, Rn, Rd
+	a64InstrTable["ADDImm"] = a64Enc{format: a64FDPIR, op: 1<<31 | 0<<30 | 0<<29 | 0x11<<24}
+	a64InstrTable["ADDWImm"] = a64Enc{format: a64FDPIR, op: 0<<31 | 0<<30 | 0<<29 | 0x11<<24}
+	a64InstrTable["SUBImm"] = a64Enc{format: a64FDPIR, op: 1<<31 | 1<<30 | 0<<29 | 0x11<<24}
+	a64InstrTable["SUBWImm"] = a64Enc{format: a64FDPIR, op: 0<<31 | 1<<30 | 0<<29 | 0x11<<24}
+	a64InstrTable["ADDSImm"] = a64Enc{format: a64FDPIR, op: 1<<31 | 0<<30 | 1<<29 | 0x11<<24}
+	a64InstrTable["SUBSImm"] = a64Enc{format: a64FDPIR, op: 1<<31 | 1<<30 | 1<<29 | 0x11<<24}
+
+	// ---- move wide ----
+	// MOVZ/MOVN/MOVK
+	a64InstrTable["MOVZ"] = a64Enc{format: a64FMovWide, op: 1<<31 | 2<<29 | 0x25<<23}
+	a64InstrTable["MOVZW"] = a64Enc{format: a64FMovWide, op: 0<<31 | 2<<29 | 0x25<<23}
+	a64InstrTable["MOVN"] = a64Enc{format: a64FMovWide, op: 1<<31 | 0<<29 | 0x25<<23}
+	a64InstrTable["MOVNW"] = a64Enc{format: a64FMovWide, op: 0<<31 | 0<<29 | 0x25<<23}
+	a64InstrTable["MOVK"] = a64Enc{format: a64FMovWide, op: 1<<31 | 3<<29 | 0x25<<23}
+	a64InstrTable["MOVKW"] = a64Enc{format: a64FMovWide, op: 0<<31 | 3<<29 | 0x25<<23}
+
+	// ---- ADR/ADRP ----
+	a64InstrTable["ADR"] = a64Enc{format: a64FADR, op: 0}
+	a64InstrTable["ADRP"] = a64Enc{format: a64FADR, op: 1}
+
+	// ---- load/store (unsigned immediate) ----
+	a64InstrTable["MOVD"] = a64Enc{format: a64FLSU, op: 3<<30 | 7<<27 | 1<<22}          // LDR 64-bit
+	a64InstrTable["MOVWU"] = a64Enc{format: a64FLSU, op: 2<<30 | 7<<27 | 1<<22}         // LDR 32-bit unsigned
+	a64InstrTable["MOVHU"] = a64Enc{format: a64FLSU, op: 1<<30 | 7<<27 | 1<<22}         // LDRH unsigned
+	a64InstrTable["MOVBU"] = a64Enc{format: a64FLSU, op: 0<<30 | 7<<27 | 1<<22}         // LDRB unsigned
+	a64InstrTable["MOVW"] = a64Enc{format: a64FLSU, op: 2<<30 | 7<<27 | 2<<22}          // LDRSW (signed 32→64)
+	a64InstrTable["MOVH"] = a64Enc{format: a64FLSU, op: 1<<30 | 7<<27 | 2<<22}          // LDRSH (signed half)
+	a64InstrTable["MOVB"] = a64Enc{format: a64FLSU, op: 0<<30 | 7<<27 | 2<<22}          // LDRSB (signed byte)
+	a64InstrTable["FMOVS"] = a64Enc{format: a64FLSU, op: 2<<30 | 7<<27 | 1<<26 | 1<<22} // FLDR 32-bit FP
+	a64InstrTable["FMOVD"] = a64Enc{format: a64FLSU, op: 3<<30 | 7<<27 | 1<<26 | 1<<22} // FLDR 64-bit FP
+
+	// Store opcodes (load ^ (1<<22)):
+	// STR 64-bit: size=3, V=0, opc=00 → 3<<30 | 7<<27 | 0<<22
+	// STR 32-bit: size=2, V=0, opc=00 → 2<<30 | 7<<27 | 0<<22
+	// STRH:      size=1, V=0, opc=00 → 1<<30 | 7<<27 | 0<<22
+	// STRB:      size=0, V=0, opc=00 → 0<<30 | 7<<27 | 0<<22
+
+	// ---- branches ----
+	a64InstrTable["B"] = a64Enc{format: a64FBranch, op: 0<<31 | 5<<26}
+	a64InstrTable["BL"] = a64Enc{format: a64FBranch, op: 1<<31 | 5<<26}
+
+	// Conditional branches.
+	condBranches := map[string]uint32{
+		"BEQ": 0x0, "BNE": 0x1, "BCS": 0x2, "BHS": 0x2,
+		"BCC": 0x3, "BLO": 0x3, "BMI": 0x4, "BPL": 0x5,
+		"BVS": 0x6, "BVC": 0x7, "BHI": 0x8, "BLS": 0x9,
+		"BGE": 0xa, "BLT": 0xb, "BGT": 0xc, "BLE": 0xd,
+	}
+	for name, cond := range condBranches {
+		a64InstrTable[name] = a64Enc{format: a64FBranchCond, op: 0x2A<<25 | cond}
+	}
+
+	// Unconditional branch register (BR/BLR/RET).
+	a64InstrTable["BR"] = a64Enc{format: a64FUncondBranch, op: 0x6B<<25 | 0<<21}
+	a64InstrTable["BLR"] = a64Enc{format: a64FUncondBranch, op: 0x6B<<25 | 1<<21}
+	a64InstrTable["RET"] = a64Enc{format: a64FUncondBranch, op: 0x6B<<25 | 2<<21}
+
+	// ---- system ----
+	a64InstrTable["NOP"] = a64Enc{format: a64FSystem, op: a64NOP}
+	a64InstrTable["NOOP"] = a64Enc{format: a64FSystem, op: a64NOP}
+	a64InstrTable["BRK"] = a64Enc{format: a64FSystem, op: 0xd4200000}
+	a64InstrTable["UNDEF"] = a64Enc{format: a64FSystem, op: a64BRK(0)}
+
+	// ---- EXTR ----
+	a64InstrTable["EXTR"] = a64Enc{format: a64FEXTR, op: 1<<31 | 0x27<<23 | 1<<22}
+	a64InstrTable["EXTRW"] = a64Enc{format: a64FEXTR, op: 0<<31 | 0x27<<23 | 0<<22}
+
+	// ---- bitfield ----
+	a64InstrTable["BFM"] = a64Enc{format: a64FBitfield, op: 1<<31 | 1<<29 | 0x26<<23 | 1<<22}
+	a64InstrTable["BFMW"] = a64Enc{format: a64FBitfield, op: 0<<31 | 1<<29 | 0x26<<23 | 0<<22}
+	a64InstrTable["SBFM"] = a64Enc{format: a64FBitfield, op: 1<<31 | 0<<29 | 0x26<<23 | 1<<22}
+	a64InstrTable["SBFMW"] = a64Enc{format: a64FBitfield, op: 0<<31 | 0<<29 | 0x26<<23 | 0<<22}
+	a64InstrTable["UBFM"] = a64Enc{format: a64FBitfield, op: 1<<31 | 2<<29 | 0x26<<23 | 1<<22}
+	a64InstrTable["UBFMW"] = a64Enc{format: a64FBitfield, op: 0<<31 | 2<<29 | 0x26<<23 | 0<<22}
+	a64InstrTable["BFI"] = a64Enc{format: a64FBitfield, op: 1<<31 | 2<<29 | 0x26<<23 | 1<<22}
+	a64InstrTable["BFIW"] = a64Enc{format: a64FBitfield, op: 0<<31 | 2<<29 | 0x26<<23 | 0<<22}
+	a64InstrTable["BFXIL"] = a64Enc{format: a64FBitfield, op: 1<<31 | 1<<29 | 0x26<<23 | 1<<22}
+	a64InstrTable["BFXILW"] = a64Enc{format: a64FBitfield, op: 0<<31 | 1<<29 | 0x26<<23 | 0<<22}
+
+	// ---- FP 3-operand (Rm, Rn, Rd): FADD, FSUB, FMUL, FDIV, FMAX, FMIN, FNMUL ----
+	fp3 := map[string]uint32{
+		"FADDS": 0x1e202800, "FADDD": 0x1e602800,
+		"FSUBS": 0x1e203800, "FSUBD": 0x1e603800,
+		"FMULS": 0x1e200800, "FMULD": 0x1e600800,
+		"FDIVS": 0x1e201800, "FDIVD": 0x1e601800,
+		"FMAXS": 0x1e204800, "FMAXD": 0x1e604800,
+		"FMINS": 0x1e205800, "FMIND": 0x1e605800,
+		"FMAXNMS": 0x1e206800, "FMAXNMD": 0x1e606800,
+		"FMINNMS": 0x1e207800, "FMINNMD": 0x1e607800,
+		"FNMULS": 0x1e208800, "FNMULD": 0x1e608800,
+	}
+	for m, op := range fp3 {
+		a64InstrTable[m] = a64Enc{format: a64FFP3, op: op}
+	}
+
+	// ---- FP unary (Rn, Rd): FMOV reg-reg, FABS, FNEG, FSQRT, FCVT, FRINT* ----
+	fp1 := map[string]uint32{
+		"FMOVS": 0x1e204000, "FMOVD": 0x1e604000,
+		"FABSS": 0x1e20c000, "FABSD": 0x1e60c000,
+		"FNEGS": 0x1e214000, "FNEGD": 0x1e614000,
+		"FSQRTS": 0x1e21c000, "FSQRTD": 0x1e61c000,
+		"FCVTSD": 0x1e22c000, "FCVTDS": 0x1e624000,
+		"FRINTNS": 0x1e244000, "FRINTND": 0x1e644000,
+		"FRINTPS": 0x1e24c000, "FRINTPD": 0x1e64c000,
+		"FRINTMS": 0x1e254000, "FRINTMD": 0x1e654000,
+		"FRINTZS": 0x1e25c000, "FRINTZD": 0x1e65c000,
+		"FRINTAS": 0x1e264000, "FRINTAD": 0x1e664000,
+		"FRINTXS": 0x1e274000, "FRINTXD": 0x1e674000,
+		"FRINTIS": 0x1e27c000, "FRINTID": 0x1e67c000,
+	}
+	for m, op := range fp1 {
+		a64InstrTable[m] = a64Enc{format: a64FFPUnary, op: op}
+	}
+
+	// ---- FP 4-operand FMA (Ra, Rm, Rn, Rd) ----
+	fp4 := map[string]uint32{
+		"FMADDS": 0x1f000000, "FMADDD": 0x1f400000,
+		"FMSUBS": 0x1f008000, "FMSUBD": 0x1f408000,
+		"FNMADDS": 0x1f200000, "FNMADDD": 0x1f600000,
+		"FNMSUBS": 0x1f208000, "FNMSUBD": 0x1f608000,
+	}
+	for m, op := range fp4 {
+		a64InstrTable[m] = a64Enc{format: a64FFP4, op: op}
+	}
+
+	// ---- FP compare (Rm, Rn or #0, Rn) ----
+	fpcmp := map[string]uint32{
+		"FCMPS": 0x1e202000, "FCMPD": 0x1e602000,
+		"FCMPES": 0x1e202010, "FCMPED": 0x1e602010,
+	}
+	for m, op := range fpcmp {
+		a64InstrTable[m] = a64Enc{format: a64FFPCmp, op: op}
+	}
+
+	// ---- FP conditional compare (Rm, Rn, #nzcv, cond) ----
+	fpccmp := map[string]uint32{
+		"FCCMPS": 0x1e200400, "FCCMPD": 0x1e600400,
+		"FCCMPES": 0x1e200410, "FCCMPED": 0x1e600410,
+	}
+	for m, op := range fpccmp {
+		a64InstrTable[m] = a64Enc{format: a64FFPCCmp, op: op}
+	}
+
+	// ---- FP conditional select (Rm, Rn, Rd, cond) ----
+	a64InstrTable["FCSELS"] = a64Enc{format: a64FFPSel, op: 0x1e200c00}
+	a64InstrTable["FCSELD"] = a64Enc{format: a64FFPSel, op: 0x1e600c00}
+
+	// ---- FP ↔ integer conversion ----
+	fpcvt := map[string]uint32{
+		"FCVTZSD": 0x9e780000, "FCVTZSDW": 0x1e780000,
+		"FCVTZSS": 0x9e380000, "FCVTZSSW": 0x1e380000,
+		"FCVTZUD": 0x9e790000, "FCVTZUDW": 0x1e790000,
+		"FCVTZUS": 0x9e390000, "FCVTZUSW": 0x1e390000,
+		"SCVTFD": 0x9e620000, "SCVTFS": 0x9e220000,
+		"SCVTFWD": 0x1e620000, "SCVTFWS": 0x1e220000,
+		"UCVTFD": 0x9e630000, "UCVTFS": 0x9e230000,
+		"UCVTFWD": 0x1e630000, "UCVTFWS": 0x1e230000,
+	}
+	for m, op := range fpcvt {
+		a64InstrTable[m] = a64Enc{format: a64FFPCvt, op: op}
+	}
+
+	// ---- FMOV between GP and FP registers ----
+	a64InstrTable["FMOVGR"] = a64Enc{format: a64FFMovGR, op: 0x1e260000} // placeholder, actual encoding depends on direction
+
+	// ---- conditional select: CSEL, CSINC, CSINV, CSNEG ----
+	csel := map[string]uint32{
+		"CSEL": 0x9a800000, "CSELW": 0x1a800000,
+		"CSINC": 0x9a800400, "CSINCW": 0x1a800400,
+		"CSINV": 0xda800000, "CSINVW": 0x5a800000,
+		"CSNEG": 0xda800400, "CSNEGW": 0x5a800400,
+	}
+	for m, op := range csel {
+		a64InstrTable[m] = a64Enc{format: a64FCSEL, op: op}
+	}
+	// Aliases
+	a64InstrTable["CSET"] = a64Enc{format: a64FCSEL, op: 0x9a800400}
+	a64InstrTable["CSETW"] = a64Enc{format: a64FCSEL, op: 0x1a800400}
+	a64InstrTable["CSETM"] = a64Enc{format: a64FCSEL, op: 0xda800000}
+	a64InstrTable["CSETMW"] = a64Enc{format: a64FCSEL, op: 0x5a800000}
+	a64InstrTable["CINC"] = a64Enc{format: a64FCSEL, op: 0x9a800400}
+	a64InstrTable["CINCW"] = a64Enc{format: a64FCSEL, op: 0x1a800400}
+	a64InstrTable["CINV"] = a64Enc{format: a64FCSEL, op: 0xda800000}
+	a64InstrTable["CINVW"] = a64Enc{format: a64FCSEL, op: 0x5a800000}
+	a64InstrTable["CNEG"] = a64Enc{format: a64FCSEL, op: 0xda800400}
+	a64InstrTable["CNEGW"] = a64Enc{format: a64FCSEL, op: 0x5a800400}
+
+	// ---- CRC32 ----
+	crc32 := map[string]uint32{
+		"CRC32B": 0x1ac04000, "CRC32H": 0x1ac04400,
+		"CRC32W": 0x1ac04800, "CRC32X": 0x9ac04c00,
+		"CRC32CB": 0x1ac05000, "CRC32CH": 0x1ac05400,
+		"CRC32CW": 0x1ac05800, "CRC32CX": 0x9ac05c00,
+	}
+	for m, op := range crc32 {
+		a64InstrTable[m] = a64Enc{format: a64FCRC32, op: op}
+	}
+
+	// ---- exclusive load/store ----
+	a64InstrTable["LDXR"] = a64Enc{format: a64FExcl, op: 0xc85f7c00}
+	a64InstrTable["LDXRB"] = a64Enc{format: a64FExcl, op: 0x085f7c00}
+	a64InstrTable["LDXRH"] = a64Enc{format: a64FExcl, op: 0x485f7c00}
+	a64InstrTable["LDXRW"] = a64Enc{format: a64FExcl, op: 0x885f7c00}
+	a64InstrTable["LDAXR"] = a64Enc{format: a64FExcl, op: 0xc85ffc00}
+	a64InstrTable["LDAXRB"] = a64Enc{format: a64FExcl, op: 0x085ffc00}
+	a64InstrTable["LDAXRH"] = a64Enc{format: a64FExcl, op: 0x485ffc00}
+	a64InstrTable["LDAXRW"] = a64Enc{format: a64FExcl, op: 0x885ffc00}
+	a64InstrTable["STXR"] = a64Enc{format: a64FExcl, op: 0xc8007c00}
+	a64InstrTable["STXRB"] = a64Enc{format: a64FExcl, op: 0x08007c00}
+	a64InstrTable["STXRH"] = a64Enc{format: a64FExcl, op: 0x48007c00}
+	a64InstrTable["STXRW"] = a64Enc{format: a64FExcl, op: 0x88007c00}
+	a64InstrTable["STLXR"] = a64Enc{format: a64FExcl, op: 0xc800fc00}
+	a64InstrTable["STLXRB"] = a64Enc{format: a64FExcl, op: 0x0800fc00}
+	a64InstrTable["STLXRH"] = a64Enc{format: a64FExcl, op: 0x4800fc00}
+	a64InstrTable["STLXRW"] = a64Enc{format: a64FExcl, op: 0x8800fc00}
+
+	// ---- LSE atomics ----
+	a64InstrTable["LDADDD"] = a64Enc{format: a64FLSE, op: 3<<30 | 0x1c1<<21 | 0x00<<10}
+	a64InstrTable["LDADDW"] = a64Enc{format: a64FLSE, op: 2<<30 | 0x1c1<<21 | 0x00<<10}
+	a64InstrTable["LDADDB"] = a64Enc{format: a64FLSE, op: 0<<30 | 0x1c1<<21 | 0x00<<10}
+	a64InstrTable["LDADDH"] = a64Enc{format: a64FLSE, op: 1<<30 | 0x1c1<<21 | 0x00<<10}
+	a64InstrTable["CASD"] = a64Enc{format: a64FLSE, op: 3<<30 | 0x45<<21 | 0x1f<<10}
+	a64InstrTable["CASW"] = a64Enc{format: a64FLSE, op: 2<<30 | 0x45<<21 | 0x1f<<10}
+	a64InstrTable["SWPD"] = a64Enc{format: a64FLSE, op: 3<<30 | 0x1c1<<21 | 0x20<<10}
+	a64InstrTable["SWPW"] = a64Enc{format: a64FLSE, op: 2<<30 | 0x1c1<<21 | 0x20<<10}
+
+	// ---- SIMD basics ----
+	a64InstrTable["VADD"] = a64Enc{format: a64FSIMD3, op: 0x0e208400}
+	a64InstrTable["VSUB"] = a64Enc{format: a64FSIMD3, op: 0x2e208400}
+	a64InstrTable["VMUL"] = a64Enc{format: a64FSIMD3, op: 0x0e209c00}
+}
+
+// ---- load/store helper tables ----
+
+// a64LSType describes the load/store parameters for a MOV width mnemonic.
+type a64LSType struct {
+	size int // 0=byte, 1=half, 2=word, 3=dword
+	V    int // 0=integer, 1=FP
+	opc  int // 00=store/unsigned load, 01=store FP, 10=signed load, 11=load FP
+}
+
+// a64LoadTable maps MOV width mnemonics to their load/store encoding parameters.
+// For loads, opc selects signed vs unsigned; for stores, we flip the opc.
+var a64LoadTable = map[string]a64LSType{
+	"MOVD":  {3, 0, 1}, // LDR X (64-bit, unsigned offset)
+	"MOVWU": {2, 0, 1}, // LDR W (32-bit unsigned)
+	"MOVW":  {2, 0, 2}, // LDRSW (32-bit signed → 64-bit)
+	"MOVHU": {1, 0, 1}, // LDRH (16-bit unsigned)
+	"MOVH":  {1, 0, 2}, // LDRSH (16-bit signed)
+	"MOVBU": {0, 0, 1}, // LDRB (8-bit unsigned)
+	"MOVB":  {0, 0, 2}, // LDRSB (8-bit signed)
+	"FMOVS": {2, 1, 1}, // LDR S (32-bit FP)
+	"FMOVD": {3, 1, 1}, // LDR D (64-bit FP)
+}
+
+// a64StoreOpc returns the store opc for a given load type.
+// For integer: store opc = 00 (the load opc bits cleared).
+// For FP: store opc = 00 (same pattern).
+func a64StoreOpc(t a64LSType) int {
+	if t.V == 1 {
+		return 0 // FP store
+	}
+	return 0 // integer store
+}
+
+// a64MovRegTable maps register-to-register MOV mnemonic expansions.
+// The Go toolchain encodes MOV Rn, Rd as ORR Rn, ZR, Rd.
+var a64MovRegTable = map[string]uint32{
+	"MOVD":  1<<31 | 1<<29 | 0x0a<<24, // ORR 64-bit
+	"MOVW":  0<<31 | 1<<29 | 0x0a<<24, // ORR 32-bit
+	"MOVB":  0<<31 | 1<<29 | 0x0a<<24, // ORR 32-bit (byte move)
+	"MOVBU": 0<<31 | 1<<29 | 0x0a<<24, // ORR 32-bit
+	"MOVH":  0<<31 | 1<<29 | 0x0a<<24, // ORR 32-bit
+	"MOVHU": 0<<31 | 1<<29 | 0x0a<<24, // ORR 32-bit
+	"MOVWU": 0<<31 | 1<<29 | 0x0a<<24, // ORR 32-bit
+}
+
+// arm64RegClass discriminates integer (R), floating-point (F) registers for
+// the MOV pseudo-instruction.
+type arm64RegClass int
+
+const (
+	arm64ClsNone arm64RegClass = iota
+	arm64ClsGR
+	arm64ClsFP
+)
+
+// arm64RegClassOf reports the register class of a register operand name.
+func arm64RegClassOf(name string) arm64RegClass {
+	switch {
+	case name == "":
+		return arm64ClsNone
+	case len(name) >= 1 && name[0] == 'F':
+		return arm64ClsFP
+	default:
+		return arm64ClsGR
+	}
+}
+
+// arm64Movcon returns the shift (in units of 16 bits) at which a non-zero
+// 16-bit chunk of v sits, or -1 if v cannot be represented as a single
+// MOVZ/MOVN immediate.  This is the Go toolchain's movcon function.
+func arm64Movcon(v int64) int {
+	for s := 0; s < 64; s += 16 {
+		if (uint64(v) &^ (uint64(0xFFFF) << uint(s))) == 0 {
+			return s
+		}
+	}
+	return -1
+}

asm/arm64_encode_test.go

@@ -0,0 +1,574 @@
+// Copyright (c) 2026 Petr Balvín <opensource@petrbalvin.org> (https://petrbalvin.org)
+// SPDX-License-Identifier: BSD-3-Clause
+
+package asm
+
+import (
+	"testing"
+
+	"sourcedock.dev/petrbalvin/gasm-devkit/ast"
+	"sourcedock.dev/petrbalvin/gasm-devkit/parser"
+)
+
+func TestArm64LDRSTREncoding(t *testing.T) {
+	tests := []struct {
+		name string
+		got  uint32
+		want uint32
+	}{
+		{"LDR X4, [SP, #56]", a64LSU(3, 0, 1, 7, 31, 4), 0xf9401fe4},
+		{"STR X4, [SP, #64]", a64LSU(3, 0, 0, 8, 31, 4), 0xf90023e4},
+		{"STR X5, [SP, #32]", a64LSU(3, 0, 0, 4, 31, 5), 0xf90013e5},
+		{"LDR X6, [SP, #32]", a64LSU(3, 0, 1, 4, 31, 6), 0xf94013e6},
+	}
+	for _, tt := range tests {
+		if tt.got != tt.want {
+			t.Errorf("%s: got %08x, want %08x", tt.name, tt.got, tt.want)
+		}
+	}
+}
+
+func TestArm64PrologueEncoding(t *testing.T) {
+	fi := arm64FrameInfo{autosize: 48, frame: 32, leaf: false}
+	pro := arm64Prologue(fi)
+	if len(pro) != 12 {
+		t.Fatalf("prologue length: got %d, want 12", len(pro))
+	}
+	expected := []uint32{0xf81d0ffe, 0xf81f83fd, 0xd10023fd}
+	for i, w := range leWords(pro) {
+		if w != expected[i] {
+			t.Errorf("prologue word %d: got %08x, want %08x", i, w, expected[i])
+		}
+	}
+}
+
+func TestArm64EpilogueSmallEncoding(t *testing.T) {
+	fi := arm64FrameInfo{autosize: 48, frame: 32, leaf: false}
+	ret := arm64Return(fi)
+	if len(ret) != 12 {
+		t.Fatalf("epilogue length: got %d, want 12", len(ret))
+	}
+	// Non-leaf small frame: LDR FP, [SP, #-8]; LDR.P LR, [SP], #48; RET
+	expected := []uint32{0xf85f83fd, 0xf84307fe, 0xd65f03c0}
+	for i, w := range leWords(ret) {
+		if w != expected[i] {
+			t.Errorf("epilogue word %d: got %08x, want %08x", i, w, expected[i])
+		}
+	}
+}
+
+func TestArm64LargeFrameEncoding(t *testing.T) {
+	fi := arm64FrameInfo{autosize: 272, frame: 256, leaf: false}
+	pro := arm64Prologue(fi)
+	if len(pro) != 16 {
+		t.Fatalf("prologue length: got %d, want 16", len(pro))
+	}
+	expected := []uint32{0xd10443f4, 0xa93ffa9d, 0x9100029f, 0xd10023fd}
+	for i, w := range leWords(pro) {
+		if w != expected[i] {
+			t.Errorf("prologue word %d: got %08x, want %08x", i, w, expected[i])
+		}
+	}
+
+	epi := arm64Return(fi)
+	if len(epi) != 12 {
+		t.Fatalf("epilogue length: got %d, want 12", len(epi))
+	}
+	eexpected := []uint32{0xa97ffbfd, 0x910443ff, 0xd65f03c0}
+	for i, w := range leWords(epi) {
+		if w != eexpected[i] {
+			t.Errorf("epilogue word %d: got %08x, want %08x", i, w, eexpected[i])
+		}
+	}
+}
+
+func TestArm64NoFrame(t *testing.T) {
+	fi := arm64FrameInfo{autosize: 0, frame: 0, leaf: true}
+	pro := arm64Prologue(fi)
+	if len(pro) != 0 {
+		t.Errorf("no-frame prologue: got %d bytes, want 0", len(pro))
+	}
+	ret := arm64Return(fi)
+	if len(ret) != 4 {
+		t.Fatalf("no-frame return: got %d bytes, want 4", len(ret))
+	}
+	if leWord(ret) != 0xd65f03c0 {
+		t.Errorf("no-frame RET: got %08x, want d65f03c0", leWord(ret))
+	}
+}
+
+func TestArm64RegNum(t *testing.T) {
+	tests := []struct {
+		name string
+		want int
+	}{
+		{"R0", 0}, {"R4", 4}, {"R29", 29}, {"R30", 30}, {"R31", 31},
+		{"FP", 29}, {"LR", 30}, {"LINK", 30}, {"SP", 31}, {"ZR", 31},
+		{"F0", 0}, {"F4", 4}, {"F31", 31},
+		{"INVALID", -1}, {"X0", -1}, {"", -1},
+	}
+	for _, tt := range tests {
+		got := arm64RegNum(tt.name)
+		if got != tt.want {
+			t.Errorf("arm64RegNum(%q) = %d, want %d", tt.name, got, tt.want)
+		}
+	}
+}
+
+func TestArm64ComputeFrame(t *testing.T) {
+	src := "TEXT ·f(SB), NOSPLIT, $32-0\n\tADD\tR4, R5\n\tRET\n"
+	f, errs := parser.Parse("test_arm64.s", src)
+	if len(errs) > 0 {
+		t.Fatalf("parse: %v", errs)
+	}
+	fi := arm64ComputeFrame(f.Decls[0].(*ast.Text))
+	if fi.frame != 32 {
+		t.Errorf("frame: got %d, want 32", fi.frame)
+	}
+	if fi.autosize != 48 { // 32+8=40, aligned to48
+		t.Errorf("autosize: got %d, want 48", fi.autosize)
+	}
+	// ADD + RET with no CALL/BL → leaf
+	if !fi.leaf {
+		t.Error("expected leaf")
+	}
+}
+
+func TestArm64IsLeaf(t *testing.T) {
+	src := "TEXT ·f(SB), NOSPLIT, $0-0\n\tADD\tR4, R5\n\tRET\n"
+	f, errs := parser.Parse("test_arm64.s", src)
+	if len(errs) > 0 {
+		t.Fatalf("parse: %v", errs)
+	}
+	if !arm64IsLeaf(f.Decls[0].(*ast.Text)) {
+		t.Error("expected leaf")
+	}
+
+	src2 := "TEXT ·f(SB), NOSPLIT, $0-0\n\tBL\tother(SB)\n\tRET\n"
+	f2, errs := parser.Parse("test_arm64.s", src2)
+	if len(errs) > 0 {
+		t.Fatalf("parse: %v", errs)
+	}
+	if arm64IsLeaf(f2.Decls[0].(*ast.Text)) {
+		t.Error("expected non-leaf")
+	}
+}
+
+func TestArm64Bitmask(t *testing.T) {
+	tests := []struct {
+		v             uint64
+		sf            int
+		N, immr, imms uint32
+		ok            bool
+	}{
+		{1, 1, 1, 0, 0, true},                     // single bit at pos 0
+		{2, 1, 1, 63, 0, true},                    // single bit at pos 1 (immr = esize-1)
+		{0, 1, 0, 0, 0, false},                    // zero is not a bitmask
+		{0xFFFFFFFFFFFFFFFF, 1, 0, 0, 0, false},   // all ones is not a bitmask
+		{0x5555555555555555, 1, 0, 0, 0x3E, true}, // alternating bits (esize=2, ones=1)
+		{0xFFFFFFFF00000000, 1, 1, 32, 31, true},  // upper 32 bits set (esize=64, ones=32)
+	}
+	for _, tt := range tests {
+		N, immr, imms, ok := arm64Bitmask(tt.v, tt.sf)
+		if ok != tt.ok {
+			t.Errorf("arm64Bitmask(%#x, %d): ok=%v, want %v", tt.v, tt.sf, ok, tt.ok)
+			continue
+		}
+		if ok && (N != tt.N || immr != tt.immr || imms != tt.imms) {
+			t.Errorf("arm64Bitmask(%#x, %d): N=%d immr=%d imms=%d, want N=%d immr=%d imms=%d",
+				tt.v, tt.sf, N, immr, imms, tt.N, tt.immr, tt.imms)
+		}
+	}
+}
+
+func TestArm64AssembleFile(t *testing.T) {
+	src := `#include "textflag.h"
+
+TEXT ·simple(SB), NOSPLIT, $0-0
+	MOV	R4, R5
+	ADD	R4, R5, R6
+	RET
+`
+	f, errs := parser.Parse("test_arm64.s", src)
+	if len(errs) > 0 {
+		t.Fatalf("parse: %v", errs)
+	}
+	img, err := AssembleFileARM64(f)
+	if err != nil {
+		t.Fatalf("AssembleFileARM64: %v", err)
+	}
+	if len(img.Funcs) != 1 {
+		t.Fatalf("got %d funcs, want 1", len(img.Funcs))
+	}
+	fn := img.Funcs[0]
+	if fn.Name != "simple" {
+		t.Errorf("func name: got %q, want %q", fn.Name, "simple")
+	}
+	//3 instructions ×4 bytes =12
+	if fn.Size != 12 {
+		t.Errorf("func size: got %d, want 12", fn.Size)
+	}
+}
+
+func TestArm64AssembleFileWithFrame(t *testing.T) {
+	src := `#include "textflag.h"
+
+TEXT ·framed(SB), NOSPLIT, $16-8
+	MOVD	arg+0(FP), R4
+	ADD	$1, R4, R4
+	MOVD	R4, ret+0(FP)
+	RET
+`
+	f, errs := parser.Parse("test_arm64.s", src)
+	if len(errs) > 0 {
+		t.Fatalf("parse: %v", errs)
+	}
+	img, err := AssembleFileARM64(f)
+	if err != nil {
+		t.Fatalf("AssembleFileARM64: %v", err)
+	}
+	if len(img.Funcs) != 1 {
+		t.Fatalf("got %d funcs, want 1", len(img.Funcs))
+	}
+	fn := img.Funcs[0]
+	if fn.Frame != 16 {
+		t.Errorf("frame: got %d, want 16", fn.Frame)
+	}
+	// Prologue (3×4=12) + body (3×4=12) + RET epilogue (3×4=12) = 36
+	if fn.Size != 36 {
+		t.Errorf("func size: got %d, want 36", fn.Size)
+	}
+}
+
+func TestArm64AssembleFileWithBranches(t *testing.T) {
+	src := `#include "textflag.h"
+
+TEXT ·branch(SB), NOSPLIT, $0-0
+	BEQ	done
+	BNE	skip
+skip:
+	ADD	R4, R5
+done:
+	RET
+`
+	f, errs := parser.Parse("test_arm64.s", src)
+	if len(errs) > 0 {
+		t.Fatalf("parse: %v", errs)
+	}
+	img, err := AssembleFileARM64(f)
+	if err != nil {
+		t.Fatalf("AssembleFileARM64: %v", err)
+	}
+	fn := img.Funcs[0]
+	if fn.Size != 16 {
+		t.Errorf("func size: got %d, want 16", fn.Size)
+	}
+}
+
+func TestArm64AssembleFileWithJumpChain(t *testing.T) {
+	src := `#include "textflag.h"
+
+TEXT ·chain(SB), NOSPLIT, $0-0
+	BNE	skip
+	ADD	R4, R5
+	RET
+skip:
+	B	target
+target:
+	ADD	R6, R7
+	RET
+`
+	f, errs := parser.Parse("test_arm64.s", src)
+	if len(errs) > 0 {
+		t.Fatalf("parse: %v", errs)
+	}
+	img, err := AssembleFileARM64(f)
+	if err != nil {
+		t.Fatalf("AssembleFileARM64: %v", err)
+	}
+	// BNE should be redirected past skip→target to target directly.
+	if img.Funcs[0].Size != 24 {
+		t.Errorf("func size: got %d, want 24", img.Funcs[0].Size)
+	}
+}
+
+func TestArm64AssembleErrors(t *testing.T) {
+	tests := []struct {
+		name string
+		src  string
+	}{
+		{"unsupported", "TEXT ·f(SB), NOSPLIT, $0-0\n\tINVALID\tR4, R5\n\tRET\n"},
+		{"undefined label", "TEXT ·f(SB), NOSPLIT, $0-0\n\tB\tnosuch\n\tRET\n"},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			f, errs := parser.Parse("test_arm64.s", tt.src)
+			if len(errs) > 0 {
+				return // parse error, that's fine
+			}
+			_, err := AssembleFileARM64(f)
+			if err == nil {
+				t.Error("expected error, got nil")
+			}
+		})
+	}
+}
+
+func TestArm64Movcon(t *testing.T) {
+	tests := []struct {
+		v    int64
+		want int
+	}{
+		{0, 0},            // 0 fits at shift 0
+		{1, 0},            // single bit at shift 0
+		{0x10000, 16},     // single bit at shift 16
+		{0x100000000, 32}, // single bit at shift 32
+		{0xFF, 0},         // 0xFF fits at shift 0
+		{0x12345, -1},     // multiple chunks, not movcon
+	}
+	for _, tt := range tests {
+		got := arm64Movcon(tt.v)
+		if got != tt.want {
+			t.Errorf("arm64Movcon(%#x) = %d, want %d", tt.v, got, tt.want)
+		}
+	}
+}
+
+func TestArm64RegClassOf(t *testing.T) {
+	if arm64RegClassOf("R4") != arm64ClsGR {
+		t.Error("R4 should be GR")
+	}
+	if arm64RegClassOf("F4") != arm64ClsFP {
+		t.Error("F4 should be FP")
+	}
+	if arm64RegClassOf("") != arm64ClsNone {
+		t.Error("empty should be None")
+	}
+}
+
+func TestArm64ResolvePseudo(t *testing.T) {
+	fi := arm64FrameInfo{autosize: 48, frame: 32}
+	// FP: offset = sym.Offset + autosize +8
+	base, off := arm64ResolvePseudo(&ast.Symbol{Pseudo: "FP", Offset: 0}, fi)
+	if base != 31 || off != 56 {
+		t.Errorf("FP: base=%d off=%d, want 31, 56", base, off)
+	}
+	// SP: offset = sym.Offset + frame +8
+	base, off = arm64ResolvePseudo(&ast.Symbol{Pseudo: "SP", Offset: -8}, fi)
+	if base != 31 || off != 32 {
+		t.Errorf("SP: base=%d off=%d, want 31, 32", base, off)
+	}
+	// SB: unresolved
+	base, _ = arm64ResolvePseudo(&ast.Symbol{Pseudo: "SB"}, fi)
+	if base != -1 {
+		t.Errorf("SB: base=%d, want -1", base)
+	}
+}
+
+// TestArm64FPSel tests FP conditional select encoding.
+func TestArm64FPSel(t *testing.T) {
+	src := `#include "textflag.h"
+TEXT ·f(SB), NOSPLIT, $0-0
+	FCSELD	GE, F10, F11, F12
+	RET
+`
+	f, errs := parser.Parse("test_arm64.s", src)
+	if len(errs) > 0 {
+		t.Fatalf("parse: %v", errs)
+	}
+	img, err := AssembleFileARM64(f)
+	if err != nil {
+		t.Fatalf("AssembleFileARM64: %v", err)
+	}
+	// FCSELD should be 4 bytes + RET 4 bytes = 8
+	if img.Funcs[0].Size != 8 {
+		t.Errorf("size: got %d, want 8", img.Funcs[0].Size)
+	}
+}
+
+// TestArm64FPCvt tests FP conversion encoding.
+func TestArm64FPCvt(t *testing.T) {
+	src := `#include "textflag.h"
+TEXT ·f(SB), NOSPLIT, $0-0
+	FCVTZSD	F4, R0
+	SCVTFD	R4, F8
+	RET
+`
+	f, errs := parser.Parse("test_arm64.s", src)
+	if len(errs) > 0 {
+		t.Fatalf("parse: %v", errs)
+	}
+	img, err := AssembleFileARM64(f)
+	if err != nil {
+		t.Fatalf("AssembleFileARM64: %v", err)
+	}
+	if img.Funcs[0].Size != 12 {
+		t.Errorf("size: got %d, want 12", img.Funcs[0].Size)
+	}
+}
+
+// TestArm64CSEL tests conditional select encoding.
+func TestArm64CSEL(t *testing.T) {
+	src := `#include "textflag.h"
+TEXT ·f(SB), NOSPLIT, $0-0
+	CSEL	EQ, R0, R1, R2
+	CSET	NE, R3
+	CINC	GE, R4, R5
+	RET
+`
+	f, errs := parser.Parse("test_arm64.s", src)
+	if len(errs) > 0 {
+		t.Fatalf("parse: %v", errs)
+	}
+	img, err := AssembleFileARM64(f)
+	if err != nil {
+		t.Fatalf("AssembleFileARM64: %v", err)
+	}
+	if img.Funcs[0].Size != 16 {
+		t.Errorf("size: got %d, want 16", img.Funcs[0].Size)
+	}
+}
+
+// TestArm64CRC32 tests CRC32 encoding.
+func TestArm64CRC32(t *testing.T) {
+	src := `#include "textflag.h"
+TEXT ·f(SB), NOSPLIT, $0-0
+	CRC32B	R0, R2
+	CRC32W	R6, R8
+	RET
+`
+	f, errs := parser.Parse("test_arm64.s", src)
+	if len(errs) > 0 {
+		t.Fatalf("parse: %v", errs)
+	}
+	img, err := AssembleFileARM64(f)
+	if err != nil {
+		t.Fatalf("AssembleFileARM64: %v", err)
+	}
+	if img.Funcs[0].Size != 12 {
+		t.Errorf("size: got %d, want 12", img.Funcs[0].Size)
+	}
+}
+
+// TestArm64Bitfield tests bitfield/shift encoding.
+func TestArm64Bitfield(t *testing.T) {
+	src := `#include "textflag.h"
+TEXT ·f(SB), NOSPLIT, $0-0
+	ASR	$4, R0, R1
+	LSL	$12, R4, R5
+	EXTR	$8, R0, R1, R2
+	RET
+`
+	f, errs := parser.Parse("test_arm64.s", src)
+	if len(errs) > 0 {
+		t.Fatalf("parse: %v", errs)
+	}
+	img, err := AssembleFileARM64(f)
+	if err != nil {
+		t.Fatalf("AssembleFileARM64: %v", err)
+	}
+	if img.Funcs[0].Size != 16 {
+		t.Errorf("size: got %d, want 16", img.Funcs[0].Size)
+	}
+}
+
+// TestArm64SIMD tests SIMD encoding (via the instruction table).
+func TestArm64SIMD(t *testing.T) {
+	// Verify SIMD instructions are in the table.
+	for _, mnem := range []string{"VADD", "VSUB", "VMUL"} {
+		if _, ok := a64InstrTable[mnem]; !ok {
+			t.Errorf("%s not in instruction table", mnem)
+		}
+	}
+}
+
+// TestArm64LoadImm64 tests 64-bit immediate loading.
+func TestArm64LoadImm64(t *testing.T) {
+	src := `#include "textflag.h"
+TEXT ·f(SB), NOSPLIT, $0-0
+	MOVD	$0x123456789ABCDEF0, R0
+	MOVD	$0, R1
+	MOVD	$1, R2
+	RET
+`
+	f, errs := parser.Parse("test_arm64.s", src)
+	if len(errs) > 0 {
+		t.Fatalf("parse: %v", errs)
+	}
+	img, err := AssembleFileARM64(f)
+	if err != nil {
+		t.Fatalf("AssembleFileARM64: %v", err)
+	}
+	// $0x123456789ABCDEF0 needs 4 MOVZ/MOVK instructions (16 bytes)
+	// $0 is 1 instruction (4 bytes)
+	// $1 is 1 bitmask instruction (4 bytes)
+	// RET is 1 instruction (4 bytes)
+	if img.Funcs[0].Size != 28 {
+		t.Errorf("size: got %d, want 28", img.Funcs[0].Size)
+	}
+}
+
+// TestArm64BranchCond tests conditional branch encoding.
+func TestArm64BranchCond(t *testing.T) {
+	src := `#include "textflag.h"
+TEXT ·f(SB), NOSPLIT, $0-0
+	BEQ	done
+	BNE	done
+	BGE	done
+	BLT	done
+	ADD	R4, R5
+done:
+	RET
+`
+	f, errs := parser.Parse("test_arm64.s", src)
+	if len(errs) > 0 {
+		t.Fatalf("parse: %v", errs)
+	}
+	img, err := AssembleFileARM64(f)
+	if err != nil {
+		t.Fatalf("AssembleFileARM64: %v", err)
+	}
+	// 4 branches + 1 ADD + 1 RET = 24 bytes
+	if img.Funcs[0].Size != 24 {
+		t.Errorf("size: got %d, want 24", img.Funcs[0].Size)
+	}
+}
+
+// TestArm64Errors tests error paths.
+func TestArm64Errors(t *testing.T) {
+	tests := []struct {
+		name string
+		src  string
+	}{
+		{"bad mnemonic", "TEXT ·f(SB), NOSPLIT, $0-0\n\tINVALID\tR4\n\tRET\n"},
+		{"bad label", "TEXT ·f(SB), NOSPLIT, $0-0\n\tB\tnosuch\n\tRET\n"},
+		{"bad register", "TEXT ·f(SB), NOSPLIT, $0-0\n\tADD\tR99, R0\n\tRET\n"},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			f, errs := parser.Parse("test_arm64.s", tt.src)
+			if len(errs) > 0 {
+				return
+			}
+			_, err := AssembleFileARM64(f)
+			if err == nil {
+				t.Error("expected error, got nil")
+			}
+		})
+	}
+}
+
+// leWord reads a little-endian uint32 from b.
+func leWord(b []byte) uint32 {
+	return uint32(b[0]) | uint32(b[1])<<8 | uint32(b[2])<<16 | uint32(b[3])<<24
+}
+
+// leWords reads all little-endian uint32s from b.
+func leWords(b []byte) []uint32 {
+	n := len(b) / 4
+	w := make([]uint32, n)
+	for i := range w {
+		w[i] = leWord(b[i*4:])
+	}
+	return w
+}

asm/arm64_frame.go

@@ -0,0 +1,237 @@
+// Copyright (c) 2026 Petr Balvín <opensource@petrbalvin.org> (https://petrbalvin.org)
+// SPDX-License-Identifier: BSD-3-Clause
+
+package asm
+
+// arm64 frame mapping, matching the Go toolchain's arm64 backend.
+//
+// Go's arm64 functions use R29 as the frame pointer (FP) and R30 as the link
+// register (LR).  R31 is the stack pointer (SP).  FP and SP in the source
+// are synthetic pseudo-registers resolved against the hardware SP and the
+// frame size.
+//
+// The autosize is the real stack adjustment: the declared local frame plus
+// 8 bytes for the saved link register, rounded up to a 16-byte multiple.
+// The toolchain adds an "extrasize" to align: if autosize%16 == 8, add 8;
+// if autosize%16 == 0, add 16.
+//
+// Prologue (autosize > 0, small frame ≤ 0xf0):
+//
+//	MOVD.W  LR, -autosize(SP)    // pre-index: SP -= autosize, store LR at SP
+//	MOVD    FP, -8(SP)            // store FP at SP-8
+//	SUB     $8, SP, FP            // FP = SP - 8
+//
+// Prologue (autosize > 0, large frame > 0xf0):
+//
+//	SUB     $autosize, SP, R20    // R20 = SP - autosize
+//	STP     (FP, LR), -8(R20)    // store FP,LR at R20-8
+//	MOVD    R20, SP               // SP = R20
+//	SUB     $8, SP, FP            // FP = SP - 8
+//
+// Epilogue (non-leaf, small frame):
+//
+//	ADD     $autosize-8, SP, FP   // restore FP
+//	ADD     $autosize, SP, SP     // deallocate frame
+//	MOVD    -8(SP), FP            // (actually the reverse of prologue)
+// Actually:
+//	MOVD    -8(SP), FP            // load FP from SP-8
+//	MOVD.P  autosize(SP), LR     // post-index: load LR, SP += autosize
+//
+// Epilogue (non-leaf, large frame):
+//	ADD     $autosize-8, SP, FP
+//	ADD     $autosize, SP, SP
+// Actually:
+//	LDP     -8(SP), (FP, LR)     // load FP,LR
+//	ADD     $autosize, SP, SP    // deallocate frame
+//
+// Epilogue (leaf with frame):
+//	ADD     $autosize-8, SP, FP
+//	ADD     $autosize, SP, SP
+//
+// RET always emits as BR LR (0xd65f03c0).
+
+import (
+	"strings"
+
+	"sourcedock.dev/petrbalvin/gasm-devkit/ast"
+)
+
+// arm64FrameInfo holds the frame layout derived from a TEXT directive.
+type arm64FrameInfo struct {
+	autosize int  // the real SP adjustment (locals + saved LR + alignment)
+	frame    int  // the declared $framesize
+	args     int  // the declared -argsize
+	noSplit  bool // the NOSPLIT flag
+	leaf     bool // no call instructions in the body
+}
+
+// arm64ComputeFrame derives the frame layout for a TEXT function.
+func arm64ComputeFrame(t *ast.Text) arm64FrameInfo {
+	fi := arm64FrameInfo{
+		frame: frameSize(t),
+		args:  argsSize(t),
+	}
+	for _, f := range t.Flags {
+		if f == "NOSPLIT" {
+			fi.noSplit = true
+		}
+	}
+	fi.leaf = arm64IsLeaf(t)
+
+	if fi.frame != 0 || !fi.leaf {
+		fi.autosize = fi.frame + 8 // space for the saved LR
+		if fi.autosize%16 != 0 {
+			// The toolchain aligns to 16: if autosize%16 == 8, add 8;
+			// otherwise add whatever is needed.
+			fi.autosize += 16 - (fi.autosize % 16)
+		}
+	}
+	return fi
+}
+
+// arm64IsLeaf reports whether a function contains no call instructions
+// (BL/CALL), matching the toolchain's LEAF mark.
+func arm64IsLeaf(t *ast.Text) bool {
+	for _, stmt := range t.Body {
+		in, ok := stmt.(*ast.Instr)
+		if !ok {
+			continue
+		}
+		switch strings.ToUpper(in.Mnemonic.Text) {
+		case "BL", "CALL":
+			return false
+		}
+	}
+	return true
+}
+
+// arm64Prologue returns the prologue bytes for an arm64 function.
+func arm64Prologue(fi arm64FrameInfo) []byte {
+	if fi.autosize == 0 {
+		return nil
+	}
+	if fi.autosize <= 0xf0 {
+		// Small frame: MOVD.W LR, -autosize(SP); MOVD FP, -8(SP); SUB $8, SP, FP
+		return a64WordsLE(
+			arm64PreStoreImm(3, 0, int32(-fi.autosize), 31, 30), // STR.W LR, -autosize(SP) (pre-index store)
+			arm64UnscaledStore(3, 0, -8, 31, 29),                // STUR FP, [SP, #-8]
+			a64AddSub(1, 1, 0, 0, 8, 31, 29),                    // SUB $8, SP, FP (op=1 for SUB)
+		)
+	}
+	// Large frame: SUB $autosize, SP, R20; STP (FP,LR), -8(R20); ADD $0, R20, SP; SUB $8, SP, FP
+	return a64WordsLE(
+		a64AddSub(1, 1, 0, 0, uint32(fi.autosize), 31, 20), // SUB $autosize, SP, R20
+		a64LSP(2, 0, 0, -1, 30, 20, 29),                    // STP FP, LR, [R20, #-8] (opc=2 for 64-bit pair)
+		a64AddSub(1, 0, 0, 0, 0, 20, 31),                   // ADD $0, R20, SP (= MOV R20, SP)
+		a64AddSub(1, 1, 0, 0, 8, 31, 29),                   // SUB $8, SP, FP (op=1 for SUB)
+	)
+}
+
+// arm64Return returns the bytes for a RET: the epilogue (restore FP/LR and
+// deallocate the frame when present) followed by RET (BR LR).
+func arm64Return(fi arm64FrameInfo) []byte {
+	var ws []uint32
+	if fi.autosize != 0 {
+		if fi.leaf {
+			// Leaf with frame: ADD $autosize-8, SP, FP; ADD $autosize, SP, SP
+			ws = append(ws,
+				a64AddSub(1, 0, 0, 0, uint32(fi.autosize-8), 31, 29), // ADD $autosize-8, SP, FP
+				a64AddSub(1, 0, 0, 0, uint32(fi.autosize), 31, 31),   // ADD $autosize, SP, SP
+			)
+		} else if fi.autosize <= 0xf0 {
+			// Non-leaf small frame: LDR FP, [SP, #-8]; LDR.P LR, [SP], #autosize
+			ws = append(ws,
+				arm64UnscaledLoad(3, 0, -8, 31, 29),             // LDR FP, [SP, #-8]
+				arm64PostLoad(3, 0, int32(fi.autosize), 31, 30), // LDR.P LR, [SP], #autosize
+			)
+		} else {
+			// Large frame: LDP -8(SP), (FP, LR); ADD $autosize, SP, SP
+			ws = append(ws,
+				a64LSP(2, 0, 1, -1, 30, 31, 29),                    // LDP FP, LR, [SP, #-8] (opc=2 for 64-bit pair)
+				a64AddSub(1, 0, 0, 0, uint32(fi.autosize), 31, 31), // ADD $autosize, SP, SP
+			)
+		}
+	}
+	// RET: BR LR (0xd65f03c0)
+	ws = append(ws, a64UncondBranch(2, 30, 0)) // opc=2(RET), Rn=LR(30), Rd=0
+	return a64WordsLE(ws...)
+}
+
+// arm64PrologueSpadjPC returns the function-relative byte offset where the
+// prologue has finished decrementing SP (the delta becomes autosize).
+func arm64PrologueSpadjPC(fi arm64FrameInfo) int {
+	if fi.autosize == 0 {
+		return 0
+	}
+	if fi.autosize <= 0xf0 {
+		return 4 // MOVD.W instruction decrements SP
+	}
+	return 8 // SUB + STP + MOVD (3 instructions, SP updated at the MOVD)
+}
+
+// arm64ReturnEpilogueLen returns the byte length of the RET's epilogue up to
+// (but not including) the final RET instruction.
+func arm64ReturnEpilogueLen(fi arm64FrameInfo) int {
+	if fi.autosize == 0 {
+		return 0
+	}
+	if fi.leaf {
+		return 8 // ADD + ADD
+	}
+	if fi.autosize <= 0xf0 {
+		return 8 // LDR + LDR.P
+	}
+	return 8 // LDP + ADD
+}
+
+// arm64ResolvePseudo translates a pseudo-register memory reference into a
+// hardware base register and offset.  x+N(FP) → (N + autosize + 8)(SP);
+// x+N(SP) → (N + frame + 8)(SP).  Returns base = -1 for an unresolvable
+// reference (SB: static data, handled by the relocation path).
+//
+// The Go toolchain resolves all pseudo-register references against the
+// hardware stack pointer (R31/SP): FP references add autosize+8 (the
+// distance from SP after the prologue to the caller's argument area),
+// SP references add frame+8 (the distance to the local area).
+func arm64ResolvePseudo(sym *ast.Symbol, fi arm64FrameInfo) (base int, off int32) {
+	if sym == nil {
+		return -1, 0
+	}
+	switch sym.Pseudo {
+	case "FP":
+		return 31, int32(sym.Offset) + int32(fi.autosize) + 8
+	case "SP":
+		return 31, int32(sym.Offset) + int32(fi.frame) + 8
+	case "SB":
+		return -1, int32(sym.Offset)
+	}
+	return -1, 0
+}
+
+// arm64PreStoreImm encodes a pre-index store (STR with writeback):
+// size<<30 | 7<<27 | V<<26 | opc<<22 | 1<<11 | 1<<10 | imm9<<12 | Rn<<5 | Rt.
+func arm64PreStoreImm(size, V int, imm9 int32, rn, rt int) uint32 {
+	return uint32(size)<<30 | 7<<27 | uint32(V)<<26 | 0<<22 |
+		3<<10 | (uint32(imm9)&0x1FF)<<12 | uint32(rn&31)<<5 | uint32(rt&31)
+}
+
+// arm64UnscaledStore encodes an unscaled store (STUR):
+// size<<30 | 7<<27 | V<<26 | opc<<22 | 0<<11 | 0<<10 | imm9<<12 | Rn<<5 | Rt.
+func arm64UnscaledStore(size, V int, imm9 int32, rn, rt int) uint32 {
+	return uint32(size)<<30 | 7<<27 | uint32(V)<<26 | 0<<22 |
+		(uint32(imm9)&0x1FF)<<12 | uint32(rn&31)<<5 | uint32(rt&31)
+}
+
+// arm64UnscaledLoad encodes an unscaled load (LDUR):
+// size<<30 | 7<<27 | V<<26 | opc<<22 | 0<<11 | 0<<10 | imm9<<12 | Rn<<5 | Rt.
+func arm64UnscaledLoad(size, V int, imm9 int32, rn, rt int) uint32 {
+	return uint32(size)<<30 | 7<<27 | uint32(V)<<26 | 1<<22 |
+		(uint32(imm9)&0x1FF)<<12 | uint32(rn&31)<<5 | uint32(rt&31)
+}
+
+// arm64PostLoad encodes a post-index load (LDR with post-increment):
+// size<<30 | 7<<27 | V<<26 | opc<<22 | 0<<11 | 1<<10 | imm9<<12 | Rn<<5 | Rt.
+func arm64PostLoad(size, V int, imm9 int32, rn, rt int) uint32 {
+	return uint32(size)<<30 | 7<<27 | uint32(V)<<26 | 1<<22 |
+		1<<10 | (uint32(imm9)&0x1FF)<<12 | uint32(rn&31)<<5 | uint32(rt&31)
+}

asm/assemble.go

@@ -23,7 +23,7 @@ import (
 // operands require relocations and are not yet supported; the SIMD (VEX/AVX2)
 // integer and shuffle/extract/permute/move set is in.
 func Assemble(t *ast.Text) ([]byte, map[string]int, error) {
-	code, _, labels, _, err := assemble(t, nil)
+	code, _, labels, _, _, err := assemble(t, nil)
 	return code, labels, err
 }
 
@@ -60,7 +60,7 @@ type spadjStep struct {
 // assemble encodes a TEXT body, returning the machine code, the static-symbol
 // patch sites (for the file-level layout to resolve), the label table and the
 // stack-adjustment boundaries.
-func assemble(t *ast.Text, link *linkInfo) ([]byte, []sbPatch, map[string]int, []spadjStep, error) {
+func assemble(t *ast.Text, link *linkInfo) ([]byte, []sbPatch, map[string]int, []spadjStep, []LineEntry, error) {
 	fi := computeFrame(t)
 	chain := jumpChain(t)
 	resolve := func(name string) string {
@@ -84,7 +84,7 @@ func assemble(t *ast.Text, link *linkInfo) ([]byte, []sbPatch, map[string]int, [
 			case *ast.Instr:
 				sz, err := instrSize(s, fi, long[i], link)
 				if err != nil {
-					return nil, nil, nil, nil, fmt.Errorf("%s: %w", s.Mnemonic.Text, err)
+					return nil, nil, nil, nil, nil, fmt.Errorf("%s: %w", s.Mnemonic.Text, err)
 				}
 				sizes[i] = sz
 				pcs[i] = pos
@@ -125,6 +125,7 @@ func assemble(t *ast.Text, link *linkInfo) ([]byte, []sbPatch, map[string]int, [
 	out := append([]byte(nil), fi.prologue...)
 	var patches []sbPatch
 	var steps []spadjStep
+	var lines []LineEntry
 	if fi.useFP {
 		// PUSHQ BP saves the return-address-relative base (+8); the MOVQ
 		// changes nothing; SUBQ $size, SP completes the frame.
@@ -150,16 +151,17 @@ func assemble(t *ast.Text, link *linkInfo) ([]byte, []sbPatch, map[string]int, [
 		}
 		code, ps, err := encodeInstr(s, pos, offsets, fi, long[i], resolve, link)
 		if err != nil {
-			return nil, nil, nil, nil, fmt.Errorf("%s: %w", s.Mnemonic.Text, err)
+			return nil, nil, nil, nil, nil, fmt.Errorf("%s: %w", s.Mnemonic.Text, err)
 		}
 		if len(code) != sizes[i] {
-			return nil, nil, nil, nil, fmt.Errorf("%s: size mismatch (%d vs %d)", s.Mnemonic.Text, len(code), sizes[i])
+			return nil, nil, nil, nil, nil, fmt.Errorf("%s: size mismatch (%d vs %d)", s.Mnemonic.Text, len(code), sizes[i])
 		}
 		patches = append(patches, ps...)
+		lines = append(lines, LineEntry{Offset: pos, Line: s.Pos().Line})
 		out = append(out, code...)
 		pos += len(code)
 	}
-	return out, patches, offsets, steps, nil
+	return out, patches, offsets, steps, lines, nil
 }
 
 // jumpChain precomputes jump-to-jump folding: a label whose first instruction

asm/elfarm64.go

@@ -0,0 +1,224 @@
+// Copyright (c) 2026 Petr Balvín <opensource@petrbalvin.org> (https://petrbalvin.org)
+// SPDX-License-Identifier: BSD-3-Clause
+
+package asm
+
+import (
+	"encoding/binary"
+	"fmt"
+)
+
+// AArch64 ELF64 relocatable object emission.
+
+const (
+	emAARCH64 = 183 // EM_AARCH64
+
+	// AArch64 relocation types (the ELF psABI).
+	rArm64PrelPgHi21   = 275 // R_AARCH64_ADR_PREL_PG_HI21 (ADRP page)
+	rArm64AddAbsLo12NC = 277 // R_AARCH64_ADD_ABS_LO12_NC (ADD/STR/LDR page offset)
+)
+
+// ELFAARCH64Object returns the image as an ELF64 relocatable object file for
+// AArch64 (EM_AARCH64, 64-bit, little-endian).  The structure mirrors the
+// amd64 and RISC-V ELF emitters: .text, .data, .symtab, .strtab and an
+// optional .rela.text.
+func (img *Image) ELFAARCH64Object() ([]byte, error) {
+	le := binary.LittleEndian
+
+	const (
+		secText = 1
+		secData = 2
+	)
+
+	// Build symbol table.
+	var locals, globals []elfSym
+	for _, fn := range img.Funcs {
+		s := elfSym{
+			name:  objectName(fn.Pkg, fn.Name),
+			info:  sttFunc,
+			shndx: secText,
+			value: uint64(fn.Offset),
+			size:  uint64(fn.Size),
+		}
+		if fn.Static {
+			locals = append(locals, s)
+		} else {
+			s.info |= stbGlobal << stInfoShift
+			globals = append(globals, s)
+		}
+	}
+	for _, d := range img.DataSyms {
+		s := elfSym{
+			name:  objectName(d.Pkg, d.Name),
+			info:  sttObject,
+			shndx: secData,
+			value: uint64(d.Offset),
+			size:  uint64(d.Size),
+		}
+		if d.Static {
+			locals = append(locals, s)
+		} else {
+			s.info |= stbGlobal << stInfoShift
+			globals = append(globals, s)
+		}
+	}
+	for _, name := range img.Externals {
+		globals = append(globals, elfSym{name: name, info: stbGlobal << stInfoShift})
+	}
+	syms := []elfSym{
+		{},
+		{name: ".text", info: sttSection, shndx: secText},
+		{name: ".data", info: sttSection, shndx: secData},
+	}
+	syms = append(syms, locals...)
+	shInfo := len(syms)
+	syms = append(syms, globals...)
+	symIdx := map[string]int{}
+	for i, s := range syms {
+		symIdx[s.name] = i
+	}
+
+	// Build relocations.  Each SB reference is an ADRP pair:
+	//   ADRP Rd, 0  → R_AARCH64_ADR_PREL_PG_HI21
+	//   ADD/LDR/STR  → R_AARCH64_ADD_ABS_LO12_NC
+	type elfRela struct {
+		off    uint64
+		typ    uint32
+		sym    int
+		addend int64
+	}
+	var relas []elfRela
+	for _, fn := range img.Funcs {
+		for _, r := range fn.Relocs {
+			idx, ok := symIdx[r.Name]
+			if !ok {
+				return nil, fmt.Errorf("relocation references unknown symbol %q", r.Name)
+			}
+			typ := uint32(rArm64PrelPgHi21)
+			if r.Kind == RelArm64Addr && r.Off%4 == 4 {
+				// The second instruction in an ADRP pair uses ADD_ABS_LO12_NC.
+				typ = rArm64AddAbsLo12NC
+			}
+			relas = append(relas, elfRela{
+				off:    uint64(fn.Offset + r.Off),
+				typ:    typ,
+				sym:    idx,
+				addend: r.Addend - int64(r.After-r.Off),
+			})
+		}
+	}
+
+	// String tables.
+	stNames := newElfStrtab()
+	for _, s := range syms {
+		stNames.add(s.name)
+	}
+	stSections := newElfStrtab()
+	for _, n := range []string{".text", ".data", ".symtab", ".strtab", ".rela.text", ".shstrtab"} {
+		stSections.add(n)
+	}
+
+	hasRela := len(relas) > 0
+	nSections := 6
+	if hasRela {
+		nSections = 7
+	}
+	secSymtab, secStrtab := 3, 4
+	secShstr := nSections - 1
+
+	// Layout.
+	var out []byte
+	out = append(out, make([]byte, 64)...)
+
+	align := func(n int) {
+		for len(out)%n != 0 {
+			out = append(out, 0)
+		}
+	}
+
+	align(16)
+	textOff := len(out)
+	out = append(out, img.Code...)
+
+	align(16)
+	dataOff := len(out)
+	out = append(out, img.Data...)
+
+	align(8)
+	symtabOff := len(out)
+	for _, s := range syms {
+		var b [24]byte
+		le.PutUint32(b[0:], uint32(stNames.at(s.name)))
+		b[4] = s.info
+		b[5] = 0
+		le.PutUint16(b[6:], s.shndx)
+		le.PutUint64(b[8:], s.value)
+		le.PutUint64(b[16:], s.size)
+		out = append(out, b[:]...)
+	}
+
+	strtabOff := len(out)
+	out = append(out, stNames.bytes()...)
+
+	var relaOff int
+	if hasRela {
+		align(8)
+		relaOff = len(out)
+		for _, r := range relas {
+			var b [24]byte
+			le.PutUint64(b[0:], r.off)
+			le.PutUint64(b[8:], uint64(r.sym)<<32|uint64(r.typ))
+			le.PutUint64(b[16:], uint64(r.addend))
+			out = append(out, b[:]...)
+		}
+	}
+
+	shstrOff := len(out)
+	out = append(out, stSections.bytes()...)
+
+	align(8)
+	shoff := len(out)
+
+	putSh := func(name string, typ int, flags uint64, off, size int, link, info int, alignV, entsize uint64) {
+		var b [64]byte
+		le.PutUint32(b[0:], uint32(stSections.at(name)))
+		le.PutUint32(b[4:], uint32(typ))
+		le.PutUint64(b[8:], flags)
+		le.PutUint64(b[16:], 0)
+		le.PutUint64(b[24:], uint64(off))
+		le.PutUint64(b[32:], uint64(size))
+		le.PutUint32(b[40:], uint32(link))
+		le.PutUint32(b[44:], uint32(info))
+		le.PutUint64(b[48:], alignV)
+		le.PutUint64(b[56:], entsize)
+		out = append(out, b[:]...)
+	}
+	putSh("", shtNull, 0, 0, 0, 0, 0, 0, 0)
+	putSh(".text", shtProgbits, shfAlloc|shfExecInstr, textOff, len(img.Code), 0, 0, 16, 0)
+	putSh(".data", shtProgbits, shfAlloc|shfWrite, dataOff, len(img.Data), 0, 0, 16, 0)
+	putSh(".symtab", shtSymtab, 0, symtabOff, 24*len(syms), secStrtab, shInfo, 8, 24)
+	putSh(".strtab", shtStrtab, 0, strtabOff, len(stNames.bytes()), 0, 0, 1, 0)
+	if hasRela {
+		putSh(".rela.text", shtRela, 0, relaOff, 24*len(relas), secSymtab, secText, 8, 24)
+	}
+	putSh(".shstrtab", shtStrtab, 0, shstrOff, len(stSections.bytes()), 0, 0, 1, 0)
+
+	// ELF header.
+	hdr := out[:64]
+	copy(hdr[0:], []byte{0x7f, 'E', 'L', 'F', elfClass64, elfDataLSB, elfVersion, 0})
+	le.PutUint16(hdr[16:], etREL)
+	le.PutUint16(hdr[18:], emAARCH64)
+	le.PutUint32(hdr[20:], elfVersion)
+	le.PutUint64(hdr[24:], 0)
+	le.PutUint64(hdr[32:], 0)
+	le.PutUint64(hdr[40:], uint64(shoff))
+	le.PutUint32(hdr[48:], 0)
+	le.PutUint16(hdr[52:], 64)
+	le.PutUint16(hdr[54:], 0)
+	le.PutUint16(hdr[56:], 0)
+	le.PutUint16(hdr[58:], 64)
+	le.PutUint16(hdr[60:], uint16(nSections))
+	le.PutUint16(hdr[62:], uint16(secShstr))
+
+	return out, nil
+}

asm/elfarm64_test.go

@@ -0,0 +1,142 @@
+// Copyright (c) 2026 Petr Balvín <opensource@petrbalvin.org> (https://petrbalvin.org)
+// SPDX-License-Identifier: BSD-3-Clause
+
+package asm
+
+import (
+	"bytes"
+	"debug/elf"
+	"testing"
+
+	"sourcedock.dev/petrbalvin/gasm-devkit/parser"
+)
+
+// TestELFAARCH64Object checks the structure of the emitted AArch64 ELF64
+// relocatable object: sections, the symbol table (bindings, types, values,
+// sizes) and the .rela.text relocation pair for the static-symbol load,
+// parsed back with debug/elf.
+func TestELFAARCH64Object(t *testing.T) {
+	f, errs := parser.Parse("k_arm64.s", `
+#include "textflag.h"
+
+TEXT ·add(SB), NOSPLIT, $0-24
+	MOVD a+0(FP), R4
+	MOVD b+8(FP), R5
+	ADD R5, R4, R4
+	MOVD R4, ret+16(FP)
+	RET
+
+TEXT ·getanswer(SB), NOSPLIT, $0-8
+	MOVD answer<>(SB), R4
+	MOVD R4, ret+0(FP)
+	RET
+
+GLOBL answer<>(SB), RODATA, $8
+DATA answer<>+0(SB)/8, $42
+`)
+	if len(errs) > 0 {
+		t.Fatalf("parse: %v", errs)
+	}
+	img, err := AssembleFileARM64(f)
+	if err != nil {
+		t.Fatalf("AssembleFileARM64: %v", err)
+	}
+	obj, err := img.ELFAARCH64Object()
+	if err != nil {
+		t.Fatalf("ELFAARCH64Object: %v", err)
+	}
+	ef, err := elf.NewFile(bytes.NewReader(obj))
+	if err != nil {
+		t.Fatalf("parse emitted object: %v", err)
+	}
+	defer ef.Close()
+
+	if ef.Type != elf.ET_REL || ef.Machine != elf.EM_AARCH64 {
+		t.Errorf("type/machine = %v/%v, want ET_REL/EM_AARCH64", ef.Type, ef.Machine)
+	}
+
+	text := ef.Section(".text")
+	data := ef.Section(".data")
+	if text == nil || data == nil {
+		t.Fatal("missing .text or .data section")
+	}
+	if text.Size == 0 {
+		t.Error(".text section is empty")
+	}
+
+	syms, err := ef.Symbols()
+	if err != nil {
+		t.Fatalf("symbols: %v", err)
+	}
+
+	foundAdd, foundGetanswer, foundAnswer := false, false, false
+	for _, s := range syms {
+		switch s.Name {
+		case "add":
+			foundAdd = true
+			if elf.SymType(s.Info&0xf) != elf.STT_FUNC || elf.SymBind(s.Info>>4) != elf.STB_GLOBAL {
+				t.Errorf("add: info=0x%02x, want STT_FUNC|STB_GLOBAL", s.Info)
+			}
+		case "getanswer":
+			foundGetanswer = true
+			if elf.SymType(s.Info&0xf) != elf.STT_FUNC || elf.SymBind(s.Info>>4) != elf.STB_GLOBAL {
+				t.Errorf("getanswer: info=0x%02x, want STT_FUNC|STB_GLOBAL", s.Info)
+			}
+		case "answer":
+			foundAnswer = true
+			if elf.SymType(s.Info&0xf) != elf.STT_OBJECT || elf.SymBind(s.Info>>4) != elf.STB_LOCAL {
+				t.Errorf("answer: info=0x%02x, want STT_OBJECT|STB_LOCAL", s.Info)
+			}
+		}
+	}
+	if !foundAdd {
+		t.Error("symbol 'add' not found")
+	}
+	if !foundGetanswer {
+		t.Error("symbol 'getanswer' not found")
+	}
+	if !foundAnswer {
+		t.Error("symbol 'answer' not found")
+	}
+
+	// Check that .rela.text exists (getanswer has SB reference).
+	relaText := ef.Section(".rela.text")
+	if relaText == nil {
+		t.Error("missing .rela.text section")
+	}
+}
+
+// TestELFAARCH64ObjectNoRelocations checks the ELF output when there are no
+// static-symbol references (no .rela.text section).
+func TestELFAARCH64ObjectNoRelocations(t *testing.T) {
+	f, errs := parser.Parse("k_arm64.s", `
+#include "textflag.h"
+
+TEXT ·add(SB), NOSPLIT, $0-24
+	MOVD a+0(FP), R4
+	MOVD b+8(FP), R5
+	ADD R5, R4, R4
+	MOVD R4, ret+16(FP)
+	RET
+`)
+	if len(errs) > 0 {
+		t.Fatalf("parse: %v", errs)
+	}
+	img, err := AssembleFileARM64(f)
+	if err != nil {
+		t.Fatalf("AssembleFileARM64: %v", err)
+	}
+	obj, err := img.ELFAARCH64Object()
+	if err != nil {
+		t.Fatalf("ELFAARCH64Object: %v", err)
+	}
+	ef, err := elf.NewFile(bytes.NewReader(obj))
+	if err != nil {
+		t.Fatalf("parse emitted object: %v", err)
+	}
+	defer ef.Close()
+
+	if ef.Section(".rela.text") != nil {
+		t.Error("unexpected .rela.text section when there are no relocations")
+	}
+}

asm/elfloong64.go

@@ -0,0 +1,223 @@
+// Copyright (c) 2026 Petr Balvín <opensource@petrbalvin.org> (https://petrbalvin.org)
+// SPDX-License-Identifier: BSD-3-Clause
+
+package asm
+
+import (
+	"encoding/binary"
+	"fmt"
+)
+
+// LoongArch ELF64 relocatable object emission.
+
+const (
+	emLOONGARCH = 258 // EM_LOONGARCH
+
+	// LoongArch relocation types (the ELF psABI).
+	rLarchPCALAHI20 = 71 // R_LARCH_PCALA_HI20 (pcalau12i)
+	rLarchPCALALO12 = 72 // R_LARCH_PCALA_LO12 (addi.d/ld/st)
+)
+
+// ELFLOONG64Object returns the image as an ELF64 relocatable object file for
+// LoongArch (EM_LOONGARCH, 64-bit, little-endian).  The structure mirrors the
+// amd64 and RISC-V ELF emitters: .text, .data, .symtab, .strtab and an
+// optional .rela.text.
+func (img *Image) ELFLOONG64Object() ([]byte, error) {
+	le := binary.LittleEndian
+
+	const (
+		secText = 1
+		secData = 2
+	)
+
+	// Build symbol table.
+	var locals, globals []elfSym
+	for _, fn := range img.Funcs {
+		s := elfSym{
+			name:  objectName(fn.Pkg, fn.Name),
+			info:  sttFunc,
+			shndx: secText,
+			value: uint64(fn.Offset),
+			size:  uint64(fn.Size),
+		}
+		if fn.Static {
+			locals = append(locals, s)
+		} else {
+			s.info |= stbGlobal << stInfoShift
+			globals = append(globals, s)
+		}
+	}
+	for _, d := range img.DataSyms {
+		s := elfSym{
+			name:  objectName(d.Pkg, d.Name),
+			info:  sttObject,
+			shndx: secData,
+			value: uint64(d.Offset),
+			size:  uint64(d.Size),
+		}
+		if d.Static {
+			locals = append(locals, s)
+		} else {
+			s.info |= stbGlobal << stInfoShift
+			globals = append(globals, s)
+		}
+	}
+	for _, name := range img.Externals {
+		globals = append(globals, elfSym{name: name, info: stbGlobal << stInfoShift})
+	}
+	syms := []elfSym{
+		{},
+		{name: ".text", info: sttSection, shndx: secText},
+		{name: ".data", info: sttSection, shndx: secData},
+	}
+	syms = append(syms, locals...)
+	shInfo := len(syms)
+	syms = append(syms, globals...)
+	symIdx := map[string]int{}
+	for i, s := range syms {
+		symIdx[s.name] = i
+	}
+
+	// Build relocations.  Each SB reference is a pcalau12i pair:
+	//   pcalau12i rd, 0  → R_LARCH_PCALA_HI20
+	//   addi.d/ld/st      → R_LARCH_PCALA_LO12
+	type elfRela struct {
+		off    uint64
+		typ    uint32
+		sym    int
+		addend int64
+	}
+	var relas []elfRela
+	for _, fn := range img.Funcs {
+		for _, r := range fn.Relocs {
+			idx, ok := symIdx[r.Name]
+			if !ok {
+				return nil, fmt.Errorf("relocation references unknown symbol %q", r.Name)
+			}
+			typ := uint32(rLarchPCALAHI20)
+			if r.Kind == RelLoong64AddrLo {
+				typ = rLarchPCALALO12
+			}
+			relas = append(relas, elfRela{
+				off:    uint64(fn.Offset + r.Off),
+				typ:    typ,
+				sym:    idx,
+				addend: r.Addend - int64(r.After-r.Off),
+			})
+		}
+	}
+
+	// String tables.
+	stNames := newElfStrtab()
+	for _, s := range syms {
+		stNames.add(s.name)
+	}
+	stSections := newElfStrtab()
+	for _, n := range []string{".text", ".data", ".symtab", ".strtab", ".rela.text", ".shstrtab"} {
+		stSections.add(n)
+	}
+
+	hasRela := len(relas) > 0
+	nSections := 6
+	if hasRela {
+		nSections = 7
+	}
+	secSymtab, secStrtab := 3, 4
+	secShstr := nSections - 1
+
+	// Layout.
+	var out []byte
+	out = append(out, make([]byte, 64)...)
+
+	align := func(n int) {
+		for len(out)%n != 0 {
+			out = append(out, 0)
+		}
+	}
+
+	align(16)
+	textOff := len(out)
+	out = append(out, img.Code...)
+
+	align(16)
+	dataOff := len(out)
+	out = append(out, img.Data...)
+
+	align(8)
+	symtabOff := len(out)
+	for _, s := range syms {
+		var b [24]byte
+		le.PutUint32(b[0:], uint32(stNames.at(s.name)))
+		b[4] = s.info
+		b[5] = 0
+		le.PutUint16(b[6:], s.shndx)
+		le.PutUint64(b[8:], s.value)
+		le.PutUint64(b[16:], s.size)
+		out = append(out, b[:]...)
+	}
+
+	strtabOff := len(out)
+	out = append(out, stNames.bytes()...)
+
+	var relaOff int
+	if hasRela {
+		align(8)
+		relaOff = len(out)
+		for _, r := range relas {
+			var b [24]byte
+			le.PutUint64(b[0:], r.off)
+			le.PutUint64(b[8:], uint64(r.sym)<<32|uint64(r.typ))
+			le.PutUint64(b[16:], uint64(r.addend))
+			out = append(out, b[:]...)
+		}
+	}
+
+	shstrOff := len(out)
+	out = append(out, stSections.bytes()...)
+
+	align(8)
+	shoff := len(out)
+
+	putSh := func(name string, typ int, flags uint64, off, size int, link, info int, alignV, entsize uint64) {
+		var b [64]byte
+		le.PutUint32(b[0:], uint32(stSections.at(name)))
+		le.PutUint32(b[4:], uint32(typ))
+		le.PutUint64(b[8:], flags)
+		le.PutUint64(b[16:], 0)
+		le.PutUint64(b[24:], uint64(off))
+		le.PutUint64(b[32:], uint64(size))
+		le.PutUint32(b[40:], uint32(link))
+		le.PutUint32(b[44:], uint32(info))
+		le.PutUint64(b[48:], alignV)
+		le.PutUint64(b[56:], entsize)
+		out = append(out, b[:]...)
+	}
+	putSh("", shtNull, 0, 0, 0, 0, 0, 0, 0)
+	putSh(".text", shtProgbits, shfAlloc|shfExecInstr, textOff, len(img.Code), 0, 0, 16, 0)
+	putSh(".data", shtProgbits, shfAlloc|shfWrite, dataOff, len(img.Data), 0, 0, 16, 0)
+	putSh(".symtab", shtSymtab, 0, symtabOff, 24*len(syms), secStrtab, shInfo, 8, 24)
+	putSh(".strtab", shtStrtab, 0, strtabOff, len(stNames.bytes()), 0, 0, 1, 0)
+	if hasRela {
+		putSh(".rela.text", shtRela, 0, relaOff, 24*len(relas), secSymtab, secText, 8, 24)
+	}
+	putSh(".shstrtab", shtStrtab, 0, shstrOff, len(stSections.bytes()), 0, 0, 1, 0)
+
+	// ELF header.
+	hdr := out[:64]
+	copy(hdr[0:], []byte{0x7f, 'E', 'L', 'F', elfClass64, elfDataLSB, elfVersion, 0})
+	le.PutUint16(hdr[16:], etREL)
+	le.PutUint16(hdr[18:], emLOONGARCH)
+	le.PutUint32(hdr[20:], elfVersion)
+	le.PutUint64(hdr[24:], 0)
+	le.PutUint64(hdr[32:], 0)
+	le.PutUint64(hdr[40:], uint64(shoff))
+	le.PutUint32(hdr[48:], 0)
+	le.PutUint16(hdr[52:], 64)
+	le.PutUint16(hdr[54:], 0)
+	le.PutUint16(hdr[56:], 0)
+	le.PutUint16(hdr[58:], 64)
+	le.PutUint16(hdr[60:], uint16(nSections))
+	le.PutUint16(hdr[62:], uint16(secShstr))
+
+	return out, nil
+}

asm/elfloong64_test.go

@@ -0,0 +1,200 @@
+// Copyright (c) 2026 Petr Balvín <opensource@petrbalvin.org> (https://petrbalvin.org)
+// SPDX-License-Identifier: BSD-3-Clause
+
+package asm
+
+import (
+	"bytes"
+	"debug/elf"
+	"encoding/binary"
+	"testing"
+
+	"sourcedock.dev/petrbalvin/gasm-devkit/parser"
+)
+
+// TestELFLOONG64Object checks the structure of the emitted LoongArch ELF64
+// relocatable object: sections, the symbol table (bindings, types, values,
+// sizes) and the .rela.text relocation pair for the static-symbol load,
+// parsed back with debug/elf.
+func TestELFLOONG64Object(t *testing.T) {
+	f, errs := parser.Parse("k_loong64.s", `
+#include "textflag.h"
+
+TEXT ·add(SB), NOSPLIT, $0-24
+	MOVV a+0(FP), R4
+	MOVV b+8(FP), R5
+	ADDV R5, R4, R4
+	MOVV R4, ret+16(FP)
+	RET
+
+TEXT ·getanswer(SB), NOSPLIT, $0-8
+	MOVV answer<>(SB), R4
+	MOVV R4, ret+0(FP)
+	RET
+
+GLOBL answer<>(SB), RODATA, $8
+DATA answer<>+0(SB)/8, $42
+`)
+	if len(errs) > 0 {
+		t.Fatalf("parse: %v", errs)
+	}
+	img, err := AssembleFileLOONG64(f)
+	if err != nil {
+		t.Fatalf("AssembleFileLOONG64: %v", err)
+	}
+	obj, err := img.ELFLOONG64Object()
+	if err != nil {
+		t.Fatalf("ELFLOONG64Object: %v", err)
+	}
+	ef, err := elf.NewFile(bytes.NewReader(obj))
+	if err != nil {
+		t.Fatalf("parse emitted object: %v", err)
+	}
+	defer ef.Close()
+
+	if ef.Type != elf.ET_REL || ef.Machine != elf.EM_LOONGARCH {
+		t.Errorf("type/machine = %v/%v, want ET_REL/EM_LOONGARCH", ef.Type, ef.Machine)
+	}
+
+	text := ef.Section(".text")
+	data := ef.Section(".data")
+	if text == nil || data == nil {
+		t.Fatal("missing .text or .data section")
+	}
+	if text.Flags&elf.SHF_EXECINSTR == 0 || text.Flags&elf.SHF_ALLOC == 0 {
+		t.Errorf(".text flags = %v", text.Flags)
+	}
+	if data.Flags&elf.SHF_WRITE == 0 {
+		t.Errorf(".data flags = %v", data.Flags)
+	}
+	textData, err := text.Data()
+	if err != nil {
+		t.Fatal(err)
+	}
+	if !bytes.Equal(textData, img.Code) {
+		t.Errorf(".text contents differ from the image code")
+	}
+	dataData, err := data.Data()
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	syms, err := ef.Symbols()
+	if err != nil {
+		t.Fatalf("symbols: %v", err)
+	}
+	byName := map[string]elf.Symbol{}
+	for _, s := range syms {
+		byName[s.Name] = s
+	}
+	wantSym := func(name string, bind elf.SymBind, typ elf.SymType, section elf.SectionIndex, size uint64) {
+		t.Helper()
+		s, ok := byName[name]
+		if !ok {
+			t.Errorf("symbol %q not found", name)
+			return
+		}
+		if elf.ST_BIND(s.Info) != bind || elf.ST_TYPE(s.Info) != typ {
+			t.Errorf("%s: bind/type = %v/%v, want %v/%v", name, elf.ST_BIND(s.Info), elf.ST_TYPE(s.Info), bind, typ)
+		}
+		if s.Section != section {
+			t.Errorf("%s: section = %v, want %v", name, s.Section, section)
+		}
+		if s.Size != size {
+			t.Errorf("%s: size = %d, want %d", name, s.Size, size)
+		}
+	}
+	if ef.Sections[1].Name != ".text" || ef.Sections[2].Name != ".data" {
+		t.Fatalf("section layout = %s, %s; want .text, .data", ef.Sections[1].Name, ef.Sections[2].Name)
+	}
+	textIdx := elf.SectionIndex(1)
+	dataIdx := elf.SectionIndex(2)
+	wantSym("add", elf.STB_GLOBAL, elf.STT_FUNC, textIdx, 20)
+	wantSym("getanswer", elf.STB_GLOBAL, elf.STT_FUNC, textIdx, 16)
+	wantSym("answer", elf.STB_LOCAL, elf.STT_OBJECT, dataIdx, 8)
+
+	// The data section carries 16-byte alignment padding; the answer
+	// symbol sits at its padded offset.
+	ans := byName["answer"]
+	if ans.Value+8 > uint64(len(dataData)) {
+		t.Fatalf("answer value %d outside .data (%d bytes)", ans.Value, len(dataData))
+	}
+	if got := dataData[ans.Value : ans.Value+8]; !bytes.Equal(got, []byte{42, 0, 0, 0, 0, 0, 0, 0}) {
+		t.Errorf("answer data = % x, want $42", got)
+	}
+
+	// Relocations: the static-symbol load is a pcalau12i+ld.d pair, so one
+	// R_LARCH_PCALA_HI20 and one R_LARCH_PCALA_LO12, both against the local
+	// data symbol.  debug/elf does not surface rela entries, so read the
+	// section directly.
+	relaSec := ef.Section(".rela.text")
+	if relaSec == nil {
+		t.Fatal("missing .rela.text")
+	}
+	raw, err := relaSec.Data()
+	if err != nil {
+		t.Fatal(err)
+	}
+	if len(raw)%24 != 0 || len(raw)/24 != 2 {
+		t.Fatalf(".rela.text has %d bytes, want two 24-byte entries", len(raw))
+	}
+	le := binary.LittleEndian
+	for i := 0; i < 2; i++ {
+		e := raw[i*24 : (i+1)*24]
+		off := le.Uint64(e[0:])
+		info := le.Uint64(e[8:])
+		typ := info & 0xffffffff
+		sym := int(info >> 32)
+		if i == 0 && (typ != uint64(elf.R_LARCH_PCALA_HI20) || off != 20) {
+			t.Errorf("reloc %d: type %d off %d, want R_LARCH_PCALA_HI20 at 20", i, typ, off)
+		}
+		if i == 1 && (typ != uint64(elf.R_LARCH_PCALA_LO12) || off != 24) {
+			t.Errorf("reloc %d: type %d off %d, want R_LARCH_PCALA_LO12 at 24", i, typ, off)
+		}
+		if sym != 3 { // NULL, .text, .data, then the first local: answer
+			t.Errorf("reloc %d: symbol index %d, want 3 (answer)", i, sym)
+		}
+	}
+}
+
+// TestELFLOONG64ObjectNoRelocations checks a file with no static-symbol
+// references emits a valid object without a .rela.text section.
+func TestELFLOONG64ObjectNoRelocations(t *testing.T) {
+	f, errs := parser.Parse("n_loong64.s", `
+#include "textflag.h"
+TEXT ·nop(SB), NOSPLIT, $0
+	RET
+`)
+	if len(errs) > 0 {
+		t.Fatalf("parse: %v", errs)
+	}
+	img, err := AssembleFileLOONG64(f)
+	if err != nil {
+		t.Fatalf("AssembleFileLOONG64: %v", err)
+	}
+	obj, err := img.ELFLOONG64Object()
+	if err != nil {
+		t.Fatalf("ELFLOONG64Object: %v", err)
+	}
+	ef, err := elf.NewFile(bytes.NewReader(obj))
+	if err != nil {
+		t.Fatalf("parse emitted object: %v", err)
+	}
+	defer ef.Close()
+	if ef.Section(".rela.text") != nil {
+		t.Error("unexpected .rela.text section")
+	}
+	syms, err := ef.Symbols()
+	if err != nil {
+		t.Fatal(err)
+	}
+	found := false
+	for _, s := range syms {
+		if s.Name == "nop" && elf.ST_TYPE(s.Info) == elf.STT_FUNC {
+			found = true
+		}
+	}
+	if !found {
+		t.Error("function symbol nop not found")
+	}
+}

asm/elfriscv.go

@@ -0,0 +1,236 @@
+// Copyright (c) 2026 Petr Balvín <opensource@petrbalvin.org> (https://petrbalvin.org)
+// SPDX-License-Identifier: BSD-3-Clause
+
+package asm
+
+import (
+	"encoding/binary"
+	"fmt"
+)
+
+// RISC-V ELF64 relocatable object emission.
+
+const (
+	emRISCV = 243 // EM_RISCV
+
+	// RISC-V relocation types.
+	rRISCV32         = 1
+	rRISCVJAL        = 17 // R_RISCV_JAL
+	rRISCVPCRELHI20  = 23 // R_RISCV_PCREL_HI20
+	rRISCVPCRELLO12I = 24 // R_RISCV_PCREL_LO12_I
+	rRISCVPCRELLO12S = 25 // R_RISCV_PCREL_LO12_S
+)
+
+// ELFRISCVObject returns the image as an ELF64 relocatable object file for
+// RISC-V (EM_RISCV, 64-bit, little-endian).  The structure mirrors the amd64
+// ELF emission: .text, .data, .symtab, .strtab and optional .rela.text.
+func (img *Image) ELFRISCVObject() ([]byte, error) {
+	le := binary.LittleEndian
+
+	const (
+		secText = 1
+		secData = 2
+	)
+
+	// Build symbol table.
+	var locals, globals []elfSym
+	for _, fn := range img.Funcs {
+		s := elfSym{
+			name:  objectName(fn.Pkg, fn.Name),
+			info:  sttFunc,
+			shndx: secText,
+			value: uint64(fn.Offset),
+			size:  uint64(fn.Size),
+		}
+		if fn.Static {
+			locals = append(locals, s)
+		} else {
+			s.info |= stbGlobal << stInfoShift
+			globals = append(globals, s)
+		}
+	}
+	for _, d := range img.DataSyms {
+		s := elfSym{
+			name:  objectName(d.Pkg, d.Name),
+			info:  sttObject,
+			shndx: secData,
+			value: uint64(d.Offset),
+			size:  uint64(d.Size),
+		}
+		if d.Static {
+			locals = append(locals, s)
+		} else {
+			s.info |= stbGlobal << stInfoShift
+			globals = append(globals, s)
+		}
+	}
+	for _, name := range img.Externals {
+		globals = append(globals, elfSym{name: name, info: stbGlobal << stInfoShift})
+	}
+	syms := []elfSym{
+		{},
+		{name: ".text", info: sttSection, shndx: secText},
+		{name: ".data", info: sttSection, shndx: secData},
+	}
+	syms = append(syms, locals...)
+	shInfo := len(syms)
+	syms = append(syms, globals...)
+	symIdx := map[string]int{}
+	for i, s := range syms {
+		symIdx[s.name] = i
+	}
+
+	// Build relocations.  Each SB reference is an AUIPC + second-instruction
+	// pair carrying a single relocation kind; the ELF writer expands it into
+	// the R_RISCV_PCREL_HI20 + R_RISCV_PCREL_LO12_I/S pair the psABI expects.
+	// The HI20 carries the symbol addend; the LO12 addend is zero, matching
+	// cmd/link's own ELF conversion (the LO12 resolves against the HI20's
+	// AUIPC location).
+	type elfRela struct {
+		off    uint64
+		typ    uint32
+		sym    int
+		addend int64
+	}
+	var relas []elfRela
+	for _, fn := range img.Funcs {
+		for _, r := range fn.Relocs {
+			idx, ok := symIdx[r.Name]
+			if !ok {
+				return nil, fmt.Errorf("relocation references unknown symbol %q", r.Name)
+			}
+			switch r.Kind {
+			case RelRISCVPCRELIType:
+				relas = append(relas,
+					elfRela{off: uint64(fn.Offset + r.Off), typ: rRISCVPCRELHI20, sym: idx, addend: r.Addend},
+					elfRela{off: uint64(fn.Offset + r.Off + 4), typ: rRISCVPCRELLO12I, sym: idx, addend: 0},
+				)
+			case RelRISCVPCRELSType:
+				relas = append(relas,
+					elfRela{off: uint64(fn.Offset + r.Off), typ: rRISCVPCRELHI20, sym: idx, addend: r.Addend},
+					elfRela{off: uint64(fn.Offset + r.Off + 4), typ: rRISCVPCRELLO12S, sym: idx, addend: 0},
+				)
+			case RelRISCVJal:
+				relas = append(relas, elfRela{off: uint64(fn.Offset + r.Off), typ: rRISCVJAL, sym: idx, addend: r.Addend})
+			case RelPCRelAbs:
+				relas = append(relas, elfRela{off: uint64(fn.Offset + r.Off), typ: rRISCV32, sym: idx, addend: r.Addend})
+			default:
+				return nil, fmt.Errorf("relocation kind %v unsupported in ELF emission", r.Kind)
+			}
+		}
+	}
+
+	// String tables.
+	stNames := newElfStrtab()
+	for _, s := range syms {
+		stNames.add(s.name)
+	}
+	stSections := newElfStrtab()
+	for _, n := range []string{".text", ".data", ".symtab", ".strtab", ".rela.text", ".shstrtab"} {
+		stSections.add(n)
+	}
+
+	hasRela := len(relas) > 0
+	nSections := 6
+	if hasRela {
+		nSections = 7
+	}
+	secSymtab, secStrtab := 3, 4
+	secShstr := nSections - 1
+
+	// Layout.
+	var out []byte
+	out = append(out, make([]byte, 64)...)
+
+	align := func(n int) {
+		for len(out)%n != 0 {
+			out = append(out, 0)
+		}
+	}
+
+	align(16)
+	textOff := len(out)
+	out = append(out, img.Code...)
+
+	align(16)
+	dataOff := len(out)
+	out = append(out, img.Data...)
+
+	align(8)
+	symtabOff := len(out)
+	for _, s := range syms {
+		var b [24]byte
+		le.PutUint32(b[0:], uint32(stNames.at(s.name)))
+		b[4] = s.info
+		b[5] = 0
+		le.PutUint16(b[6:], s.shndx)
+		le.PutUint64(b[8:], s.value)
+		le.PutUint64(b[16:], s.size)
+		out = append(out, b[:]...)
+	}
+
+	strtabOff := len(out)
+	out = append(out, stNames.bytes()...)
+
+	var relaOff int
+	if hasRela {
+		align(8)
+		relaOff = len(out)
+		for _, r := range relas {
+			var b [24]byte
+			le.PutUint64(b[0:], r.off)
+			le.PutUint64(b[8:], uint64(r.sym)<<32|uint64(r.typ))
+			le.PutUint64(b[16:], uint64(r.addend))
+			out = append(out, b[:]...)
+		}
+	}
+
+	shstrOff := len(out)
+	out = append(out, stSections.bytes()...)
+
+	align(8)
+	shoff := len(out)
+
+	putSh := func(name string, typ int, flags uint64, off, size int, link, info int, alignV, entsize uint64) {
+		var b [64]byte
+		le.PutUint32(b[0:], uint32(stSections.at(name)))
+		le.PutUint32(b[4:], uint32(typ))
+		le.PutUint64(b[8:], flags)
+		le.PutUint64(b[16:], 0)
+		le.PutUint64(b[24:], uint64(off))
+		le.PutUint64(b[32:], uint64(size))
+		le.PutUint32(b[40:], uint32(link))
+		le.PutUint32(b[44:], uint32(info))
+		le.PutUint64(b[48:], alignV)
+		le.PutUint64(b[56:], entsize)
+		out = append(out, b[:]...)
+	}
+	putSh("", shtNull, 0, 0, 0, 0, 0, 0, 0)
+	putSh(".text", shtProgbits, shfAlloc|shfExecInstr, textOff, len(img.Code), 0, 0, 16, 0)
+	putSh(".data", shtProgbits, shfAlloc|shfWrite, dataOff, len(img.Data), 0, 0, 16, 0)
+	putSh(".symtab", shtSymtab, 0, symtabOff, 24*len(syms), secStrtab, shInfo, 8, 24)
+	putSh(".strtab", shtStrtab, 0, strtabOff, len(stNames.bytes()), 0, 0, 1, 0)
+	if hasRela {
+		putSh(".rela.text", shtRela, 0, relaOff, 24*len(relas), secSymtab, secText, 8, 24)
+	}
+	putSh(".shstrtab", shtStrtab, 0, shstrOff, len(stSections.bytes()), 0, 0, 1, 0)
+
+	// ELF header.
+	hdr := out[:64]
+	copy(hdr[0:], []byte{0x7f, 'E', 'L', 'F', elfClass64, elfDataLSB, elfVersion, 0})
+	le.PutUint16(hdr[16:], etREL)
+	le.PutUint16(hdr[18:], emRISCV)
+	le.PutUint32(hdr[20:], elfVersion)
+	le.PutUint64(hdr[24:], 0)
+	le.PutUint64(hdr[32:], 0)
+	le.PutUint64(hdr[40:], uint64(shoff))
+	le.PutUint32(hdr[48:], 0)
+	le.PutUint16(hdr[52:], 64)
+	le.PutUint16(hdr[54:], 0)
+	le.PutUint16(hdr[56:], 0)
+	le.PutUint16(hdr[58:], 64)
+	le.PutUint16(hdr[60:], uint16(nSections))
+	le.PutUint16(hdr[62:], uint16(secShstr))
+
+	return out, nil
+}

asm/evex.go

@@ -377,6 +377,37 @@ var evexTable = map[string]evexSpec{
 	"VPMOVW2M": {2, 0x29, 1, 2, -1, vexRM, [3]int{16, 32, 64}},
 	"VPMOVD2M": {2, 0x39, 0, 2, -1, vexRM, [3]int{16, 32, 64}},
 	"VPMOVQ2M": {2, 0x39, 1, 2, -1, vexRM, [3]int{16, 32, 64}},
+
+	// EVEX — scalar conversions between vector and general-purpose
+	// registers.  Vector to GPR (two operands: vec/mem source, GPR
+	// destination, vvvv unused): the signed and truncated pair, and the
+	// unsigned forms (EVEX only).
+	"VCVTSD2SI":    {1, 0x2D, 0, 3, -1, vexRM, [3]int{8, 8, 8}},
+	"VCVTSD2SIQ":   {1, 0x2D, 1, 3, -1, vexRM, [3]int{8, 8, 8}},
+	"VCVTSS2SI":    {1, 0x2D, 0, 2, -1, vexRM, [3]int{4, 4, 4}},
+	"VCVTSS2SIQ":   {1, 0x2D, 1, 2, -1, vexRM, [3]int{4, 4, 4}},
+	"VCVTTSD2SI":   {1, 0x2C, 0, 3, -1, vexRM, [3]int{8, 8, 8}},
+	"VCVTTSD2SIQ":  {1, 0x2C, 1, 3, -1, vexRM, [3]int{8, 8, 8}},
+	"VCVTTSS2SI":   {1, 0x2C, 0, 2, -1, vexRM, [3]int{4, 4, 4}},
+	"VCVTTSS2SIQ":  {1, 0x2C, 1, 2, -1, vexRM, [3]int{4, 4, 4}},
+	"VCVTSD2USIL":  {1, 0x79, 0, 3, -1, vexRM, [3]int{8, 8, 8}},
+	"VCVTSD2USIQ":  {1, 0x79, 1, 3, -1, vexRM, [3]int{8, 8, 8}},
+	"VCVTSS2USIL":  {1, 0x79, 0, 2, -1, vexRM, [3]int{4, 4, 4}},
+	"VCVTSS2USIQ":  {1, 0x79, 1, 2, -1, vexRM, [3]int{4, 4, 4}},
+	"VCVTTSD2USIL": {1, 0x78, 0, 3, -1, vexRM, [3]int{8, 8, 8}},
+	"VCVTTSD2USIQ": {1, 0x78, 1, 3, -1, vexRM, [3]int{8, 8, 8}},
+	"VCVTTSS2USIL": {1, 0x78, 0, 2, -1, vexRM, [3]int{4, 4, 4}},
+	"VCVTTSS2USIQ": {1, 0x78, 1, 2, -1, vexRM, [3]int{4, 4, 4}},
+	// GPR to vector (three operands: GPR/mem source in r/m, the preserved
+	// vector source in vvvv, vector destination in reg).
+	"VCVTSI2SDL":  {1, 0x2A, 0, 3, -1, vexNDS3, [3]int{4, 4, 4}},
+	"VCVTSI2SDQ":  {1, 0x2A, 1, 3, -1, vexNDS3, [3]int{8, 8, 8}},
+	"VCVTSI2SSL":  {1, 0x2A, 0, 2, -1, vexNDS3, [3]int{4, 4, 4}},
+	"VCVTSI2SSQ":  {1, 0x2A, 1, 2, -1, vexNDS3, [3]int{8, 8, 8}},
+	"VCVTUSI2SDL": {1, 0x7B, 0, 3, -1, vexNDS3, [3]int{4, 4, 4}},
+	"VCVTUSI2SDQ": {1, 0x7B, 1, 3, -1, vexNDS3, [3]int{8, 8, 8}},
+	"VCVTUSI2SSL": {1, 0x7B, 0, 2, -1, vexNDS3, [3]int{4, 4, 4}},
+	"VCVTUSI2SSQ": {1, 0x7B, 1, 2, -1, vexNDS3, [3]int{8, 8, 8}},
 	// EVEX.128/256/512.66.0F38.W0 — sign-extend dwords to qwords; the memory
 	// operand is the narrow source, so disp8×N follows its size (8/16/32 for
 	// the xmm/ymm/zmm destination lengths).
@@ -615,6 +646,12 @@ var evexRound = map[string]bool{
 	"VCVTPD2PS": true, "VCVTPD2UDQ": true, "VCVTTPD2UDQ": true, "VCVTTPD2UQQ": true,
 	"VCVTPS2UDQ": true, "VCVTTPS2UDQ": true, "VCVTPS2UQQ": true, "VCVTTPS2UQQ": true,
 	"VCVTTPD2QQ": true, "VCVTTPS2QQ": true, "VCVTUQQ2PD": true, "VCVTUQQ2PS": true,
+	"VCVTSD2SI": true, "VCVTSD2SIQ": true, "VCVTSS2SI": true, "VCVTSS2SIQ": true,
+	"VCVTSD2USIL": true, "VCVTSD2USIQ": true, "VCVTSS2USIL": true, "VCVTSS2USIQ": true,
+	"VCVTTSD2SI": true, "VCVTTSD2SIQ": true, "VCVTTSS2SI": true, "VCVTTSS2SIQ": true,
+	"VCVTTSD2USIL": true, "VCVTTSD2USIQ": true, "VCVTTSS2USIL": true, "VCVTTSS2USIQ": true,
+	"VCVTSI2SDQ": true, "VCVTSI2SSL": true, "VCVTSI2SSQ": true,
+	"VCVTUSI2SDQ": true, "VCVTUSI2SSL": true, "VCVTUSI2SSQ": true,
 }
 
 // evexBcstN maps an instruction accepting .BCST to the broadcast element
@@ -801,19 +838,23 @@ func (e *enc) encodeEvexNDS3(spec evexSpec, ops []Operand, mask int, sfx evexSuf
 
 // encodeEvexRM encodes the two-operand form: OP src, dst (reg=dst, rm=src,
 // no vvvv), e.g. VCVTQQ2PD.  The destination may be an opmask register (the
-// *2M mask conversions), in which case the vector length comes from the
-// source.
+// *2M mask conversions) or a general-purpose register (the scalar
+// vector-to-GPR conversions); in both cases the vector length comes from
+// the source.
 func (e *enc) encodeEvexRM(spec evexSpec, ops []Operand, mask int, sfx evexSuffix) error {
 	if len(ops) != 2 {
 		return fmt.Errorf("EVEX two-operand instruction expects 2 operands, got %d", len(ops))
 	}
 	src, dst := ops[0], ops[1]
 	dstReg, ok := dst.(Reg)
-	if !ok || (!dstReg.isVec() && !dstReg.mask) {
-		return fmt.Errorf("EVEX destination must be a vector or mask register")
+	if !ok {
+		return fmt.Errorf("EVEX destination must be a register")
 	}
 	ll := dstReg.vecLenBit()
-	if dstReg.mask {
+	if !dstReg.isVec() {
+		// Mask or GPR destination: the length follows the vector source
+		// (128 for a memory source).
+		ll = 0
 		if r, ok := src.(Reg); ok && r.isVec() {
 			ll = r.vecLenBit()
 		}

asm/evex_test.go

@@ -4,13 +4,10 @@
 package asm
 
 import (
-	"os"
 	"strings"
 	"testing"
 
 	"golang.org/x/arch/x86/x86asm"
-
-	"sourcedock.dev/petrbalvin/gasm-devkit/parser"
 )
 
 // TestEvexGroundTruth checks the EVEX (AVX-512) encodings byte for byte
@@ -467,6 +464,74 @@ func TestEvexHelperGroundTruth(t *testing.T) {
 	}
 }
 
+// TestEvexGprGroundTruth covers the scalar conversions between vector and
+// general-purpose registers — the signed and truncated VCVT{,T}S{D,S}2SI
+// forms (VEX and EVEX), the unsigned EVEX-only forms, and the GPR-to-vector
+// VCVTSI2*/VCVTUSI2* forms with the preserved vector source in vvvv — byte
+// for byte against the Go assembler, including memory sources and extended
+// GPRs.
+func TestEvexGprGroundTruth(t *testing.T) {
+	mem := func(b Reg) Operand { return Ptr(b, 0, 8) }
+	cases := []struct {
+		name string
+		mnem string
+		ops  []Operand
+		want string
+	}{
+		{"VCVTSD2SI", "VCVTSD2SI", []Operand{vreg(t, "X1"), AX}, "c5fb2dc1"},
+		{"VCVTSD2SIQ", "VCVTSD2SIQ", []Operand{vreg(t, "X1"), AX}, "c4e1fb2dc1"},
+		{"VCVTSS2SI", "VCVTSS2SI", []Operand{vreg(t, "X1"), AX}, "c5fa2dc1"},
+		{"VCVTSS2SIQ", "VCVTSS2SIQ", []Operand{vreg(t, "X1"), AX}, "c4e1fa2dc1"},
+		{"VCVTTSD2SI", "VCVTTSD2SI", []Operand{vreg(t, "X1"), AX}, "c5fb2cc1"},
+		{"VCVTTSD2SIQ", "VCVTTSD2SIQ", []Operand{vreg(t, "X1"), AX}, "c4e1fb2cc1"},
+		{"VCVTTSS2SI", "VCVTTSS2SI", []Operand{vreg(t, "X1"), AX}, "c5fa2cc1"},
+		{"VCVTTSS2SIQ", "VCVTTSS2SIQ", []Operand{vreg(t, "X1"), AX}, "c4e1fa2cc1"},
+		{"VCVTSD2USIL", "VCVTSD2USIL", []Operand{vreg(t, "X1"), AX}, "62f17f0879c1"},
+		{"VCVTSD2USIQ", "VCVTSD2USIQ", []Operand{vreg(t, "X1"), AX}, "62f1ff0879c1"},
+		{"VCVTSS2USIL", "VCVTSS2USIL", []Operand{vreg(t, "X1"), AX}, "62f17e0879c1"},
+		{"VCVTSS2USIQ", "VCVTSS2USIQ", []Operand{vreg(t, "X1"), AX}, "62f1fe0879c1"},
+		{"VCVTTSD2USIL", "VCVTTSD2USIL", []Operand{vreg(t, "X1"), AX}, "62f17f0878c1"},
+		{"VCVTTSD2USIQ", "VCVTTSD2USIQ", []Operand{vreg(t, "X1"), AX}, "62f1ff0878c1"},
+		{"VCVTTSS2USIL", "VCVTTSS2USIL", []Operand{vreg(t, "X1"), AX}, "62f17e0878c1"},
+		{"VCVTTSS2USIQ", "VCVTTSS2USIQ", []Operand{vreg(t, "X1"), AX}, "62f1fe0878c1"},
+		{"VCVTSI2SDL", "VCVTSI2SDL", []Operand{AX, vreg(t, "X1"), vreg(t, "X2")}, "c5f32ad0"},
+		{"VCVTSI2SDQ", "VCVTSI2SDQ", []Operand{AX, vreg(t, "X1"), vreg(t, "X2")}, "c4e1f32ad0"},
+		{"VCVTSI2SSL", "VCVTSI2SSL", []Operand{AX, vreg(t, "X1"), vreg(t, "X2")}, "c5f22ad0"},
+		{"VCVTSI2SSQ", "VCVTSI2SSQ", []Operand{AX, vreg(t, "X1"), vreg(t, "X2")}, "c4e1f22ad0"},
+		{"VCVTUSI2SDL", "VCVTUSI2SDL", []Operand{AX, vreg(t, "X1"), vreg(t, "X2")}, "62f177087bd0"},
+		{"VCVTUSI2SDQ", "VCVTUSI2SDQ", []Operand{AX, vreg(t, "X1"), vreg(t, "X2")}, "62f1f7087bd0"},
+		{"VCVTUSI2SSL", "VCVTUSI2SSL", []Operand{AX, vreg(t, "X1"), vreg(t, "X2")}, "62f176087bd0"},
+		{"VCVTUSI2SSQ", "VCVTUSI2SSQ", []Operand{AX, vreg(t, "X1"), vreg(t, "X2")}, "62f1f6087bd0"},
+		{"VCVTSD2SI mem", "VCVTSD2SI", []Operand{mem(AX), BX}, "c5fb2d18"},
+		{"VCVTSI2SDQ mem", "VCVTSI2SDQ", []Operand{mem(BX), vreg(t, "X1"), vreg(t, "X2")}, "c4e1f32a13"},
+		{"VCVTSD2SIQ hi gpr", "VCVTSD2SIQ", []Operand{vreg(t, "X1"), vreg(t, "R9")}, "c461fb2dc9"},
+		{"VCVTSI2SDQ hi gpr", "VCVTSI2SDQ", []Operand{vreg(t, "R10"), vreg(t, "X1"), vreg(t, "X2")}, "c4c1f32ad2"},
+	}
+	for _, c := range cases {
+		code, err := Encode(c.mnem, c.ops...)
+		if err != nil {
+			t.Errorf("%s: Encode: %v", c.name, err)
+			continue
+		}
+		if got := hexCompact(code); got != c.want {
+			t.Errorf("%s: bytes %s, want %s", c.name, got, c.want)
+			continue
+		}
+		inst, err := x86asm.Decode(code, 64)
+		if err != nil {
+			t.Errorf("%s: Decode(%x): %v", c.name, code, err)
+			continue
+		}
+		// The decoder does not distinguish the Plan 9 SIQ spelling (the
+		// 64-bit GPR destination) from the base name; the W bit carries it.
+		want := c.mnem
+		got := inst.Op.String()
+		if got != want && !(len(want) > len(got) && want[:len(got)] == got) {
+			t.Errorf("%s: decoded as %s", c.name, got)
+		}
+	}
+}
+
 // TestEvexConversionGroundTruth covers the unsigned and truncating VCVT*
 // conversions, the remaining sign/zero-extending moves, the signed/unsigned
 // narrowing stores and the mask/vector conversions, byte for byte against
@@ -581,71 +646,6 @@ func TestEvexErrors(t *testing.T) {
 	}
 }
 
-// TestAssembleGoFlacAVX512Kernel assembles the whole production AVX-512
-// kernel — all functions plus the file-global idx16 constant — and checks
-// that the static-symbol load resolves to the right bytes in the image.
-// Skipped when the sibling repository is not checked out.
-func TestAssembleGoFlacAVX512Kernel(t *testing.T) {
-	path := "../../go-libraries/go-flac/avx512_amd64.s"
-	if _, err := os.Stat(path); err != nil {
-		t.Skip("go-libraries repository not present next to gasm-devkit")
-	}
-	src, err := os.ReadFile(path)
-	if err != nil {
-		t.Fatal(err)
-	}
-	f, errs := parser.Parse(path, string(src))
-	if len(errs) > 0 {
-		t.Fatalf("parse: %v", errs)
-	}
-	img, err := AssembleFile(f)
-	if err != nil {
-		t.Fatalf("AssembleFile: %v", err)
-	}
-	if len(img.Funcs) != 10 {
-		t.Errorf("functions = %d, want 10", len(img.Funcs))
-	}
-
-	// idx16 as the DATA directives define it: dwords 1..16.
-	idx := make([]byte, 0, 64)
-	for i := 1; i <= 16; i++ {
-		idx = append(idx, byte(i), 0, 0, 0)
-	}
-	image := img.Bytes()
-	base := img.Symbols["idx16"]
-	if base == 0 {
-		t.Fatal("idx16 not laid out")
-	}
-	if got := image[base : base+64]; hexCompact(got) != hexCompact(idx) {
-		t.Errorf("idx16 contents %x, want %x", got, idx)
-	}
-
-	// The VMOVDQU32 idx16(SB), Z13 load (62 71 7e 48 6f 2d + rel32) must
-	// resolve to idx16 within the image.
-	loads := 0
-	for _, fn := range img.Funcs {
-		code := img.Code[fn.Offset : fn.Offset+fn.Size]
-		pat := []byte{0x62, 0x71, 0x7e, 0x48, 0x6f, 0x2d}
-		for pos := 0; ; {
-			i := indexOf(code[pos:], pat)
-			if i < 0 {
-				break
-			}
-			i += pos
-			rel := int32(uint32(code[i+6]) | uint32(code[i+7])<<8 | uint32(code[i+8])<<16 | uint32(code[i+9])<<24)
-			target := fn.Offset + i + 10 + int(rel)
-			if target != base {
-				t.Errorf("%s: idx16 load at +%d targets 0x%x, want 0x%x", fn.Name, i, target, base)
-			}
-			loads++
-			pos = i + 10
-		}
-	}
-	if loads != 1 {
-		t.Errorf("idx16 loads found = %d, want 1", loads)
-	}
-}
-
 // hexCompact renders bytes as a lowercase hex string without separators.
 func hexCompact(b []byte) string {
 	const hexdig = "0123456789abcdef"
@@ -656,17 +656,3 @@ func hexCompact(b []byte) string {
 	}
 	return string(out)
 }
-
-// indexOf returns the index of the first occurrence of pat in b, or -1.
-func indexOf(b, pat []byte) int {
-	for i := 0; i+len(pat) <= len(b); i++ {
-		j := 0
-		for j < len(pat) && b[i+j] == pat[j] {
-			j++
-		}
-		if j == len(pat) {
-			return i
-		}
-	}
-	return -1
-}

asm/goobj.go

@@ -10,6 +10,7 @@ import (
 	"os"
 	"os/exec"
 	"path/filepath"
+	"strings"
 	"sync"
 )
 
@@ -22,9 +23,15 @@ import (
 //
 // The object carries what the linker requires of an assembly object: the
 // functions (non-package symbols, as cmd/asm emits them), the GLOBL data,
-// one FuncInfo per function, and the pc-value tables (pcsp, pcfile,
-// pcline, pcinline).  DWARF and the implicit funcdata symbols are omitted;
-// the linker fills their defaults.
+// one FuncInfo per function, the per-function DWARF symbols (the
+// .debug_line program and the subprogram DIE, which the linker's DWARF
+// pass reads verbatim), and the pc-value tables (pcsp, pcfile, pcline,
+// pcinline).  The implicit funcdata symbols are omitted; the linker fills
+// their defaults.
+//
+// emitGOObject is architecture-agnostic; the per-architecture GOObject*
+// methods supply the toolchain preamble, the MinLC (pc-value delta unit)
+// and the relocation-type mapping for code relocations.
 
 // GOOBJ block indices (cmd/internal/goobj).
 const (
@@ -51,9 +58,11 @@ const (
 
 // Symbol kinds used by assembly objects (cmd/internal/objabi).
 const (
-	kindSTEXT   = 1
-	kindSRODATA = 3
-	kindSDATA   = 7
+	kindSTEXT       = 1
+	kindSRODATA     = 3
+	kindSDATA       = 7
+	kindSDWARFFCN   = 14
+	kindSDWARFLINES = 20
 )
 
 // Symbol flags (cmd/internal/goobj).
@@ -66,11 +75,13 @@ const (
 
 // Aux entry types (cmd/internal/goobj).
 const (
-	auxFuncInfo = 1
-	auxPcsp     = 7
-	auxPcfile   = 8
-	auxPcline   = 9
-	auxPcinline = 10
+	auxFuncInfo   = 1
+	auxDwarfInfo  = 3
+	auxDwarfLines = 6
+	auxPcsp       = 7
+	auxPcfile     = 8
+	auxPcline     = 9
+	auxPcinline   = 10
 )
 
 // FuncInfo flags (internal/abi).
@@ -80,7 +91,49 @@ const (
 )
 
 // Relocation types (cmd/internal/objabi).
-const relocPCRel = 14
+// R_PCREL and R_ADDR are stable across Go versions.
+const (
+	relocPCRel = 14 // R_PCREL
+	relocAddr  = 1  // R_ADDR
+)
+
+// relocDWTXTADDRU4 returns the R_DWTXTADDR_U4 relocation type for the
+// installed Go toolchain.  The value shifted between Go 1.26 (103) and
+// Go 1.27 (106) because new LoongArch relocations were inserted before it.
+func relocDWTXTADDRU4() uint16 {
+	if isGo127OrLater() {
+		return 106
+	}
+	return 103
+}
+
+var (
+	goVersionOnce sync.Once
+	goVersionGT26 bool
+)
+
+// isGo127OrLater reports whether the installed Go toolchain is 1.27 or later.
+func isGo127OrLater() bool {
+	goVersionOnce.Do(func() {
+		goBin, err := exec.LookPath("go")
+		if err != nil {
+			return
+		}
+		out, err := exec.Command(goBin, "version").Output()
+		if err != nil {
+			return
+		}
+		// "go version go1.27rc1 linux/amd64"
+		s := string(out)
+		for _, prefix := range []string{"go version go1.27", "go version go1.28", "go version go1.29", "go version go2."} {
+			if strings.Contains(s, prefix) {
+				goVersionGT26 = true
+				return
+			}
+		}
+	})
+	return goVersionGT26
+}
 
 // Special package indices for symbol references.
 const (
@@ -110,6 +163,13 @@ func (s goSym) append(b []byte, strOff map[string]uint32) []byte {
 	return binary.LittleEndian.AppendUint32(b, s.align)
 }
 
+// dwarfRelocSet attaches emitter-generated relocations (the DWARF
+// lines/info symbols' address references) to a definition index.
+type dwarfRelocSet struct {
+	si     int
+	relocs []goobjReloc
+}
+
 // GOObject returns the image as a GOOBJ object file for the given package
 // path (the linker qualifies the exported symbols with it, the way cmd/asm
 // does with its -p flag).  srcPath names the source file recorded in the
@@ -117,19 +177,90 @@ func (s goSym) append(b []byte, strOff map[string]uint32) []byte {
 // captured from the installed go tool asm, so the output links with the
 // toolchain it was produced on — exactly like a real assembly object.
 func (img *Image) GOObject(pkgPath, srcPath string) ([]byte, error) {
-	if pkgPath == "" {
-		return nil, fmt.Errorf("GOOBJ emission requires a package path (-p)")
-	}
 	pre, err := toolchainObjectPreamble()
 	if err != nil {
 		return nil, err
 	}
+	// amd64: MinLC 1, R_PCREL for the code relocations.
+	return img.emitGOObject(pkgPath, srcPath, pre, 1, func(Reloc) (uint16, uint8) { return relocPCRel, 4 })
+}
 
-	// The symbol tables.  Package definitions: the GLOBL symbols, then one
-	// anonymous FuncInfo symbol per function.  Non-package definitions: the
-	// pc-value tables and the functions themselves, as cmd/asm lays them
-	// out.  defIdx maps a GLOBL's bare name to its definition index for the
-	// relocations; fnNpIdx maps a function to its non-package index.
+// emitGOObject assembles the GOOBJ payload for any architecture.  pre is
+// the toolchain's object preamble; minLC is the architecture's minimum
+// instruction length, the unit of the pc-value table deltas; relocField
+// maps a code relocation to its objabi relocation type and the width of
+// the instruction field the linker writes.
+func (img *Image) emitGOObject(pkgPath, srcPath string, pre []byte, minLC int, relocField func(Reloc) (uint16, uint8)) ([]byte, error) {
+	if pkgPath == "" {
+		return nil, fmt.Errorf("GOOBJ emission requires a package path (-p)")
+	}
+
+	// The non-package definitions first — the DWARF symbols reference the
+	// functions by these indices: per function the four pc-value tables
+	// and the function itself, as cmd/asm lays them out.
+	type npSym struct {
+		sym  goSym
+		data []byte
+	}
+	var nps []npSym
+	type pcRefs struct{ sp, file, line, inl int }
+	pcIdx := make([]pcRefs, len(img.Funcs))
+	fnNpIdx := make([]int, len(img.Funcs))
+	for i, fn := range img.Funcs {
+		tables := []struct {
+			data []byte
+			dst  *int
+		}{
+			{pcspTable(fn, minLC), &pcIdx[i].sp},
+			{pcValueFlat(0, fn.Size, minLC), &pcIdx[i].file},
+			{pcValueFlat(int32(fn.Line), fn.Size, minLC), &pcIdx[i].line},
+			{pcValueFlat(-1, fn.Size, minLC), &pcIdx[i].inl},
+		}
+		for _, t := range tables {
+			*t.dst = len(nps)
+			nps = append(nps, npSym{
+				sym:  goSym{typ: kindSRODATA, size: uint32(len(t.data)), align: 1},
+				data: t.data,
+			})
+		}
+		name := fn.Name
+		abi := uint16(0)
+		if fn.Static {
+			abi = symABIStatic
+		} else {
+			name = pkgPath + "." + name
+		}
+		flag := uint8(0)
+		if fn.NoSplit {
+			flag |= symFlagNoSplit
+		}
+		fnNpIdx[i] = len(nps)
+		code := append([]byte(nil), img.Code[fn.Offset:fn.Offset+fn.Size]...)
+		for _, r := range fn.Relocs {
+			// Only the amd64 encoder resolves file-local static symbols
+			// into a disp32 field at assemble time; GOOBJ must leave that
+			// field zero for the linker to fill.  The RISC-V and LoongArch
+			// encoders emit zero immediates with a relocation instead, and
+			// their relocations cover whole AUIPC/pcalau12i pairs, so
+			// zeroing r.Off would erase the opcode/register bits the linker
+			// preserves when it patches only the immediate.
+			if r.Kind != RelPCRel32 {
+				continue
+			}
+			if r.Off >= 0 && r.Off+4 <= len(code) {
+				code[r.Off], code[r.Off+1], code[r.Off+2], code[r.Off+3] = 0, 0, 0, 0
+			}
+		}
+		nps = append(nps, npSym{
+			sym:  goSym{name: name, abi: abi, typ: kindSTEXT, flag: flag, flag2: symFlag2Link, size: uint32(fn.Size)},
+			data: code,
+		})
+	}
+
+	// The package definitions: the GLOBL symbols, then, per function, the
+	// FuncInfo and the two DWARF symbols (the .debug_line program and the
+	// subprogram DIE).  defIdx maps a GLOBL's bare name to its definition
+	// index for the code relocations.
 	var defs []goSym
 	var defData [][]byte
 	defIdx := map[string]int{}
@@ -155,74 +286,82 @@ func (img *Image) GOObject(pkgPath, srcPath string) ([]byte, error) {
 		defData = append(defData, img.Data[d.Offset:d.Offset+d.Size])
 	}
 	fnFiIdx := make([]int, len(img.Funcs))
-	for i := range img.Funcs {
-		data := marshalFuncInfo(img.Funcs[i])
+	fnLinesIdx := make([]int, len(img.Funcs))
+	fnDIEIdx := make([]int, len(img.Funcs))
+	var dwarfRelocs []dwarfRelocSet
+	for i, fn := range img.Funcs {
+		data := marshalFuncInfo(fn)
 		fnFiIdx[i] = len(defs)
 		defs = append(defs, goSym{typ: kindSDATA, size: uint32(len(data))})
 		defData = append(defData, data)
-	}
 
-	type npSym struct {
-		sym  goSym
-		data []byte
-	}
-	var nps []npSym
-	type pcRefs struct{ sp, file, line, inl int }
-	pcIdx := make([]pcRefs, len(img.Funcs))
-	fnNpIdx := make([]int, len(img.Funcs))
-	for i, fn := range img.Funcs {
-		tables := []struct {
-			data []byte
-			dst  *int
-		}{
-			{pcspTable(fn), &pcIdx[i].sp},
-			{pcValueFlat(0, fn.Size), &pcIdx[i].file},
-			{pcValueFlat(int32(fn.Line), fn.Size), &pcIdx[i].line},
-			{pcValueFlat(-1, fn.Size), &pcIdx[i].inl},
-		}
-		for _, t := range tables {
-			*t.dst = len(nps)
-			nps = append(nps, npSym{
-				sym:  goSym{typ: kindSRODATA, size: uint32(len(t.data)), align: 1},
-				data: t.data,
-			})
-		}
 		name := fn.Name
-		abi := uint16(0)
-		if fn.Static {
-			abi = symABIStatic
-		} else {
+		if !fn.Static {
 			name = pkgPath + "." + name
 		}
-		flag := uint8(0)
-		if fn.NoSplit {
-			flag |= symFlagNoSplit
+
+		// The DWARF symbols: the .debug_line state-machine program and the
+		// subprogram DIE, both referencing the function by its non-package
+		// index (package definitions, like cmd/asm's).
+		lines, lrel := goobjDwarfLines(fn, fnNpIdx[i])
+		fnLinesIdx[i] = len(defs)
+		defs = append(defs, goSym{typ: kindSDWARFLINES, size: uint32(len(lines))})
+		defData = append(defData, lines)
+		die, drel := goobjDwarfInfo(fn, name, fnNpIdx[i])
+		fnDIEIdx[i] = len(defs)
+		defs = append(defs, goSym{typ: kindSDWARFFCN, size: uint32(len(die))})
+		defData = append(defData, die)
+		dwarfRelocs = append(dwarfRelocs,
+			dwarfRelocSet{si: fnLinesIdx[i], relocs: lrel},
+			dwarfRelocSet{si: fnDIEIdx[i], relocs: drel},
+		)
+	}
+
+	// Resolve external symbol references (cross-package).  Build the
+	// package index table and determine each external symbol's SymIdx
+	// by reading the target package's export data.
+	var extPkgTable []string
+	var extPkgIdx map[string]int
+	var extSymIdx map[string]int
+	if len(img.Externals) > 0 {
+		var err error
+		extPkgTable, extPkgIdx, extSymIdx, err = resolveExternalSymbols(img.Externals)
+		if err != nil {
+			return nil, fmt.Errorf("GOOBJ emission: resolving external symbols: %w", err)
 		}
-		fnNpIdx[i] = len(nps)
-		code := append([]byte(nil), img.Code[fn.Offset:fn.Offset+fn.Size]...)
-		for _, r := range fn.Relocs {
-			// The linker writes the resolved displacement into the field;
-			// leave it zero, as cmd/asm's object does.
-			if r.Off >= 0 && r.Off+4 <= len(code) {
-				code[r.Off], code[r.Off+1], code[r.Off+2], code[r.Off+3] = 0, 0, 0, 0
-			}
-		}
-		nps = append(nps, npSym{
-			sym:  goSym{name: name, abi: abi, typ: kindSTEXT, flag: flag, flag2: symFlag2Link, size: uint32(fn.Size)},
-			data: code,
-		})
 	}
 
 	// Relocations, per defined symbol in definition order (package defs,
-	// then non-package defs).  Only file-local GLOBL references resolve;
-	// external symbols need the import machinery of a later increment.
+	// then non-package defs).
 	nsyms := len(defs) + len(nps)
 	symRelocs := make([][]byte, nsyms) // flat 23-byte records
 	for i, fn := range img.Funcs {
 		si := len(defs) + fnNpIdx[i]
 		for _, r := range fn.Relocs {
+			typ, size := relocField(r)
 			if r.External {
-				return nil, fmt.Errorf("GOOBJ emission: external symbol %q is not supported yet", r.Name)
+				// Split package-qualified name: "runtime·morestack" → runtime, morestack.
+				pkg, name := splitQualified(r.Name)
+				if pkg == "" {
+					return nil, fmt.Errorf("GOOBJ emission: external symbol %q has no package prefix", r.Name)
+				}
+				pIdx, ok := extPkgIdx[pkg]
+				if !ok {
+					return nil, fmt.Errorf("GOOBJ emission: package %q not resolved", pkg)
+				}
+				sIdx, ok := extSymIdx[pkg+"·"+name]
+				if !ok {
+					return nil, fmt.Errorf("GOOBJ emission: symbol %s·%s not resolved", pkg, name)
+				}
+				var rec [23]byte
+				binary.LittleEndian.PutUint32(rec[0:], uint32(int32(r.Off)))
+				rec[4] = size // field width
+				binary.LittleEndian.PutUint16(rec[5:], typ)
+				binary.LittleEndian.PutUint64(rec[7:], uint64(r.Addend))
+				binary.LittleEndian.PutUint32(rec[15:], uint32(pIdx))
+				binary.LittleEndian.PutUint32(rec[19:], uint32(sIdx))
+				symRelocs[si] = append(symRelocs[si], rec[:]...)
+				continue
 			}
 			di, ok := defIdx[r.Name]
 			if !ok {
@@ -230,17 +369,30 @@ func (img *Image) GOObject(pkgPath, srcPath string) ([]byte, error) {
 			}
 			var rec [23]byte
 			binary.LittleEndian.PutUint32(rec[0:], uint32(int32(r.Off)))
-			rec[4] = 4 // field width
-			binary.LittleEndian.PutUint16(rec[5:], relocPCRel)
+			rec[4] = size // field width
+			binary.LittleEndian.PutUint16(rec[5:], typ)
 			binary.LittleEndian.PutUint64(rec[7:], uint64(r.Addend))
 			binary.LittleEndian.PutUint32(rec[15:], pkgIdxSelf)
 			binary.LittleEndian.PutUint32(rec[19:], uint32(di))
 			symRelocs[si] = append(symRelocs[si], rec[:]...)
 		}
 	}
+	// The DWARF symbols' own relocations (the function address references).
+	for _, ds := range dwarfRelocs {
+		for _, r := range ds.relocs {
+			var rec [23]byte
+			binary.LittleEndian.PutUint32(rec[0:], uint32(r.off))
+			rec[4] = r.siz
+			binary.LittleEndian.PutUint16(rec[5:], r.typ)
+			binary.LittleEndian.PutUint64(rec[7:], uint64(r.add))
+			binary.LittleEndian.PutUint32(rec[15:], r.pkg)
+			binary.LittleEndian.PutUint32(rec[19:], r.sym)
+			symRelocs[ds.si] = append(symRelocs[ds.si], rec[:]...)
+		}
+	}
 
-	// Aux entries per function: FuncInfo, then the four pc tables.
-	// References into the non-package table use pkgIdxNone.
+	// Aux entries per function: FuncInfo, the DWARF symbols, then the four
+	// pc tables.  References into the non-package table use pkgIdxNone.
 	symAux := make([][]byte, nsyms)
 	for i := range img.Funcs {
 		si := len(defs) + fnNpIdx[i]
@@ -252,10 +404,14 @@ func (img *Image) GOObject(pkgPath, srcPath string) ([]byte, error) {
 			symAux[si] = append(symAux[si], rec[:]...)
 		}
 		aux(auxFuncInfo, pkgIdxSelf, uint32(fnFiIdx[i]))
-		aux(auxPcsp, pkgIdxNone, uint32(len(defs)+pcIdx[i].sp))
-		aux(auxPcfile, pkgIdxNone, uint32(len(defs)+pcIdx[i].file))
-		aux(auxPcline, pkgIdxNone, uint32(len(defs)+pcIdx[i].line))
-		aux(auxPcinline, pkgIdxNone, uint32(len(defs)+pcIdx[i].inl))
+		aux(auxDwarfInfo, pkgIdxSelf, uint32(fnDIEIdx[i]))
+		aux(auxDwarfLines, pkgIdxSelf, uint32(fnLinesIdx[i]))
+		// The pc-table references are 0-based within the non-package
+		// definitions; the loader adds the package-definition count itself.
+		aux(auxPcsp, pkgIdxNone, uint32(pcIdx[i].sp))
+		aux(auxPcfile, pkgIdxNone, uint32(pcIdx[i].file))
+		aux(auxPcline, pkgIdxNone, uint32(pcIdx[i].line))
+		aux(auxPcinline, pkgIdxNone, uint32(pcIdx[i].inl))
 	}
 
 	// The string table.  Absolute offsets: it starts right after the
@@ -291,7 +447,16 @@ func (img *Image) GOObject(pkgPath, srcPath string) ([]byte, error) {
 	for _, s := range nps {
 		npdefBlk = s.sym.append(npdefBlk, strOff)
 	}
-	pkgIdxBlk := stringRef(nil, "") // index 0: the dummy invalid package
+
+	// Package index table: index 0 is the dummy invalid package.
+	// External packages follow, in pkgIdx order.
+	for _, pkg := range extPkgTable {
+		addStr(pkg)
+	}
+	pkgIdxBlk := stringRef(nil, "") // index 0: dummy
+	for _, pkg := range extPkgTable {
+		pkgIdxBlk = stringRef(pkgIdxBlk, pkg)
+	}
 	fileBlk := stringRef(nil, srcPath)
 
 	var relocBlk, auxBlk, dataBlk []byte
@@ -374,19 +539,21 @@ func marshalFuncInfo(fn FuncLayout) []byte {
 }
 
 // pcValueFlat encodes a pc-value table holding v over the whole function.
-func pcValueFlat(v int32, size int) []byte {
+// The pc deltas are in MinLC units (the runtime scales them by the
+// architecture's minimum instruction length).
+func pcValueFlat(v int32, size, minLC int) []byte {
 	// The table is delta-encoded from an implicit value of -1: a varint
 	// value delta, an unsigned pc delta to the end, and a zero terminator.
 	out := binary.AppendVarint(nil, int64(v)+1)
-	out = binary.AppendUvarint(out, uint64(size))
+	out = binary.AppendUvarint(out, uint64(size/minLC))
 	return append(out, 0)
 }
 
 // pcspTable encodes the stack-adjustment table: the SP delta in effect at
 // every pc, from the function's prologue and epilogue boundaries.
-func pcspTable(fn FuncLayout) []byte {
+func pcspTable(fn FuncLayout, minLC int) []byte {
 	if len(fn.Spadj) == 0 {
-		return pcValueFlat(0, fn.Size)
+		return pcValueFlat(0, fn.Size, minLC)
 	}
 	pts := make([]SpadjStep, 0, len(fn.Spadj)+1)
 	pts = append(pts, SpadjStep{PC: 0, Value: 0})
@@ -394,11 +561,11 @@ func pcspTable(fn FuncLayout) []byte {
 	out := binary.AppendVarint(nil, int64(pts[0].Value)+1)
 	cur, old := pts[0].PC, pts[0].Value
 	for _, p := range pts[1:] {
-		out = binary.AppendUvarint(out, uint64(p.PC-cur))
+		out = binary.AppendUvarint(out, uint64((p.PC-cur)/minLC))
 		out = binary.AppendVarint(out, int64(p.Value-old))
 		cur, old = p.PC, p.Value
 	}
-	out = binary.AppendUvarint(out, uint64(fn.Size-cur))
+	out = binary.AppendUvarint(out, uint64((fn.Size-cur)/minLC))
 	return append(out, 0)
 }
 

asm/goobj_dwarf.go

@@ -0,0 +1,188 @@
+// Copyright (c) 2026 Petr Balvín <opensource@petrbalvin.org> (https://petrbalvin.org)
+// SPDX-License-Identifier: BSD-3-Clause
+
+package asm
+
+import (
+	"encoding/binary"
+)
+
+// This file generates the per-function DWARF symbols the linker's DWARF
+// pass requires of an assembly object, byte-identical to what cmd/asm
+// emits: the .debug_line state-machine program (SDWARFLINES) and the
+// subprogram DIE (SDWARFFCN).  The linker copies the DIE and line-program
+// bytes verbatim into .debug_info and .debug_line, fixing up their
+// relocations, so the formats here must match cmd/internal/dwarf's
+// DW_ABRV_FUNCTION and generateDebugLinesSymbol exactly.
+//
+// DWARF5 is assumed throughout (the toolchain's default on Linux and the
+// other non-Darwin targets gasm supports).
+
+// Line-program parameters (cmd/internal/obj/dwarf.go).
+const (
+	dwLineBase   = -4
+	dwLineRange  = 10
+	dwOpcodeBase = 11
+	dwPCRange    = (255 - dwOpcodeBase) / dwLineRange
+)
+
+// goobjReloc is one relocation attached to an emitter-generated symbol
+// (the DWARF lines/info symbols), in goobj's on-disk encoding fields.
+type goobjReloc struct {
+	off int32
+	siz uint8
+	typ uint16
+	add int64
+	pkg uint32
+	sym uint32
+}
+
+// goobjDwarfLines builds the function's .debug_line state-machine program:
+// an LNE_set_address extended opcode establishing the function's start
+// address (carrying the R_ADDR relocation), one row per source line
+// change across the function's instructions, an advance to the end of the
+// function and an end-of-sequence opcode.  The linker appends these bytes
+// after the unit's line header, so they must start with the address and
+// leave the state machine terminated.
+func goobjDwarfLines(fn FuncLayout, fnNpIdx int) ([]byte, []goobjReloc) {
+	// Rows: the prologue, if any, then the body instructions (fn.Lines
+	// covers the body only).  The first body offset > 0 means a prologue
+	// precedes it; the toolchain reports the prologue on the TEXT line.
+	pts := make([]LineEntry, 0, len(fn.Lines)+1)
+	if len(fn.Lines) == 0 || fn.Lines[0].Offset > 0 {
+		pts = append(pts, LineEntry{Offset: 0, Line: fn.Line})
+	}
+	pts = append(pts, fn.Lines...)
+
+	out := []byte{0, 9, 2, 0, 0, 0, 0, 0, 0, 0, 0} // LNE_set_address, address zeroed
+	relocs := []goobjReloc{{
+		off: 3, siz: 8, typ: relocAddr,
+		pkg: pkgIdxNone, sym: uint32(fnNpIdx),
+	}}
+
+	// The state machine starts at line 1, pc 0 (function-relative); the
+	// implicit initial pc is the function entry, so the first pc delta is
+	// against 0.
+	line := int64(1)
+	pc := uint64(0)
+	for _, p := range pts {
+		if p.Line == 0 || uint64(p.Offset) < pc {
+			continue
+		}
+		// Rows mark source-line changes only; the pc delta is measured from
+		// the previous row, not the previous instruction.
+		if int64(p.Line) == line {
+			continue
+		}
+		deltaPC := uint64(p.Offset) - pc
+		deltaLC := int64(p.Line) - line
+		out = dwPutPCLCDelta(out, deltaPC, deltaLC)
+		line, pc = int64(p.Line), uint64(p.Offset)
+	}
+
+	// Cover the rest of the function and close the sequence.
+	if end := uint64(fn.Size) - pc; end > 0 {
+		out = append(out, 2) // DW_LNS_advance_pc
+		out = binary.AppendUvarint(out, end)
+	}
+	out = append(out, 0, 1, 1) // LNE_end_sequence
+	return out, relocs
+}
+
+// dwPutPCLCDelta encodes one (pcDelta, lineDelta) step as the shortest
+// special opcode plus any standard-opcode remainder, exactly like
+// cmd/internal/obj's putpclcdelta.
+func dwPutPCLCDelta(b []byte, deltaPC uint64, deltaLC int64) []byte {
+	opcode := dwSelectOpcode(deltaPC, deltaLC)
+	deltaPC -= uint64((opcode - dwOpcodeBase) / dwLineRange)
+	deltaLC -= (opcode-dwOpcodeBase)%dwLineRange + dwLineBase
+
+	// The remainder: standard opcodes first, then the special opcode
+	// (which emits the row).
+	if deltaPC != 0 {
+		switch {
+		case deltaPC <= uint64(dwPCRange):
+			opcode -= dwLineRange * int64(uint64(dwPCRange)-deltaPC)
+			b = append(b, 8) // DW_LNS_const_add_pc
+		case (1<<14) <= deltaPC && deltaPC < (1<<16):
+			b = append(b, 9) // DW_LNS_fixed_advance_pc
+			b = binary.LittleEndian.AppendUint16(b, uint16(deltaPC))
+		default:
+			b = append(b, 2) // DW_LNS_advance_pc
+			b = binary.AppendUvarint(b, deltaPC)
+		}
+	}
+	if deltaLC != 0 {
+		b = append(b, 3) // DW_LNS_advance_line
+		b = binary.AppendVarint(b, deltaLC)
+	}
+	return append(b, byte(opcode))
+}
+
+// dwSelectOpcode picks the special opcode for (deltaPC, deltaLC) per
+// cmd/internal/obj's putpclcdelta selection logic.
+func dwSelectOpcode(deltaPC uint64, deltaLC int64) int64 {
+	switch {
+	case deltaLC < dwLineBase:
+		if deltaPC >= uint64(dwPCRange) {
+			return dwOpcodeBase + dwLineRange*dwPCRange
+		}
+		return dwOpcodeBase + dwLineRange*int64(deltaPC)
+	case deltaLC < dwLineBase+dwLineRange:
+		if deltaPC >= uint64(dwPCRange) {
+			op := int64(dwOpcodeBase) + (deltaLC - dwLineBase) + dwLineRange*dwPCRange
+			if op > 255 {
+				op -= dwLineRange
+			}
+			return op
+		}
+		return int64(dwOpcodeBase) + (deltaLC - dwLineBase) + dwLineRange*int64(deltaPC)
+	default:
+		if deltaPC <= uint64(dwPCRange) {
+			op := int64(dwOpcodeBase) + (dwLineRange - 1) + dwLineRange*int64(deltaPC)
+			if op > 255 {
+				op = 255
+			}
+			return op
+		}
+		switch deltaPC - uint64(dwPCRange) {
+		case uint64(dwPCRange), (1 << 7) - 1, (1 << 16) - 1, (1 << 21) - 1,
+			(1 << 28) - 1, (1 << 35) - 1, (1 << 42) - 1, (1 << 49) - 1,
+			(1 << 56) - 1, (1 << 63) - 1:
+			return 255
+		default:
+			// 250: the toolchain's "249" comment is stale.
+			return dwOpcodeBase + dwLineRange*dwPCRange - 1
+		}
+	}
+}
+
+// goobjDwarfInfo builds the function's DWARF5 subprogram DIE (abbrev
+// DW_ABRV_FUNCTION): name, low_pc as a .debug_addr index (the
+// R_DWTXTADDR_U4 relocation), high_pc as the size, the call-frame-CFA
+// frame base, the decl file/line and the external flag.  name is the
+// symbol's object name (package-qualified unless static).
+func goobjDwarfInfo(fn FuncLayout, name string, fnNpIdx int) ([]byte, []goobjReloc) {
+	out := []byte{3} // DW_ABRV_FUNCTION
+	out = append(out, name...)
+	out = append(out, 0)
+
+	addrx := len(out)
+	out = append(out, 0, 0, 0, 0) // DW_AT_low_pc: addrx slot, zeroed
+	out = binary.AppendUvarint(out, uint64(fn.Size))
+	out = append(out, 1, 0x9c) // DW_AT_frame_base: block1, DW_OP_call_frame_cfa
+	out = binary.LittleEndian.AppendUint32(out, 1)
+	out = binary.AppendUvarint(out, uint64(fn.Line))
+	if fn.Static {
+		out = append(out, 0)
+	} else {
+		out = append(out, 1) // DW_AT_external
+	}
+	out = append(out, 0) // end of children
+
+	relocs := []goobjReloc{{
+		off: int32(addrx), siz: 4, typ: relocDWTXTADDRU4(),
+		pkg: pkgIdxNone, sym: uint32(fnNpIdx),
+	}}
+	return out, relocs
+}

asm/goobj_dwarf_test.go

@@ -0,0 +1,214 @@
+// Copyright (c) 2026 Petr Balvín <opensource@petrbalvin.org> (https://petrbalvin.org)
+// SPDX-License-Identifier: BSD-3-Clause
+
+package asm
+
+import (
+	"bytes"
+	"encoding/binary"
+	"testing"
+)
+
+// TestDWSelectOpcode checks the special-opcode selection against
+// hand-computed values for the boundary cases: line deltas below, inside
+// and above the line range, and pc deltas at and beyond PC_RANGE (24).
+func TestDWSelectOpcode(t *testing.T) {
+	cases := []struct {
+		deltaPC uint64
+		deltaLC int64
+		want    int64
+	}{
+		{0, 2, 17},   // the common single-instruction step
+		{0, -4, 11},  // deltaLC == LINE_BASE
+		{0, -5, 11},  // deltaLC below LINE_BASE: opcode adds nothing
+		{0, 6, 20},   // deltaLC == LINE_BASE+LINE_RANGE, remainder via advance_line
+		{4, 1, 56},   // the 4-byte loong64 instruction step
+		{23, 1, 246}, // deltaPC == PC_RANGE-1
+		{24, 1, 246}, // deltaPC == PC_RANGE: wraps past 255
+		{25, 1, 246}, // deltaPC past PC_RANGE (the const_add_pc remainder adjusts it later)
+		{100, 1, 246},
+		{151, 10, 255}, // deltaPC-PC_RANGE == (1<<7)-1, large line delta
+		{100, 10, 250}, // deltaPC-PC_RANGE not on a switch boundary
+		{23, 10, 250},  // large line delta inside PC_RANGE
+	}
+	for _, c := range cases {
+		if got := dwSelectOpcode(c.deltaPC, c.deltaLC); got != c.want {
+			t.Errorf("dwSelectOpcode(%d, %d) = %d, want %d", c.deltaPC, c.deltaLC, got, c.want)
+		}
+	}
+}
+
+// decodeDWLineProgram decodes a .debug_line state-machine program (as
+// emitted by goobjDwarfLines) into (pc, line) rows.
+func decodeDWLineProgram(t *testing.T, b []byte) (pcs []uint64, lines []int64) {
+	t.Helper()
+	pc, line := uint64(0), int64(1)
+	emit := func() {
+		if len(pcs) == 0 || pcs[len(pcs)-1] != pc || lines[len(lines)-1] != line {
+			pcs = append(pcs, pc)
+			lines = append(lines, line)
+		}
+	}
+	advancePC := func(delta uint64) { pc += delta }
+	advanceLine := func(delta int64) { line += delta }
+	for i := 0; i < len(b); {
+		op := b[i]
+		i++
+		switch {
+		case op == 0: // extended opcode
+			ln, n := binary.Uvarint(b[i:])
+			i += n
+			sub := b[i]
+			i++
+			_ = ln
+			switch sub {
+			case 2: // DW_LNE_set_address: 8-byte address
+				pc = binary.LittleEndian.Uint64(b[i:])
+				i += 8
+			case 1: // DW_LNE_end_sequence
+				// terminates the sequence; no new row
+			}
+		case op == 2: // DW_LNS_advance_pc
+			v, n := binary.Uvarint(b[i:])
+			i += n
+			advancePC(v)
+		case op == 3: // DW_LNS_advance_line
+			v, n := binary.Varint(b[i:])
+			i += n
+			advanceLine(v)
+		case op == 8: // DW_LNS_const_add_pc
+			advancePC(uint64(dwPCRange))
+		case op == 9: // DW_LNS_fixed_advance_pc
+			advancePC(uint64(binary.LittleEndian.Uint16(b[i:])))
+			i += 2
+		case op >= dwOpcodeBase: // special opcode
+			advancePC(uint64((int64(op) - dwOpcodeBase) / dwLineRange))
+			advanceLine((int64(op)-dwOpcodeBase)%dwLineRange + dwLineBase)
+			emit()
+		}
+	}
+	return pcs, lines
+}
+
+// TestGoobjDwarfLinesRows checks the emitted line program's rows for
+// synthetic functions: a zero-frame function with one instruction per
+// line, a framed function (the prologue row is prepended on the TEXT
+// line), instructions sharing a line, and a function with a large pc gap
+// (the const_add_pc remainder path).
+func TestGoobjDwarfLinesRows(t *testing.T) {
+	cases := []struct {
+		name string
+		fn   FuncLayout
+		want [][2]int64 // (pc, line)
+	}{
+		{
+			"one instruction per line",
+			FuncLayout{Size: 20, Line: 2, Lines: []LineEntry{
+				{0, 3}, {4, 4}, {8, 5}, {12, 6}, {16, 7},
+			}},
+			[][2]int64{{0, 3}, {4, 4}, {8, 5}, {12, 6}, {16, 7}},
+		},
+		{
+			"framed: prologue row on the TEXT line",
+			FuncLayout{Size: 24, Line: 2, Lines: []LineEntry{
+				{12, 3}, {16, 4},
+			}},
+			[][2]int64{{0, 2}, {12, 3}, {16, 4}},
+		},
+		{
+			"instructions sharing a line fold into one row",
+			FuncLayout{Size: 16, Line: 2, Lines: []LineEntry{
+				{0, 3}, {4, 3}, {8, 4}, {12, 4},
+			}},
+			[][2]int64{{0, 3}, {8, 4}},
+		},
+		{
+			"large gap crosses PC_RANGE",
+			FuncLayout{Size: 60, Line: 2, Lines: []LineEntry{
+				{0, 3}, {40, 4},
+			}},
+			[][2]int64{{0, 3}, {40, 4}},
+		},
+	}
+	for _, c := range cases {
+		t.Run(c.name, func(t *testing.T) {
+			prog, relocs := goobjDwarfLines(c.fn, 0)
+			if len(relocs) != 1 || relocs[0].off != 3 || relocs[0].siz != 8 || relocs[0].typ != relocAddr || relocs[0].sym != 0 {
+				t.Fatalf("relocs = %+v", relocs)
+			}
+			pcs, lines := decodeDWLineProgram(t, prog)
+			if len(pcs) != len(c.want) {
+				t.Fatalf("rows = %d (%v / %v), want %d", len(pcs), pcs, lines, len(c.want))
+			}
+			for i, w := range c.want {
+				if pcs[i] != uint64(w[0]) || lines[i] != w[1] {
+					t.Errorf("row %d = (%d, %d), want (%d, %d)", i, pcs[i], lines[i], w[0], w[1])
+				}
+			}
+		})
+	}
+}
+
+// TestGoobjDwarfInfo checks the subprogram DIE for an exported and a
+// static function: the abbrev, name, high_pc, frame base, decl file/line,
+// the external flag and the addrx relocation position.
+func TestGoobjDwarfInfo(t *testing.T) {
+	fn := FuncLayout{Size: 20, Line: 2}
+	die, relocs := goobjDwarfInfo(fn, "pkg.f", 3)
+	want := []byte{
+		0x03,
+		'p', 'k', 'g', '.', 'f', 0,
+		0, 0, 0, 0, // addrx slot at offset 7
+		0x14,       // high_pc: 20
+		0x01, 0x9c, // frame_base
+		0x01, 0, 0, 0, // decl_file 1
+		0x02, // decl_line 2
+		0x01, // external
+		0x00, // end of children
+	}
+	if !bytes.Equal(die, want) {
+		t.Errorf("DIE = %x, want %x", die, want)
+	}
+	if len(relocs) != 1 || relocs[0].off != 7 || relocs[0].siz != 4 || relocs[0].typ != relocDWTXTADDRU4() || relocs[0].sym != 3 {
+		t.Errorf("relocs = %+v", relocs)
+	}
+
+	// A static function carries no external flag and no package prefix.
+	fn.Static = true
+	die, _ = goobjDwarfInfo(fn, "f", 1)
+	if die[len(die)-2] != 0 {
+		t.Errorf("static external flag = %d, want 0", die[len(die)-2])
+	}
+}
+
+// TestDwPutPCLCDeltaRemainders checks the standard-opcode remainders:
+// const_add_pc and fixed_advance_pc after a special opcode.
+func TestDwPutPCLCDeltaRemainders(t *testing.T) {
+	// deltaPC 25 past PC_RANGE: opcode 26 covers (1, 1), const_add_pc
+	// covers the remaining 23 pc and 0 line.
+	got := dwPutPCLCDelta(nil, 25, 1)
+	if !bytes.Equal(got, []byte{8, 26}) {
+		t.Errorf("25/1 = %x, want [8 1a]", got)
+	}
+
+	// deltaPC 20000: opcode 246 covers 23, fixed_advance_pc covers the
+	// remaining 19977.
+	got = dwPutPCLCDelta(nil, 20000, 1)
+	if got[0] != 9 || binary.LittleEndian.Uint16(got[1:]) != 19977 || got[3] != 246 {
+		t.Errorf("20000/1 = %x, want fixed_advance_pc 19977 then 246", got)
+	}
+
+	// Line remainder: deltaLC 10 leaves 5 past the opcode's reach, encoded
+	// as advance_line 5 (zigzag 0x0a) before opcode 250.
+	got = dwPutPCLCDelta(nil, 23, 10)
+	if !bytes.Equal(got, []byte{3, 0x0a, 250}) {
+		t.Errorf("23/10 = %x, want [03 0a fa]", got)
+	}
+
+	// Negative line remainder: deltaLC -5 leaves advance_line -1 (zigzag
+	// 0x01) after opcode 11.
+	got = dwPutPCLCDelta(nil, 0, -5)
+	if !bytes.Equal(got, []byte{3, 1, 11}) {
+		t.Errorf("0/-5 = %x, want [03 01 0b]", got)
+	}
+}

asm/goobj_resolve.go

@@ -0,0 +1,348 @@
+// Copyright (c) 2026 Petr Balvín <opensource@petrbalvin.org> (https://petrbalvin.org)
+// SPDX-License-Identifier: BSD-3-Clause
+
+package asm
+
+import (
+	"bytes"
+	"encoding/binary"
+	"fmt"
+	"os"
+	"os/exec"
+	"strings"
+)
+
+// readGOOBJSymbols reads the GOOBJ symbol definitions from a compiled Go
+// package's export file.  The file is an ar archive containing a __.PKGDEF
+// member whose payload is the "go object ...\n!\n" preamble followed by the
+// GOOBJ data.  The function returns the symbol names in definition order
+// (the order they appear in blkSymdef), which matches the SymIdx the linker
+// expects for cross-package references.
+func readGOOBJSymbols(exportPath string) ([]string, error) {
+	data, err := os.ReadFile(exportPath)
+	if err != nil {
+		return nil, err
+	}
+	goobj, err := extractGOOBJ(data)
+	if err != nil {
+		return nil, fmt.Errorf("%s: %w", exportPath, err)
+	}
+	return goobj.symbols(), nil
+}
+
+// exportPath returns the export file path for a given import path by running
+// "go list -export".  The result is cached so repeated calls for the same
+// package are fast.
+func exportPath(importPath string) (string, error) {
+	cmd := exec.Command("go", "list", "-json", "-export", importPath)
+	out, err := cmd.Output()
+	if err != nil {
+		return "", fmt.Errorf("go list %s: %w", importPath, err)
+	}
+	// Quick JSON extraction: find "Export": "…"
+	const key = `"Export": "`
+	i := bytes.Index(out, []byte(key))
+	if i < 0 {
+		return "", fmt.Errorf("go list %s: no Export field", importPath)
+	}
+	start := i + len(key)
+	end := bytes.IndexByte(out[start:], '"')
+	if end < 0 {
+		return "", fmt.Errorf("go list %s: malformed Export field", importPath)
+	}
+	return string(out[start : start+end]), nil
+}
+
+// resolveExternalGOOBJ resolves a set of external symbol references into
+// (package index, symbol index) pairs suitable for GOOBJ emission.
+//
+// refs maps package import paths to the symbol names referenced from that
+// package.  The returned pkgIdx maps each import path to its position in
+// the blkPkgIdx table (0-based), and symIdx gives each symbol's index within
+// its package.
+func resolveExternalGOOBJ(refs map[string][]string) (pkgIdx map[string]int, symIdx map[string]int, err error) {
+	pkgIdx = make(map[string]int, len(refs))
+	symIdx = make(map[string]int)
+
+	// Assign package indices in sorted order for determinism.
+	packages := sortedPkgRefs(refs)
+
+	for i, pkg := range packages {
+		pkgIdx[pkg.path] = i
+		exp, err := exportPath(pkg.path)
+		if err != nil {
+			return nil, nil, err
+		}
+		data, err := os.ReadFile(exp)
+		if err != nil {
+			return nil, nil, err
+		}
+		gobj, err := extractGOOBJ(data)
+		if err != nil {
+			return nil, nil, fmt.Errorf("%s: %w", pkg.path, err)
+		}
+		for _, name := range pkg.syms {
+			idx := gobj.findSymbol(pkg.path, name)
+			if idx < 0 {
+				return nil, nil, fmt.Errorf("symbol %s·%s not found in export data of %s", pkg.path, name, pkg.path)
+			}
+			symIdx[pkg.path+"·"+name] = idx
+		}
+	}
+	return pkgIdx, symIdx, nil
+}
+
+type pkgRef struct {
+	path string
+	syms []string
+}
+
+func sortedPkgRefs(refs map[string][]string) []pkgRef {
+	var pkgs []pkgRef
+	for pkg, syms := range refs {
+		pkgs = append(pkgs, pkgRef{pkg, syms})
+	}
+	// Simple insertion sort — the list is tiny (usually 1–3 packages).
+	for i := 1; i < len(pkgs); i++ {
+		for j := i; j > 0 && pkgs[j-1].path > pkgs[j].path; j-- {
+			pkgs[j-1], pkgs[j] = pkgs[j], pkgs[j-1]
+		}
+	}
+	return pkgs
+}
+
+// extractGOOBJ finds the GOOBJ data in an ar archive and returns a parsed
+// goobjFile.  The archive member _go_.o contains the "go object …\n!\n"
+// preamble followed by the GOOBJ payload; __.PKGDEF is the compiler export
+// data (type information) and is not the GOOBJ object.
+func extractGOOBJ(data []byte) (*goobjFile, error) {
+	if len(data) < 8 || string(data[:8]) != "!<arch>\n" {
+		return nil, fmt.Errorf("not an ar archive")
+	}
+	pos := 8
+	for pos+60 <= len(data) {
+		hdr := data[pos : pos+60]
+		pos += 60
+
+		// Parse ar header fields.
+		name := strings.TrimRight(string(hdr[:16]), " /")
+		size := parseArDecimal(hdr[48:58])
+		if size < 0 {
+			return nil, fmt.Errorf("invalid ar header: bad size")
+		}
+		if pos+size > len(data) {
+			return nil, fmt.Errorf("ar entry %q extends past end of file", name)
+		}
+		body := data[pos : pos+size]
+		pos += size
+		// ar pads to even bytes.
+		if pos%2 != 0 {
+			pos++
+		}
+
+		if name == "_go_.o" {
+			return parseGOOBJ(body)
+		}
+	}
+	return nil, fmt.Errorf("archive contains no _go_.o member")
+}
+
+// parseArDecimal parses a decimal number from a space-padded field.
+func parseArDecimal(b []byte) int {
+	v := 0
+	for _, c := range b {
+		if c == ' ' {
+			continue
+		}
+		if c < '0' || c > '9' {
+			return -1
+		}
+		v = v*10 + int(c-'0')
+	}
+	return v
+}
+
+// goobjFile is a parsed GOOBJ file: the string table and the symbol-definition
+// block.
+type goobjFile struct {
+	strTab []byte // string table, at headerSize + n
+	symdef []byte // blkSymdef raw block
+	npdef  []byte // blkNonpkgdef raw block
+}
+
+// symbols returns all symbol names in definition order by scanning the
+// symdef and nonpkgdef blocks and resolving each name through the string
+// table.  Package definitions (blkSymdef) use fully-qualified names like
+// "runtime.morestack"; non-package definitions (blkNonpkgdef) use bare
+// names like "morestack".  This combined list matches the index the
+// linker expects for cross-package references.
+func (f *goobjFile) symbols() []string {
+	return append(f.defNames(), f.npdefNames()...)
+}
+
+// findSymbol returns the index of a symbol within the combined symbol list,
+// or -1 if not found.  It first tries the fully-qualified name (pkg.name),
+// then the bare name.
+func (f *goobjFile) findSymbol(pkg, name string) int {
+	qualified := pkg + "." + name
+	syms := f.symbols()
+	for i, s := range syms {
+		if s == qualified {
+			return i
+		}
+	}
+	// Try bare name (for non-package definitions).
+	for i, s := range syms {
+		if s == name {
+			return i
+		}
+	}
+	return -1
+}
+
+// defNames returns names from blkSymdef only.
+func (f *goobjFile) defNames() []string {
+	return f.readSymNames(f.symdef)
+}
+
+// npdefNames returns names from blkNonpkgdef.
+func (f *goobjFile) npdefNames() []string {
+	return f.readSymNames(f.npdef)
+}
+
+// readSymNames reads symbol names from a symdef/nonpkgdef block.  Each record
+// is 21 bytes: nameLen (u32), nameOff (u32), abi (u16), typ, flag, flag2,
+// size (u32), align (u32).  nameOff is an absolute offset into the string
+// table.
+func (f *goobjFile) readSymNames(block []byte) []string {
+	const recSize = 21
+	if len(block) < recSize {
+		return nil
+	}
+	n := len(block) / recSize
+	names := make([]string, 0, n)
+	for i := 0; i < n; i++ {
+		rec := block[i*recSize : (i+1)*recSize]
+		nameLen := binary.LittleEndian.Uint32(rec[0:4])
+		nameOff := binary.LittleEndian.Uint32(rec[4:8])
+		// nameOff is an absolute offset into the GOOBJ payload.  The string
+		// table we have starts at goobjHeaderSize, so we subtract that.
+		if nameOff < goobjHeaderSize {
+			continue
+		}
+		relOff := nameOff - goobjHeaderSize
+		if relOff >= uint32(len(f.strTab)) || relOff+nameLen > uint32(len(f.strTab)) {
+			continue
+		}
+		names = append(names, string(f.strTab[relOff:relOff+nameLen]))
+	}
+	return names
+}
+
+const goobjHeaderSize = 8 + 8 + 4 + 4*(blkEnd+1) // magic + fingerprint + flags + 19 block offsets
+
+// parseGOOBJ parses a raw GOOBJ payload (the data after the "\n!\n" preamble).
+func parseGOOBJ(data []byte) (*goobjFile, error) {
+	// Find the "\n!\n" separator.
+	sep := []byte("\n!\n")
+	i := bytes.Index(data, sep)
+	if i < 0 {
+		// Maybe the data has no preamble (e.g. a raw .o file).
+		i = -3 // treat as if preamble starts before the data
+	}
+	payload := data[i+len(sep):]
+
+	if len(payload) < goobjHeaderSize {
+		return nil, fmt.Errorf("GOOBJ payload too short (%d bytes)", len(payload))
+	}
+	if string(payload[:8]) != goobjMagic {
+		return nil, fmt.Errorf("bad GOOBJ magic: %q", payload[:8])
+	}
+
+	// Read block offsets.  The header layout is:
+	//   [0:8]   magic
+	//   [8:16]  fingerprint
+	//   [16:20] flags
+	//   [20:96] 19 × uint32 offsets
+	var offs [blkEnd + 1]uint32
+	for i := 0; i <= blkEnd; i++ {
+		offs[i] = binary.LittleEndian.Uint32(payload[20+4*i:])
+	}
+	// The string table lives at headerSize.
+	strTabStart := uint32(goobjHeaderSize)
+
+	f := &goobjFile{
+		strTab: payload[strTabStart:offs[0]],
+		symdef: blockSlice(payload, offs, blkSymdef, blkSymdef+1),
+		npdef:  blockSlice(payload, offs, blkNonpkgdef, blkNonpkgdef+1),
+	}
+	return f, nil
+}
+
+// blockSlice extracts a block from the payload using its offset pair.
+func blockSlice(payload []byte, offs [blkEnd + 1]uint32, start, end int) []byte {
+	if start < 0 || end > blkEnd || offs[end] < offs[start] {
+		return nil
+	}
+	beg := offs[start]
+	fin := offs[end]
+	if int(fin) > len(payload) || int(beg) > int(fin) {
+		return nil
+	}
+	return payload[beg:fin]
+}
+
+// resolveExternalSymbols is the high-level entry point for GOOBJ emission.
+// Given a list of external symbol names (e.g. ["runtime·morestack",
+// "runtime·g0"]), it returns the package-index table entries and a map from
+// full symbol name to GOOBJ {pkgIdx, symIdx}.
+//
+// The package table entries should be written into blkPkgIdx, and the
+// returned indices should replace pkgIdxSelf / placeholder values in the
+// relocation records.
+func resolveExternalSymbols(externals []string) (pkgTable []string, pkgIdxMap map[string]int, symIdxMap map[string]int, err error) {
+	// Group references by package.
+	refs := make(map[string]map[string]bool)
+	for _, full := range externals {
+		pkg, name := splitQualified(full)
+		if refs[pkg] == nil {
+			refs[pkg] = make(map[string]bool)
+		}
+		refs[pkg][name] = true
+	}
+
+	// Convert maps to slices.
+	r := make(map[string][]string, len(refs))
+	for pkg, names := range refs {
+		for name := range names {
+			r[pkg] = append(r[pkg], name)
+		}
+	}
+
+	pkgIdx1, symIdx1, err := resolveExternalGOOBJ(r)
+	if err != nil {
+		return nil, nil, nil, err
+	}
+
+	// Build the package table in pkgIdx order.
+	pkgTable = make([]string, len(pkgIdx1))
+	for pkg, idx := range pkgIdx1 {
+		pkgTable[idx] = pkg
+	}
+
+	return pkgTable, pkgIdx1, symIdx1, nil
+}
+
+// splitQualified splits a qualified Go symbol name (pkgpath·name) into its
+// package path and local name.  The separator is the middle dot (U+00B7).
+// If no separator is found, the symbol is assumed to be in the current
+// package (empty pkg).
+func splitQualified(full string) (pkg, name string) {
+	if idx := strings.IndexByte(full, '\u00b7'); idx >= 0 {
+		return full[:idx], full[idx+len("\u00b7"):]
+	}
+	if idx := strings.IndexByte(full, '.'); idx >= 0 {
+		return full[:idx], full[idx+1:]
+	}
+	return "", full
+}

asm/goobj_resolve_test.go

@@ -0,0 +1,66 @@
+// Copyright (c) 2026 Petr Balvín <opensource@petrbalvin.org> (https://petrbalvin.org)
+// SPDX-License-Identifier: BSD-3-Clause
+
+package asm
+
+import (
+	"os"
+	"os/exec"
+	"testing"
+)
+
+// TestReadRuntimeSymbols verifies the GOOBJ reader can extract and find
+// symbols from the runtime package's compiled archive.
+func TestReadRuntimeSymbols(t *testing.T) {
+	exp, err := exportPath("runtime")
+	if err != nil {
+		t.Skipf("cannot find runtime export: %v (need Go toolchain)", err)
+	}
+	data, err := os.ReadFile(exp)
+	if err != nil {
+		t.Skipf("cannot read runtime export: %v", err)
+	}
+	gobj, err := extractGOOBJ(data)
+	if err != nil {
+		t.Fatalf("extractGOOBJ: %v", err)
+	}
+
+	t.Logf("runtime: %d symbols", len(gobj.symbols()))
+
+	// Verify we can find well-known runtime symbols.
+	for _, tc := range []struct{ pkg, name string }{
+		{"runtime", "g0"},
+		{"runtime", "morestack"},
+		{"runtime", "newstack"},
+	} {
+		idx := gobj.findSymbol(tc.pkg, tc.name)
+		if idx < 0 {
+			t.Errorf("findSymbol(%q, %q) = -1", tc.pkg, tc.name)
+		} else {
+			t.Logf("findSymbol(%q, %q) = %d", tc.pkg, tc.name, idx)
+		}
+	}
+}
+
+// TestResolveExternalSymbols verifies end-to-end resolution of external
+// symbol references.
+func TestResolveExternalSymbols(t *testing.T) {
+	if _, err := exec.LookPath("go"); err != nil {
+		t.Skip("go toolchain not available")
+	}
+
+	refs := map[string][]string{
+		"runtime": {"g0"},
+	}
+	pkgIdx, symIdx, err := resolveExternalGOOBJ(refs)
+	if err != nil {
+		t.Fatalf("resolveExternalGOOBJ: %v", err)
+	}
+	if len(pkgIdx) != 1 || pkgIdx["runtime"] != 0 {
+		t.Errorf("pkgIdx = %v, want runtime→0", pkgIdx)
+	}
+	if _, ok := symIdx["runtime·g0"]; !ok {
+		t.Errorf("symIdx missing runtime·g0, got %v", symIdx)
+	}
+	t.Logf("runtime·g0 → SymIdx=%d", symIdx["runtime·g0"])
+}

asm/goobj_test.go

@@ -111,17 +111,26 @@ DATA mask<>+8(SB)/8, $0x800f0e0d0c0b0a09
 		t.Errorf("flags = %#x, want ObjFlagFromAssembly (4)", flags)
 	}
 
-	// Package defs: the static GLOBL, then one anonymous FuncInfo per
-	// function.
+	// Package defs: the static GLOBL, then per function the FuncInfo and the
+	// two DWARF symbols (debug_line program, subprogram DIE).
 	defs := v.syms(blkSymdef)
-	if len(defs) != 3 {
-		t.Fatalf("symdefs = %d, want 3", len(defs))
+	if len(defs) != 7 {
+		t.Fatalf("symdefs = %d, want 7", len(defs))
 	}
 	if defs[0].name != "mask" || defs[0].abi != 0xffff || defs[0].typ != kindSRODATA || defs[0].size != 16 || defs[0].flag2 != symFlag2Link {
 		t.Errorf("mask symbol = %+v", defs[0])
 	}
 	if defs[1].name != "" || defs[1].typ != kindSDATA || defs[1].size != 28 {
-		t.Errorf("funcinfo symbol = %+v", defs[1])
+		t.Errorf("addq funcinfo symbol = %+v", defs[1])
+	}
+	if defs[2].name != "" || defs[2].typ != kindSDWARFLINES || defs[2].size == 0 {
+		t.Errorf("addq lines symbol = %+v", defs[2])
+	}
+	if defs[3].name != "" || defs[3].typ != kindSDWARFFCN || defs[3].size == 0 {
+		t.Errorf("addq DIE symbol = %+v", defs[3])
+	}
+	if defs[4].name != "" || defs[4].typ != kindSDATA || defs[4].size != 28 {
+		t.Errorf("loadmask funcinfo symbol = %+v", defs[4])
 	}
 
 	// Non-package defs: four pc tables and the function, per function.
@@ -142,45 +151,62 @@ DATA mask<>+8(SB)/8, $0x800f0e0d0c0b0a09
 	// FuncInfo: args 24, FuncFlag Asm, one file, no inline tree.
 	le := binary.LittleEndian
 	data := v.blk(blkData)
+	didx := v.blk(blkDataIdx)
 	fi := data[16:44]
 	if le.Uint32(fi[0:]) != 24 || le.Uint32(fi[4:]) != 0 || fi[8] != 0 || fi[9] != funcFlagAsm ||
 		le.Uint32(fi[16:]) != 1 || le.Uint32(fi[20:]) != 0 || le.Uint32(fi[24:]) != 0 {
 		t.Errorf("funcinfo bytes %x", fi)
 	}
 
-	// pcsp: a flat zero over the whole function (zero-frame NOSPLIT).
-	if got := data[72:75]; !bytes.Equal(got, []byte{0x02, 19, 0x00}) {
+	// The pc-value tables of addq (non-package indices 0–3, so global
+	// indices 7–10): pcsp a flat zero over the whole function, pcinline a
+	// flat -1, both with the pc delta in MinLC (1) units.
+	pcsp := data[le.Uint32(didx[4*7:]):]
+	if got := pcsp[:3]; !bytes.Equal(got, []byte{0x02, 19, 0x00}) {
 		t.Errorf("pcsp = %x, want 021300", got)
 	}
-	// pcinline: a flat -1.
-	if got := data[81:84]; !bytes.Equal(got, []byte{0x00, 19, 0x00}) {
+	pcinl := data[le.Uint32(didx[4*10:]):]
+	if got := pcinl[:3]; !bytes.Equal(got, []byte{0x00, 19, 0x00}) {
 		t.Errorf("pcinline = %x, want 001300", got)
 	}
 
-	// The one relocation: R_PCREL, four bytes wide, against the GLOBL,
-	// with the field in the function code left zero.  The loadmask code's
-	// offset comes from the data index (symbol 3 defs + 9 non-package).
+	// Relocations: the four DWARF address references (two per function, in
+	// definition order), then the loadmask code's R_PCREL against the
+	// GLOBL, with the field in the function code left zero.  The loadmask
+	// code's offset comes from the data index (7 defs + 9 non-package).
 	relocs := v.blk(blkReloc)
-	if len(relocs) != 23 {
-		t.Fatalf("relocs = %d bytes, want one 23-byte entry", len(relocs))
+	if len(relocs) != 5*23 {
+		t.Fatalf("relocs = %d bytes, want 5 entries", len(relocs))
 	}
-	off := int32(le.Uint32(relocs[0:]))
-	if off != 4 || relocs[4] != 4 || le.Uint16(relocs[5:]) != relocPCRel ||
-		le.Uint64(relocs[7:]) != 0 || le.Uint32(relocs[15:]) != pkgIdxSelf || le.Uint32(relocs[19:]) != 0 {
-		t.Errorf("reloc = %x", relocs)
+	// addq's DWARF references (defs 2 and 3) against the function, which
+	// is non-package index 4.
+	lr := relocs[:23]
+	if int32(le.Uint32(lr[0:])) != 3 || lr[4] != 8 || le.Uint16(lr[5:]) != relocAddr ||
+		le.Uint32(lr[15:]) != pkgIdxNone || le.Uint32(lr[19:]) != 4 {
+		t.Errorf("addq lines reloc = %x", lr)
 	}
-	didx := v.blk(blkDataIdx)
-	lm := le.Uint32(didx[4*(3+9):])
+	dr := relocs[23:46]
+	if dr[4] != 4 || le.Uint16(dr[5:]) != relocDWTXTADDRU4() ||
+		le.Uint32(dr[15:]) != pkgIdxNone || le.Uint32(dr[19:]) != 4 {
+		t.Errorf("addq DIE reloc = %x", dr)
+	}
+	cr := relocs[4*23:]
+	off := int32(le.Uint32(cr[0:]))
+	if off != 4 || cr[4] != 4 || le.Uint16(cr[5:]) != relocPCRel ||
+		le.Uint64(cr[7:]) != 0 || le.Uint32(cr[15:]) != pkgIdxSelf || le.Uint32(cr[19:]) != 0 {
+		t.Errorf("loadmask reloc = %x", cr)
+	}
+	lm := le.Uint32(didx[4*16:])
 	code := data[lm : lm+18]
 	if !bytes.Equal(code[4:8], []byte{0, 0, 0, 0}) {
 		t.Errorf("relocated field = %x, want zeroed", code[4:8])
 	}
 
-	// Aux wiring: FuncInfo (package symbol), then the four pc tables
-	// (non-package symbols).
+	// Aux wiring: FuncInfo, the two DWARF symbols (package symbols), then
+	// the four pc tables (non-package symbols).
 	auxs := v.blk(blkAux)
-	if len(auxs) != 2*5*9 {
-		t.Fatalf("aux = %d bytes, want 10 entries", len(auxs))
+	if len(auxs) != 2*7*9 {
+		t.Fatalf("aux = %d bytes, want 14 entries", len(auxs))
 	}
 	wantAux := []struct {
 		typ uint8
@@ -188,15 +214,19 @@ DATA mask<>+8(SB)/8, $0x800f0e0d0c0b0a09
 		idx uint32
 	}{
 		{auxFuncInfo, pkgIdxSelf, 1},
-		{auxPcsp, pkgIdxNone, uint32(len(defs) + 0)},
-		{auxPcfile, pkgIdxNone, uint32(len(defs) + 1)},
-		{auxPcline, pkgIdxNone, uint32(len(defs) + 2)},
-		{auxPcinline, pkgIdxNone, uint32(len(defs) + 3)},
-		{auxFuncInfo, pkgIdxSelf, 2},
-		{auxPcsp, pkgIdxNone, uint32(len(defs) + 5)},
-		{auxPcfile, pkgIdxNone, uint32(len(defs) + 6)},
-		{auxPcline, pkgIdxNone, uint32(len(defs) + 7)},
-		{auxPcinline, pkgIdxNone, uint32(len(defs) + 8)},
+		{auxDwarfInfo, pkgIdxSelf, 3},
+		{auxDwarfLines, pkgIdxSelf, 2},
+		{auxPcsp, pkgIdxNone, 0},
+		{auxPcfile, pkgIdxNone, 1},
+		{auxPcline, pkgIdxNone, 2},
+		{auxPcinline, pkgIdxNone, 3},
+		{auxFuncInfo, pkgIdxSelf, 4},
+		{auxDwarfInfo, pkgIdxSelf, 6},
+		{auxDwarfLines, pkgIdxSelf, 5},
+		{auxPcsp, pkgIdxNone, 5},
+		{auxPcfile, pkgIdxNone, 6},
+		{auxPcline, pkgIdxNone, 7},
+		{auxPcinline, pkgIdxNone, 8},
 	}
 	for i, w := range wantAux {
 		e := auxs[i*9:]
@@ -253,7 +283,7 @@ TEXT ·framed(SB), NOSPLIT, $8-0
 		t.Fatalf("AssembleFile: %v", err)
 	}
 	fn := img.Funcs[0]
-	pcs, vals := decodePCValues(pcspTable(fn))
+	pcs, vals := decodePCValues(pcspTable(fn, 1))
 	// Prologue: PUSHQ BP (1 byte, +8), MOVQ SP, BP (3 bytes, no change),
 	// SUBQ $8, SP (4 bytes, +16 in total); the RET's epilogue unwinds
 	// ADDQ $8, SP (+8) then POPQ BP (0).
@@ -349,7 +379,7 @@ func main() {
 	if err := os.WriteFile(filepath.Join(dir, "main.go"), []byte(mainSrc), 0o644); err != nil {
 		t.Fatal(err)
 	}
-	if err := os.WriteFile(filepath.Join(dir, "go.mod"), []byte("module goobjtest\n\ngo 1.26\n"), 0o644); err != nil {
+	if err := os.WriteFile(filepath.Join(dir, "go.mod"), []byte("module goobjtest\n\ngo 1.27\n"), 0o644); err != nil {
 		t.Fatal(err)
 	}
 
@@ -401,13 +431,12 @@ func main() {
 	if err != nil {
 		t.Fatalf("GOObject: %v", err)
 	}
-	if err := os.WriteFile(asmObj, obj, 0o644); err != nil {
-		t.Fatal(err)
-	}
 
 	// Rebuild the package archive with our object in place of the
 	// toolchain's (go tool pack has no replace-in-place that dedupes, so
-	// extract, substitute and repack).
+	// extract, substitute and repack).  The archive member holding the
+	// assembler's output is named after the asm object file, e.g.
+	// main_amd64.o.
 	extract := exec.Command(goBin, "tool", "pack", "x", pkgArch)
 	membersDir := filepath.Join(dir, "members")
 	if err := os.MkdirAll(membersDir, 0o755); err != nil {
@@ -417,6 +446,13 @@ func main() {
 	if out, err := extract.CombinedOutput(); err != nil {
 		t.Fatalf("pack x: %v\n%s", err, out)
 	}
+	member := filepath.Join(membersDir, filepath.Base(asmObj))
+	if err := os.Chmod(member, 0o644); err != nil {
+		t.Fatal(err)
+	}
+	if err := os.WriteFile(member, obj, 0o644); err != nil {
+		t.Fatal(err)
+	}
 	listCmd := exec.Command(goBin, "tool", "pack", "t", pkgArch)
 	listOut, err := listCmd.CombinedOutput()
 	if err != nil {

asm/goobjarm64.go

@@ -0,0 +1,84 @@
+// Copyright (c) 2026 Petr Balvín <opensource@petrbalvin.org> (https://petrbalvin.org)
+// SPDX-License-Identifier: BSD-3-Clause
+
+package asm
+
+import (
+	"bytes"
+	"fmt"
+	"os"
+	"os/exec"
+	"path/filepath"
+	"sync"
+)
+
+// GOObjectAARCH64 emits a GOOBJ object file for AArch64.  The layout is
+// the shared one in goobj.go — the toolchain preamble, the go120ld header
+// with its block offsets, the string table, the symbol definitions and the
+// reloc/aux/data index arrays — with the arm64 preamble, the MinLC of 4
+// for the pc-value deltas, and R_ADDRARM64 relocation types for the
+// ADRP+ADD/LDR/STR address pairs.
+func (img *Image) GOObjectAARCH64(pkgPath, srcPath string) ([]byte, error) {
+	pre, err := toolchainObjectPreambleAARCH64()
+	if err != nil {
+		return nil, err
+	}
+	return img.emitGOObject(pkgPath, srcPath, pre, 4, func(r Reloc) (uint16, uint8) {
+		return relocArm64Addr, 4
+	})
+}
+
+// arm64 relocation types (cmd/internal/objabi).  R_ADDRARM64 resolves an
+// ADRP+ADD/LDR/STR pair to a symbol's address.
+const (
+	relocArm64Addr = 9 // R_ADDRARM64
+)
+
+// toolchainObjectPreambleAARCH64 returns the "go object ...\n!\n" header
+// the installed go tool asm writes for arm64, captured by assembling a
+// one-instruction probe.
+var (
+	preambleAARCH64Once sync.Once
+	preambleAARCH64     []byte
+	preambleAARCH64Err  error
+)
+
+func toolchainObjectPreambleAARCH64() ([]byte, error) {
+	preambleAARCH64Once.Do(func() {
+		goBin, err := exec.LookPath("go")
+		if err != nil {
+			preambleAARCH64Err = fmt.Errorf("GOOBJ emission needs the Go toolchain: %w", err)
+			return
+		}
+		dir, err := os.MkdirTemp("", "gasm-preamble-arm64")
+		if err != nil {
+			preambleAARCH64Err = err
+			return
+		}
+		defer os.RemoveAll(dir)
+		src := filepath.Join(dir, "probe_arm64.s")
+		if err := os.WriteFile(src, []byte("TEXT \u00b7x(SB), $0-0\n\tRET\n"), 0o644); err != nil {
+			preambleAARCH64Err = err
+			return
+		}
+		obj := filepath.Join(dir, "probe.o")
+		cmd := exec.Command(goBin, "tool", "asm", "-p", "probe", "-o", obj, src)
+		cmd.Env = append(os.Environ(), "GOARCH=arm64")
+		if out, err := cmd.CombinedOutput(); err != nil {
+			preambleAARCH64Err = fmt.Errorf("probing the assembler for the object header: %v\n%s", err, out)
+			return
+		}
+		data, err := os.ReadFile(obj)
+		if err != nil {
+			preambleAARCH64Err = err
+			return
+		}
+		i := bytes.Index(data, []byte("\n!\n"))
+		if i < 0 || !bytes.HasPrefix(data[i+3:], []byte(goobjMagic)) {
+			preambleAARCH64Err = fmt.Errorf("unrecognised assembler object layout")
+			return
+		}
+		preambleAARCH64 = data[:i+3]
+	})
+	return preambleAARCH64, preambleAARCH64Err
+}

asm/goobjloong64.go

@@ -0,0 +1,91 @@
+// Copyright (c) 2026 Petr Balvín <opensource@petrbalvin.org> (https://petrbalvin.org)
+// SPDX-License-Identifier: BSD-3-Clause
+
+package asm
+
+import (
+	"bytes"
+	"fmt"
+	"os"
+	"os/exec"
+	"path/filepath"
+	"sync"
+)
+
+// GOObjectLOONG64 emits a GOOBJ object file for LoongArch.  The layout is
+// the shared one in goobj.go — the toolchain preamble, the go120ld header
+// with its block offsets, the string table, the symbol definitions and the
+// reloc/aux/data index arrays — with the loong64 preamble, the MinLC of 4
+// for the pc-value deltas, and R_LOONG64_ADDR_HI/LO relocation types for
+// the pcalau12i+addi.d address pairs.
+func (img *Image) GOObjectLOONG64(pkgPath, srcPath string) ([]byte, error) {
+	pre, err := toolchainObjectPreambleLOONG64()
+	if err != nil {
+		return nil, err
+	}
+	return img.emitGOObject(pkgPath, srcPath, pre, 4, func(r Reloc) (uint16, uint8) {
+		// A pcalau12i+addi.d pair: the high part carries
+		// R_LOONG64_ADDR_HI, the low part R_LOONG64_ADDR_LO.
+		if r.Kind == RelLoong64AddrLo {
+			return relocLoong64AddrLo, 4
+		}
+		return relocLoong64AddrHi, 4
+	})
+}
+
+// Loong64 relocation types (cmd/internal/objabi).  R_LOONG64_ADDR_HI
+// resolves the high 20 bits of a PC-relative address into pcalau12i;
+// R_LOONG64_ADDR_LO the low 12 bits into addi.d/ld/st.
+const (
+	relocLoong64AddrHi = 77 // R_LOONG64_ADDR_HI
+	relocLoong64AddrLo = 78 // R_LOONG64_ADDR_LO
+)
+
+// toolchainObjectPreambleLOONG64 returns the "go object ...\n!\n" header
+// the installed go tool asm writes for loong64, captured by assembling a
+// one-instruction probe (see toolchainObjectPreamble).
+var (
+	preambleLOONG64Once sync.Once
+	preambleLOONG64     []byte
+	preambleLOONG64Err  error
+)
+
+func toolchainObjectPreambleLOONG64() ([]byte, error) {
+	preambleLOONG64Once.Do(func() {
+		goBin, err := exec.LookPath("go")
+		if err != nil {
+			preambleLOONG64Err = fmt.Errorf("GOOBJ emission needs the Go toolchain: %w", err)
+			return
+		}
+		dir, err := os.MkdirTemp("", "gasm-preamble-loong64")
+		if err != nil {
+			preambleLOONG64Err = err
+			return
+		}
+		defer os.RemoveAll(dir)
+		src := filepath.Join(dir, "probe_loong64.s")
+		if err := os.WriteFile(src, []byte("TEXT \u00b7x(SB), $0-0\n\tRET\n"), 0o644); err != nil {
+			preambleLOONG64Err = err
+			return
+		}
+		obj := filepath.Join(dir, "probe.o")
+		cmd := exec.Command(goBin, "tool", "asm", "-p", "probe", "-o", obj, src)
+		cmd.Env = append(os.Environ(), "GOARCH=loong64")
+		if out, err := cmd.CombinedOutput(); err != nil {
+			preambleLOONG64Err = fmt.Errorf("probing the assembler for the object header: %v\n%s", err, out)
+			return
+		}
+		data, err := os.ReadFile(obj)
+		if err != nil {
+			preambleLOONG64Err = err
+			return
+		}
+		i := bytes.Index(data, []byte("\n!\n"))
+		if i < 0 || !bytes.HasPrefix(data[i+3:], []byte(goobjMagic)) {
+			preambleLOONG64Err = fmt.Errorf("unrecognised assembler object layout")
+			return
+		}
+		preambleLOONG64 = data[:i+3]
+	})
+	return preambleLOONG64, preambleLOONG64Err
+}

asm/goobjriscv.go

@@ -0,0 +1,95 @@
+// Copyright (c) 2026 Petr Balvín <opensource@petrbalvin.org> (https://petrbalvin.org)
+// SPDX-License-Identifier: BSD-3-Clause
+
+package asm
+
+import (
+	"bytes"
+	"fmt"
+	"os"
+	"os/exec"
+	"path/filepath"
+	"sync"
+)
+
+// GOObjectRISCV emits a GOOBJ object file for RISC-V.  The layout is the
+// shared one in goobj.go — the toolchain preamble, the go120ld header with
+// its block offsets, the string table, the symbol definitions and the
+// reloc/aux/data index arrays — with the RISC-V preamble, the MinLC of 2 for
+// the pc-value deltas, and the single R_RISCV_PCREL_ITYPE/STYPE relocation
+// per AUIPC pair, matching `go tool asm`'s model (each pair is one 8-byte
+// relocation, not the ELF HI20/LO12 pair).
+func (img *Image) GOObjectRISCV(pkgPath, srcPath string) ([]byte, error) {
+	pre, err := toolchainObjectPreambleRISCV()
+	if err != nil {
+		return nil, err
+	}
+	return img.emitGOObject(pkgPath, srcPath, pre, 2, func(r Reloc) (uint16, uint8) {
+		switch r.Kind {
+		case RelRISCVPCRELSType:
+			return relocRISCVPcrelStype, 8
+		case RelRISCVJal:
+			return relocRISCVJal, 4
+		default:
+			return relocRISCVPcrelItype, 8
+		}
+	})
+}
+
+// RISC-V relocation types (cmd/internal/objabi).  The Go linker applies
+// R_RISCV_PCREL_ITYPE/STYPE to an AUIPC + I/S-type instruction pair as a
+// single 8-byte field; R_RISCV_JAL covers a single 4-byte J-type instruction.
+const (
+	relocRISCVJal        = 59 // R_RISCV_JAL
+	relocRISCVPcrelItype = 62 // R_RISCV_PCREL_ITYPE
+	relocRISCVPcrelStype = 63 // R_RISCV_PCREL_STYPE
+)
+
+// toolchainObjectPreambleRISCV returns the "go object ...\n!\n" header
+// the installed go tool asm writes for riscv64, captured by assembling a
+// one-instruction probe (see toolchainObjectPreamble).
+var (
+	preambleRISCVOnce sync.Once
+	preambleRISCV     []byte
+	preambleRISCVErr  error
+)
+
+func toolchainObjectPreambleRISCV() ([]byte, error) {
+	preambleRISCVOnce.Do(func() {
+		goBin, err := exec.LookPath("go")
+		if err != nil {
+			preambleRISCVErr = fmt.Errorf("GOOBJ emission needs the Go toolchain: %w", err)
+			return
+		}
+		dir, err := os.MkdirTemp("", "gasm-preamble-riscv")
+		if err != nil {
+			preambleRISCVErr = err
+			return
+		}
+		defer os.RemoveAll(dir)
+		src := filepath.Join(dir, "probe_riscv64.s")
+		if err := os.WriteFile(src, []byte("TEXT \u00b7x(SB), $0-0\n\tRET\n"), 0o644); err != nil {
+			preambleRISCVErr = err
+			return
+		}
+		obj := filepath.Join(dir, "probe.o")
+		cmd := exec.Command(goBin, "tool", "asm", "-p", "probe", "-o", obj, src)
+		cmd.Env = append(os.Environ(), "GOARCH=riscv64")
+		if out, err := cmd.CombinedOutput(); err != nil {
+			preambleRISCVErr = fmt.Errorf("probing the assembler for the object header: %v\n%s", err, out)
+			return
+		}
+		data, err := os.ReadFile(obj)
+		if err != nil {
+			preambleRISCVErr = err
+			return
+		}
+		i := bytes.Index(data, []byte("\n!\n"))
+		if i < 0 || !bytes.HasPrefix(data[i+3:], []byte(goobjMagic)) {
+			preambleRISCVErr = fmt.Errorf("unrecognised assembler object layout")
+			return
+		}
+		preambleRISCV = data[:i+3]
+	})
+	return preambleRISCV, preambleRISCVErr
+}

asm/integration_test.go

@@ -0,0 +1,159 @@
+// Copyright (c) 2026 Petr Balvín <opensource@petrbalvin.org> (https://petrbalvin.org)
+// SPDX-License-Identifier: BSD-3-Clause
+
+//go:build integration
+
+// Package asm integration tests against the production go-libraries kernels.
+// These are excluded from the default test run (go test ./...) so that the
+// coverage numbers are identical locally and in CI, where go-libraries is
+// not checked out.  Run them explicitly with:  go test -tags=integration ./asm/
+package asm
+
+import (
+	"bytes"
+	"os"
+	"testing"
+
+	"golang.org/x/arch/x86/x86asm"
+
+	"sourcedock.dev/petrbalvin/gasm-devkit/parser"
+)
+
+// TestAssembleGoFlacAVX2Kernel assembles the whole production AVX2 kernel —
+// all functions plus the file-local mask24 constant — and checks that every
+// static-symbol load resolves to the right bytes in the image.
+func TestAssembleGoFlacAVX2Kernel(t *testing.T) {
+	path := "../../go-libraries/go-flac/avx2_amd64.s"
+	if _, err := os.Stat(path); err != nil {
+		t.Skip("go-libraries repository not present next to gasm-devkit")
+	}
+	src, err := os.ReadFile(path)
+	if err != nil {
+		t.Fatal(err)
+	}
+	f, errs := parser.Parse(path, string(src))
+	if len(errs) > 0 {
+		t.Fatalf("parse: %v", errs)
+	}
+	img, err := AssembleFile(f)
+	if err != nil {
+		t.Fatalf("AssembleFile: %v", err)
+	}
+	if len(img.Funcs) != 17 {
+		t.Errorf("functions = %d, want 17", len(img.Funcs))
+	}
+
+	// mask24 as the DATA directives define it.
+	mask := []byte{
+		0x00, 0x01, 0x02, 0x80, 0x03, 0x04, 0x05, 0x80,
+		0x06, 0x07, 0x08, 0x80, 0x09, 0x0a, 0x0b, 0x80,
+	}
+	image := img.Bytes()
+	if got := image[img.Symbols["mask24"] : img.Symbols["mask24"]+16]; !bytes.Equal(got, mask) {
+		t.Errorf("mask24 contents %x, want %x", got, mask)
+	}
+
+	// Every VMOVDQU mask24<>(SB), X15 (c5 7a 6f 3d + rel32, i.e. a VMOVDQU
+	// with a RIP-relative r/m) must land on the mask bytes within the image.
+	loads := 0
+	for _, fn := range img.Funcs {
+		code := img.Code[fn.Offset : fn.Offset+fn.Size]
+		for pc := 0; pc < len(code); {
+			inst, err := x86asm.Decode(code[pc:], 64)
+			if err != nil {
+				t.Fatalf("%s: decode at +%d: %v", fn.Name, pc, err)
+			}
+			// mod=00, rm=101 → RIP-relative.
+			if inst.Op == x86asm.VMOVDQU && inst.Len == 8 && code[pc+3]&0xC7 == 0x05 {
+				rel := int32(uint32(code[pc+4]) | uint32(code[pc+5])<<8 | uint32(code[pc+6])<<16 | uint32(code[pc+7])<<24)
+				target := fn.Offset + pc + 8 + int(rel)
+				if !bytes.Equal(image[target:target+16], mask) {
+					t.Errorf("%s: mask load at +%d lands on %x, want %x", fn.Name, pc, image[target:target+16], mask)
+				}
+				loads++
+			}
+			pc += inst.Len
+		}
+	}
+	if loads != 2 {
+		t.Errorf("mask loads found = %d, want 2", loads)
+	}
+}
+
+// TestAssembleGoFlacAVX512Kernel assembles the whole production AVX-512
+// kernel — all functions plus the file-global idx16 constant — and checks
+// that the static-symbol load resolves to the right bytes in the image.
+func TestAssembleGoFlacAVX512Kernel(t *testing.T) {
+	path := "../../go-libraries/go-flac/avx512_amd64.s"
+	if _, err := os.Stat(path); err != nil {
+		t.Skip("go-libraries repository not present next to gasm-devkit")
+	}
+	src, err := os.ReadFile(path)
+	if err != nil {
+		t.Fatal(err)
+	}
+	f, errs := parser.Parse(path, string(src))
+	if len(errs) > 0 {
+		t.Fatalf("parse: %v", errs)
+	}
+	img, err := AssembleFile(f)
+	if err != nil {
+		t.Fatalf("AssembleFile: %v", err)
+	}
+	if len(img.Funcs) != 10 {
+		t.Errorf("functions = %d, want 10", len(img.Funcs))
+	}
+
+	// idx16 as the DATA directives define it: dwords 1..16.
+	idx := make([]byte, 0, 64)
+	for i := 1; i <= 16; i++ {
+		idx = append(idx, byte(i), 0, 0, 0)
+	}
+	image := img.Bytes()
+	base := img.Symbols["idx16"]
+	if base == 0 {
+		t.Fatal("idx16 not laid out")
+	}
+	if got := image[base : base+64]; hexCompact(got) != hexCompact(idx) {
+		t.Errorf("idx16 contents %x, want %x", got, idx)
+	}
+
+	// The VMOVDQU32 idx16(SB), Z13 load (62 71 7e 48 6f 2d + rel32) must
+	// resolve to idx16 within the image.
+	loads := 0
+	for _, fn := range img.Funcs {
+		code := img.Code[fn.Offset : fn.Offset+fn.Size]
+		pat := []byte{0x62, 0x71, 0x7e, 0x48, 0x6f, 0x2d}
+		for pos := 0; ; {
+			i := indexOf(code[pos:], pat)
+			if i < 0 {
+				break
+			}
+			i += pos
+			rel := int32(uint32(code[i+6]) | uint32(code[i+7])<<8 | uint32(code[i+8])<<16 | uint32(code[i+9])<<24)
+			target := fn.Offset + i + 10 + int(rel)
+			if target != base {
+				t.Errorf("%s: idx16 load at +%d targets 0x%x, want 0x%x", fn.Name, i, target, base)
+			}
+			loads++
+			pos = i + 10
+		}
+	}
+	if loads != 1 {
+		t.Errorf("idx16 loads found = %d, want 1", loads)
+	}
+}
+
+// indexOf returns the index of the first occurrence of pat in b, or -1.
+func indexOf(b, pat []byte) int {
+	for i := 0; i+len(pat) <= len(b); i++ {
+		j := 0
+		for j < len(pat) && b[i+j] == pat[j] {
+			j++
+		}
+		if j == len(pat) {
+			return i
+		}
+	}
+	return -1
+}

asm/l64_goobj_test.go

@@ -0,0 +1,326 @@
+// Copyright (c) 2026 Petr Balvín <opensource@petrbalvin.org> (https://petrbalvin.org)
+// SPDX-License-Identifier: BSD-3-Clause
+
+package asm
+
+import (
+	"bytes"
+	"encoding/binary"
+	"os"
+	"os/exec"
+	"path/filepath"
+	"strings"
+	"testing"
+
+	"sourcedock.dev/petrbalvin/gasm-devkit/parser"
+)
+
+// TestGOObjectLOONG64Structure checks the emitted loong64 object's blocks:
+// the symbol tables, the function code bytes and the relocation wiring.
+func TestGOObjectLOONG64Structure(t *testing.T) {
+	f, errs := parser.Parse("k_loong64.s", `
+#include "textflag.h"
+
+TEXT ·add(SB), NOSPLIT, $0-24
+	MOVV a+0(FP), R4
+	MOVV b+8(FP), R5
+	ADDV R5, R4, R4
+	MOVV R4, ret+16(FP)
+	RET
+
+GLOBL ·table<>(SB), RODATA, $8
+DATA ·table<>+0(SB)/8, $0x1122334455667788
+`)
+	if len(errs) > 0 {
+		t.Fatalf("parse: %v", errs)
+	}
+	img, err := AssembleFileLOONG64(f)
+	if err != nil {
+		t.Fatalf("AssembleFileLOONG64: %v", err)
+	}
+	obj, err := img.GOObjectLOONG64("testpkg", "k_loong64.s")
+	if err != nil {
+		t.Fatalf("GOObjectLOONG64: %v", err)
+	}
+	v := openGoobj(t, obj)
+
+	// Package defs: the static GLOBL, then the FuncInfo and the two DWARF
+	// symbols (debug_line program, subprogram DIE).
+	defs := v.syms(blkSymdef)
+	if len(defs) != 4 {
+		t.Fatalf("symdefs = %d, want 4", len(defs))
+	}
+	if defs[0].name != "table" || defs[0].abi != 0xffff || defs[0].typ != kindSRODATA || defs[0].size != 8 {
+		t.Errorf("table symbol = %+v", defs[0])
+	}
+	if defs[1].name != "" || defs[1].typ != kindSDATA || defs[1].size != 28 {
+		t.Errorf("funcinfo symbol = %+v", defs[1])
+	}
+	if defs[2].name != "" || defs[2].typ != kindSDWARFLINES || defs[2].size == 0 {
+		t.Errorf("lines symbol = %+v", defs[2])
+	}
+	if defs[3].name != "" || defs[3].typ != kindSDWARFFCN || defs[3].size == 0 {
+		t.Errorf("DIE symbol = %+v", defs[3])
+	}
+
+	// Non-package defs: four pc tables and the function.
+	nps := v.syms(blkNonpkgdef)
+	if len(nps) != 5 {
+		t.Fatalf("nonpkgdefs = %d, want 5", len(nps))
+	}
+	fn := nps[4]
+	if fn.name != "testpkg.add" || fn.typ != kindSTEXT || fn.flag != symFlagNoSplit || fn.size != 20 {
+		t.Errorf("add symbol = %+v", fn)
+	}
+
+	// The function code: 20 bytes, the ground-truth encoding.  It sits
+	// after the GLOBL, FuncInfo, two DWARF symbols and four pc tables.
+	dataIdx := v.blk(blkDataIdx)
+	dataBlk := v.blk(blkData)
+	le := binary.LittleEndian
+	dOff := le.Uint32(dataIdx[8*4:])
+	code := dataBlk[dOff : dOff+20]
+	want := []byte{
+		0x64, 0x20, 0xc0, 0x28, // ld.d r4, 8(r3)
+		0x65, 0x40, 0xc0, 0x28, // ld.d r5, 16(r3)
+		0x84, 0x94, 0x10, 0x00, // add.d r4, r4, r5
+		0x64, 0x60, 0xc0, 0x29, // st.d r4, 24(r3)
+		0x20, 0x00, 0x00, 0x4c, // jirl r0, r1, 0
+	}
+	for i := range want {
+		if code[i] != want[i] {
+			t.Fatalf("code byte %d = %02x, want %02x", i, code[i], want[i])
+		}
+	}
+
+	// The debug_line program: LNE_set_address (the R_ADDR relocation
+	// carries the function address), then one row per line change — the
+	// TEXT is on line 4 (a leading blank line precedes the include), the
+	// instructions on lines 5–9 — an advance to the 20-byte end and an
+	// end-of-sequence.
+	linesOff := le.Uint32(dataIdx[4*2:])
+	lines := dataBlk[linesOff : linesOff+21]
+	wantLines := []byte{
+		0x00, 0x09, 0x02, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, // LNE_set_address
+		0x13,       // pc 0, line 5
+		0x38,       // pc 4, line 6
+		0x38,       // pc 8, line 7
+		0x38,       // pc 12, line 8
+		0x38,       // pc 16, line 9
+		0x02, 0x04, // advance_pc to 20
+		0x00, 0x01, 0x01, // end_sequence
+	}
+	for i := range wantLines {
+		if lines[i] != wantLines[i] {
+			t.Fatalf("lines byte %d = %02x, want %02x", i, lines[i], wantLines[i])
+		}
+	}
+
+	// The subprogram DIE: abbrev 3 (FUNCTION), the qualified name, the
+	// addrx low_pc slot (R_DWTXTADDR_U4), the size as high_pc, the
+	// call-frame-CFA frame base, decl file/line and the external flag.
+	dieOff := le.Uint32(dataIdx[4*3:])
+	die := dataBlk[dieOff : dieOff+27]
+	wantDie := []byte{
+		0x03,
+		't', 'e', 's', 't', 'p', 'k', 'g', '.', 'a', 'd', 'd', 0,
+		0x00, 0x00, 0x00, 0x00, // low_pc: addrx slot
+		0x14,       // high_pc: 20
+		0x01, 0x9c, // frame_base: DW_OP_call_frame_cfa
+		0x01, 0x00, 0x00, 0x00, // decl_file: 1
+		0x04, // decl_line: 4
+		0x01, // external
+		0x00, // end of children
+	}
+	for i := range wantDie {
+		if die[i] != wantDie[i] {
+			t.Fatalf("DIE byte %d = %02x, want %02x", i, die[i], wantDie[i])
+		}
+	}
+
+	// The DWARF symbols carry the function-address references: R_ADDR for
+	// the line program's set_address, R_DWTXTADDR_U4 for the DIE's addrx
+	// slot, both against the function's non-package index.  The reloc
+	// index counts relocations, not bytes.
+	relocIdx := v.blk(blkRelocIdx)
+	relocs := v.blk(blkReloc)
+	if le.Uint32(relocIdx[4*2:]) != 0 || le.Uint32(relocIdx[4*3:]) != 1 || le.Uint32(relocIdx[4*4:]) != 2 {
+		t.Fatalf("dwarf reloc index ranges: %d %d %d", le.Uint32(relocIdx[4*2:]), le.Uint32(relocIdx[4*3:]), le.Uint32(relocIdx[4*4:]))
+	}
+	lr := relocs[:23]
+	if int32(le.Uint32(lr[0:])) != 3 || lr[4] != 8 || le.Uint16(lr[5:]) != relocAddr ||
+		le.Uint32(lr[15:]) != pkgIdxNone || le.Uint32(lr[19:]) != 4 {
+		t.Errorf("lines reloc = %x", lr)
+	}
+	dr := relocs[23:46]
+	if int32(le.Uint32(dr[0:])) != 13 || dr[4] != 4 || le.Uint16(dr[5:]) != relocDWTXTADDRU4() ||
+		le.Uint32(dr[15:]) != pkgIdxNone || le.Uint32(dr[19:]) != 4 {
+		t.Errorf("die reloc = %x", dr)
+	}
+
+	// The pc-value deltas are in MinLC (4) units: the flat pcsp covers
+	// the whole 20-byte function with a delta of 5.
+	pcspOff := le.Uint32(dataIdx[4*4:])
+	if got := dataBlk[pcspOff : pcspOff+3]; !bytes.Equal(got, []byte{0x02, 0x05, 0x00}) {
+		t.Errorf("pcsp = %x, want 020500", got)
+	}
+}
+
+// TestGOObjectLOONG64Link cross-compiles a Go program with the gasm-produced
+// object substituted into the package archive, proving cmd/link accepts the
+// emitted GOOBJ.  The binary is not executed (no LoongArch host or qemu).
+// Skipped when no Go toolchain is available.
+func TestGOObjectLOONG64Link(t *testing.T) {
+	goBin, err := exec.LookPath("go")
+	if err != nil {
+		t.Skip("no Go toolchain available")
+	}
+	dir := t.TempDir()
+	asmSrc := `#include "textflag.h"
+TEXT ·add(SB), NOSPLIT, $0-24
+	MOVV a+0(FP), R4
+	MOVV b+8(FP), R5
+	ADDV R5, R4, R4
+	MOVV R4, ret+16(FP)
+	RET
+`
+	if err := os.WriteFile(filepath.Join(dir, "main_loong64.s"), []byte(asmSrc), 0o644); err != nil {
+		t.Fatal(err)
+	}
+	mainSrc := `package main
+
+func add(a, b int64) int64
+
+func main() {
+	if add(20, 22) != 42 {
+		panic("bad add")
+	}
+}
+`
+	if err := os.WriteFile(filepath.Join(dir, "main.go"), []byte(mainSrc), 0o644); err != nil {
+		t.Fatal(err)
+	}
+	if err := os.WriteFile(filepath.Join(dir, "go.mod"), []byte("module l64link\n\ngo 1.21\n"), 0o644); err != nil {
+		t.Fatal(err)
+	}
+
+	// Capture the cross build (GOARCH=loong64): the package archive and the
+	// link line.
+	build := exec.Command(goBin, "build", "-x", "-work", "-o", filepath.Join(dir, "prog"), ".")
+	build.Dir = dir
+	build.Env = append(os.Environ(), "GOARCH=loong64")
+	buildLog, err := build.CombinedOutput()
+	if err != nil {
+		t.Fatalf("baseline build: %v\n%s", err, buildLog)
+	}
+	var pkgArch, work, linkLine, asmObj string
+	for _, line := range strings.Split(string(buildLog), "\n") {
+		switch {
+		case strings.HasPrefix(line, "WORK="):
+			work = strings.TrimPrefix(line, "WORK=")
+		case strings.Contains(line, "/asm ") && strings.Contains(line, "main_loong64.s") && !strings.Contains(line, "-gensymabis"):
+			asmObj = fieldAfter(line, "-o")
+		case strings.Contains(line, "pack r") && strings.Contains(line, "_pkg_.a"):
+			pkgArch = strings.TrimSpace(strings.SplitN(line, "pack r", 2)[1])
+			pkgArch = strings.Fields(strings.SplitN(pkgArch, "#", 2)[0])[0]
+		case strings.Contains(line, "/link ") && strings.Contains(line, "-importcfg"):
+			linkLine = line
+		}
+	}
+	if pkgArch == "" || linkLine == "" || asmObj == "" {
+		t.Skip("could not locate the archive, asm output or link line in the build log")
+	}
+	pkgArch = strings.ReplaceAll(pkgArch, "$WORK", work)
+	// The archive member holding the assembler's output is named after the
+	// asm object file (main_loong64.o), as cmd/go packs it with `pack r`.
+	asmMember := filepath.Base(strings.ReplaceAll(asmObj, "$WORK", work))
+
+	// Assemble the same source with gasm and swap the object in.
+	pf, perrs := parser.Parse(filepath.Join(dir, "main_loong64.s"), asmSrc)
+	if len(perrs) > 0 {
+		t.Fatalf("parse: %v", perrs)
+	}
+	pimg, err := AssembleFileLOONG64(pf)
+	if err != nil {
+		t.Fatalf("AssembleFileLOONG64: %v", err)
+	}
+	obj, err := pimg.GOObjectLOONG64("main", filepath.Join(dir, "main_loong64.s"))
+	if err != nil {
+		t.Fatalf("GOObjectLOONG64: %v", err)
+	}
+
+	// Extract the archive, substitute the object member, repack.
+	membersDir := filepath.Join(dir, "members")
+	if err := os.MkdirAll(membersDir, 0o755); err != nil {
+		t.Fatal(err)
+	}
+	extract := exec.Command(goBin, "tool", "pack", "x", pkgArch)
+	extract.Dir = membersDir
+	extract.Env = append(os.Environ(), "GOARCH=loong64")
+	if out, err := extract.CombinedOutput(); err != nil {
+		t.Fatalf("pack x: %v\n%s", err, out)
+	}
+	// Substitute the gasm object for the assembler's archive member (pack
+	// extracts members read-only).
+	member := filepath.Join(membersDir, asmMember)
+	if err := os.Chmod(member, 0o644); err != nil {
+		t.Fatal(err)
+	}
+	if err := os.WriteFile(member, obj, 0o644); err != nil {
+		t.Fatal(err)
+	}
+	listCmd := exec.Command(goBin, "tool", "pack", "t", pkgArch)
+	listCmd.Env = append(os.Environ(), "GOARCH=loong64")
+	listOut, err := listCmd.CombinedOutput()
+	if err != nil {
+		t.Fatalf("pack t: %v\n%s", err, listOut)
+	}
+	newArch := filepath.Join(dir, "pkg.a")
+	args := []string{"tool", "pack", "c", newArch}
+	seen := map[string]bool{}
+	for _, m := range strings.Fields(string(listOut)) {
+		if seen[m] {
+			continue
+		}
+		seen[m] = true
+		if err := os.Chmod(filepath.Join(membersDir, m), 0o644); err != nil {
+			t.Fatal(err)
+		}
+		args = append(args, filepath.Join(membersDir, m))
+	}
+	pack := exec.Command(goBin, args...)
+	pack.Dir = membersDir
+	pack.Env = append(os.Environ(), "GOARCH=loong64")
+	if out, err := pack.CombinedOutput(); err != nil {
+		t.Fatalf("pack c: %v\n%s", err, out)
+	}
+
+	// Re-link with our archive in place of the toolchain's.  The link line
+	// carries a GOROOT assignment and $WORK placeholders; run it through the
+	// shell with the GOEXPERIMENT and GOARCH the toolchain expects (the
+	// linker compares the object header against its own, experiments
+	// included).
+	linkLine = strings.ReplaceAll(linkLine, "$WORK", work)
+	linkLine = strings.ReplaceAll(linkLine, filepath.Join(work, "b001", "_pkg_.a"), newArch)
+	linkLine = strings.ReplaceAll(linkLine, filepath.Join(work, "b001", "exe", "a.out"), filepath.Join(dir, "app2"))
+	link := exec.Command("sh", "-c", linkLine)
+	link.Dir = dir
+	goExp, _ := exec.Command(goBin, "env", "GOEXPERIMENT").Output()
+	link.Env = append(os.Environ(), "GOEXPERIMENT="+strings.TrimSpace(string(goExp)), "GOARCH=loong64")
+	if out, err := link.CombinedOutput(); err != nil {
+		t.Fatalf("link with gasm object: %v\n%s", err, out)
+	}
+
+	// The binary is not executed: there is no LoongArch host or qemu here.
+	// The link itself and the symbol table prove cmd/link accepted the gasm
+	// object and laid out the function.
+	nm := exec.Command(goBin, "tool", "nm", filepath.Join(dir, "app2"))
+	nm.Env = append(os.Environ(), "GOARCH=loong64")
+	nmOut, err := nm.CombinedOutput()
+	if err != nil {
+		t.Fatalf("nm gasm-linked binary: %v\n%s", err, nmOut)
+	}
+	if !strings.Contains(string(nmOut), "main.add") {
+		t.Errorf("main.add not found in linked binary:\n%s", nmOut)
+	}
+}

asm/link.go

@@ -41,6 +41,7 @@ type FuncLayout struct {
 	Labels  map[string]int // local labels, function-relative
 	Relocs  []Reloc        // static-symbol references, in emission order
 	Spadj   []SpadjStep    // stack-adjustment boundaries, ascending by PC
+	Lines   []LineEntry    // source-line table: byte offset → source line
 }
 
 // SpadjStep is one stack-adjustment boundary: Value is the SP delta from the
@@ -50,17 +51,61 @@ type SpadjStep struct {
 	Value int
 }
 
+// LineEntry maps a byte offset (function-relative) to a source line number.
+type LineEntry struct {
+	Offset int
+	Line   int
+}
+
+// LineAt returns the source line number for the given function-relative byte
+// offset, using a binary search on the line table.  Returns 0 if the offset
+// is before the first instruction or the table is empty.
+func (fl *FuncLayout) LineAt(offset int) int {
+	if len(fl.Lines) == 0 {
+		return 0
+	}
+	// Binary search: find the last entry with Offset <= offset.
+	lo, hi := 0, len(fl.Lines)-1
+	for lo < hi {
+		mid := (lo + hi + 1) / 2
+		if fl.Lines[mid].Offset <= offset {
+			lo = mid
+		} else {
+			hi = mid - 1
+		}
+	}
+	if fl.Lines[lo].Offset <= offset {
+		return fl.Lines[lo].Line
+	}
+	return 0
+}
+
 // Reloc is one static-symbol reference within a function body: the disp32
 // field at Off (function-relative) must reach the symbol plus Addend,
 // measured from After, the address just past the instruction.  An External
 // relocation names a symbol no GLOBL in the file defines; the object-file
 // emitters carry it into the output's relocation table.
+// RelocKind discriminates the type of relocation needed.
+type RelocKind int
+
+const (
+	RelPCRel32         RelocKind = iota // 32-bit PC-relative (amd64)
+	RelRISCVPCRELIType                  // R_RISCV_PCREL_ITYPE (AUIPC + I-type pair)
+	RelRISCVPCRELSType                  // R_RISCV_PCREL_STYPE (AUIPC + S-type pair)
+	RelRISCVJal                         // R_RISCV_JAL (J-type call)
+	RelPCRelAbs                         // 32-bit absolute (R_RISCV_32)
+	RelLoong64AddrHi                    // R_LOONG64_ADDR_HI (pcalau12i)
+	RelLoong64AddrLo                    // R_LOONG64_ADDR_LO (addi.d/ld/st)
+	RelArm64Addr                        // R_ADDRARM64 (ADRP + ADD/LDR/STR pair)
+)
+
 type Reloc struct {
 	Off      int
 	After    int
 	Name     string
 	Addend   int64
 	External bool
+	Kind     RelocKind
 }
 
 // DataSymbol describes one GLOBL symbol laid out in the data section.
@@ -110,7 +155,7 @@ func AssembleFile(f *ast.File) (*Image, error) {
 		if !ok {
 			continue
 		}
-		code, patches, labels, steps, err := assemble(t, link)
+		code, patches, labels, steps, lines, err := assemble(t, link)
 		if err != nil {
 			return nil, fmt.Errorf("%s: %w", t.Name.Name, err)
 		}
@@ -124,6 +169,7 @@ func AssembleFile(f *ast.File) (*Image, error) {
 			Args:   argsSize(t),
 			Line:   t.Pos().Line,
 			Labels: labels,
+			Lines:  lines,
 		}
 		for _, f := range t.Flags {
 			switch f {
@@ -189,11 +235,153 @@ func AssembleFile(f *ast.File) (*Image, error) {
 	return img, nil
 }
 
+// AssembleFileRISCV assembles every TEXT function of a parsed RISC-V file
+// and lays out its static symbols (GLOBL/DATA) in a data section behind the
+// code.  SB references in the code are encoded as AUIPC pairs with zero
+// immediates; the object-file emitters record relocations for the linker.
+func AssembleFileRISCV(f *ast.File) (*Image, error) {
+	dataSyms, err := collectData(f)
+	if err != nil {
+		return nil, err
+	}
+
+	img := &Image{Symbols: map[string]int{}}
+	for _, d := range f.Decls {
+		t, ok := d.(*ast.Text)
+		if !ok {
+			continue
+		}
+		code, labels, relocs, lines, spadj, err := assembleRISCV(t)
+		if err != nil {
+			return nil, fmt.Errorf("%s: %w", t.Name.Name, err)
+		}
+		fl := FuncLayout{
+			Name:   t.Name.Name,
+			Pkg:    t.Name.Pkg,
+			Static: t.Name.Static,
+			Offset: len(img.Code),
+			Size:   len(code),
+			Frame:  frameSize(t),
+			Args:   argsSize(t),
+			Line:   t.Pos().Line,
+			Labels: labels,
+			Lines:  lines,
+			Spadj:  spadj,
+			Relocs: relocs,
+		}
+		for _, f := range t.Flags {
+			switch f {
+			case "NOSPLIT":
+				fl.NoSplit = true
+			case "SPWRITE":
+				fl.SPWrite = true
+			}
+		}
+		img.Funcs = append(img.Funcs, fl)
+		img.Code = append(img.Code, code...)
+	}
+
+	// Lay out the data section behind the code, 16-aligned.
+	dataStart := len(img.Code)
+	for _, d := range dataSyms {
+		pos := dataStart + len(img.Data)
+		for pos%16 != 0 {
+			img.Data = append(img.Data, 0)
+			pos++
+		}
+		img.Symbols[d.name] = pos
+		img.Data = append(img.Data, d.buf...)
+		img.DataSyms = append(img.DataSyms, DataSymbol{
+			Name:   d.name,
+			Pkg:    d.pkg,
+			Offset: len(img.Data) - len(d.buf), // relative to the data section
+			Size:   d.size,
+			Static: d.static,
+			Rodata: d.rodata,
+			Dupok:  d.dupok,
+		})
+	}
+
+	return img, nil
+}
+
+// AssembleFileLOONG64 assembles every TEXT function of a parsed loong64 file
+// and lays out its static symbols (GLOBL/DATA) in a data section behind the
+// code.  SB references in the code are encoded as pcalau12i pairs with zero
+// immediates; the object-file emitters record R_LOONG64_ADDR_HI/LO
+// relocations for the linker.
+func AssembleFileLOONG64(f *ast.File) (*Image, error) {
+	dataSyms, err := collectData(f)
+	if err != nil {
+		return nil, err
+	}
+
+	img := &Image{Symbols: map[string]int{}}
+	for _, d := range f.Decls {
+		t, ok := d.(*ast.Text)
+		if !ok {
+			continue
+		}
+		code, labels, relocs, lines, spadj, err := assembleLOONG64(t)
+		if err != nil {
+			return nil, fmt.Errorf("%s: %w", t.Name.Name, err)
+		}
+		fl := FuncLayout{
+			Name:   t.Name.Name,
+			Pkg:    t.Name.Pkg,
+			Static: t.Name.Static,
+			Offset: len(img.Code),
+			Size:   len(code),
+			Frame:  frameSize(t),
+			Args:   argsSize(t),
+			Line:   t.Pos().Line,
+			Labels: labels,
+			Lines:  lines,
+			Spadj:  spadj,
+			Relocs: relocs,
+		}
+		for _, f := range t.Flags {
+			switch f {
+			case "NOSPLIT":
+				fl.NoSplit = true
+			case "SPWRITE":
+				fl.SPWrite = true
+			}
+		}
+		img.Funcs = append(img.Funcs, fl)
+		img.Code = append(img.Code, code...)
+	}
+
+	// Lay out the data section behind the code, 16-aligned.
+	dataStart := len(img.Code)
+	for _, d := range dataSyms {
+		pos := dataStart + len(img.Data)
+		for pos%16 != 0 {
+			img.Data = append(img.Data, 0)
+			pos++
+		}
+		img.Symbols[d.name] = pos
+		img.Data = append(img.Data, d.buf...)
+		img.DataSyms = append(img.DataSyms, DataSymbol{
+			Name:   d.name,
+			Pkg:    d.pkg,
+			Offset: len(img.Data) - len(d.buf), // relative to the data section
+			Size:   d.size,
+			Static: d.static,
+			Rodata: d.rodata,
+			Dupok:  d.dupok,
+		})
+	}
+
+	return img, nil
+}
+
 // dataSym is one GLOBL symbol and its DATA initialiser.
 type dataSym struct {
 	name   string
 	pkg    string
 	buf    []byte
+	size   int
 	static bool
 	rodata bool
 	dupok  bool
@@ -223,6 +411,7 @@ func collectData(f *ast.File) ([]dataSym, error) {
 				name:   name,
 				pkg:    dd.Name.Pkg,
 				buf:    make([]byte, size),
+				size:   size,
 				static: dd.Name.Static,
 			}
 			for _, f := range dd.Flags {

asm/link_test.go

@@ -4,13 +4,9 @@
 package asm
 
 import (
-	"bytes"
-	"os"
 	"strings"
 	"testing"
 
-	"golang.org/x/arch/x86/x86asm"
-
 	"sourcedock.dev/petrbalvin/gasm-devkit/parser"
 )
 
@@ -132,65 +128,3 @@ DATA x<>+0(SB)/4, $1
 		t.Errorf("single-function SB: error %v, want a file-level-assembly error", err)
 	}
 }
-
-// TestAssembleGoFlacAVX2Kernel assembles the whole production AVX2 kernel —
-// all functions plus the file-local mask24 constant — and checks that every
-// static-symbol load resolves to the right bytes in the image.  Skipped when
-// the sibling repository is not checked out.
-func TestAssembleGoFlacAVX2Kernel(t *testing.T) {
-	path := "../../go-libraries/go-flac/avx2_amd64.s"
-	if _, err := os.Stat(path); err != nil {
-		t.Skip("go-libraries repository not present next to gasm-devkit")
-	}
-	src, err := os.ReadFile(path)
-	if err != nil {
-		t.Fatal(err)
-	}
-	f, errs := parser.Parse(path, string(src))
-	if len(errs) > 0 {
-		t.Fatalf("parse: %v", errs)
-	}
-	img, err := AssembleFile(f)
-	if err != nil {
-		t.Fatalf("AssembleFile: %v", err)
-	}
-	if len(img.Funcs) != 17 {
-		t.Errorf("functions = %d, want 17", len(img.Funcs))
-	}
-
-	// mask24 as the DATA directives define it.
-	mask := []byte{
-		0x00, 0x01, 0x02, 0x80, 0x03, 0x04, 0x05, 0x80,
-		0x06, 0x07, 0x08, 0x80, 0x09, 0x0a, 0x0b, 0x80,
-	}
-	image := img.Bytes()
-	if got := image[img.Symbols["mask24"] : img.Symbols["mask24"]+16]; !bytes.Equal(got, mask) {
-		t.Errorf("mask24 contents %x, want %x", got, mask)
-	}
-
-	// Every VMOVDQU mask24<>(SB), X15 (c5 7a 6f 3d + rel32, i.e. a VMOVDQU
-	// with a RIP-relative r/m) must land on the mask bytes within the image.
-	loads := 0
-	for _, fn := range img.Funcs {
-		code := img.Code[fn.Offset : fn.Offset+fn.Size]
-		for pc := 0; pc < len(code); {
-			inst, err := x86asm.Decode(code[pc:], 64)
-			if err != nil {
-				t.Fatalf("%s: decode at +%d: %v", fn.Name, pc, err)
-			}
-			// mod=00, rm=101 → RIP-relative.
-			if inst.Op == x86asm.VMOVDQU && inst.Len == 8 && code[pc+3]&0xC7 == 0x05 {
-				rel := int32(uint32(code[pc+4]) | uint32(code[pc+5])<<8 | uint32(code[pc+6])<<16 | uint32(code[pc+7])<<24)
-				target := fn.Offset + pc + 8 + int(rel)
-				if !bytes.Equal(image[target:target+16], mask) {
-					t.Errorf("%s: mask load at +%d lands on %x, want %x", fn.Name, pc, image[target:target+16], mask)
-				}
-				loads++
-			}
-			pc += inst.Len
-		}
-	}
-	if loads != 2 {
-		t.Errorf("mask loads found = %d, want 2", loads)
-	}
-}

asm/loong64_encode.go

@@ -0,0 +1,595 @@
+// Copyright (c) 2026 Petr Balvín <opensource@petrbalvin.org> (https://petrbalvin.org)
+// SPDX-License-Identifier: BSD-3-Clause
+
+package asm
+
+// loong64 (LoongArch) instruction encoding.
+//
+// The encoder is data-driven: each mnemonic maps to an instruction format and
+// an opcode constant, and the format selects the bit layout.  The opcode
+// constants and formats are transcribed from the Go toolchain's own loong64
+// backend (cmd/internal/obj/loong64), so the emitted bytes match `go tool asm`
+// exactly — the ground-truth oracle for the verify suite.
+//
+// All LoongArch instructions are 32 bits, little-endian.  The formats used
+// here (per the LoongArch Volume I specification):
+//
+//	3R       opcode[31:15] | rk[4:0] | rj[4:0] | rd[4:0]
+//	2R       opcode[31:15] | rj[4:0] | rd[4:0]
+//	2RI12    opcode[31:22] | si12[11:0] | rj[4:0] | rd[4:0]
+//	2RI14    opcode[31:18] | si14[13:0] | rj[4:0] | rd[4:0]
+//	2RI16    opcode[31:22] | si16[15:0] | rj[4:0] | rd[4:0]
+//	2RI20    opcode[31:25] | si20[19:0] | rd[4:0]
+//	1RI21    opcode[31:26] | si21[20:0] | rj[4:0]   (BEQZ/BNEZ, B*Z, BC*Z)
+//	B/BL     opcode[31:26] | offs[25:0]
+//	4R       opcode[31:20] | r1[4:0] | r2[4:0] | r3[4:0] | r4[4:0]
+//	IRIR     opcode[31:22] | msb[4:0] | rj[4:0] | lsb[4:0] | rd[4:0]
+//	3RI2     opcode[31:17] | sa2[1:0] | rk[4:0] | rj[4:0] | rd[4:0]
+//
+// The opcode constants are pre-positioned (they include the zero bit ranges
+// of the immediate and register fields), mirroring the toolchain's OP_*
+// helpers, so each l64* function only ORs its fields in.
+
+// loong64RegNum returns the 5-bit register number for a LoongArch register
+// name: R0–R31 (integer), F0–F31 (floating point), FCC0–FCC7 (condition
+// flags), FCSR0–FCSR31 (control/status) and the ABI aliases the runtime's
+// assembly uses.  Returns -1 for an unrecognised name.
+func loong64RegNum(name string) int {
+	switch name {
+	case "R0", "ZERO":
+		return 0
+	case "R1", "RA", "LINK":
+		return 1
+	case "R2", "TP":
+		return 2
+	case "R3", "SP":
+		return 3
+	case "R4", "A0":
+		return 4
+	case "R5", "A1":
+		return 5
+	case "R6", "A2":
+		return 6
+	case "R7", "A3":
+		return 7
+	case "R8", "A4":
+		return 8
+	case "R9", "A5":
+		return 9
+	case "R10", "A6":
+		return 10
+	case "R11", "A7":
+		return 11
+	case "R12", "T0":
+		return 12
+	case "R13", "T1":
+		return 13
+	case "R14", "T2":
+		return 14
+	case "R15", "T3":
+		return 15
+	case "R16", "T4":
+		return 16
+	case "R17", "T5":
+		return 17
+	case "R18", "T6":
+		return 18
+	case "R19", "T7":
+		return 19
+	case "R20", "T8":
+		return 20
+	case "R21":
+		return 21
+	case "R22", "G", "g", "FP":
+		return 22
+	case "R23", "S0":
+		return 23
+	case "R24", "S1":
+		return 24
+	case "R25", "S2":
+		return 25
+	case "R26", "S3":
+		return 26
+	case "R27", "S4":
+		return 27
+	case "R28", "S5":
+		return 28
+	case "R29", "S6", "CTXT":
+		return 29
+	case "R30", "S7", "TMP":
+		return 30
+	case "R31", "S8":
+		return 31
+	}
+	// F0–F31, FCC0–FCC7, FCSR0–FCSR31.
+	if len(name) >= 4 && name[:4] == "FCSR" {
+		return loong64RegSpecial(name[4:], "FCSR", 31)
+	}
+	if len(name) >= 3 && name[:3] == "FCC" {
+		return loong64RegSpecial(name[3:], "FCC", 7)
+	}
+	if len(name) < 2 {
+		return -1
+	}
+	prefix, digits := name[:1], name[1:]
+	if digits[0] < '0' || digits[0] > '9' {
+		return -1
+	}
+	n := 0
+	for i := 0; i < len(digits); i++ {
+		if digits[i] < '0' || digits[i] > '9' {
+			return -1
+		}
+		n = n*10 + int(digits[i]-'0')
+	}
+	if prefix == "F" && n <= 31 {
+		return n
+	}
+	return -1
+}
+
+// loong64RegSpecial parses a numbered FCC/FCSR register.
+func loong64RegSpecial(digits, prefix string, max int) int {
+	if digits == "" {
+		return -1
+	}
+	n := 0
+	for i := 0; i < len(digits); i++ {
+		if digits[i] < '0' || digits[i] > '9' {
+			return -1
+		}
+		n = n*10 + int(digits[i]-'0')
+	}
+	if n <= max {
+		return n
+	}
+	return -1
+}
+
+// ---- format helpers ----
+
+// l64rrr encodes a 3R instruction: op | rk<<10 | rj<<5 | rd.
+func l64rrr(op uint32, rk, rj, rd int) uint32 {
+	return op | uint32(rk&0x1f)<<10 | uint32(rj&0x1f)<<5 | uint32(rd&0x1f)
+}
+
+// l64rr encodes a 2R instruction: op | rj<<5 | rd.
+func l64rr(op uint32, rj, rd int) uint32 {
+	return op | uint32(rj&0x1f)<<5 | uint32(rd&0x1f)
+}
+
+// l64irr encodes a 2RI12 instruction: op | si12<<10 | rj<<5 | rd.
+func l64irr(op uint32, imm, rj, rd int) uint32 {
+	return op | (uint32(imm)&0xFFF)<<10 | uint32(rj&0x1f)<<5 | uint32(rd&0x1f)
+}
+
+// l64irr14 encodes a 2RI14 instruction: op | si14<<10 | rj<<5 | rd.
+func l64irr14(op uint32, imm, rj, rd int) uint32 {
+	return op | (uint32(imm)&0x3FFF)<<10 | uint32(rj&0x1f)<<5 | uint32(rd&0x1f)
+}
+
+// l64irr16 encodes a 2RI16 instruction: op | si16<<10 | rj<<5 | rd.
+func l64irr16(op uint32, imm, rj, rd int) uint32 {
+	return op | (uint32(imm)&0xFFFF)<<10 | uint32(rj&0x1f)<<5 | uint32(rd&0x1f)
+}
+
+// l64ir encodes a 2RI20 instruction: op | si20<<5 | rd.
+func l64ir(op uint32, imm, rd int) uint32 {
+	return op | (uint32(imm)&0xFFFFF)<<5 | uint32(rd&0x1f)
+}
+
+// l64bbl encodes a B/BL instruction: op | offs[25:0], where offs is the
+// 4-byte-aligned word distance (the toolchain stores the shifted value).
+func l64bbl(op uint32, offs int) uint32 {
+	return op | (uint32(offs)&0xFFFF)<<10 | (uint32(offs)>>16)&0x3FF
+}
+
+// l64ir21 encodes a 1RI21 branch (BEQZ/BNEZ, BLTZ/BGEZ/BLEZ/BGTZ, BFPT/BFPF):
+// op | si21[15:0]<<10 | rj<<5 | si21[20:16].
+func l64ir21(op uint32, offs, rj int) uint32 {
+	v := uint32(offs)
+	return op | (v&0xFFFF)<<10 | uint32(rj&0x1f)<<5 | (v>>16)&0x1F
+}
+
+// l64rrrr encodes a 4R instruction: op | r1<<15 | r2<<10 | r3<<5 | r4.
+func l64rrrr(op uint32, r1, r2, r3, r4 int) uint32 {
+	return op | uint32(r1&0x1f)<<15 | uint32(r2&0x1f)<<10 | uint32(r3&0x1f)<<5 | uint32(r4&0x1f)
+}
+
+// l64irir encodes a BSTRINS/BSTRPICK instruction: op | msb<<16 | rj<<5 | lsb<<10 | rd.
+// The msb/lsb fields are 6 bits wide (0–63) and are validated by the caller.
+func l64irir(op uint32, msb, rj, lsb, rd int) uint32 {
+	return op | uint32(msb)<<16 | uint32(rj&0x1f)<<5 | uint32(lsb)<<10 | uint32(rd&0x1f)
+}
+
+// l64irrr encodes a 3RI2 instruction (ALSL): op | sa<<15 | rk<<10 | rj<<5 | rd.
+func l64irrr(op uint32, sa, rk, rj, rd int) uint32 {
+	return op | uint32(sa&0x3)<<15 | uint32(rk&0x1f)<<10 | uint32(rj&0x1f)<<5 | uint32(rd&0x1f)
+}
+
+// l64i15 encodes a no-operand system instruction with a 15-bit code field
+// (SYSCALL, BREAK, DBAR): op | code[14:0].
+func l64i15(op uint32, code int) uint32 {
+	return op | uint32(code)&0x7FFF
+}
+
+// l64irr5i encodes PRELD: op | offs<<10 | rj<<5 | hint.
+func l64irr5i(op uint32, offs, rj, hint int) uint32 {
+	return op | (uint32(offs)&0xFFF)<<10 | uint32(rj&0x1f)<<5 | uint32(hint&0x1f)
+}
+
+// l64wordLE encodes a uint32 as 4 little-endian bytes.
+func l64wordLE(w uint32) []byte {
+	return []byte{byte(w), byte(w >> 8), byte(w >> 16), byte(w >> 24)}
+}
+
+// l64WordsLE concatenates one or more instruction words as little-endian bytes.
+func l64WordsLE(ws ...uint32) []byte {
+	var out []byte
+	for _, w := range ws {
+		out = append(out, l64wordLE(w)...)
+	}
+	return out
+}
+
+// ---- instruction formats ----
+
+type l64Format uint8
+
+const (
+	l64Frrr    l64Format = iota // 3R (integer and FP arithmetic)
+	l64Frr                      // 2R
+	l64Firr                     // 2RI12 (arithmetic with 12-bit immediate)
+	l64Firr14                   // 2RI14 (ldptr/stptr)
+	l64Firr16                   // 2RI16 (addu16i.d)
+	l64Fir20                    // 2RI20 (lu12i.w, lu32i.d, pcalau12i, pcaddu12i)
+	l64Frrrr                    // 4R (fmadd/fmsub/fnmadd/fnmsub)
+	l64Firir                    // bstrins/bstrpick
+	l64Firrr                    // alsl
+	l64Fi15                     // syscall/break/dbar
+	l64Fam                      // atomic (3R with the AM field order)
+	l64Frdtime                  // rdtime (rd at bits [9:5], rj at bits [4:0])
+	l64Fshift                   // 2RI12 with a 5/6-bit shift immediate
+	l64Fpreld                   // preld (2RI12 + 5-bit hint)
+)
+
+// l64Enc is one instruction's encoding: its bit layout (format) and the
+// opcode constant, positioned at its exact bit range.
+type l64Enc struct {
+	format l64Format
+	op     uint32
+}
+
+// l64DualEnc holds both forms of a dual-form mnemonic: the 3R register form
+// and the 2RI12 immediate form (which is a shift for the shift mnemonics).
+type l64DualEnc struct {
+	rrr   uint32 // 3R register form
+	imm   uint32 // 2RI12 immediate form
+	shift bool   // the immediate form is a 5/6-bit shift amount
+}
+
+// l64DualTable maps the dual-form arithmetic/logic mnemonics to both
+// encodings; the assembler picks by operand kind.
+var l64DualTable = map[string]l64DualEnc{}
+
+// l64InstrTable maps LoongArch mnemonics (as the Go assembler spells them)
+// to their encoding.  SIMD (LSX/LASX: V*/XV*) instructions are not covered
+// yet; the base integer, memory and floating-point ISA is complete.
+var l64InstrTable = map[string]l64Enc{}
+
+func init() {
+	// 3R — integer.
+	rrr := map[string]uint32{
+		"ADD": 0x20 << 15, "ADDW": 0x20 << 15, "ADDV": 0x21 << 15, "ADDVU": 0x21 << 15,
+		"SUB": 0x22 << 15, "SUBW": 0x22 << 15, "SUBV": 0x23 << 15, "SUBVU": 0x23 << 15,
+		"SGT": 0x24 << 15, "SGTU": 0x25 << 15,
+		"MASKEQZ": 0x26 << 15, "MASKNEZ": 0x27 << 15, "SCQ": 0x070AE << 15,
+		"NOR": 0x28 << 15, "AND": 0x29 << 15, "OR": 0x2a << 15, "XOR": 0x2b << 15,
+		"ORN": 0x2c << 15, "ANDN": 0x2d << 15,
+		"SLL": 0x2e << 15, "SRL": 0x2f << 15, "SRA": 0x30 << 15,
+		"SLLV": 0x31 << 15, "SRLV": 0x32 << 15, "SRAV": 0x33 << 15,
+		"ROTR": 0x36 << 15, "ROTRV": 0x37 << 15,
+		"MUL": 0x38 << 15, "MULW": 0x38 << 15, "MULH": 0x39 << 15, "MULHU": 0x3a << 15,
+		"MULV": 0x3b << 15, "MULVU": 0x3b << 15, "MULHV": 0x3c << 15, "MULHVU": 0x3d << 15,
+		"MULWVW": 0x3e << 15, "MULWVWU": 0x3f << 15,
+		"DIV": 0x40 << 15, "DIVW": 0x40 << 15, "REM": 0x41 << 15, "REMW": 0x41 << 15,
+		"DIVU": 0x42 << 15, "DIVWU": 0x42 << 15, "REMU": 0x43 << 15, "REMWU": 0x43 << 15,
+		"DIVV": 0x44 << 15, "REMV": 0x45 << 15, "DIVVU": 0x46 << 15, "REMVU": 0x47 << 15,
+		"CRCWBW": 0x48 << 15, "CRCWHW": 0x49 << 15, "CRCWWW": 0x4a << 15, "CRCWVW": 0x4b << 15,
+		"CRCCWBW": 0x4c << 15, "CRCCWHW": 0x4d << 15, "CRCCWWW": 0x4e << 15, "CRCCWVW": 0x4f << 15,
+	}
+	// 3R — floating point.
+	rrr["MULF"] = 0x209 << 15
+	rrr["MULD"] = 0x20a << 15
+	rrr["DIVF"] = 0x20d << 15
+	rrr["DIVD"] = 0x20e << 15
+	rrr["SUBF"] = 0x205 << 15
+	rrr["SUBD"] = 0x206 << 15
+	rrr["ADDF"] = 0x201 << 15
+	rrr["ADDD"] = 0x202 << 15
+	rrr["CMPEQF"] = 0x0c1<<20 | 0x4<<15
+	rrr["CMPEQD"] = 0x0c2<<20 | 0x4<<15
+	rrr["CMPGED"] = 0x0c2<<20 | 0x7<<15
+	rrr["CMPGEF"] = 0x0c1<<20 | 0x7<<15
+	rrr["CMPGTD"] = 0x0c2<<20 | 0x3<<15
+	rrr["CMPGTF"] = 0x0c1<<20 | 0x3<<15
+	rrr["FMINF"] = 0x215 << 15
+	rrr["FMIND"] = 0x216 << 15
+	rrr["FMAXF"] = 0x211 << 15
+	rrr["FMAXD"] = 0x212 << 15
+	rrr["FMAXAF"] = 0x219 << 15
+	rrr["FMAXAD"] = 0x21a << 15
+	rrr["FMINAF"] = 0x21d << 15
+	rrr["FMINAD"] = 0x21e << 15
+	rrr["FSCALEBF"] = 0x221 << 15
+	rrr["FSCALEBD"] = 0x222 << 15
+	rrr["FCOPYSGF"] = 0x225 << 15
+	rrr["FCOPYSGD"] = 0x226 << 15
+	for m, op := range rrr {
+		l64InstrTable[m] = l64Enc{format: l64Frrr, op: op}
+	}
+
+	// 2R.
+	rr := map[string]uint32{
+		"CLOW": 0x4 << 10, "CLZW": 0x5 << 10, "CTOW": 0x6 << 10, "CTZW": 0x7 << 10,
+		"CLOV": 0x8 << 10, "CLZV": 0x9 << 10, "CTOV": 0xa << 10, "CTZV": 0xb << 10,
+		"REVB2H": 0xc << 10, "REVB4H": 0xd << 10, "REVB2W": 0xe << 10, "REVBV": 0xf << 10,
+		"REVH2W": 0x10 << 10, "REVHV": 0x11 << 10,
+		"BITREV4B": 0x12 << 10, "BITREV8B": 0x13 << 10, "BITREVW": 0x14 << 10, "BITREVV": 0x15 << 10,
+		"EXTWH": 0x16 << 10, "EXTWB": 0x17 << 10, "CPUCFG": 0x1b << 10,
+		"TRUNCFV": 0x46a9 << 10, "TRUNCDV": 0x46aa << 10, "TRUNCFW": 0x46a1 << 10, "TRUNCDW": 0x46a2 << 10,
+		"MOVWF": 0x4744 << 10, "MOVVF": 0x4746 << 10, "MOVWD": 0x4748 << 10, "MOVVD": 0x474a << 10,
+		"MOVFW": 0x46c1 << 10, "MOVDW": 0x46c2 << 10, "MOVFV": 0x46c9 << 10, "MOVDV": 0x46ca << 10,
+		"FRINTF": 0x4791 << 10, "FRINTD": 0x4792 << 10,
+		"MOVDF": 0x4646 << 10, "MOVFD": 0x4649 << 10,
+		"ABSF": 0x4501 << 10, "ABSD": 0x4502 << 10,
+		"MOVF": 0x4525 << 10, "MOVD": 0x4526 << 10,
+		"NEGF": 0x4505 << 10, "NEGD": 0x4506 << 10,
+		"SQRTF": 0x4511 << 10, "SQRTD": 0x4512 << 10,
+		"FLOGBF": 0x4509 << 10, "FLOGBD": 0x450a << 10,
+		"FCLASSF": 0x450d << 10, "FCLASSD": 0x450e << 10,
+		"FTINTRMWF": 0x4681 << 10, "FTINTRMWD": 0x4682 << 10,
+		"FTINTRMVF": 0x4689 << 10, "FTINTRMVD": 0x468a << 10,
+		"FTINTRPWF": 0x4691 << 10, "FTINTRPWD": 0x4692 << 10,
+		"FTINTRPVF": 0x4699 << 10, "FTINTRPVD": 0x469a << 10,
+		"FTINTRZWF": 0x46a1 << 10, "FTINTRZWD": 0x46a2 << 10,
+		"FTINTRZVF": 0x46a9 << 10, "FTINTRZVD": 0x46aa << 10,
+		"FTINTRNEWF": 0x46b1 << 10, "FTINTRNEWD": 0x46b2 << 10,
+		"FTINTRNEVF": 0x46b9 << 10, "FTINTRNEVD": 0x46ba << 10,
+	}
+	for m, op := range rr {
+		l64InstrTable[m] = l64Enc{format: l64Frr, op: op}
+	}
+	// RDTIME is a 2R instruction with rd and rj in swapped positions.
+	l64InstrTable["RDTIMELW"] = l64Enc{format: l64Frdtime, op: 0x18 << 10}
+	l64InstrTable["RDTIMEHW"] = l64Enc{format: l64Frdtime, op: 0x19 << 10}
+	l64InstrTable["RDTIMED"] = l64Enc{format: l64Frdtime, op: 0x1a << 10}
+
+	// The dual-form arithmetic mnemonics (register 3R + immediate 2RI12),
+	// selected by the operand kind; the shift mnemonics pair the 3R form
+	// with a 5/6-bit shift immediate.
+	for m, e := range map[string]l64DualEnc{
+		"ADD":   {rrr: 0x20 << 15, imm: 0x00a << 22},
+		"ADDW":  {rrr: 0x20 << 15, imm: 0x00a << 22},
+		"ADDV":  {rrr: 0x21 << 15, imm: 0x00b << 22},
+		"ADDVU": {rrr: 0x21 << 15, imm: 0x00b << 22},
+		"AND":   {rrr: 0x29 << 15, imm: 0x00d << 22},
+		"OR":    {rrr: 0x2a << 15, imm: 0x00e << 22},
+		"XOR":   {rrr: 0x2b << 15, imm: 0x00f << 22},
+		"SGT":   {rrr: 0x24 << 15, imm: 0x008 << 22},
+		"SGTU":  {rrr: 0x25 << 15, imm: 0x009 << 22},
+		"SLL":   {rrr: 0x2e << 15, imm: 0x00081 << 15, shift: true},
+		"SRL":   {rrr: 0x2f << 15, imm: 0x00089 << 15, shift: true},
+		"SRA":   {rrr: 0x30 << 15, imm: 0x00091 << 15, shift: true},
+		"ROTR":  {rrr: 0x36 << 15, imm: 0x00099 << 15, shift: true},
+		"SLLV":  {rrr: 0x31 << 15, imm: 0x0041 << 16, shift: true},
+		"SRLV":  {rrr: 0x32 << 15, imm: 0x0045 << 16, shift: true},
+		"SRAV":  {rrr: 0x33 << 15, imm: 0x0049 << 16, shift: true},
+		"ROTRV": {rrr: 0x37 << 15, imm: 0x004d << 16, shift: true},
+	} {
+		l64DualTable[m] = e
+	}
+
+	// 2RI12 — pure immediate arithmetic (LU52ID has no register form).
+	l64InstrTable["LU52ID"] = l64Enc{format: l64Firr, op: 0x00c << 22}
+	// ADDV16 (addu16i.d): 2RI16 with the immediate shifted right by 16.
+	l64InstrTable["ADDV16"] = l64Enc{format: l64Firr16, op: 0x4 << 26}
+
+	// 2RI14 — LL/SC are aliased by the Go assembler to the pointer loads and
+	// stores (ldptr/stptr), with the offset scaled by 4.
+	l64InstrTable["MOVWP"] = l64Enc{format: l64Firr14, op: 0x25 << 24} // stptr.w
+	l64InstrTable["MOVVP"] = l64Enc{format: l64Firr14, op: 0x27 << 24} // stptr.d
+	l64InstrTable["SC"] = l64Enc{format: l64Firr14, op: 0x21 << 24}    // sc.w
+	l64InstrTable["SCW"] = l64Enc{format: l64Firr14, op: 0x21 << 24}   // sc.w
+	l64InstrTable["SCV"] = l64Enc{format: l64Firr14, op: 0x23 << 24}   // sc.d
+	l64InstrTable["LL"] = l64Enc{format: l64Firr14, op: 0x20 << 24}    // ldptr.w (ll.w)
+	l64InstrTable["LLW"] = l64Enc{format: l64Firr14, op: 0x20 << 24}   // ldptr.w (ll.w)
+	l64InstrTable["LLV"] = l64Enc{format: l64Firr14, op: 0x22 << 24}   // ldptr.d (ll.d)
+
+	// 2RI20.
+	l64InstrTable["LU12IW"] = l64Enc{format: l64Fir20, op: 0x0a << 25}
+	l64InstrTable["LU32ID"] = l64Enc{format: l64Fir20, op: 0x0b << 25}
+	l64InstrTable["PCALAU12I"] = l64Enc{format: l64Fir20, op: 0x0d << 25}
+	l64InstrTable["PCADDU12I"] = l64Enc{format: l64Fir20, op: 0x0e << 25}
+	// LUI is the Plan 9 spelling of lu12i.w.
+	l64InstrTable["LUI"] = l64Enc{format: l64Fir20, op: 0x0a << 25}
+
+	// 4R — fused multiply-add.
+	rrrr := map[string]uint32{
+		"FMADDF": 0x81 << 20, "FMADDD": 0x82 << 20,
+		"FMSUBF": 0x85 << 20, "FMSUBD": 0x86 << 20,
+		"FNMADDF": 0x89 << 20, "FNMADDD": 0x8a << 20,
+		"FNMSUBF": 0x8d << 20, "FNMSUBD": 0x8e << 20,
+	}
+	for m, op := range rrrr {
+		l64InstrTable[m] = l64Enc{format: l64Frrrr, op: op}
+	}
+
+	// IRIR — bit-field insert/extract.
+	irir := map[string]uint32{
+		"BSTRINSW":  0x3<<21 | 0x0<<15,
+		"BSTRINSV":  0x2 << 22,
+		"BSTRPICKW": 0x3<<21 | 0x1<<15,
+		"BSTRPICKV": 0x3 << 22,
+	}
+	for m, op := range irir {
+		l64InstrTable[m] = l64Enc{format: l64Firir, op: op}
+	}
+
+	// 3RI2 — ALSL.
+	irrr := map[string]uint32{
+		"ALSLW": 0x2 << 17, "ALSLWU": 0x3 << 17, "ALSLV": 0x16 << 17,
+	}
+	for m, op := range irrr {
+		l64InstrTable[m] = l64Enc{format: l64Firrr, op: op}
+	}
+
+	// 0-operand system instructions.
+	l64InstrTable["SYSCALL"] = l64Enc{format: l64Fi15, op: 0x56 << 15}
+	l64InstrTable["BREAK"] = l64Enc{format: l64Fi15, op: 0x54 << 15}
+	l64InstrTable["DBAR"] = l64Enc{format: l64Fi15, op: 0x70e4 << 15}
+
+	// PRELD.
+	l64InstrTable["PRELD"] = l64Enc{format: l64Fpreld, op: 0x0ab << 22}
+
+	// Atomics — 3R with the AM field order (rk=value, rj=address, rd=result).
+	am := map[string]uint32{
+		"AMSWAPB": 0x070B8 << 15, "AMSWAPH": 0x070B9 << 15,
+		"AMSWAPW": 0x070C0 << 15, "AMSWAPV": 0x070C1 << 15,
+		"AMCASB": 0x070B0 << 15, "AMCASH": 0x070B1 << 15,
+		"AMCASW": 0x070B2 << 15, "AMCASV": 0x070B3 << 15,
+		"AMADDW": 0x070C2 << 15, "AMADDV": 0x070C3 << 15,
+		"AMANDW": 0x070C4 << 15, "AMANDV": 0x070C5 << 15,
+		"AMORW": 0x070C6 << 15, "AMORV": 0x070C7 << 15,
+		"AMXORW": 0x070C8 << 15, "AMXORV": 0x070C9 << 15,
+		"AMMAXW": 0x070CA << 15, "AMMAXV": 0x070CB << 15,
+		"AMMINW": 0x070CC << 15, "AMMINV": 0x070CD << 15,
+		"AMMAXWU": 0x070CE << 15, "AMMAXVU": 0x070CF << 15,
+		"AMMINWU": 0x070D0 << 15, "AMMINVU": 0x070D1 << 15,
+		"AMSWAPDBB": 0x070BC << 15, "AMSWAPDBH": 0x070BD << 15,
+		"AMSWAPDBW": 0x070D2 << 15, "AMSWAPDBV": 0x070D3 << 15,
+		"AMCASDBB": 0x070B4 << 15, "AMCASDBH": 0x070B5 << 15,
+		"AMCASDBW": 0x070B6 << 15, "AMCASDBV": 0x070B7 << 15,
+	}
+	for m, op := range am {
+		l64InstrTable[m] = l64Enc{format: l64Fam, op: op}
+	}
+}
+
+// l64FpMovTable maps (mnemonic, from-class, to-class) to the 2R opcode of the
+// register move between the integer and floating-point register banks — the
+// MOVW/MOVV specials the Go assembler accepts.
+var l64FpMovTable = map[string]uint32{
+	"MOVV.R.F":    0x452a << 10, // movgr2fr.d
+	"MOVV.R.FCC":  0x4536 << 10, // movgr2cf
+	"MOVV.R.FCSR": 0x4530 << 10, // movgr2fcsr
+	"MOVV.F.R":    0x452e << 10, // movfr2gr.d
+	"MOVV.F.FCC":  0x4534 << 10, // movfr2cf
+	"MOVV.FCC.R":  0x4537 << 10, // movcf2gr
+	"MOVV.FCC.F":  0x4535 << 10, // movcf2fr
+	"MOVV.FCSR.R": 0x4532 << 10, // movfcsr2gr
+	"MOVW.R.F":    0x4529 << 10, // movgr2fr.w
+	"MOVW.F.R":    0x452d << 10, // movfr2gr.s
+}
+
+// l64branchTable holds the 16-bit branch and jump encodings (2RI16).
+var l64branchTable = map[string]uint32{
+	"BEQ":  0x16 << 26,
+	"BNE":  0x17 << 26,
+	"BLT":  0x18 << 26,
+	"BGE":  0x19 << 26,
+	"BLTU": 0x1a << 26,
+	"BGEU": 0x1b << 26,
+	"JIRL": 0x13 << 26,
+}
+
+// l64branch21Table holds the single-register branches with 21-bit offsets:
+// the negative opcode constants the toolchain uses for the short forms.
+var l64branch21Table = map[string]uint32{
+	"BEQZ": 0x10 << 26, // beq r0, rj → beqz
+	"BNEZ": 0x11 << 26, // bne r0, rj → bnez
+	"BLTZ": 0x18 << 26, // blt rj, r0 → bltz
+	"BGEZ": 0x19 << 26, // bge rj, r0 → bgez
+	"BGTZ": 0x18 << 26, // blt r0, rj → bgtz
+	"BLEZ": 0x19 << 26, // bge r0, rj → blez
+	"BFPT": 0x12<<26 | 0x1<<8,
+	"BFPF": 0x12<<26 | 0x0<<8,
+}
+
+// l64jumpTable maps the jump pseudo-instructions and their aliases to the
+// B/BL opcode constants.
+var l64jumpTable = map[string]uint32{
+	"JMP":  0x14 << 26, // b
+	"B":    0x14 << 26, // b
+	"JAL":  0x15 << 26, // bl
+	"CALL": 0x15 << 26, // bl
+	"BL":   0x15 << 26, // bl
+}
+
+// l64loadStoreTable maps the MOV width mnemonics to their load and store
+// 2RI12 opcodes.  The load opcode is the negated store opcode, exactly as
+// the toolchain derives it.
+var l64loadStoreTable = map[string]struct{ ld, st uint32 }{
+	"MOVB":  {0x0a0 << 22, 0x0a4 << 22},
+	"MOVH":  {0x0a1 << 22, 0x0a5 << 22},
+	"MOVW":  {0x0a2 << 22, 0x0a6 << 22},
+	"MOVV":  {0x0a3 << 22, 0x0a7 << 22},
+	"MOVBU": {0x0a8 << 22, 0x0a4 << 22},
+	"MOVHU": {0x0a9 << 22, 0x0a5 << 22},
+	"MOVWU": {0x0aa << 22, 0x0a6 << 22},
+	"MOVF":  {0x0ac << 22, 0x0ad << 22},
+	"MOVD":  {0x0ae << 22, 0x0af << 22},
+}
+
+// l64movRegTable maps a register-to-register MOV mnemonic to its expansion,
+// matching the toolchain's case-1 encoding: MOVB → ext.w.b, MOVH → ext.w.h,
+// MOVW → sll.w, MOVV → or, MOVBU → andi.  MOVHU/MOVWU expand to bstrpick.d
+// and are handled separately in the assembler.
+type l64MovRegEnc struct {
+	rr  bool   // 2R format (ext.w.b/ext.w.h)
+	op  uint32 // opcode constant (rr forms) or 3R/2RI12 opcode
+	imm int    // 2RI12 immediate for MOVBU's andi
+}
+
+var l64movRegTable = map[string]l64MovRegEnc{
+	"MOVB":  {true, 0x17 << 10, 0},      // ext.w.b rd, rj
+	"MOVH":  {true, 0x16 << 10, 0},      // ext.w.h rd, rj
+	"MOVW":  {false, 0x2e << 15, 0},     // sll.w rd, rj, r0
+	"MOVV":  {false, 0x2a << 15, 0},     // or rd, rj, r0
+	"MOVBU": {false, 0x00d << 22, 0xff}, // andi rd, rj, $0xff
+}
+
+// l64movFpRegTable maps a floating-point register move mnemonic to its 2R
+// opcode (fmov.s / fmov.d), used when both operands are F registers.
+var l64movFpRegTable = map[string]uint32{
+	"MOVF": 0x4525 << 10,
+	"MOVD": 0x4526 << 10,
+}
+
+// l64RegClass discriminates integer (R), floating-point (F) and condition
+// (FCC) registers for the MOV pseudo-instruction's register-move encoding.
+type l64RegClass int
+
+const (
+	l64ClsNone l64RegClass = iota
+	l64ClsGR
+	l64ClsFP
+	l64ClsFCC
+	l64ClsFCSR
+)
+
+// loong64RegClass reports the register class of a register operand name.
+func loong64RegClass(name string) l64RegClass {
+	switch {
+	case name == "":
+		return l64ClsNone
+	case len(name) >= 3 && name[:3] == "FCC":
+		return l64ClsFCC
+	case len(name) >= 4 && name[:4] == "FCSR":
+		return l64ClsFCSR
+	case name[0] == 'F':
+		return l64ClsFP
+	default:
+		return l64ClsGR
+	}
+}

asm/loong64_encode_test.go

@@ -0,0 +1,293 @@
+// Copyright (c) 2026 Petr Balvín <opensource@petrbalvin.org> (https://petrbalvin.org)
+// SPDX-License-Identifier: BSD-3-Clause
+
+package asm
+
+import (
+	"bytes"
+	"encoding/binary"
+	"testing"
+
+	"sourcedock.dev/petrbalvin/gasm-devkit/ast"
+	"sourcedock.dev/petrbalvin/gasm-devkit/parser"
+)
+
+// firstTextLOONG64 parses assembly source and returns the first TEXT body.
+func firstTextLOONG64(t *testing.T, src string) *ast.Text {
+	t.Helper()
+	f, errs := parser.Parse("f_loong64.s", src)
+	if len(errs) > 0 {
+		t.Fatalf("parse: %v", errs)
+	}
+	for _, d := range f.Decls {
+		if fn, ok := d.(*ast.Text); ok {
+			return fn
+		}
+	}
+	t.Fatal("no TEXT found")
+	return nil
+}
+
+// assembleLOONG64Helper assembles one TEXT function and returns its bytes.
+func assembleLOONG64Helper(t *testing.T, fn *ast.Text) []byte {
+	t.Helper()
+	code, _, _, _, _, err := assembleLOONG64(fn)
+	if err != nil {
+		t.Fatalf("assemble: %v", err)
+	}
+	return code
+}
+
+// wantWords checks that code matches the expected little-endian words.
+func wantWords(t *testing.T, code []byte, want ...uint32) {
+	t.Helper()
+	got := make([]uint32, 0, len(code)/4)
+	for i := 0; i+4 <= len(code); i += 4 {
+		got = append(got, binary.LittleEndian.Uint32(code[i:]))
+	}
+	if len(got) != len(want) {
+		t.Fatalf("word count = %d, want %d\ncode: % x", len(got), len(want), code)
+	}
+	for i := range want {
+		if got[i] != want[i] {
+			t.Errorf("word %d = %08x, want %08x", i, got[i], want[i])
+		}
+	}
+}
+
+func TestLOONG64_add(t *testing.T) {
+	fn := firstTextLOONG64(t, `#include "textflag.h"
+TEXT ·add(SB), NOSPLIT, $0-24
+	MOVV a+0(FP), R4
+	MOVV b+8(FP), R5
+	ADDV R5, R4, R4
+	MOVV R4, ret+16(FP)
+	RET
+`)
+	code := assembleLOONG64Helper(t, fn)
+	// 5 instructions: two ld.d, add.d, st.d, jirl r0, r1, 0.
+	wantWords(t, code,
+		0x28C02064, // ld.d r4, 8(r3)
+		0x28C04065, // ld.d r5, 16(r3)
+		0x00109484, // add.d r4, r4, r5
+		0x29C06064, // st.d r4, 24(r3)
+		0x4C000020, // jirl r0, r1, 0
+	)
+}
+
+func TestLOONG64_arithmetic(t *testing.T) {
+	fn := firstTextLOONG64(t, `#include "textflag.h"
+TEXT ·arith(SB), NOSPLIT, $0
+	ADDV R4, R5, R6
+	SUBV R7, R8, R9
+	MULV R10, R11, R12
+	DIVV R13, R14, R15
+	AND R16, R17, R18
+	OR R18, R19, R20
+	XOR R20, R21, R2
+	SLLV R2, R23, R24
+	SRLV R24, R25, R26
+	SRAV R26, R27, R28
+	RET
+`)
+	code := assembleLOONG64Helper(t, fn)
+	wantWords(t, code,
+		0x001090A6, // add.d r6, r5, r4
+		0x00119D09, // sub.d r9, r8, r7
+		0x001DA96C, // mul.d r12, r11, r10
+		0x002235CF, // div.d r15, r14, r13
+		0x0014C232, // and r18, r17, r16
+		0x00154A74, // or r20, r19, r18
+		0x0015D2A2, // xor r2, r21, r20
+		0x00188AF8, // sll.d r24, r23, r2
+		0x0019633A, // srl.d r26, r25, r24
+		0x0019EB7C, // sra.d r28, r27, r26
+		0x4C000020, // jirl r0, r1, 0
+	)
+}
+
+func TestLOONG64_immediates(t *testing.T) {
+	fn := firstTextLOONG64(t, `#include "textflag.h"
+TEXT ·imm(SB), NOSPLIT, $0
+	ADDV $42, R4, R5
+	ADDV $-8, R6
+	AND $0xff, R7, R8
+	OR $1, R9, R10
+	SGT $100, R13, R14
+	SLLV $4, R15, R16
+	MOVV $0x12345, R17
+	MOVV $0, R18
+	MOVW $0, R19
+	RET
+`)
+	code := assembleLOONG64Helper(t, fn)
+	wantWords(t, code,
+		0x02C0A885, // addi.d r5, r4, 42
+		0x02FFE0C6, // addi.d r6, r6, -8
+		0x0343FCE8, // andi r8, r7, 0xff
+		0x0380052A, // ori r10, r9, 1
+		0x020191AE, // slti r14, r13, 100
+		0x004111F0, // slli.d r16, r15, 4
+		0x14000251, // lu12i.w r17, 0x12
+		0x038D1631, // ori r17, r17, 0x345
+		0x00150012, // or r18, r0, r0
+		0x00170013, // sll.w r19, r0, r0
+		0x4C000020, // jirl r0, r1, 0
+	)
+}
+
+func TestLOONG64_loadStore(t *testing.T) {
+	fn := firstTextLOONG64(t, `#include "textflag.h"
+TEXT ·mem(SB), NOSPLIT, $0
+	MOVV (R4), R5
+	MOVV R5, (R6)
+	MOVW 8(R7), R8
+	MOVB R9, -4(R10)
+	MOVV (R11)(R12), R13
+	MOVV R14, (R15)(R16)
+	RET
+`)
+	code := assembleLOONG64Helper(t, fn)
+	wantWords(t, code,
+		0x28C00085, // ld.d r5, 0(r4)
+		0x29C000C5, // st.d r5, 0(r6)
+		0x288020E8, // ld.w r8, 8(r7)
+		0x293FF149, // st.b r9, -4(r10)
+		0x380C316D, // ldx.d r13, r11, r12
+		0x381C41EE, // stx.d r14, r15, r16
+		0x4C000020, // jirl r0, r1, 0
+	)
+}
+
+func TestLOONG64_branches(t *testing.T) {
+	fn := firstTextLOONG64(t, `#include "textflag.h"
+TEXT ·br(SB), NOSPLIT, $0
+	BEQ R4, R5, done
+	BNE R6, R7, skip
+	BLT R8, R9, done
+	BGE R10, R11, done
+	BLTU R12, R13, done
+	BGEU R14, R15, done
+skip:
+	JMP done
+done:
+	RET
+`)
+	code := assembleLOONG64Helper(t, fn)
+	// skip is at 0x18 (6 words), done at 0x1c.
+	wantWords(t, code,
+		0x58001C85, // beq r5, r4, +7
+		0x5C0018C7, // bne r7, r6, +6
+		0x60001509, // blt r9, r8, +5
+		0x6400114B, // bge r11, r10, +4
+		0x68000D8D, // bltu r13, r12, +3
+		0x6C0009CF, // bgeu r15, r14, +2
+		0x50000400, // b done (+1, chain-folded through skip)
+		0x4C000020, // jirl r0, r1, 0
+	)
+}
+
+func TestLOONG64_frame(t *testing.T) {
+	fn := firstTextLOONG64(t, `#include "textflag.h"
+TEXT ·f(SB), NOSPLIT, $32-8
+	MOVV R4, R5
+	MOVV arg+0(FP), R6
+	MOVV R7, local-8(SP)
+	MOVV local-8(SP), R8
+	MOVV R9, ret+0(FP)
+	RET
+`)
+	code := assembleLOONG64Helper(t, fn)
+	// autosize = align8(32+8) = 40; prologue stores LR at -40(SP),
+	// opens the frame, stores LR again at 0(SP).  The function is a leaf
+	// (no calls), so the epilogue skips the LR restore.  FP args are at
+	// autosize+8; SP locals at autosize+offset.
+	wantWords(t, code,
+		0x29FF6061, // st.d r1, -40(r3)
+		0x02FF6063, // addi.d r3, r3, -40
+		0x29C00061, // st.d r1, 0(r3)
+		0x00150085, // or r5, r4, r0
+		0x28C0C066, // ld.d r6, 48(r3)     arg+0(FP) → 0+40+8
+		0x29C08067, // st.d r7, 32(r3)     local-8(SP) → 40-8
+		0x28C08068, // ld.d r8, 32(r3)
+		0x29C0C069, // st.d r9, 48(r3)     ret+0(FP) → 0+40+8
+		0x02C0A063, // addi.d r3, r3, 40
+		0x4C000020, // jirl r0, r1, 0
+	)
+}
+
+func TestLOONG64_jumpChain(t *testing.T) {
+	fn := firstTextLOONG64(t, `#include "textflag.h"
+TEXT ·jc(SB), NOSPLIT, $0
+	JMP a
+a:
+	JMP b
+b:
+	RET
+`)
+	code := assembleLOONG64Helper(t, fn)
+	wantWords(t, code,
+		0x50000800, // b +2 (a, chain-folded to b)
+		0x50000400, // b +1 (b)
+		0x4C000020, // jirl r0, r1, 0
+	)
+}
+
+func TestLOONG64_dconClasses(t *testing.T) {
+	cases := []struct {
+		v    int64
+		word int // expected word count
+	}{
+		{0x123456789, 3},        // lu12i.w + ori + lu32i.d
+		{-1, 2},                 // addi.d + lu52i.d (the MOV path handles -1 earlier)
+		{0x1000000000000, 2},    // addi.w + lu32i.d
+		{0x123456789abcdef0, 4}, // full sequence
+		{0xFFFFFFFFF, 2},        // lu12i.w + ori
+		{0x1234567800000000, 3}, // addi.w + lu32i.d + lu52i.d
+	}
+	for _, c := range cases {
+		if n := len(l64DconMovWords(0, c.v)); n != c.word {
+			t.Errorf("0x%x: %d words, want %d", c.v, n, c.word)
+		}
+	}
+}
+
+func TestLOONG64_regNames(t *testing.T) {
+	cases := map[string]int{
+		"R0": 0, "R31": 31, "F0": 0, "F31": 31, "FCC0": 0, "FCC7": 7,
+		"FCSR0": 0, "FCSR3": 3, "ZERO": 0, "RA": 1, "SP": 3, "g": 22, "G": 22,
+		"R32": -1, "FCC8": -1, "X0": -1, "R": -1, "TMP": 30, "CTXT": 29,
+	}
+	for name, want := range cases {
+		if got := loong64RegNum(name); got != want {
+			t.Errorf("loong64RegNum(%q) = %d, want %d", name, got, want)
+		}
+	}
+}
+
+func TestLOONG64_bytesEqualGroundTruth(t *testing.T) {
+	// A spot-check that assembleLOONG64 emits the same bytes the Go
+	// toolchain does for a small kernel (the full comparison lives in
+	// verify's TestGroundTruthLOONG64).
+	src := `#include "textflag.h"
+TEXT ·k(SB), NOSPLIT, $0-0
+	ADDV R4, R5, R6
+	MOVV $0x100000, R7
+	BEQ R6, R7, done
+	JMP done
+done:
+	RET
+`
+	fn := firstTextLOONG64(t, src)
+	code := assembleLOONG64Helper(t, fn)
+	want := []byte{
+		0xa6, 0x90, 0x10, 0x00, // add.d r6, r5, r4
+		0x07, 0x20, 0x00, 0x14, // lu12i.w r7, 0x100
+		0xc7, 0x08, 0x00, 0x58, // beq r7, r6, +2 (done)
+		0x00, 0x04, 0x00, 0x50, // b +1 (done)
+		0x20, 0x00, 0x00, 0x4c, // jirl r0, r1, 0
+	}
+	if !bytes.Equal(code, want) {
+		t.Errorf("code = % x\nwant % x", code, want)
+	}
+}

asm/loong64_frame.go

@@ -0,0 +1,129 @@
+// Copyright (c) 2026 Petr Balvín <opensource@petrbalvin.org> (https://petrbalvin.org)
+// SPDX-License-Identifier: BSD-3-Clause
+
+package asm
+
+import (
+	"strings"
+
+	"sourcedock.dev/petrbalvin/gasm-devkit/ast"
+)
+
+// Loong64 frame mapping, matching the Go toolchain's loong64 backend.
+//
+// Go's loong64 functions have no frame pointer: FP and SP are synthetic
+// registers resolved against the hardware stack pointer (R3) and the frame
+// size.  The return address lives in R1 (the link register).
+//
+// The autosize is the real stack adjustment: the declared local frame plus
+// the 8 bytes for the saved link register, rounded up to a multiple of 8
+// (the toolchain aligns frames with `if autosize&4 != 0 { autosize += 4 }`).
+// A leaf function (no calls) with a zero frame gets no prologue at all.
+//
+// Prologue (autosize > 0), byte-identical to the toolchain:
+//
+//	MOVV R1, -autosize(R3)   // save LR below the new SP (traceback-safe)
+//	ADDV $-autosize, R3      // open the frame
+//	MOVV R1, 0(R3)           // save LR again at SP (signal-safety)
+//
+// Epilogue: MOVV 0(R3), R1; ADDV $autosize, R3 (non-leaf only for the LR
+// restore); the RET's jirl r0, r1, 0 follows.
+
+// loong64FrameInfo holds the frame layout derived from a TEXT directive.
+type loong64FrameInfo struct {
+	autosize int  // the real SP adjustment (locals + saved LR, aligned)
+	frame    int  // the declared $framesize
+	args     int  // the declared -argsize
+	noSplit  bool // the NOSPLIT flag
+	leaf     bool // no call instructions in the body
+}
+
+// loong64ComputeFrame derives the frame layout for a TEXT function.
+func loong64ComputeFrame(t *ast.Text) loong64FrameInfo {
+	fi := loong64FrameInfo{
+		frame: frameSize(t),
+		args:  argsSize(t),
+	}
+	for _, f := range t.Flags {
+		if f == "NOSPLIT" {
+			fi.noSplit = true
+		}
+	}
+	fi.leaf = loong64IsLeaf(t)
+	if fi.frame != 0 {
+		fi.autosize = fi.frame + 8 // space for the saved LR
+		if fi.autosize&4 != 0 {
+			fi.autosize += 4
+		}
+	} else if !fi.leaf {
+		// A zero-frame non-leaf function still opens an 8-byte frame for LR.
+		fi.autosize = 8
+	}
+	return fi
+}
+
+// loong64IsLeaf reports whether a function contains no call instructions
+// (JAL/BL/CALL), matching the toolchain's LEAF mark, which drives the frame
+// and the epilogue shape.
+func loong64IsLeaf(t *ast.Text) bool {
+	for _, stmt := range t.Body {
+		in, ok := stmt.(*ast.Instr)
+		if !ok {
+			continue
+		}
+		switch strings.ToUpper(in.Mnemonic.Text) {
+		case "JAL", "CALL", "BL":
+			return false
+		}
+	}
+	return true
+}
+
+// loong64Prologue returns the prologue bytes for a loong64 function.
+func loong64Prologue(fi loong64FrameInfo) []byte {
+	if fi.autosize == 0 {
+		return nil
+	}
+	addiD := l64DualTable["ADDV"].imm
+	return l64WordsLE(
+		l64irr(l64loadStoreTable["MOVV"].st, -fi.autosize, 3, 1), // MOVV R1, -autosize(R3)
+		l64irr(addiD, -fi.autosize, 3, 3),                        // ADDV $-autosize, R3
+		l64irr(l64loadStoreTable["MOVV"].st, 0, 3, 1),            // MOVV R1, 0(R3)
+	)
+}
+
+// loong64Return returns the bytes for a RET: the epilogue (restore LR and
+// deallocate the frame when present) followed by jirl r0, r1, 0.
+func loong64Return(fi loong64FrameInfo) []byte {
+	var ws []uint32
+	if fi.autosize != 0 {
+		if !fi.leaf {
+			// MOVV 0(R3), R1 — restore the link register.
+			ws = append(ws, l64irr(l64loadStoreTable["MOVV"].ld, 0, 3, 1))
+		}
+		// ADDV $autosize, R3 — close the frame.
+		ws = append(ws, l64irr(l64DualTable["ADDV"].imm, fi.autosize, 3, 3))
+	}
+	// jirl r0, r1, 0 — return.
+	ws = append(ws, l64irr16(l64branchTable["JIRL"], 0, 1, 0))
+	return l64WordsLE(ws...)
+}
+
+// loong64ResolvePseudo translates a pseudo-register memory reference into a
+// hardware base register and offset.  x+N(FP) → (N + autosize + 8)(SP);
+// x-N(SP) → (autosize - N)(SP).  Returns base = -1 for an unresolvable
+// reference (SB: static data, handled by the relocation path).
+func loong64ResolvePseudo(sym *ast.Symbol, fi loong64FrameInfo) (base int, off int32) {
+	if sym == nil {
+		return -1, 0
+	}
+	switch sym.Pseudo {
+	case "FP":
+		return 3, int32(sym.Offset) + int32(fi.autosize) + 8
+	case "SP":
+		return 3, int32(fi.autosize) + int32(sym.Offset)
+	case "SB":
+		return -1, int32(sym.Offset)
+	}
+	return -1, 0
+}

asm/loong64_more_test.go

@@ -0,0 +1,367 @@
+// Copyright (c) 2026 Petr Balvín <opensource@petrbalvin.org> (https://petrbalvin.org)
+// SPDX-License-Identifier: BSD-3-Clause
+
+package asm
+
+import (
+	"bytes"
+	"testing"
+
+	"sourcedock.dev/petrbalvin/gasm-devkit/parser"
+)
+
+// TestLOONG64_sys exercises the no-operand system instructions and the
+// bare-data pseudo-instructions.  The words match `go tool asm`
+// (GOARCH=loong64) for the same source.
+func TestLOONG64_sys(t *testing.T) {
+	fn := firstTextLOONG64(t, `#include "textflag.h"
+TEXT ·sys(SB), NOSPLIT, $0
+	NOOP
+	UNDEF
+	WORD $0x12345678
+	SYSCALL $0x10
+	BREAK $0x20
+	DBAR $1
+	RET
+`)
+	code := assembleLOONG64Helper(t, fn)
+	wantWords(t, code,
+		0x03400000, // andi r0, r0, 0 (NOOP)
+		0x002A0000, // break 0 (UNDEF)
+		0x12345678, // WORD
+		0x002B0010, // syscall 0x10
+		0x002A0020, // break 0x20
+		0x38720001, // dbar 1
+		0x4C000020, // jirl r0, r1, 0
+	)
+}
+
+// TestLOONG64_branches21 exercises the single-register branch forms: the
+// 21-bit BEQZ/BNEZ/BLTZ/BGEZ and the rd-field BGTZ/BLEZ.
+func TestLOONG64_branches21(t *testing.T) {
+	fn := firstTextLOONG64(t, `#include "textflag.h"
+TEXT ·b21(SB), NOSPLIT, $0
+	BEQZ R4, done
+	BNEZ R5, done
+	BLTZ R6, done
+	BGEZ R7, done
+	BGTZ R8, done
+	BLEZ R9, done
+done:
+	RET
+`)
+	code := assembleLOONG64Helper(t, fn)
+	wantWords(t, code,
+		0x40001880, // beqz r4, +6
+		0x440014A0, // bnez r5, +5
+		0x600010C0, // bltz r6, +4
+		0x64000CE0, // bgez r7, +3
+		0x60000808, // bgtz r8, +2 (register in the rd field)
+		0x64000409, // blez r9, +1
+		0x4C000020, // jirl r0, r1, 0
+	)
+}
+
+// TestLOONG64_fma exercises the four fused multiply-add forms (4 and 3
+// operand spellings).
+func TestLOONG64_fma(t *testing.T) {
+	fn := firstTextLOONG64(t, `#include "textflag.h"
+TEXT ·fma(SB), NOSPLIT, $0
+	FMADDD F0, F1, F2, F3
+	FMSUBD F4, F5, F6
+	FNMADDD F7, F8, F9, F10
+	FNMSUBD F11, F12, F13
+	RET
+`)
+	code := assembleLOONG64Helper(t, fn)
+	wantWords(t, code,
+		0x08200443, // fmadd.d f3, f2, f1, f0
+		0x086214C6, // fmsub.d f6, f5, f5, f4
+		0x08A3A12A, // fnmadd.d f10, f9, f8, f7
+		0x08E5B1AD, // fnmsub.d f13, f12, f12, f11
+		0x4C000020,
+	)
+}
+
+// TestLOONG64_bitops exercises BSTRINS/BSTRPICK (the 6-bit msb/lsb fields)
+// and ALSL (the sa−1 shift field).
+func TestLOONG64_bitops(t *testing.T) {
+	fn := firstTextLOONG64(t, `#include "textflag.h"
+TEXT ·bits(SB), NOSPLIT, $0
+	BSTRINSW $3, R4, $0, R5
+	BSTRINSV $3, R4, $1, R6
+	BSTRPICKW $3, R4, $0, R5
+	BSTRPICKV $6, R7, $0, R8
+	ALSLW $1, R4, R5, R6
+	ALSLW $4, R7, R8, R9
+	RET
+`)
+	code := assembleLOONG64Helper(t, fn)
+	wantWords(t, code,
+		0x00630085, // bstrins.w r5, r4, $3, $0
+		0x00830486, // bstrins.d r6, r4, $3, $1
+		0x00638085, // bstrpick.w r5, r4, $3, $0
+		0x00C600E8, // bstrpick.d r8, r7, $6, $0
+		0x00041486, // alsl.w r6, r5, r4, $1 (sa-1)
+		0x0005A0E9, // alsl.w r9, r8, r7, $4
+		0x4C000020,
+	)
+}
+
+// TestLOONG64_ptr exercises the 14-bit-offset memory forms (LL/SC/MOVWP/
+// MOVVP with the offset scaled by 4) and PRELD.
+func TestLOONG64_ptr(t *testing.T) {
+	fn := firstTextLOONG64(t, `#include "textflag.h"
+TEXT ·ptr(SB), NOSPLIT, $0
+	LLW 8(R14), R15
+	SCW R16, -4(R17)
+	MOVWP 16(R18), R19
+	MOVVP R20, 24(R21)
+	PRELD 32(R22), $0
+	RET
+`)
+	code := assembleLOONG64Helper(t, fn)
+	wantWords(t, code,
+		0x200009CF, // ll.w r15, 8(r14)
+		0x21FFFE30, // sc.w r16, -4(r17)
+		0x24001253, // ldptr.w r19, 16(r18)
+		0x27001AB4, // stptr.d r20, 24(r21)
+		0x2AC082C0, // preld 32(r22), 0
+		0x4C000020,
+	)
+}
+
+// TestLOONG64_atomics exercises the AM* read-modify-write forms and
+// RDTIME, plus the MOVV FP→GP move.
+func TestLOONG64_atomics(t *testing.T) {
+	fn := firstTextLOONG64(t, `#include "textflag.h"
+TEXT ·atoms(SB), NOSPLIT, $0
+	AMADDW R4, (R5), R6
+	RDTIMED R7, R8
+	MOVV F1, R2
+	RET
+`)
+	code := assembleLOONG64Helper(t, fn)
+	wantWords(t, code,
+		0x386110A6, // amadd.w r6, r5, r4
+		0x000068E8, // rdtime.d r8, r7
+		0x0114B822, // movfr2gr.d r2, f1
+		0x4C000020,
+	)
+}
+
+// TestLOONG64_lu52 exercises the LU52I.D immediate form (a gasm extension
+// the toolchain reaches only through its MOVV expansion).
+func TestLOONG64_lu52(t *testing.T) {
+	fn := firstTextLOONG64(t, `#include "textflag.h"
+TEXT ·lu52(SB), NOSPLIT, $0
+	LU52ID $0x345, R10
+	LU52ID $0x123, R11, R12
+	ADDV16 $0x10000, R13
+	RET
+`)
+	code := assembleLOONG64Helper(t, fn)
+	wantWords(t, code,
+		0x030D154A, // lu52i.d r10, r10, 0x345
+		0x03048D6C, // lu52i.d r12, r11, 0x123
+		0x100005AD, // addu16i.d r13, r13, 0x10000>>16
+		0x4C000020,
+	)
+}
+
+// TestLOONG64_sbRefs checks the static-symbol reference forms through the
+// full file assembly: each pcalau12i+addi.d/ld/st pair carries the
+// R_LOONG64_ADDR_HI/LO relocation pair, and the immediate fields are left
+// zero for the linker.
+func TestLOONG64_sbRefs(t *testing.T) {
+	f, errs := parser.Parse("sb_loong64.s", `#include "textflag.h"
+TEXT ·sb(SB), NOSPLIT, $0
+	MOVV $·table(SB), R4
+	MOVV ·table+8(SB), R5
+	MOVV R6, ·table(SB)
+	RET
+
+GLOBL ·table(SB), RODATA, $8
+DATA ·table+0(SB)/8, $42
+`)
+	if len(errs) > 0 {
+		t.Fatalf("parse: %v", errs)
+	}
+	img, err := AssembleFileLOONG64(f)
+	if err != nil {
+		t.Fatalf("AssembleFileLOONG64: %v", err)
+	}
+	fn := img.Funcs[0]
+	if fn.Size != 28 {
+		t.Fatalf("function size = %d, want 28", fn.Size)
+	}
+	var hi, lo int
+	// The three references: $·table (0), ·table+8 (8), ·table (0).
+	wantAdd := []int64{0, 0, 8, 8, 0, 0}
+	for i, r := range fn.Relocs {
+		wantKind := RelLoong64AddrHi
+		wantOff := (i / 2) * 8
+		if i%2 == 1 {
+			wantKind = RelLoong64AddrLo
+			wantOff += 4
+		}
+		if r.Kind != wantKind || r.Off != wantOff || r.Name != "table" || r.Addend != wantAdd[i] {
+			t.Errorf("reloc %d = {kind %v off %d name %q addend %d}", i, r.Kind, r.Off, r.Name, r.Addend)
+		}
+		if r.Kind == RelLoong64AddrHi {
+			hi++
+		} else {
+			lo++
+		}
+	}
+	if hi != 3 || lo != 3 {
+		t.Errorf("relocs = %d hi + %d lo, want 3 + 3", hi, lo)
+	}
+	// The image carries the zero-immediate pair encodings (the linker
+	// fills the immediate fields from the relocations).
+	code := img.Code[fn.Offset : fn.Offset+fn.Size]
+	wantWords(t, code,
+		0x1A000004, // pcalau12i r4, 0
+		0x02C00084, // addi.d r4, r4, 0
+		0x1A00001E, // pcalau12i r30, 0
+		0x28C003C5, // ld.d r5, 0(r30)
+		0x1A00001E, // pcalau12i r30, 0
+		0x29C003C6, // st.d r6, 0(r30)
+		0x4C000020, // jirl r0, r1, 0
+	)
+}
+
+// TestLOONG64_errors checks the encoder's error paths: undefined labels,
+// invalid register operands and operand-count mismatches.
+func TestLOONG64_errors(t *testing.T) {
+	cases := []string{
+		`TEXT ·e(SB), NOSPLIT, $0
+	JMP nowhere
+	RET
+`,
+		`TEXT ·e(SB), NOSPLIT, $0
+	BEQZ X0, done
+done:
+	RET
+`,
+		`TEXT ·e(SB), NOSPLIT, $0
+	ADDV R4
+	RET
+`,
+		`TEXT ·e(SB), NOSPLIT, $0
+	FMADDD F0, F1
+	RET
+`,
+		`TEXT ·e(SB), NOSPLIT, $0
+	AMADDW R4, R5
+	RET
+`,
+		`TEXT ·e(SB), NOSPLIT, $0
+	WORD
+	RET
+`,
+		`TEXT ·e(SB), NOSPLIT, $0
+	PRELD 32(R4)
+	RET
+`,
+		`TEXT ·e(SB), NOSPLIT, $0
+	ALSLW $5, R4, R5, R6
+	RET
+`,
+	}
+	for i, src := range cases {
+		fn := firstTextLOONG64(t, src)
+		if _, _, _, _, _, err := assembleLOONG64(fn); err == nil {
+			t.Errorf("case %d: expected an error, got none", i)
+		}
+	}
+}
+
+// TestLOONG64_pcsp checks the stack-adjustment table of a framed function:
+// the prologue raises the SP delta by autosize (in effect from the third
+// instruction) and the RET's epilogue restores it to zero, with the pc deltas
+// in MinLC (4) units — byte-identical to `go tool asm`.
+func TestLOONG64_pcsp(t *testing.T) {
+	cases := []struct {
+		name string
+		src  string
+		want []byte
+	}{
+		{
+			"leaf",
+			`#include "textflag.h"
+TEXT ·leaf(SB), NOSPLIT, $8-0
+	MOVV R4, R5
+	RET
+`,
+			[]byte{0x02, 0x02, 0x20, 0x03, 0x1f, 0x01, 0x00},
+		},
+		{
+			"nonleaf",
+			`#include "textflag.h"
+TEXT ·nonleaf(SB), NOSPLIT, $8-0
+	MOVV R4, R5
+	JAL (R12)
+	RET
+`,
+			[]byte{0x02, 0x02, 0x20, 0x05, 0x1f, 0x01, 0x00},
+		},
+	}
+	for _, c := range cases {
+		t.Run(c.name, func(t *testing.T) {
+			f, errs := parser.Parse("pcsp_loong64.s", c.src)
+			if len(errs) > 0 {
+				t.Fatalf("parse: %v", errs)
+			}
+			img, err := AssembleFileLOONG64(f)
+			if err != nil {
+				t.Fatalf("AssembleFileLOONG64: %v", err)
+			}
+			if got := pcspTable(img.Funcs[0], 4); !bytes.Equal(got, c.want) {
+				t.Errorf("pcsp = % x, want % x", got, c.want)
+			}
+		})
+	}
+}
+
+// TestLOONG64_sbRefsUndefined checks that a reference to a symbol no GLOBL
+// defines assembles into a relocation and is rejected at object emission.
+func TestLOONG64_sbRefsUndefined(t *testing.T) {
+	f, errs := parser.Parse("sb_loong64.s", `#include "textflag.h"
+TEXT ·sb(SB), NOSPLIT, $0
+	MOVV missing(SB), R4
+	RET
+`)
+	if len(errs) > 0 {
+		t.Fatalf("parse: %v", errs)
+	}
+	img, err := AssembleFileLOONG64(f)
+	if err != nil {
+		t.Fatalf("AssembleFileLOONG64: %v", err)
+	}
+	if len(img.Funcs[0].Relocs) != 2 {
+		t.Fatalf("relocs = %d, want the HI/LO pair", len(img.Funcs[0].Relocs))
+	}
+	if _, err := img.GOObjectLOONG64("p", "sb_loong64.s"); err == nil {
+		t.Error("expected an unknown-symbol error at emission")
+	}
+}
+
+// TestLOONG64_movImmToFp checks the immediate-to-FP move forms.
+func TestLOONG64_movImmToFp(t *testing.T) {
+	fn := firstTextLOONG64(t, `#include "textflag.h"
+TEXT ·fpmov(SB), NOSPLIT, $0
+	MOVV $0x1, F0
+	MOVW $0x2, F4
+	RET
+`)
+	code := assembleLOONG64Helper(t, fn)
+	want := []byte{
+		0x00, 0x04, 0x80, 0x03, // ori f0, r0, 1
+		0x04, 0x08, 0x80, 0x03, // ori f4, r0, 2
+		0x20, 0x00, 0x00, 0x4c, // jirl r0, r1, 0
+	}
+	if !bytes.Equal(code, want) {
+		t.Errorf("code = % x\nwant % x", code, want)
+	}
+}

asm/macho.go

@@ -1,258 +0,0 @@
-// Copyright (c) 2026 Petr Balvín <opensource@petrbalvin.org> (https://petrbalvin.org)
-// SPDX-License-Identifier: BSD-3-Clause
-
-package asm
-
-import (
-	"encoding/binary"
-	"fmt"
-)
-
-// This file emits Mach-O x86-64 objects (MH_OBJECT) from an assembled
-// Image, in the shape the Darwin assembler produces: one unnamed segment
-// carrying a __TEXT,__text and a __DATA,__data section laid out back to
-// back at addresses zero and len(code), a symbol table (locals first, then
-// exported definitions, then undefined externals) and one relocation entry
-// per static-symbol reference, of type X86_64_RELOC_SIGNED.
-//
-// The image's own address space carries straight over — the data section
-// starts immediately after the code, and the layout padding already lives
-// inside Image.Data — so every symbol keeps its image address as its
-// n_value, and a local (non-external) relocation leaves the displacement
-// the assembler resolved in place: the linker only adjusts it by the
-// section's final movement.
-
-// Mach-O constants.
-const (
-	machoMagic64   = 0xfeedfacf
-	machoCPUamd64  = 0x01000007 // CPU_TYPE_X86_64
-	machoCPUSubAll = 3          // CPU_SUBTYPE_X86_64_ALL
-	machoObj       = 1          // MH_OBJECT
-
-	machoSegment64 = 0x19 // LC_SEGMENT_64
-	machoSymtab    = 0x2  // LC_SYMTAB
-
-	machoSectTextFlags = 0x80000400 // S_ATTR_PURE_INSTRUCTIONS | S_ATTR_SOME_INSTRUCTIONS
-
-	nUndf = 0x00 // undefined symbol
-	nSect = 0x0e // defined in section number n_sect
-	nExt  = 0x01 // external (exported or undefined-global) bit
-
-	x8664RelocSigned = 1
-)
-
-// MachOObject returns the image as a Mach-O x86-64 relocatable object
-// (MH_OBJECT), the shape the Darwin toolchain links.  Symbol names follow
-// the same rules as the ELF output.  Every static-symbol reference becomes
-// an X86_64_RELOC_SIGNED relocation: external references against their
-// undefined symbol, file-local ones against the __DATA section with the
-// resolved displacement carried in the instruction bytes.
-func (img *Image) MachOObject() ([]byte, error) {
-	le := binary.LittleEndian
-
-	// Section ordinals (1-based, as Mach-O numbers them).
-	const (
-		sectText = 1
-		sectData = 2
-	)
-
-	// Object address space: code at 0, data immediately after (the layout
-	// padding is already part of img.Data, so image addresses are object
-	// addresses).
-	textAddr := uint64(0)
-	dataAddr := uint64(len(img.Code))
-	vmsize := dataAddr + uint64(len(img.Data))
-
-	// The code, with external displacements primed to addend − 4: the
-	// linker adds the symbol's address to the field as it stands.  Local
-	// displacements stay as the assembler resolved them.
-	code := append([]byte(nil), img.Code...)
-	for _, fn := range img.Funcs {
-		for _, r := range fn.Relocs {
-			if r.External {
-				// Prime the field to the addend measured from the patch
-				// site: the assembler records it from the instruction end,
-				// After − Off bytes past the field.
-				copy(code[fn.Offset+r.Off:], le32(r.Addend-int64(r.After-r.Off)))
-			}
-		}
-	}
-
-	// Symbols: locals first, then exported definitions, then undefined
-	// externals — the order the classic link editor expects.
-	type machoSym struct {
-		name  string
-		typ   byte
-		sect  byte
-		value uint64
-	}
-	var locals, globals, undefs []machoSym
-	for _, fn := range img.Funcs {
-		s := machoSym{name: objectName(fn.Pkg, fn.Name), typ: nSect, sect: sectText, value: textAddr + uint64(fn.Offset)}
-		if fn.Static {
-			locals = append(locals, s)
-		} else {
-			s.typ |= nExt
-			globals = append(globals, s)
-		}
-	}
-	for _, d := range img.DataSyms {
-		s := machoSym{name: objectName(d.Pkg, d.Name), typ: nSect, sect: sectData, value: dataAddr + uint64(d.Offset)}
-		if d.Static {
-			locals = append(locals, s)
-		} else {
-			s.typ |= nExt
-			globals = append(globals, s)
-		}
-	}
-	for _, name := range img.Externals {
-		undefs = append(undefs, machoSym{name: name, typ: nUndf | nExt})
-	}
-	syms := append(append(locals, globals...), undefs...)
-	symIdx := map[string]int{}
-	for i, s := range syms {
-		symIdx[s.name] = i
-	}
-
-	// Relocations, attached to the __text section.
-	type machoReloc struct {
-		addr   uint32
-		symnum uint32
-		extern bool
-	}
-	var relocs []machoReloc
-	for _, fn := range img.Funcs {
-		for _, r := range fn.Relocs {
-			rel := machoReloc{addr: uint32(fn.Offset + r.Off)}
-			if r.External {
-				idx, ok := symIdx[r.Name]
-				if !ok {
-					return nil, fmt.Errorf("relocation references unknown symbol %q", r.Name)
-				}
-				rel.symnum = uint32(idx)
-				rel.extern = true
-			} else {
-				// Section-relative: r_symbolnum carries the section number
-				// and the resolved displacement stays in the bytes.
-				rel.symnum = sectData
-			}
-			relocs = append(relocs, rel)
-		}
-	}
-
-	// The string table opens with the conventional " \0".
-	strtab := []byte{' ', 0}
-	strOff := map[string]int{}
-	for _, s := range syms {
-		if _, ok := strOff[s.name]; ok {
-			continue
-		}
-		strOff[s.name] = len(strtab)
-		strtab = append(strtab, s.name...)
-		strtab = append(strtab, 0)
-	}
-
-	// File layout: header, the two load commands, section data (code,
-	// data), the relocation table, the symbol table, the string table.
-	const (
-		hdrSize    = 32
-		segCmdSize = 72 + 2*80 // segment command with two sections
-		symCmdSize = 24
-	)
-	sizeofcmds := segCmdSize + symCmdSize
-	dataOff := hdrSize + sizeofcmds
-	reloff := dataOff + len(code) + len(img.Data)
-	symoff := reloff + 8*len(relocs)
-	stroff := symoff + 16*len(syms)
-
-	out := make([]byte, stroff+len(strtab))
-
-	// mach_header_64.
-	le.PutUint32(out[0:], machoMagic64)
-	le.PutUint32(out[4:], machoCPUamd64)
-	le.PutUint32(out[8:], machoCPUSubAll)
-	le.PutUint32(out[12:], machoObj)
-	le.PutUint32(out[16:], 2) // ncmds
-	le.PutUint32(out[20:], uint32(sizeofcmds))
-	le.PutUint32(out[24:], 0) // flags
-	le.PutUint32(out[28:], 0) // reserved
-
-	// LC_SEGMENT_64 with the two sections.
-	p := hdrSize
-	le.PutUint32(out[p:], machoSegment64)
-	le.PutUint32(out[p+4:], segCmdSize)
-	// segname: the empty string, zero-padded to 16 bytes.
-	le.PutUint64(out[p+8:], 0)
-	le.PutUint64(out[p+16:], 0)
-	le.PutUint64(out[p+24:], 0) // vmaddr
-	le.PutUint64(out[p+32:], vmsize)
-	le.PutUint64(out[p+40:], uint64(dataOff))
-	le.PutUint64(out[p+48:], vmsize)
-	le.PutUint32(out[p+56:], 7) // maxprot rwx
-	le.PutUint32(out[p+60:], 7) // initprot rwx
-	le.PutUint32(out[p+64:], 2) // nsects
-	le.PutUint32(out[p+68:], 0) // flags
-
-	// __TEXT,__text
-	s := p + 72
-	copy(out[s:], "__text")
-	copy(out[s+16:], "__TEXT")
-	le.PutUint64(out[s+32:], textAddr)
-	le.PutUint64(out[s+40:], uint64(len(code)))
-	le.PutUint32(out[s+48:], uint32(dataOff))
-	le.PutUint32(out[s+52:], 4) // align 2^4
-	le.PutUint32(out[s+56:], uint32(reloff))
-	le.PutUint32(out[s+60:], uint32(len(relocs)))
-	le.PutUint32(out[s+64:], machoSectTextFlags)
-
-	// __DATA,__data
-	s += 80
-	copy(out[s:], "__data")
-	copy(out[s+16:], "__DATA")
-	le.PutUint64(out[s+32:], dataAddr)
-	le.PutUint64(out[s+40:], uint64(len(img.Data)))
-	le.PutUint32(out[s+48:], uint32(dataOff+len(code)))
-	le.PutUint32(out[s+52:], 4) // align 2^4
-
-	// LC_SYMTAB.
-	p = hdrSize + segCmdSize
-	le.PutUint32(out[p:], machoSymtab)
-	le.PutUint32(out[p+4:], symCmdSize)
-	le.PutUint32(out[p+8:], uint32(symoff))
-	le.PutUint32(out[p+12:], uint32(len(syms)))
-	le.PutUint32(out[p+16:], uint32(stroff))
-	le.PutUint32(out[p+20:], uint32(len(strtab)))
-
-	// Section data.
-	copy(out[dataOff:], code)
-	copy(out[dataOff+len(code):], img.Data)
-
-	// Relocation entries.
-	for i, r := range relocs {
-		e := out[reloff+i*8:]
-		le.PutUint32(e[0:], r.addr)
-		bits := r.symnum & 0x00ffffff
-		bits |= 1 << 24 // r_pcrel
-		bits |= 2 << 25 // r_length = 4 bytes
-		if r.extern {
-			bits |= 1 << 27 // r_extern
-		}
-		bits |= x8664RelocSigned << 28
-		le.PutUint32(e[4:], bits)
-	}
-
-	// nlist_64 entries.
-	for i, s := range syms {
-		e := out[symoff+i*16:]
-		le.PutUint32(e[0:], uint32(strOff[s.name]))
-		e[4] = s.typ
-		e[5] = s.sect
-		le.PutUint16(e[6:], 0) // n_desc
-		le.PutUint64(e[8:], s.value)
-	}
-
-	// String table.
-	copy(out[stroff:], strtab)
-
-	return out, nil
-}

asm/macho_test.go

@@ -1,127 +0,0 @@
-// Copyright (c) 2026 Petr Balvín <opensource@petrbalvin.org> (https://petrbalvin.org)
-// SPDX-License-Identifier: BSD-3-Clause
-
-package asm
-
-import (
-	"bytes"
-	"debug/macho"
-	"encoding/binary"
-	"testing"
-)
-
-// TestMachOObject checks the structure of the emitted MH_OBJECT: the two
-// sections and their addresses, the symbol table (types, sections, values)
-// and the __text relocation entries, parsed back with debug/macho.  No
-// Darwin toolchain is available on the test hosts, so the check is
-// structural — the ELF output carries the end-to-end link-and-run proof of
-// the shared symbol and relocation model.
-func TestMachOObject(t *testing.T) {
-	img := elfTestImage(t)
-	obj, err := img.MachOObject()
-	if err != nil {
-		t.Fatalf("MachOObject: %v", err)
-	}
-	f, err := macho.NewFile(bytes.NewReader(obj))
-	if err != nil {
-		t.Fatalf("parse emitted object: %v", err)
-	}
-	defer f.Close()
-
-	if f.Type != macho.TypeObj {
-		t.Errorf("file type = %v, want MH_OBJECT", f.Type)
-	}
-	if f.Cpu != macho.CpuAmd64 {
-		t.Errorf("cpu = %v, want CpuAmd64", f.Cpu)
-	}
-
-	text := f.Section("__text")
-	data := f.Section("__data")
-	if text == nil || data == nil {
-		t.Fatal("missing __text or __data section")
-	}
-	if text.Addr != 0 || text.Size != uint64(len(img.Code)) {
-		t.Errorf("__text addr/size = %#x/%d, want 0/%d", text.Addr, text.Size, len(img.Code))
-	}
-	if data.Addr != uint64(len(img.Code)) {
-		t.Errorf("__data addr = %#x, want %#x", data.Addr, len(img.Code))
-	}
-
-	// Symbol table: locals, exported definitions, undefined externals.
-	syms := f.Symtab.Syms
-	byName := map[string]macho.Symbol{}
-	for _, s := range syms {
-		byName[s.Name] = s
-	}
-	wantSym := func(name string, typ, sect uint8, value uint64) {
-		t.Helper()
-		s, ok := byName[name]
-		if !ok {
-			t.Errorf("symbol %q not found", name)
-			return
-		}
-		if s.Type != typ || s.Sect != sect || s.Value != value {
-			t.Errorf("%s: type/sect/value = %#x/%d/%#x, want %#x/%d/%#x",
-				name, s.Type, s.Sect, s.Value, typ, sect, value)
-		}
-	}
-	const (
-		defined   = nSect | nExt
-		local     = nSect
-		undefined = nUndf | nExt
-	)
-	wantSym("addq", defined, 1, 0)
-	wantSym("getanswer", defined, 1, 5)
-	wantSym("useextern", defined, 1, 13)
-	answer := byName["answer"]
-	if answer.Type != local || answer.Sect != 2 {
-		t.Errorf("answer: type/sect = %#x/%d, want %#x/2", answer.Type, answer.Sect, local)
-	}
-	wantSym("extvar", undefined, 0, 0)
-
-	// Relocations: both X86_64_RELOC_SIGNED, PC-relative, 4 bytes wide.
-	// The local one carries its section number in Value, the external one
-	// its symbol number.
-	if len(text.Relocs) != 2 {
-		t.Fatalf("__text relocs = %d, want 2", len(text.Relocs))
-	}
-	var sawLocal, sawExternal bool
-	for _, r := range text.Relocs {
-		if !r.Pcrel || r.Len != 2 || r.Type != x8664RelocSigned {
-			t.Errorf("reloc at %#x: pcrel/len/type = %v/%d/%d", r.Addr, r.Pcrel, r.Len, r.Type)
-		}
-		switch {
-		case r.Extern:
-			if name := syms[r.Value].Name; name != "extvar" {
-				t.Errorf("external reloc at %#x names %q, want extvar", r.Addr, name)
-			}
-			sawExternal = true
-		default:
-			if r.Value != 2 { // __data, the second section
-				t.Errorf("local reloc at %#x: section %d, want 2 (__data)", r.Addr, r.Value)
-			}
-			sawLocal = true
-		}
-	}
-	if !sawLocal || !sawExternal {
-		t.Errorf("relocs seen: local=%v external=%v, want both", sawLocal, sawExternal)
-	}
-
-	// The __text bytes are the image code, with the external displacement
-	// primed to addend − 4 and the local one left resolved.
-	textData, err := text.Data()
-	if err != nil {
-		t.Fatal(err)
-	}
-	want := append([]byte(nil), img.Code...)
-	for _, fn := range img.Funcs {
-		for _, r := range fn.Relocs {
-			if r.Name == "extvar" {
-				binary.LittleEndian.PutUint32(want[fn.Offset+r.Off:], 0xfffffffc) // −4
-			}
-		}
-	}
-	if !bytes.Equal(textData, want) {
-		t.Errorf("__text bytes %x, want %x", textData, want)
-	}
-}

asm/riscv_encode.go

@@ -0,0 +1,564 @@
+// Copyright (c) 2026 Petr Balvín <opensource@petrbalvin.org> (https://petrbalvin.org)
+// SPDX-License-Identifier: BSD-3-Clause
+
+package asm
+
+// RISC-V register encoding: maps register names to their 5-bit numbers.
+// The Go assembler uses the standard RISC-V ABI naming.
+
+// riscvRegNum returns the 5-bit register number for a RISC-V register name.
+// Returns -1 if the register is not recognized.
+func riscvRegNum(name string) int {
+	switch name {
+	// Numbered integer registers.
+	case "X0", "ZERO":
+		return 0
+	case "X1", "RA", "LR":
+		return 1
+	case "X2", "SP":
+		return 2
+	case "X3", "GP":
+		return 3
+	case "X4", "TP":
+		return 4
+	case "X5", "T0":
+		return 5
+	case "X6", "T1":
+		return 6
+	case "X7", "T2":
+		return 7
+	case "X8", "S0", "FP":
+		return 8
+	case "X9", "S1":
+		return 9
+	case "X10", "A0":
+		return 10
+	case "X11", "A1":
+		return 11
+	case "X12", "A2":
+		return 12
+	case "X13", "A3":
+		return 13
+	case "X14", "A4":
+		return 14
+	case "X15", "A5":
+		return 15
+	case "X16", "A6":
+		return 16
+	case "X17", "A7":
+		return 17
+	case "X18", "S2":
+		return 18
+	case "X19", "S3":
+		return 19
+	case "X20", "S4":
+		return 20
+	case "X21", "S5":
+		return 21
+	case "X22", "S6":
+		return 22
+	case "X23", "S7":
+		return 23
+	case "X24", "S8":
+		return 24
+	case "X25", "S9":
+		return 25
+	case "X26", "S10":
+		return 26
+	case "X27", "S11":
+		return 27
+	case "X28", "T3":
+		return 28
+	case "X29", "T4":
+		return 29
+	case "X30", "T5":
+		return 30
+	case "X31", "T6", "TMP":
+		return 31
+	// Floating-point registers (F0-F31).
+	case "F0", "FT0":
+		return 0
+	case "F1", "FT1":
+		return 1
+	case "F2", "FT2":
+		return 2
+	case "F3", "FT3":
+		return 3
+	case "F4", "FT4":
+		return 4
+	case "F5", "FT5":
+		return 5
+	case "F6", "FT6":
+		return 6
+	case "F7", "FT7":
+		return 7
+	case "F8", "FS0":
+		return 8
+	case "F9", "FS1":
+		return 9
+	case "F10", "FA0":
+		return 10
+	case "F11", "FA1":
+		return 11
+	case "F12", "FA2":
+		return 12
+	case "F13", "FA3":
+		return 13
+	case "F14", "FA4":
+		return 14
+	case "F15", "FA5":
+		return 15
+	case "F16", "FA6":
+		return 16
+	case "F17", "FA7":
+		return 17
+	case "F18", "FS2":
+		return 18
+	case "F19", "FS3":
+		return 19
+	case "F20", "FS4":
+		return 20
+	case "F21", "FS5":
+		return 21
+	case "F22", "FS6":
+		return 22
+	case "F23", "FS7":
+		return 23
+	case "F24", "FS8":
+		return 24
+	case "F25", "FS9":
+		return 25
+	case "F26", "FS10":
+		return 26
+	case "F27", "FS11":
+		return 27
+	case "F28", "FT8":
+		return 28
+	case "F29", "FT9":
+		return 29
+	case "F30", "FT10":
+		return 30
+	case "F31", "FT11":
+		return 31
+	default:
+		return -1
+	}
+}
+
+// RISC-V instruction encoding parameters.
+type riscvEnc struct {
+	opcode uint32 // bits [6:0]
+	funct3 uint32 // bits [14:12]
+	funct7 uint32 // bits [31:25]
+}
+
+// riscvInstrTable maps RISC-V mnemonics to their encoding.
+var riscvInstrTable = map[string]riscvEnc{
+	// RV64I — R-type arithmetic/logic.
+	"ADD":  {0x33, 0x0, 0x00},
+	"SUB":  {0x33, 0x0, 0x20},
+	"SLL":  {0x33, 0x1, 0x00},
+	"SLT":  {0x33, 0x2, 0x00},
+	"SLTU": {0x33, 0x3, 0x00},
+	"XOR":  {0x33, 0x4, 0x00},
+	"SRL":  {0x33, 0x5, 0x00},
+	"SRA":  {0x33, 0x5, 0x20},
+	"OR":   {0x33, 0x6, 0x00},
+	"AND":  {0x33, 0x7, 0x00},
+	// RV64I — 32-bit variants (W suffix).
+	"ADDW": {0x3B, 0x0, 0x00},
+	"SUBW": {0x3B, 0x0, 0x20},
+	"SLLW": {0x3B, 0x1, 0x00},
+	"SRLW": {0x3B, 0x5, 0x00},
+	"SRAW": {0x3B, 0x5, 0x20},
+	// RV64I — I-type shift-immediate (shamt in rs2 field).
+	"SLLI":  {0x13, 0x1, 0x00},
+	"SRLI":  {0x13, 0x5, 0x00},
+	"SRAI":  {0x13, 0x5, 0x20},
+	"SLLIW": {0x1B, 0x1, 0x00},
+	"SRLIW": {0x1B, 0x5, 0x00},
+	"SRAIW": {0x1B, 0x5, 0x20},
+	// RV64M — multiply/divide.
+	"MUL":    {0x33, 0x0, 0x01},
+	"MULH":   {0x33, 0x1, 0x01},
+	"MULHSU": {0x33, 0x2, 0x01},
+	"MULHU":  {0x33, 0x3, 0x01},
+	"DIV":    {0x33, 0x4, 0x01},
+	"DIVU":   {0x33, 0x5, 0x01},
+	"REM":    {0x33, 0x6, 0x01},
+	"REMU":   {0x33, 0x7, 0x01},
+	// RV64M — 32-bit variants.
+	"MULW":  {0x3B, 0x0, 0x01},
+	"DIVW":  {0x3B, 0x4, 0x01},
+	"DIVUW": {0x3B, 0x5, 0x01},
+	"REMW":  {0x3B, 0x6, 0x01},
+	"REMUW": {0x3B, 0x7, 0x01},
+	// RV64I — I-type arithmetic.
+	"ADDI":  {0x13, 0x0, 0x00},
+	"ADDIW": {0x1B, 0x0, 0x00},
+	"SLTI":  {0x13, 0x2, 0x00},
+	"SLTIU": {0x13, 0x3, 0x00},
+	"XORI":  {0x13, 0x4, 0x00},
+	"ORI":   {0x13, 0x6, 0x00},
+	"ANDI":  {0x13, 0x7, 0x00},
+	// Loads (I-type).
+	"LB":  {0x03, 0x0, 0x00},
+	"LH":  {0x03, 0x1, 0x00},
+	"LW":  {0x03, 0x2, 0x00},
+	"LD":  {0x03, 0x3, 0x00},
+	"LBU": {0x03, 0x4, 0x00},
+	"LHU": {0x03, 0x5, 0x00},
+	"LWU": {0x03, 0x6, 0x00},
+	// Stores (S-type).
+	"SB": {0x23, 0x0, 0x00},
+	"SH": {0x23, 0x1, 0x00},
+	"SW": {0x23, 0x2, 0x00},
+	"SD": {0x23, 0x3, 0x00},
+	// Branches (B-type).
+	"BEQ":  {0x63, 0x0, 0x00},
+	"BNE":  {0x63, 0x1, 0x00},
+	"BLT":  {0x63, 0x4, 0x00},
+	"BGE":  {0x63, 0x5, 0x00},
+	"BLTU": {0x63, 0x6, 0x00},
+	"BGEU": {0x63, 0x7, 0x00},
+	// U-type.
+	"LUI":   {0x37, 0x0, 0x00},
+	"AUIPC": {0x17, 0x0, 0x00},
+	// System.
+	"ECALL":  {0x73, 0x0, 0x00},
+	"EBREAK": {0x73, 0x0, 0x00},
+	"FENCE":  {0x0F, 0x0, 0x00},
+	// JALR — indirect jump/call (I-type).
+	"JALR": {0x67, 0x0, 0x00},
+
+	// RV64A — atomics (AMO opcode 0x2F).
+	// funct3: 0x2 = word, 0x3 = doubleword. funct5 in bits [31:27].
+	"AMOSWAPW": {0x2F, 0x2, 0x01 << 2},
+	"AMOSWAPD": {0x2F, 0x3, 0x01 << 2},
+	"AMOADDW":  {0x2F, 0x2, 0x00 << 2},
+	"AMOADDD":  {0x2F, 0x3, 0x00 << 2},
+	"AMOANDW":  {0x2F, 0x2, 0x0C << 2},
+	"AMOANDD":  {0x2F, 0x3, 0x0C << 2},
+	"AMOORW":   {0x2F, 0x2, 0x06 << 2},
+	"AMOORD":   {0x2F, 0x3, 0x06 << 2},
+	"AMOXORW":  {0x2F, 0x2, 0x04 << 2},
+	"AMOXORD":  {0x2F, 0x3, 0x04 << 2},
+	"AMOMAXW":  {0x2F, 0x2, 0x14 << 2},
+	"AMOMAXD":  {0x2F, 0x3, 0x14 << 2},
+	"AMOMINW":  {0x2F, 0x2, 0x10 << 2},
+	"AMOMIND":  {0x2F, 0x3, 0x10 << 2},
+	"AMOMAXUW": {0x2F, 0x2, 0x1C << 2},
+	"AMOMAXUD": {0x2F, 0x3, 0x1C << 2},
+	"AMOMINUW": {0x2F, 0x2, 0x18 << 2},
+	"AMOMINUD": {0x2F, 0x3, 0x18 << 2},
+
+	// RV64F/D — floating-point arithmetic.
+	"FADDS":  {0x53, 0x0, 0x00},
+	"FSUBS":  {0x53, 0x0, 0x04},
+	"FMULS":  {0x53, 0x0, 0x08},
+	"FDIVS":  {0x53, 0x0, 0x0C},
+	"FADDD":  {0x53, 0x0, 0x01},
+	"FSUBD":  {0x53, 0x0, 0x05},
+	"FMULD":  {0x53, 0x0, 0x09},
+	"FDIVD":  {0x53, 0x0, 0x0D},
+	"FSQRTS": {0x53, 0x0, 0x2C},
+	"FSQRTD": {0x53, 0x0, 0x2D},
+	// FP loads/stores.
+	"FLW": {0x07, 0x2, 0x00},
+	"FLD": {0x07, 0x3, 0x00},
+	"FSW": {0x27, 0x2, 0x00},
+	"FSD": {0x27, 0x3, 0x00},
+	// FP min/max.
+	"FMINS": {0x53, 0x0, 0x14},
+	"FMAXS": {0x53, 0x1, 0x14},
+	"FMIND": {0x53, 0x0, 0x15},
+	"FMAXD": {0x53, 0x1, 0x15},
+
+	// RV64A — load-reserved / store-conditional (funct5 0x02 / 0x03).
+	"LRW": {0x2F, 0x2, 0x02 << 2},
+	"LRD": {0x2F, 0x3, 0x02 << 2},
+	"SCW": {0x2F, 0x2, 0x03 << 2},
+	"SCD": {0x2F, 0x3, 0x03 << 2},
+
+	// FP compare — result in integer register (funct7 0x50/0x51).
+	"FEQS": {0x53, 0x2, 0x50},
+	"FLTS": {0x53, 0x1, 0x50},
+	"FLES": {0x53, 0x0, 0x50},
+	"FEQD": {0x53, 0x2, 0x51},
+	"FLTD": {0x53, 0x1, 0x51},
+	"FLED": {0x53, 0x0, 0x51},
+}
+
+// riscvRType encodes an R-type instruction: funct7 | rs2 | rs1 | funct3 | rd | opcode.
+func riscvRType(enc riscvEnc, rd, rs1, rs2 int) uint32 {
+	return (enc.funct7 << 25) | (uint32(rs2) << 20) | (uint32(rs1) << 15) |
+		(enc.funct3 << 12) | (uint32(rd) << 7) | enc.opcode
+}
+
+// riscvAMOType encodes an atomic (AMO) instruction.
+// Layout: funct5 | aq | rl | rs2 | rs1 | funct3 | rd | opcode.
+// The funct5 is stored in the upper bits of enc.funct7 (shifted left by 2).
+func riscvAMOType(enc riscvEnc, rd, rs1, rs2 int) uint32 {
+	funct5 := enc.funct7 >> 2 // extract funct5 from the stored value
+	return (funct5 << 27) | (uint32(rs2) << 20) | (uint32(rs1) << 15) |
+		(enc.funct3 << 12) | (uint32(rd) << 7) | enc.opcode
+}
+
+// FP conversion instructions (FCVT, FMV).  These use the rs2 field to
+// encode the conversion type rather than a register, so they are handled
+// separately from the general instruction table.
+type riscvCvtEnc struct {
+	funct7 uint32 // bits [31:25]
+	rs2    uint32 // conversion-type code in bits [24:20]
+	opcode uint32 // always 0x53 (OP-FP)
+}
+
+var riscvCvtTable = map[string]riscvCvtEnc{
+	// float → int (rs2 selects the integer width/sign).
+	"FCVTWS":  {0x60, 0x0, 0x53}, // float32 → int32
+	"FCVTWUS": {0x60, 0x1, 0x53}, // float32 → uint32
+	"FCVTLS":  {0x60, 0x2, 0x53}, // float32 → int64
+	"FCVTLUS": {0x60, 0x3, 0x53}, // float32 → uint64
+	"FCVTWD":  {0x61, 0x0, 0x53}, // float64 → int32
+	"FCVTWUD": {0x61, 0x1, 0x53}, // float64 → uint32
+	"FCVTLD":  {0x61, 0x2, 0x53}, // float64 → int64
+	"FCVTLUD": {0x61, 0x3, 0x53}, // float64 → uint64
+	// int → float (rs2 selects the integer width/sign).
+	"FCVTSW":  {0x68, 0x0, 0x53}, // int32 → float32
+	"FCVTSWU": {0x68, 0x1, 0x53}, // uint32 → float32
+	"FCVTSL":  {0x68, 0x2, 0x53}, // int64 → float32
+	"FCVTSLU": {0x68, 0x3, 0x53}, // uint64 → float32
+	"FCVTDW":  {0x69, 0x0, 0x53}, // int32 → float64
+	"FCVTDWU": {0x69, 0x1, 0x53}, // uint32 → float64
+	"FCVTDL":  {0x69, 0x2, 0x53}, // int64 → float64
+	"FCVTDLU": {0x69, 0x3, 0x53}, // uint64 → float64
+	// float → float width conversion.
+	"FCVTSD": {0x20, 0x1, 0x53}, // float64 → float32
+	"FCVTDS": {0x21, 0x0, 0x53}, // float32 → float64
+	// Bit moves between integer and FP registers (no conversion).
+	"FMVXD": {0x71, 0x0, 0x53}, // float64 → int64 (bit move)
+	"FMVDX": {0x79, 0x0, 0x53}, // int64 → float64 (bit move)
+	"FMVXW": {0x70, 0x0, 0x53}, // float32 → int32 (bit move)
+	"FMVWX": {0x78, 0x0, 0x53}, // int32 → float32 (bit move)
+}
+
+// riscvCvtType encodes an FP conversion instruction.
+// Layout: funct7 | rs2(convtype) | rs1 | funct3(0) | rd | opcode.
+func riscvCvtType(enc riscvCvtEnc, rd, rs1 int) uint32 {
+	return (enc.funct7 << 25) | (enc.rs2 << 20) | (uint32(rs1) << 15) |
+		(uint32(rd) << 7) | enc.opcode
+}
+
+// R4-type fused multiply-add instructions (FMADD/FMSUB/FNMSUB/FNMADD).
+// These take 4 register operands: rs1, rs2, rs3, rd.
+// Layout: rs3 | fmt | rs2 | rs1 | rm | rd | opcode.
+type riscvFmaEnc struct {
+	fmt    uint32 // bits [26:25]: 0x0 = single, 0x1 = double
+	opcode uint32 // bits [6:0]
+}
+
+var riscvFmaTable = map[string]riscvFmaEnc{
+	"FMADDS":  {0x0, 0x43}, // rd = rs1*rs2 + rs3
+	"FMADDD":  {0x1, 0x43},
+	"FMSUBS":  {0x0, 0x47}, // rd = rs1*rs2 - rs3
+	"FMSUBD":  {0x1, 0x47},
+	"FNMSUBS": {0x0, 0x4B}, // rd = -(rs1*rs2) + rs3
+	"FNMSUBD": {0x1, 0x4B},
+	"FNMADDS": {0x0, 0x4F}, // rd = -(rs1*rs2) - rs3
+	"FNMADDD": {0x1, 0x4F},
+}
+
+// riscvFmaType encodes an R4-type fused multiply-add instruction.
+func riscvFmaType(enc riscvFmaEnc, rd, rs1, rs2, rs3 int) uint32 {
+	return (uint32(rs3) << 27) | (enc.fmt << 25) | (uint32(rs2) << 20) |
+		(uint32(rs1) << 15) | (0x0 << 12) /* rm=dynamic */ | (uint32(rd) << 7) | enc.opcode
+}
+
+// CSR (Control and Status Register) instructions.
+// Format: csr[11:0] | rs1/zimm | funct3 | rd | opcode (0x73).
+type riscvCsrEnc struct {
+	funct3 uint32 // bits [14:12]
+	imm    bool   // true for CSRRWI/CSRRSI/CSRRCI (5-bit uimm variant)
+}
+
+var riscvCsrTable = map[string]riscvCsrEnc{
+	"CSRRW":  {0x1, false}, // rd=CSR, CSR=rs1
+	"CSRRS":  {0x2, false}, // rd=CSR, CSR |= rs1
+	"CSRRC":  {0x3, false}, // rd=CSR, CSR &= ~rs1
+	"CSRRWI": {0x5, true},  // rd=CSR, CSR=uimm
+	"CSRRSI": {0x6, true},  // rd=CSR, CSR |= uimm
+	"CSRRCI": {0x7, true},  // rd=CSR, CSR &= ~uimm
+}
+
+// riscvCsrType encodes a CSR instruction.
+// csr is the 12-bit CSR address; src is either a register number or a 5-bit
+// unsigned immediate (depending on enc.imm).
+func riscvCsrType(enc riscvCsrEnc, rd, src int, csr int32) uint32 {
+	return (uint32(csr&0xFFF) << 20) | (uint32(src&0x1F) << 15) |
+		(enc.funct3 << 12) | (uint32(rd) << 7) | 0x73
+}
+
+// riscvIType encodes an I-type instruction: imm[11:0] | rs1 | funct3 | rd | opcode.
+func riscvIType(enc riscvEnc, rd, rs1 int, imm int32) uint32 {
+	return (uint32(imm&0xFFF) << 20) | (uint32(rs1) << 15) |
+		(enc.funct3 << 12) | (uint32(rd) << 7) | enc.opcode
+}
+
+// riscvSType encodes an S-type instruction: imm[11:5] | rs2 | rs1 | funct3 | imm[4:0] | opcode.
+func riscvSType(enc riscvEnc, rs1, rs2 int, imm int32) uint32 {
+	immU := uint32(imm) & 0xFFF
+	return ((immU >> 5) << 25) | (uint32(rs2) << 20) | (uint32(rs1) << 15) |
+		(enc.funct3 << 12) | ((immU & 0x1F) << 7) | enc.opcode
+}
+
+// riscvBType encodes a B-type instruction (branches).
+func riscvBType(enc riscvEnc, rs1, rs2 int, offset int32) uint32 {
+	imm := uint32(offset) & 0x1FFE     // bits [12:1], bit 0 is always 0
+	return (((imm >> 12) & 1) << 31) | // imm[12]
+		(((imm >> 5) & 0x3F) << 25) | // imm[10:5]
+		(uint32(rs2) << 20) | (uint32(rs1) << 15) |
+		(enc.funct3 << 12) |
+		(((imm >> 1) & 0xF) << 8) | // imm[4:1]
+		(((imm >> 11) & 1) << 7) | // imm[11]
+		enc.opcode
+}
+
+// riscvUType encodes a U-type instruction: imm[31:12] | rd | opcode.
+func riscvUType(enc riscvEnc, rd int, imm int32) uint32 {
+	return (uint32(imm) & 0xFFFFF000) | (uint32(rd) << 7) | enc.opcode
+}
+
+// riscvJType encodes a J-type instruction (JAL).
+func riscvJType(rd int, offset int32) uint32 {
+	imm := uint32(offset) & 0x1FFFFE   // bits [20:1]
+	return (((imm >> 20) & 1) << 31) | // imm[20]
+		(((imm >> 1) & 0x3FF) << 21) | // imm[10:1]
+		(((imm >> 11) & 1) << 20) | // imm[11]
+		(((imm >> 12) & 0xFF) << 12) | // imm[19:12]
+		(uint32(rd) << 7) |
+		0x6F // JAL opcode
+}
+
+// ---- RVC (compressed) encoding helpers ----
+
+// isRVCIntReg reports whether a register number can be encoded in the 3-bit
+// prime register field used by compressed instructions (x8–x15).
+func isRVCIntReg(r int) bool { return r >= 8 && r <= 15 }
+
+// rvcReg3 returns the 3-bit encoding for registers x8–x15 (0–7).
+func rvcReg3(r int) uint32 { return uint32(r - 8) }
+
+// rvcCR encodes a CR-type (register) compressed instruction.
+// Format: funct4 | rd/rs1 | rs2 | op=2.
+func rvcCR(funct4, rd, rs2 uint32) uint16 {
+	return uint16((funct4 << 12) | (rd << 7) | (rs2 << 2) | 0x2)
+}
+
+// rvcCI encodes a CI-type (immediate) compressed instruction.
+// Used for C.ADDI, C.LI, C.LUI, C.ADDIW — linear 6-bit immediate.
+func rvcCI(funct3, rd uint32, imm uint32) uint16 {
+	return uint16((funct3 << 13) | ((imm>>5)&1)<<12 | (rd << 7) | (imm&0x1F)<<2 | 0x1)
+}
+
+// rvcSLLI encodes C.SLLI, which shares funct3=0 with C.ADDI but lives in the
+// op=10 quadrant (unlike C.ADDI's op=01).
+func rvcSLLI(rd, shamt uint32) uint16 {
+	return uint16(((shamt>>5)&1)<<12 | (rd << 7) | (shamt&0x1F)<<2 | 0x2)
+}
+
+// encodeRVCPattern extracts the bits listed in pattern (MSB first) from imm
+// into a packed value, matching cmd/internal/obj/riscv's encodeBitPattern.
+func encodeRVCPattern(imm uint32, pattern []int) uint32 {
+	packed := uint32(0)
+	for _, bit := range pattern {
+		packed = packed<<1 | (imm>>bit)&1
+	}
+	return packed
+}
+
+// rvcLSP encodes a stack-relative compressed load (op=10 quadrant): C.LWSP
+// (funct3=2, 4-byte scale), C.LDSP (funct3=3) or C.FLDSP (funct3=1, 8-byte
+// scale).  offset is the full byte offset.
+func rvcLSP(funct3, rd uint32, offset uint32) uint16 {
+	pattern := []int{5, 4, 3, 8, 7, 6}
+	if funct3 == 0x2 {
+		pattern = []int{5, 4, 3, 2, 7, 6}
+	}
+	packed := uint32(0)
+	for i, b := range pattern {
+		packed |= ((offset >> b) & 1) << (5 - i)
+	}
+	return uint16((funct3 << 13) | ((packed>>5)&1)<<12 | (rd << 7) | (packed&0x1F)<<2 | 0x2)
+}
+
+// rvcSSP encodes a stack-relative compressed store (op=10 quadrant): C.SWSP
+// (funct3=6, 4-byte scale), C.SDSP (funct3=7) or C.FSDSP (funct3=5, 8-byte
+// scale).  offset is the full byte offset.
+func rvcSSP(funct3, rs2 uint32, offset uint32) uint16 {
+	pattern := []int{5, 4, 3, 8, 7, 6}
+	if funct3 == 0x6 {
+		pattern = []int{5, 4, 3, 2, 7, 6}
+	}
+	packed := uint32(0)
+	for i, b := range pattern {
+		packed |= ((offset >> b) & 1) << (5 - i)
+	}
+	return uint16((funct3 << 13) | (packed << 7) | (rs2 << 2) | 0x2)
+}
+
+// rvcCL encodes a register-relative compressed load (op=00 quadrant): C.LW
+// (funct3=2), C.LD (funct3=3) or C.FLD (funct3=1).  imm is the full byte
+// offset; the immediate bits are extracted per the RISC-V CL format.
+func rvcCL(funct3, rd, rs1 uint32, imm uint32) uint16 {
+	pattern := []int{5, 4, 3, 7, 6}
+	if funct3 == 0x2 {
+		pattern = []int{5, 4, 3, 2, 6}
+	}
+	packed := encodeRVCPattern(imm, pattern)
+	return uint16((funct3 << 13) | ((packed>>2)&0x7)<<10 | (rs1 << 7) | ((packed & 0x3) << 5) | (rd << 2))
+}
+
+// rvcCS encodes a register-relative compressed store (op=00 quadrant): C.SW
+// (funct3=6), C.SD (funct3=7) or C.FSD (funct3=5).  imm is the full byte
+// offset; the immediate bits are extracted per the RISC-V CS format.
+func rvcCS(funct3, rs2, rs1 uint32, imm uint32) uint16 {
+	pattern := []int{5, 3, 7, 6}
+	if funct3 == 0x6 {
+		pattern = []int{5, 3, 2, 6}
+	}
+	packed := encodeRVCPattern(imm, pattern)
+	return uint16((funct3 << 13) | ((packed>>2)&0x7)<<10 | (rs1 << 7) | ((packed & 0x3) << 5) | (rs2 << 2))
+}
+
+// rvcCIW encodes a CIW-type compressed immediate wide instruction: C.ADDI4SPN
+// (funct3=0).  imm is the raw byte offset.
+func rvcCIW(funct3, rd uint32, imm uint32) uint16 {
+	packed := encodeRVCPattern(imm, []int{5, 4, 9, 8, 7, 6, 2, 3})
+	return uint16((funct3 << 13) | (packed << 5) | (rd << 2))
+}
+
+// rvcCA encodes a CA-type (arithmetic) compressed instruction.
+// Format: funct6[15:10] | rd'/rs1'[9:7] | funct2[6:5] | rs2'[4:2] | op=01.
+func rvcCA(funct6, funct2, rd, rs2 uint32) uint16 {
+	return uint16((funct6 << 10) | (rd << 7) | (funct2 << 5) | (rs2 << 2) | 0x1)
+}
+
+// rvcCBShift encodes a CB-type shift/immediate compressed instruction
+// (C.SRLI, C.SRAI, C.ANDI).  rd is the 3-bit prime-register index; imm is
+// the 6-bit shamt/immediate; funct2 selects the operation (0=SRLI, 1=SRAI,
+// 2=ANDI).
+func rvcCBShift(funct2, rd, imm uint32) uint16 {
+	return uint16((0x4 << 13) | ((imm>>5)&1)<<12 | (funct2 << 10) | (rd << 7) | (imm&0x1F)<<2 | 0x1)
+}
+
+// rvcADDI16SP encodes C.ADDI16SP: ADDI rd, imm, rd for the stack pointer
+// with a 10-bit signed, 16-byte-scaled immediate.  imm is the raw byte
+// offset; the immediate bits are extracted in the order [9|4|6|8:7|5].
+func rvcADDI16SP(rd uint32, imm int32) uint16 {
+	u := uint32(imm)
+	packed := uint32(0)
+	for _, bit := range []uint{9, 4, 6, 8, 7, 5} {
+		packed = packed<<1 | (u>>bit)&1
+	}
+	return uint16((0x3 << 13) | ((packed>>5)&1)<<12 | (rd << 7) | (packed&0x1F)<<2 | 0x1)
+}

asm/riscv_encode_test.go

@@ -0,0 +1,763 @@
+// Copyright (c) 2026 Petr Balvín <opensource@petrbalvin.org> (https://petrbalvin.org)
+// SPDX-License-Identifier: BSD-3-Clause
+
+package asm
+
+import (
+	"bytes"
+	"testing"
+
+	"sourcedock.dev/petrbalvin/gasm-devkit/ast"
+	"sourcedock.dev/petrbalvin/gasm-devkit/parser"
+)
+
+// firstTextRISCV parses assembly source and returns the first TEXT function body.
+func firstTextRISCV(t *testing.T, src string) *ast.Text {
+	t.Helper()
+	f, errs := parser.Parse("f_riscv64.s", src)
+	if len(errs) > 0 {
+		t.Fatalf("parse: %v", errs)
+	}
+	for _, d := range f.Decls {
+		if fn, ok := d.(*ast.Text); ok {
+			return fn
+		}
+	}
+	t.Fatal("no TEXT found")
+	return nil
+}
+
+// assembleRISCVHelper assembles one TEXT function and returns its code bytes.
+func assembleRISCVHelper(t *testing.T, fn *ast.Text) []byte {
+	t.Helper()
+	code, _, _, _, _, err := assembleRISCV(fn)
+	if err != nil {
+		t.Fatalf("assemble: %v", err)
+	}
+	return code
+}
+
+func TestRISCV_add(t *testing.T) {
+	// func add(a, b int64) int64
+	fn := firstTextRISCV(t, `#include "textflag.h"
+TEXT ·add(SB), NOSPLIT, $0-24
+	MOV a+0(FP), X10
+	MOV b+8(FP), X11
+	ADD X11, X10, X10
+	MOV X10, ret+16(FP)
+	RET
+`)
+	code := assembleRISCVHelper(t, fn)
+	// should be 12 bytes with RVC: C.LDSP + C.LDSP + ADD + C.SDSP + C.JR
+	_ = code
+	if len(code) == 0 {
+		t.Error("empty output")
+	}
+}
+
+func TestRISCV_arithmetic(t *testing.T) {
+	fn := firstTextRISCV(t, `#include "textflag.h"
+TEXT ·arith(SB), NOSPLIT, $0
+	ADD X10, X11, X12
+	SUB X12, X13, X14
+	MUL X14, X15, X16
+	DIV X16, X17, X18
+	REM X18, X19, X20
+	RET
+`)
+	code := assembleRISCVHelper(t, fn)
+	// 5 R-type instructions + RET = 5*4 + 4 = 24
+	if len(code) != 24 {
+		t.Errorf("expected 24 bytes, got %d", len(code))
+	}
+}
+
+func TestRISCV_loadStore(t *testing.T) {
+	fn := firstTextRISCV(t, `#include "textflag.h"
+TEXT ·mem(SB), NOSPLIT, $0
+	LD (X10), X11
+	SD X11, (X12)
+	LW (X13), X14
+	SW X14, (X15)
+	RET
+`)
+	code := assembleRISCVHelper(t, fn)
+	// Four register-relative loads/stores compress (2B each) + JALR (4B) = 12.
+	if len(code) != 12 {
+		t.Errorf("expected 12 bytes, got %d", len(code))
+	}
+}
+
+func TestRISCV_immediate(t *testing.T) {
+	fn := firstTextRISCV(t, `#include "textflag.h"
+TEXT ·imm(SB), NOSPLIT, $0
+	ADDI $42, X10, X11
+	ANDI $0xFF, X11, X12
+	ORI $1, X12, X13
+	XORI $0, X13, X14
+	RET
+`)
+	code := assembleRISCVHelper(t, fn)
+	// 4 I-type + JALR = 4*4 + 4 = 20
+	if len(code) != 20 {
+		t.Errorf("expected 20 bytes, got %d", len(code))
+	}
+}
+
+func TestRISCV_branches(t *testing.T) {
+	fn := firstTextRISCV(t, `#include "textflag.h"
+TEXT ·br(SB), NOSPLIT, $0
+	ADDI $1, X10, X10
+loop:
+	BEQ X10, X11, done
+	ADDI $1, X10, X10
+	JMP loop
+done:
+	RET
+`)
+	code := assembleRISCVHelper(t, fn)
+	_ = code
+	if len(code) == 0 {
+		t.Error("empty output")
+	}
+}
+
+func TestRISCV_MOV_imm_small(t *testing.T) {
+	// MOV $42, rd → ADDI (fits in 12 bits, but not C.LI's 6-bit immediate).
+	fn := firstTextRISCV(t, `#include "textflag.h"
+TEXT ·small(SB), NOSPLIT, $0
+	MOV $42, X10
+	RET
+`)
+	code := assembleRISCVHelper(t, fn)
+	// ADDI (4B) + JALR (4B) = 8
+	if len(code) != 8 {
+		t.Errorf("expected 8 bytes, got %d", len(code))
+	}
+}
+
+func TestRISCV_MOV_imm_large(t *testing.T) {
+	// MOV $0x12345, rd → C.LUI $18 (2B) + ADDIW $837 (4B).
+	fn := firstTextRISCV(t, `#include "textflag.h"
+TEXT ·large(SB), NOSPLIT, $0
+	MOV $0x12345, X10
+	RET
+`)
+	code := assembleRISCVHelper(t, fn)
+	// C.LUI (2B) + ADDIW (4B) + JALR (4B) = 10
+	if len(code) != 10 {
+		t.Errorf("expected 10 bytes, got %d", len(code))
+	}
+}
+
+func TestRISCV_MOV_reg(t *testing.T) {
+	// MOV rs, rd → ADDI $0, rs, rd, compresses to C.MV
+	fn := firstTextRISCV(t, `#include "textflag.h"
+TEXT ·reg(SB), NOSPLIT, $0
+	MOV X10, X11
+	RET
+`)
+	code := assembleRISCVHelper(t, fn)
+	// C.MV (2B) + JALR (4B) = 6
+	if len(code) != 6 {
+		t.Errorf("expected 6 bytes, got %d (% x)", len(code), code)
+	}
+}
+
+func TestRISCV_MOV_frame(t *testing.T) {
+	// MOV name+off(FP), rd → load with frame mapping
+	fn := firstTextRISCV(t, `#include "textflag.h"
+TEXT ·frame(SB), NOSPLIT, $0-8
+	MOV a+0(FP), X10
+	MOV X10, ret+0(FP)
+	RET
+`)
+	code := assembleRISCVHelper(t, fn)
+	// C.LDSP (2B) + C.SDSP (2B) + JALR (4B) = 8
+	if len(code) != 8 {
+		t.Errorf("expected 8 bytes, got %d", len(code))
+	}
+}
+
+func TestRISCV_RVC_loadStore(t *testing.T) {
+	// Verify that loads/stores from SP are compressed.
+	fn := firstTextRISCV(t, `#include "textflag.h"
+TEXT ·rvcstore(SB), NOSPLIT, $0
+	LD 0(SP), X10
+	SD X10, 8(SP)
+	RET
+`)
+	code := assembleRISCVHelper(t, fn)
+	// C.LDSP (2B) + C.SDSP (2B) + JALR (4B) = 8
+	if len(code) != 8 {
+		t.Errorf("expected 8 bytes, got %d (% x)", len(code), code)
+	}
+}
+
+func TestRISCV_atomics(t *testing.T) {
+	fn := firstTextRISCV(t, `#include "textflag.h"
+TEXT ·amo(SB), NOSPLIT, $0
+	AMOADDD X10, (X11), X12
+	LRD (X13), X14
+	SCD X15, (X16), X17
+	RET
+`)
+	code := assembleRISCVHelper(t, fn)
+	// 3 AMO instructions (4B each) + JALR (4B) = 16
+	if len(code) != 16 {
+		t.Errorf("expected 16 bytes, got %d", len(code))
+	}
+}
+
+func TestRISCV_fpArith(t *testing.T) {
+	fn := firstTextRISCV(t, `#include "textflag.h"
+TEXT ·fpadd(SB), NOSPLIT, $0
+	FADDD F10, F11, F12
+	FSUBD F12, F13, F14
+	FMULD F14, F15, F16
+	FDIVD F16, F17, F18
+	FSQRTD F18, F19
+	RET
+`)
+	code := assembleRISCVHelper(t, fn)
+	// 5 FP instructions (4B each) + JALR (4B) = 24
+	if len(code) != 24 {
+		t.Errorf("expected 24 bytes, got %d (%d)", len(code), len(code))
+	}
+}
+
+func TestRISCV_csr(t *testing.T) {
+	fn := firstTextRISCV(t, `#include "textflag.h"
+TEXT ·csrtest(SB), NOSPLIT, $0
+	CSRRS $0x300, X0, X10
+	CSRRW $0x305, X10, X11
+	CSRRSI $0x304, $5, X12
+	RET
+`)
+	code := assembleRISCVHelper(t, fn)
+	// 3 CSR instructions (4B each) + JALR (4B) = 16
+	if len(code) != 16 {
+		t.Errorf("expected 16 bytes, got %d", len(code))
+	}
+}
+
+func TestRISCV_fma(t *testing.T) {
+	fn := firstTextRISCV(t, `#include "textflag.h"
+TEXT ·fmatest(SB), NOSPLIT, $0
+	FMADDD F10, F11, F12, F13
+	FMSUBD F13, F14, F15, F16
+	FNMSUBD F16, F17, F18, F19
+	FNMADDD F19, F10, F11, F12
+	RET
+`)
+	code := assembleRISCVHelper(t, fn)
+	// 4 FMA instructions (4B each) + JALR (4B) = 20
+	if len(code) != 20 {
+		t.Errorf("expected 20 bytes, got %d", len(code))
+	}
+}
+
+func TestRISCV_conversions(t *testing.T) {
+	fn := firstTextRISCV(t, `#include "textflag.h"
+TEXT ·cvt(SB), NOSPLIT, $0
+	FCVTDL X10, F10
+	FCVTLD F10, X11
+	FMVXD F10, X12
+	FMVDX X12, F11
+	RET
+`)
+	code := assembleRISCVHelper(t, fn)
+	// 4 conversion instructions (4B each) + JALR (4B) = 20
+	if len(code) != 20 {
+		t.Errorf("expected 20 bytes, got %d", len(code))
+	}
+}
+
+func TestRISCV_fpCmp(t *testing.T) {
+	fn := firstTextRISCV(t, `#include "textflag.h"
+TEXT ·cmp(SB), NOSPLIT, $0
+	FEQD F10, F11, X10
+	FLTD F12, F13, X11
+	FLED F14, F15, X12
+	RET
+`)
+	code := assembleRISCVHelper(t, fn)
+	// 3 FP compare (4B each) + JALR (4B) = 16
+	if len(code) != 16 {
+		t.Errorf("expected 16 bytes, got %d", len(code))
+	}
+}
+
+func TestRISCV_forwardBranch(t *testing.T) {
+	// Forward label reference — must not fail.
+	fn := firstTextRISCV(t, `#include "textflag.h"
+TEXT ·fwd(SB), NOSPLIT, $0
+	ADDI $1, X10, X10
+	BEQ X10, X11, done
+	ADDI $1, X10, X10
+done:
+	RET
+`)
+	code := assembleRISCVHelper(t, fn)
+	_ = code
+	if len(code) == 0 {
+		t.Error("empty output")
+	}
+}
+
+func TestRISCV_RVC_ADDI(t *testing.T) {
+	// ADDI where rd=rs1 and small imm → C.ADDI
+	fn := firstTextRISCV(t, `#include "textflag.h"
+TEXT ·caddi(SB), NOSPLIT, $0
+	ADDI $5, X10, X10
+	RET
+`)
+	code := assembleRISCVHelper(t, fn)
+	// C.ADDI (2B) + JALR (4B) = 6
+	if len(code) != 6 {
+		t.Errorf("expected 6 bytes, got %d", len(code))
+	}
+}
+
+func TestRISCV_RVC_LI(t *testing.T) {
+	// ADDI X0, $imm, rd → C.LI
+	fn := firstTextRISCV(t, `#include "textflag.h"
+TEXT ·cli(SB), NOSPLIT, $0
+	ADDI $7, X0, X10
+	RET
+`)
+	code := assembleRISCVHelper(t, fn)
+	// C.LI (2B) + JALR (4B) = 6
+	if len(code) != 6 {
+		t.Errorf("expected 6 bytes, got %d", len(code))
+	}
+}
+
+func TestRISCV_RVC_LUI(t *testing.T) {
+	// LUI rd, small nonzero imm → C.LUI
+	fn := firstTextRISCV(t, `#include "textflag.h"
+TEXT ·clui(SB), NOSPLIT, $0
+	LUI X10, $1
+	RET
+`)
+	code := assembleRISCVHelper(t, fn)
+	// C.LUI (2B) + JALR (4B) = 6
+	if len(code) != 6 {
+		t.Errorf("expected 6 bytes, got %d", len(code))
+	}
+}
+
+func TestRISCV_AssembleFile(t *testing.T) {
+	src := `#include "textflag.h"
+
+TEXT ·add(SB), NOSPLIT, $0-24
+	MOV a+0(FP), X10
+	RET
+
+TEXT ·sub(SB), NOSPLIT, $0
+	SUB X10, X11, X12
+	RET
+`
+	f, errs := parser.Parse("t_riscv64.s", src)
+	if len(errs) > 0 {
+		t.Fatalf("parse: %v", errs)
+	}
+	img, err := AssembleFileRISCV(f)
+	if err != nil {
+		t.Fatalf("AssembleFileRISCV: %v", err)
+	}
+	if len(img.Funcs) != 2 {
+		t.Fatalf("expected 2 functions, got %d", len(img.Funcs))
+	}
+	// func add: C.LDSP(2) + JALR(4) = 6
+	if img.Funcs[0].Size != 6 {
+		t.Errorf("add: expected 6 bytes, got %d", img.Funcs[0].Size)
+	}
+	// func sub: SUB(4) + JALR(4) = 8
+	if img.Funcs[1].Size != 8 {
+		t.Errorf("sub: expected 8 bytes, got %d", img.Funcs[1].Size)
+	}
+}
+
+func TestRISCV_encodings(t *testing.T) {
+	// Smoke test that all known RISC-V mnemonics encode successfully.
+	tests := []struct {
+		name, src string
+		wantBytes int
+	}{
+		{"ADD", "ADD X10, X11, X12\nRET\n", 8},
+		{"SUBW", "SUBW X10, X11, X12\nRET\n", 8},
+		{"MUL", "MUL X10, X11, X12\nRET\n", 8},
+		{"DIVW", "DIVW X10, X11, X12\nRET\n", 8},
+		{"REMUW", "REMUW X10, X11, X12\nRET\n", 8},
+		{"ADDIW", "ADDIW $5, X10, X11\nRET\n", 8},
+		{"SLLI", "SLLI $3, X10, X11\nRET\n", 8}, // ADDI+SLLI? No, SLLI uses I-type
+		{"SRLI", "SRLI $2, X10, X11\nRET\n", 8},
+		{"SRAI", "SRAI $1, X10, X11\nRET\n", 8},
+		{"LB", "LB (X10), X11\nRET\n", 8},
+		{"LBU", "LBU (X10), X11\nRET\n", 8},
+		{"LH", "LH (X10), X11\nRET\n", 8},
+		{"LHU", "LHU (X10), X11\nRET\n", 8},
+		{"LWU", "LWU (X10), X11\nRET\n", 8},
+		{"SB", "SB X10, (X11)\nRET\n", 8},
+		{"SH", "SH X10, (X11)\nRET\n", 8},
+		{"SW", "SW X10, (X11)\nRET\n", 6},
+		{"LUI", "LUI X10, $0x12345\nRET\n", 8},
+		{"AUIPC", "AUIPC X10, $0\nRET\n", 8},
+		{"FLW", "FLW (X10), F10\nRET\n", 8},
+		{"FSW", "FSW F10, (X11)\nRET\n", 8},
+		{"FADDS", "FADDS F10, F11, F12\nRET\n", 8},
+		{"FMINS", "FMINS F10, F11, F12\nRET\n", 8},
+		{"FMAXD", "FMAXD F10, F11, F12\nRET\n", 8},
+		{"FCVTSD", "FCVTSD F10, F11\nRET\n", 8},
+		{"FCVTDS", "FCVTDS F10, F11\nRET\n", 8},
+		{"FMVXW", "FMVXW F10, X10\nRET\n", 8},
+		{"FMADD_S", "FMADDS F10, F11, F12, F13\nRET\n", 8},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			fn := firstTextRISCV(t, `#include "textflag.h"
+TEXT ·`+tt.name+`(SB), NOSPLIT, $0
+	`+tt.src)
+			code := assembleRISCVHelper(t, fn)
+			if len(code) != tt.wantBytes {
+				t.Errorf("expected %d bytes, got %d", tt.wantBytes, len(code))
+			}
+		})
+	}
+}
+
+func TestRISCV_RVC_branch(t *testing.T) {
+	// Branches are never RVC-compressed (no C.BEQZ/C.BNEZ), matching go tool asm.
+	fn := firstTextRISCV(t, `#include "textflag.h"
+TEXT ·cbeqz(SB), NOSPLIT, $0
+	ADDI $1, X10, X10
+	BEQ X10, X0, done
+	ADDI $1, X10, X10
+done:
+	RET
+`)
+	code := assembleRISCVHelper(t, fn)
+	// C.ADDI(2) + BEQ(4) + C.ADDI(2) + JALR(4) = 12
+	if len(code) != 12 {
+		t.Errorf("expected 12 bytes with uncompressed BEQ, got %d", len(code))
+	}
+}
+
+func TestRISCV_RVC_CJ(t *testing.T) {
+	// JMP target → JAL X0 (never compressed to C.J), matching go tool asm.
+	fn := firstTextRISCV(t, `#include "textflag.h"
+	TEXT ·cj(SB), NOSPLIT, $0
+		JMP done
+	done:
+		RET
+	`)
+	code := assembleRISCVHelper(t, fn)
+	// JAL(4) + JALR(4) = 8
+	if len(code) != 8 {
+		t.Errorf("expected 8 bytes with uncompressed JMP, got %d", len(code))
+	}
+}
+
+func TestRISCV_RVC_CADD(t *testing.T) {
+	// ADD where rd==rs1 and both in prime regs → C.ADD.
+	fn := firstTextRISCV(t, `#include "textflag.h"
+	TEXT ·cadd(SB), NOSPLIT, $0
+		ADD X10, X11, X10
+		RET
+	`)
+	code := assembleRISCVHelper(t, fn)
+	// C.ADD(2) + JALR(4) = 6
+	if len(code) != 6 {
+		t.Errorf("expected 6 bytes with C.ADD, got %d", len(code))
+	}
+}
+
+func TestRISCV_RVC_CADD_commute(t *testing.T) {
+	// ADD where rd==rs2 (commutative swap) → C.ADD.
+	fn := firstTextRISCV(t, `#include "textflag.h"
+	TEXT ·cadd2(SB), NOSPLIT, $0
+		ADD X11, X10, X10
+		RET
+	`)
+	code := assembleRISCVHelper(t, fn)
+	// C.ADD(2) + JALR(4) = 6
+	if len(code) != 6 {
+		t.Errorf("expected 6 bytes with C.ADD (commuted), got %d", len(code))
+	}
+}
+
+func TestRISCV_RVC_CSUB(t *testing.T) {
+	// SUB rs2, rs1, rd → C.SUB when rd == rs1 and both in prime regs.
+	fn := firstTextRISCV(t, `#include "textflag.h"
+TEXT ·csub(SB), NOSPLIT, $0
+	SUB X11, X10, X10
+	RET
+`)
+	code := assembleRISCVHelper(t, fn)
+	// SUB X11, X10, X10 → rs2=X11, rs1=X10, rd=X10; rd==rs1 → C.SUB (2B) + JALR (4B) = 6.
+	if len(code) != 6 {
+		t.Errorf("expected 6 bytes with C.SUB, got %d (% x)", len(code), code)
+	}
+}
+
+func TestRISCV_RVC_CXOR(t *testing.T) {
+	fn := firstTextRISCV(t, `#include "textflag.h"
+TEXT ·cxor(SB), NOSPLIT, $0
+	XOR X10, X11, X10
+	RET
+`)
+	code := assembleRISCVHelper(t, fn)
+	if len(code) != 6 {
+		t.Errorf("expected 6 bytes with C.XOR, got %d", len(code))
+	}
+}
+
+func TestRISCV_RVC_COR(t *testing.T) {
+	fn := firstTextRISCV(t, `#include "textflag.h"
+TEXT ·cor(SB), NOSPLIT, $0
+	OR X10, X11, X10
+	RET
+`)
+	code := assembleRISCVHelper(t, fn)
+	if len(code) != 6 {
+		t.Errorf("expected 6 bytes with C.OR, got %d", len(code))
+	}
+}
+
+func TestRISCV_RVC_CAND(t *testing.T) {
+	fn := firstTextRISCV(t, `#include "textflag.h"
+TEXT ·cand(SB), NOSPLIT, $0
+	AND X10, X11, X10
+	RET
+`)
+	code := assembleRISCVHelper(t, fn)
+	if len(code) != 6 {
+		t.Errorf("expected 6 bytes with C.AND, got %d", len(code))
+	}
+}
+
+func TestRISCV_RVC_CFLDSP(t *testing.T) {
+	fn := firstTextRISCV(t, `#include "textflag.h"
+TEXT ·cfldsp(SB), NOSPLIT, $0-8
+	FLD a+0(FP), F10
+	RET
+`)
+	code := assembleRISCVHelper(t, fn)
+	// C.FLDSP(2) + JALR(4) = 6
+	if len(code) != 6 {
+		t.Errorf("expected 6 bytes with C.FLDSP, got %d", len(code))
+	}
+}
+
+func TestRISCV_RVC_CFSDSP(t *testing.T) {
+	fn := firstTextRISCV(t, `#include "textflag.h"
+TEXT ·cfsdsp(SB), NOSPLIT, $0-8
+	FSD F10, ret+0(FP)
+	RET
+`)
+	code := assembleRISCVHelper(t, fn)
+	// C.FSDSP(2) + JALR(4) = 6
+	if len(code) != 6 {
+		t.Errorf("expected 6 bytes with C.FSDSP, got %d", len(code))
+	}
+}
+
+func TestRISCV_SB_addr(t *testing.T) {
+	// MOV $sym<>(SB), rd → AUIPC + ADDI (8 bytes for SB).
+	src := `#include "textflag.h"
+TEXT ·sbaddr(SB), NOSPLIT, $0
+	MOV $answer<>(SB), X10
+	RET
+GLOBL answer<>(SB), RODATA, $8
+DATA answer<>+0(SB)/8, $42
+`
+	f, errs := parser.Parse("t_riscv64.s", src)
+	if len(errs) > 0 {
+		t.Fatalf("parse: %v", errs)
+	}
+	img, err := AssembleFileRISCV(f)
+	if err != nil {
+		t.Fatalf("AssembleFileRISCV: %v", err)
+	}
+	// AUIPC(4) + ADDI(4) + JALR(4) = 12
+	if img.Funcs[0].Size != 12 {
+		t.Errorf("expected 12 bytes, got %d", img.Funcs[0].Size)
+	}
+}
+
+func TestRISCV_SB_store(t *testing.T) {
+	// MOV rd, sym<>(SB) → AUIPC + SD (8 bytes for SB).
+	src := `#include "textflag.h"
+TEXT ·sbstore(SB), NOSPLIT, $0
+	MOV X10, result<>(SB)
+	RET
+GLOBL result<>(SB), NOPTR, $8
+`
+	f, errs := parser.Parse("t_riscv64.s", src)
+	if len(errs) > 0 {
+		t.Fatalf("parse: %v", errs)
+	}
+	img, err := AssembleFileRISCV(f)
+	if err != nil {
+		t.Fatalf("AssembleFileRISCV: %v", err)
+	}
+	// AUIPC X31(4) + SD X10,0(X31)(4) + JALR(4) = 12
+	if img.Funcs[0].Size != 12 {
+		t.Errorf("expected 12 bytes, got %d", img.Funcs[0].Size)
+	}
+}
+
+func TestRISCV_ELF(t *testing.T) {
+	src := `#include "textflag.h"
+TEXT ·simple(SB), NOSPLIT, $0
+	RET
+`
+	f, errs := parser.Parse("t_riscv64.s", src)
+	if len(errs) > 0 {
+		t.Fatalf("parse: %v", errs)
+	}
+	img, err := AssembleFileRISCV(f)
+	if err != nil {
+		t.Fatalf("AssembleFileRISCV: %v", err)
+	}
+	obj, err := img.ELFRISCVObject()
+	if err != nil {
+		t.Fatalf("ELFRISCVObject: %v", err)
+	}
+	if len(obj) < 4 || obj[0] != 0x7f || obj[1] != 'E' || obj[2] != 'L' || obj[3] != 'F' {
+		t.Fatal("not a valid ELF file")
+	}
+	if len(obj) >= 20 {
+		machine := uint16(obj[18]) | uint16(obj[19])<<8
+		if machine != 243 {
+			t.Errorf("e_machine = %d, want 243 (EM_RISCV)", machine)
+		}
+	}
+}
+
+func TestRISCV_ELF_withData(t *testing.T) {
+	src := `#include "textflag.h"
+TEXT ·get(SB), NOSPLIT, $0
+	RET
+GLOBL val<>(SB), RODATA, $4
+DATA val<>+0(SB)/4, $7
+`
+	f, errs := parser.Parse("t_riscv64.s", src)
+	if len(errs) > 0 {
+		t.Fatalf("parse: %v", errs)
+	}
+	img, err := AssembleFileRISCV(f)
+	if err != nil {
+		t.Fatalf("AssembleFileRISCV: %v", err)
+	}
+	if len(img.DataSyms) != 1 {
+		t.Fatalf("expected 1 data symbol, got %d", len(img.DataSyms))
+	}
+	if img.DataSyms[0].Name != "val" {
+		t.Errorf("data symbol name = %q, want val", img.DataSyms[0].Name)
+	}
+	if img.DataSyms[0].Size != 4 {
+		t.Errorf("data symbol size = %d, want 4", img.DataSyms[0].Size)
+	}
+	obj, err := img.ELFRISCVObject()
+	if err != nil {
+		t.Fatalf("ELFRISCVObject: %v", err)
+	}
+	_ = obj
+}
+
+func TestRISCV_SB_load(t *testing.T) {
+	// MOV sym<>(SB), rd → AUIPC + LD (8 bytes for SB).
+	src := `#include "textflag.h"
+TEXT ·sbload(SB), NOSPLIT, $0
+	MOV answer<>(SB), X10
+	RET
+GLOBL answer<>(SB), RODATA, $8
+DATA answer<>+0(SB)/8, $42
+`
+	f, errs := parser.Parse("t_riscv64.s", src)
+	if len(errs) > 0 {
+		t.Fatalf("parse: %v", errs)
+	}
+	img, err := AssembleFileRISCV(f)
+	if err != nil {
+		t.Fatalf("AssembleFileRISCV: %v", err)
+	}
+	// AUIPC(4) + LD(4) + JALR(4) = 12
+	if img.Funcs[0].Size != 12 {
+		t.Errorf("expected 12 bytes, got %d", img.Funcs[0].Size)
+	}
+}
+
+func TestRISCV_system_instrs(t *testing.T) {
+	// Test FENCE, ECALL, EBREAK encoding.
+	fn := firstTextRISCV(t, `#include "textflag.h"
+TEXT ·sys(SB), NOSPLIT, $0
+	FENCE
+	ECALL
+	EBREAK
+	RET
+`)
+	code := assembleRISCVHelper(t, fn)
+	// FENCE(4) + ECALL(4) + C.EBREAK(2) + JALR(4) = 14
+	if len(code) != 14 {
+		t.Errorf("expected 14 bytes, got %d (% x)", len(code), code)
+	}
+}
+
+func TestRISCV_MOV_sym_FP_error(t *testing.T) {
+	// MOV $sym(FP), rd should return an error (unsupported).
+	fn := firstTextRISCV(t, `#include "textflag.h"
+TEXT ·badfp(SB), NOSPLIT, $0
+	MOV $arg(FP), X10
+	RET
+`)
+	_, _, _, _, _, err := assembleRISCV(fn)
+	if err == nil {
+		t.Error("expected error for MOV $arg(FP), got nil")
+	}
+}
+
+func TestRISCV_CALL(t *testing.T) {
+	// CALL sym(SB) → JAL X1, sym(SB) with a single R_RISCV_JAL relocation.
+	fn := firstTextRISCV(t, `#include "textflag.h"
+TEXT ·calltest(SB), NOSPLIT, $0
+	CALL ext(SB)
+	RET
+`)
+	code, _, relocs, _, _, err := assembleRISCV(fn)
+	if err != nil {
+		t.Fatalf("assemble: %v", err)
+	}
+	// prologue (8) + JAL (4) + epilogue+JALR (8) = 20
+	if len(code) != 20 {
+		t.Fatalf("expected 20 bytes with CALL sym(SB), got %d", len(code))
+	}
+	if len(relocs) != 1 {
+		t.Fatalf("relocs = %d, want 1", len(relocs))
+	}
+	r := relocs[0]
+	if r.Kind != RelRISCVJal || r.Name != "ext" || r.Off != 8 || r.After != 12 || r.Addend != 0 {
+		t.Errorf("reloc = {kind %v off %d after %d name %q addend %d}", r.Kind, r.Off, r.After, r.Name, r.Addend)
+	}
+	// The JAL instruction itself is JAL X1, 0 at function offset 8.
+	wantJAL := wordLE(riscvJType(1, 0))
+	if !bytes.Equal(code[8:12], wantJAL) {
+		t.Errorf("JAL = % x, want % x", code[8:12], wantJAL)
+	}
+}
+
+func TestRISCV_CALL_local_error(t *testing.T) {
+	fn := firstTextRISCV(t, `#include "textflag.h"
+TEXT ·calllocal(SB), NOSPLIT, $0
+	CALL sub
+sub:
+	RET
+`)
+	_, _, _, _, _, err := assembleRISCV(fn)
+	if err == nil {
+		t.Error("expected error for CALL to local label, got nil")
+	}
+}

asm/riscv_frame.go

@@ -0,0 +1,182 @@
+// Copyright (c) 2026 Petr Balvín <opensource@petrbalvin.org> (https://petrbalvin.org)
+// SPDX-License-Identifier: BSD-3-Clause
+
+package asm
+
+import (
+	"strings"
+
+	"sourcedock.dev/petrbalvin/gasm-devkit/ast"
+)
+
+// RISC-V frame mapping, matching the Go toolchain's riscv64 backend.
+//
+// Go's riscv64 functions have no hardware frame pointer: FP and SP are
+// synthetic registers resolved against the hardware stack pointer (X2) and
+// the frame size.  The return address lives in the link register (X1, RA/LR).
+//
+// The autosize is the real stack adjustment: the declared local frame plus
+// the 8 bytes for the saved link register (the toolchain's FixedFrameSize).
+// A leaf function with a zero frame gets no prologue at all.
+//
+// Prologue (autosize > 0), byte-identical to the toolchain:
+//
+//	MOV  LR, -autosize(SP)   // save LR below the new SP (traceback-safe)
+//	ADDI $-autosize, SP, SP  // open the frame
+//	MOV  LR, 0(SP)           // save LR again at SP (signal-safety)
+//
+// Epilogue (autosize > 0): MOV 0(SP), LR; ADDI $autosize, SP, SP; the RET's
+// uncompressed JALR X0, 0(X1) follows.  The toolchain restores LR on every
+// frame, leaf or not.
+
+// riscvFrameInfo holds the frame layout derived from a TEXT directive.
+type riscvFrameInfo struct {
+	autosize int // the real SP adjustment (locals + saved LR)
+}
+
+// riscvComputeFrame derives the frame layout for a TEXT function.
+func riscvComputeFrame(t *ast.Text) riscvFrameInfo {
+	frame := frameSize(t)
+	if frame != 0 || !riscvIsLeaf(t) {
+		// FixedFrameSize = 8: space for the saved link register.  A
+		// zero-frame non-leaf function still opens an 8-byte frame for LR.
+		return riscvFrameInfo{autosize: frame + 8}
+	}
+	return riscvFrameInfo{}
+}
+
+// riscvIsLeaf reports whether a function contains no call instructions.
+// CALL always links; JAL/JALR link only when their destination register is
+// the link register (X1), matching cmd/internal/obj/riscv's containsCall.
+func riscvIsLeaf(t *ast.Text) bool {
+	for _, stmt := range t.Body {
+		in, ok := stmt.(*ast.Instr)
+		if !ok {
+			continue
+		}
+		switch strings.ToUpper(in.Mnemonic.Text) {
+		case "CALL":
+			return false
+		case "JAL":
+			// JAL rd, target — a call only when rd is the link register.
+			if len(in.Operands) >= 2 && regFromOperand(in.Operands[0]) == 1 {
+				return false
+			}
+		case "JALR":
+			// JALR rs1, rd — a call when rd is X1; JALR offset(rs1) always
+			// links to X1.
+			if len(in.Operands) == 1 {
+				return false
+			}
+			if len(in.Operands) >= 2 && regFromOperand(in.Operands[1]) == 1 {
+				return false
+			}
+		}
+	}
+	return true
+}
+
+// riscvPrologue returns the prologue bytes for a RISC-V function, matching
+// the toolchain's compression: the SP adjustment compresses to C.ADDI when
+// the immediate fits, and the second LR save compresses to C.SDSP.
+func riscvPrologue(fi riscvFrameInfo) []byte {
+	if fi.autosize == 0 {
+		return nil
+	}
+	var out []byte
+	// MOV LR, -autosize(SP) — SD X1, -autosize(X2).  The negative offset is
+	// not compressible to C.SDSP (unsigned), so it stays 4 bytes.
+	out = append(out, wordLE(riscvSType(riscvEnc{0x23, 0x3, 0x00}, 2, 1, int32(-fi.autosize)))...)
+	// ADDI $-autosize, SP, SP — open the frame (C.ADDI when it fits).
+	out = append(out, riscvSPAdjust(int32(-fi.autosize))...)
+	// MOV LR, 0(SP) — SD X1, 0(X2) → C.SDSP X1, 0.
+	c := rvcSSP(0x7, 1, 0)
+	out = append(out, byte(c), byte(c>>8))
+	return out
+}
+
+// riscvReturn returns the bytes for a RET: the epilogue (restore LR and
+// deallocate the frame when present) followed by the uncompressed JALR X0,
+// 0(X1) the toolchain emits for RET (it never compresses RET to C.JR).
+func riscvReturn(fi riscvFrameInfo) []byte {
+	var out []byte
+	if fi.autosize != 0 {
+		// MOV 0(SP), LR — LD X1, 0(X2) → C.LDSP X1, 0.
+		c := rvcLSP(0x3, 1, 0)
+		out = append(out, byte(c), byte(c>>8))
+		// ADDI $autosize, SP, SP — close the frame (C.ADDI when it fits).
+		out = append(out, riscvSPAdjust(int32(fi.autosize))...)
+	}
+	// JALR X0, 0(X1).
+	return append(out, wordLE(riscvIType(riscvEnc{0x67, 0x0, 0x00}, 0, 1, 0))...)
+}
+
+// riscvSPAdjust emits an ADDI rd, imm, rd for the stack pointer (rd = rs1 =
+// X2), compressed to C.ADDI16SP when the immediate is a nonzero 16-byte
+// multiple, else C.ADDI when it fits 6-bit signed.
+func riscvSPAdjust(imm int32) []byte {
+	if imm != 0 && imm%16 == 0 && imm >= -512 && imm <= 511 {
+		c := rvcADDI16SP(2, imm)
+		return []byte{byte(c), byte(c >> 8)}
+	}
+	if riscvFitsCAddi(imm) {
+		c := rvcCI(0x0, 2, uint32(imm)&0x3F)
+		return []byte{byte(c), byte(c >> 8)}
+	}
+	return wordLE(riscvIType(riscvEnc{0x13, 0x0, 0x00}, 2, 2, imm))
+}
+
+// riscvFitsCAddi reports whether imm compresses to C.ADDI (a nonzero 6-bit
+// signed immediate).
+func riscvFitsCAddi(imm int32) bool {
+	return imm != 0 && imm >= -32 && imm <= 31
+}
+
+// riscvPrologueSpadjPC returns the function-relative byte offset where the
+// prologue has finished decrementing SP (the delta becomes autosize).
+func riscvPrologueSpadjPC(fi riscvFrameInfo) int {
+	if fi.autosize == 0 {
+		return 0
+	}
+	// SD (4 bytes) + ADDI/C.ADDI (2 or 4 bytes).
+	return 4 + riscvSPAdjustLen(int32(-fi.autosize))
+}
+
+// riscvReturnEpilogueLen returns the byte length of the RET's epilogue up to
+// (but not including) the final JALR — the point where SP is restored.
+func riscvReturnEpilogueLen(fi riscvFrameInfo) int {
+	if fi.autosize == 0 {
+		return 0
+	}
+	// C.LDSP (2 bytes) + ADDI/C.ADDI (2 or 4 bytes).
+	return 2 + riscvSPAdjustLen(int32(fi.autosize))
+}
+
+func riscvSPAdjustLen(imm int32) int {
+	if imm != 0 && imm%16 == 0 && imm >= -512 && imm <= 511 {
+		return 2
+	}
+	if riscvFitsCAddi(imm) {
+		return 2
+	}
+	return 4
+}
+
+// riscvResolvePseudo translates a pseudo-register memory reference into a
+// hardware base register and offset.  x+N(FP) → (N + autosize + 8)(SP);
+// x+N(SP) → (N + autosize)(SP).  Returns base = -1 for an unresolvable
+// reference (SB: static data, handled by the relocation path).
+func riscvResolvePseudo(sym *ast.Symbol, fi riscvFrameInfo) (base int, off int32) {
+	if sym == nil {
+		return -1, 0
+	}
+	switch sym.Pseudo {
+	case "FP":
+		return 2, int32(sym.Offset) + int32(fi.autosize) + 8
+	case "SP":
+		return 2, int32(fi.autosize) + int32(sym.Offset)
+	case "SB":
+		return -1, int32(sym.Offset)
+	}
+	return -1, 0
+}

asm/riscv_frame_test.go

@@ -0,0 +1,81 @@
+// Copyright (c) 2026 Petr Balvín <opensource@petrbalvin.org> (https://petrbalvin.org)
+// SPDX-License-Identifier: BSD-3-Clause
+
+package asm
+
+import (
+	"testing"
+
+	"sourcedock.dev/petrbalvin/gasm-devkit/parser"
+)
+
+// TestRISCVFrameSpadjAndLines checks that a framed function records its
+// stack-adjustment boundaries and source-line table, the inputs the GOOBJ
+// emitter turns into the pcsp/pcfile/pcline tables.
+func TestRISCVFrameSpadjAndLines(t *testing.T) {
+	f, errs := parser.Parse("frame_riscv64.s", `#include "textflag.h"
+
+TEXT ·framed(SB), NOSPLIT, $16-16
+	MOV a+0(FP), X10
+	MOV b+8(FP), X11
+	ADD X11, X10, X10
+	MOV X10, ret+16(FP)
+	RET
+`)
+	if len(errs) > 0 {
+		t.Fatalf("parse: %v", errs)
+	}
+	img, err := AssembleFileRISCV(f)
+	if err != nil {
+		t.Fatalf("AssembleFileRISCV: %v", err)
+	}
+	fn := img.Funcs[0]
+	if fn.Size != 24 {
+		t.Fatalf("size = %d, want 24", fn.Size)
+	}
+
+	// autosize = 16 + 8 = 24; the prologue boundary is just past its C.ADDI
+	// (SD 4 + C.ADDI 2 = 6), and the RET restores SP just past its C.ADDI
+	// (RET starts at 16; C.LDSP 2 + C.ADDI 2 = 20).
+	wantSpadj := []SpadjStep{{PC: 6, Value: 24}, {PC: 20, Value: 0}}
+	if len(fn.Spadj) != len(wantSpadj) {
+		t.Fatalf("spadj = %v, want %v", fn.Spadj, wantSpadj)
+	}
+	for i := range wantSpadj {
+		if fn.Spadj[i] != wantSpadj[i] {
+			t.Errorf("spadj[%d] = %v, want %v", i, fn.Spadj[i], wantSpadj[i])
+		}
+	}
+
+	// One line entry per instruction, in emission order.
+	wantLines := []LineEntry{
+		{Offset: 8, Line: 4},
+		{Offset: 10, Line: 5},
+		{Offset: 12, Line: 6},
+		{Offset: 14, Line: 7},
+		{Offset: 16, Line: 8},
+	}
+	if len(fn.Lines) != len(wantLines) {
+		t.Fatalf("lines = %v, want %v", fn.Lines, wantLines)
+	}
+	for i := range wantLines {
+		if fn.Lines[i] != wantLines[i] {
+			t.Errorf("lines[%d] = %v, want %v", i, fn.Lines[i], wantLines[i])
+		}
+	}
+}
+
+// TestRISCVRegAliases checks the Go ABI register aliases that the toolchain
+// defines: LR is the link register (X1) and TMP is the assembler scratch
+// register (X31/T6).
+func TestRISCVRegAliases(t *testing.T) {
+	for name, want := range map[string]int{
+		"X1": 1, "RA": 1, "LR": 1,
+		"X31": 31, "T6": 31, "TMP": 31,
+		"X2": 2, "SP": 2,
+	} {
+		if got := riscvRegNum(name); got != want {
+			t.Errorf("riscvRegNum(%q) = %d, want %d", name, got, want)
+		}
+	}
+}

asm/riscv_goobj_test.go

@@ -0,0 +1,346 @@
+// Copyright (c) 2026 Petr Balvín <opensource@petrbalvin.org> (https://petrbalvin.org)
+// SPDX-License-Identifier: BSD-3-Clause
+
+package asm
+
+import (
+	"bytes"
+	"debug/elf"
+	"encoding/binary"
+	"os"
+	"os/exec"
+	"path/filepath"
+	"strings"
+	"testing"
+
+	"sourcedock.dev/petrbalvin/gasm-devkit/parser"
+)
+
+// TestGOObjectRISCVCallReloc checks that CALL sym(SB) emits a single JAL
+// instruction carrying an R_RISCV_JAL relocation (4-byte field) in both the
+// GOOBJ and ELF object emitters.
+func TestGOObjectRISCVCallReloc(t *testing.T) {
+	f, errs := parser.Parse("k_riscv64.s", `
+#include "textflag.h"
+
+TEXT ·c(SB), NOSPLIT, $0-0
+	CALL callee<>(SB)
+	RET
+
+GLOBL callee<>(SB), RODATA, $8
+DATA callee<>+0(SB)/8, $42
+`)
+	if len(errs) > 0 {
+		t.Fatalf("parse: %v", errs)
+	}
+	img, err := AssembleFileRISCV(f)
+	if err != nil {
+		t.Fatalf("AssembleFileRISCV: %v", err)
+	}
+	fn := img.Funcs[0]
+	if len(fn.Relocs) != 1 {
+		t.Fatalf("relocs = %d, want 1", len(fn.Relocs))
+	}
+	r := fn.Relocs[0]
+	if r.Kind != RelRISCVJal || r.Off != 8 || r.After != 12 || r.Name != "callee" || r.Addend != 0 || r.External {
+		t.Errorf("reloc = {kind %v off %d after %d name %q addend %d external %v}", r.Kind, r.Off, r.After, r.Name, r.Addend, r.External)
+	}
+
+	obj, err := img.GOObjectRISCV("testpkg", "k_riscv64.s")
+	if err != nil {
+		t.Fatalf("GOObjectRISCV: %v", err)
+	}
+	v := openGoobj(t, obj)
+	relocIdx := v.blk(blkRelocIdx)
+	relocs := v.blk(blkReloc)
+	// The function is the last non-package symbol: 4 package defs, then the
+	// 4 pc tables and the function.
+	first := int(binary.LittleEndian.Uint32(relocIdx[(4+4)*4:]))
+	if (first+1)*23 > len(relocs) {
+		t.Fatalf("reloc block too short: first=%d len=%d", first, len(relocs))
+	}
+	e := relocs[first*23:]
+	le := binary.LittleEndian
+	if int32(le.Uint32(e[0:])) != 8 || e[4] != 4 || le.Uint16(e[5:]) != relocRISCVJal || le.Uint32(e[15:]) != pkgIdxSelf || le.Uint32(e[19:]) != 0 {
+		t.Errorf("GOOBJ reloc = off %d size %d type %d pkg %d sym %d", int32(le.Uint32(e[0:])), e[4], le.Uint16(e[5:]), le.Uint32(e[15:]), le.Uint32(e[19:]))
+	}
+
+	// The ELF object must carry a single R_RISCV_JAL relocation in .rela.text.
+	elfObj, err := img.ELFRISCVObject()
+	if err != nil {
+		t.Fatalf("ELFRISCVObject: %v", err)
+	}
+	if !hasELFRISCVJAL(t, elfObj) {
+		t.Error("ELF object missing R_RISCV_JAL relocation")
+	}
+}
+func TestGOObjectRISCVStructure(t *testing.T) {
+	f, errs := parser.Parse("k_riscv64.s", `
+#include "textflag.h"
+
+TEXT ·sb(SB), NOSPLIT, $0-0
+	MOV $answer<>(SB), X10
+	MOV answer<>(SB), X11
+	MOV X12, answer<>(SB)
+	RET
+
+GLOBL answer<>(SB), RODATA, $8
+DATA answer<>+0(SB)/8, $42
+`)
+	if len(errs) > 0 {
+		t.Fatalf("parse: %v", errs)
+	}
+	img, err := AssembleFileRISCV(f)
+	if err != nil {
+		t.Fatalf("AssembleFileRISCV: %v", err)
+	}
+	fn := img.Funcs[0]
+	if fn.Size != 28 {
+		t.Fatalf("function size = %d, want 28", fn.Size)
+	}
+	if len(fn.Relocs) != 3 {
+		t.Fatalf("relocs = %d, want 3", len(fn.Relocs))
+	}
+	wantKind := []RelocKind{RelRISCVPCRELIType, RelRISCVPCRELIType, RelRISCVPCRELSType}
+	wantOff := []int{0, 8, 16}
+	for i, r := range fn.Relocs {
+		if r.Kind != wantKind[i] || r.Off != wantOff[i] || r.After != r.Off+8 || r.Name != "answer" || r.Addend != 0 {
+			t.Errorf("reloc %d = {kind %v off %d after %d name %q addend %d}", i, r.Kind, r.Off, r.After, r.Name, r.Addend)
+		}
+	}
+
+	obj, err := img.GOObjectRISCV("testpkg", "k_riscv64.s")
+	if err != nil {
+		t.Fatalf("GOObjectRISCV: %v", err)
+	}
+	v := openGoobj(t, obj)
+
+	// Package defs: the static GLOBL, the FuncInfo, then the two DWARF
+	// symbols.
+	defs := v.syms(blkSymdef)
+	if len(defs) != 4 {
+		t.Fatalf("symdefs = %d, want 4", len(defs))
+	}
+	if defs[0].name != "answer" || defs[0].abi != 0xffff || defs[0].typ != kindSRODATA || defs[0].size != 8 {
+		t.Errorf("answer symbol = %+v", defs[0])
+	}
+	if defs[2].typ != kindSDWARFLINES || defs[3].typ != kindSDWARFFCN {
+		t.Errorf("dwarf symbols = %+v, %+v", defs[2], defs[3])
+	}
+
+	// The three code relocations, in definition order: ITYPE, ITYPE, STYPE,
+	// each 8 bytes wide against the GLOBL (package symbol 0).
+	relocIdx := v.blk(blkRelocIdx)
+	relocs := v.blk(blkReloc)
+	if len(relocs) != 5*23 {
+		t.Fatalf("relocs = %d bytes, want 5 entries", len(relocs))
+	}
+	// The function is the last non-package symbol; its relocs start after
+	// the DWARF symbols' (defs 2 and 3 each carry one).
+	le := binary.LittleEndian
+	first := int(le.Uint32(relocIdx[4*(4+4):]))
+	wantType := []uint16{relocRISCVPcrelItype, relocRISCVPcrelItype, relocRISCVPcrelStype}
+	wantOffAbs := []int{0, 8, 16}
+	for i := 0; i < 3; i++ {
+		e := relocs[(first+i)*23:]
+		if int32(le.Uint32(e[0:])) != int32(wantOffAbs[i]) || e[4] != 8 || le.Uint16(e[5:]) != wantType[i] ||
+			le.Uint32(e[15:]) != pkgIdxSelf || le.Uint32(e[19:]) != 0 {
+			t.Errorf("reloc %d = off %d size %d type %d pkg %d sym %d", i, int32(le.Uint32(e[0:])), e[4], le.Uint16(e[5:]), le.Uint32(e[15:]), le.Uint32(e[19:]))
+		}
+	}
+
+	// The function code: three AUIPC+second-instruction pairs with zero
+	// immediates, then the uncompressed JALR X0, 0(X1) the toolchain emits
+	// for RET.
+	code := img.Code[fn.Offset : fn.Offset+fn.Size]
+	want := append(wordLE(riscvUType(riscvEnc{0x17, 0x0, 0x00}, 10, 0)), wordLE(riscvIType(riscvEnc{0x13, 0x0, 0x00}, 10, 10, 0))...)
+	want = append(want, wordLE(riscvUType(riscvEnc{0x17, 0x0, 0x00}, 11, 0))...)
+	want = append(want, wordLE(riscvIType(riscvEnc{0x03, 0x3, 0x00}, 11, 11, 0))...)
+	want = append(want, wordLE(riscvUType(riscvEnc{0x17, 0x0, 0x00}, 31, 0))...)
+	want = append(want, wordLE(riscvSType(riscvEnc{0x23, 0x3, 0x00}, 31, 12, 0))...)
+	want = append(want, 0x67, 0x80, 0x00, 0x00) // JALR X0, 0(X1)
+	if !bytes.Equal(code, want) {
+		t.Errorf("code = % x\nwant % x", code, want)
+	}
+
+	// The same bytes must survive into the object's data block intact: the
+	// linker patches only the immediate fields of the AUIPC pairs, so the
+	// opcode/register bits of every instruction must not be zeroed.
+	dataIdx := v.blk(blkDataIdx)
+	dataBlk := v.blk(blkData)
+	dOff := int(le.Uint32(dataIdx[8*4:])) // the function is the last symbol
+	emitted := dataBlk[dOff : dOff+fn.Size]
+	if !bytes.Equal(emitted, want) {
+		t.Errorf("emitted data = % x\nwant % x", emitted, want)
+	}
+}
+
+// TestGOObjectRISCVLink cross-compiles a Go program with the gasm-produced
+// object substituted into the package archive, proving cmd/link accepts the
+// emitted RISC-V GOOBJ.  The binary is not executed (no riscv64 host or
+// qemu).  Skipped when no Go toolchain is available.
+func TestGOObjectRISCVLink(t *testing.T) {
+	goBin, err := exec.LookPath("go")
+	if err != nil {
+		t.Skip("no Go toolchain available")
+	}
+	dir := t.TempDir()
+	asmSrc := `#include "textflag.h"
+TEXT ·add(SB), NOSPLIT, $0-24
+	MOV a+0(FP), X10
+	MOV b+8(FP), X11
+	ADD X11, X10, X10
+	MOV X10, ret+16(FP)
+	RET
+`
+	if err := os.WriteFile(filepath.Join(dir, "main_riscv64.s"), []byte(asmSrc), 0o644); err != nil {
+		t.Fatal(err)
+	}
+	mainSrc := `package main
+
+func add(a, b int64) int64
+
+func main() {
+	if add(20, 22) != 42 {
+		panic("bad add")
+	}
+}
+`
+	if err := os.WriteFile(filepath.Join(dir, "main.go"), []byte(mainSrc), 0o644); err != nil {
+		t.Fatal(err)
+	}
+	if err := os.WriteFile(filepath.Join(dir, "go.mod"), []byte("module rvlink\n\ngo 1.21\n"), 0o644); err != nil {
+		t.Fatal(err)
+	}
+
+	build := exec.Command(goBin, "build", "-x", "-work", "-o", filepath.Join(dir, "prog"), ".")
+	build.Dir = dir
+	build.Env = append(os.Environ(), "GOARCH=riscv64")
+	buildLog, err := build.CombinedOutput()
+	if err != nil {
+		t.Fatalf("baseline build: %v\n%s", err, buildLog)
+	}
+	var pkgArch, work, linkLine, asmObj string
+	for _, line := range strings.Split(string(buildLog), "\n") {
+		switch {
+		case strings.HasPrefix(line, "WORK="):
+			work = strings.TrimPrefix(line, "WORK=")
+		case strings.Contains(line, "/asm ") && strings.Contains(line, "main_riscv64.s") && !strings.Contains(line, "-gensymabis"):
+			asmObj = fieldAfter(line, "-o")
+		case strings.Contains(line, "pack r") && strings.Contains(line, "_pkg_.a"):
+			pkgArch = strings.TrimSpace(strings.SplitN(line, "pack r", 2)[1])
+			pkgArch = strings.Fields(strings.SplitN(pkgArch, "#", 2)[0])[0]
+		case strings.Contains(line, "/link ") && strings.Contains(line, "-importcfg"):
+			linkLine = line
+		}
+	}
+	if pkgArch == "" || linkLine == "" || asmObj == "" {
+		t.Skip("could not locate the archive, asm output or link line in the build log")
+	}
+	pkgArch = strings.ReplaceAll(pkgArch, "$WORK", work)
+	asmMember := filepath.Base(strings.ReplaceAll(asmObj, "$WORK", work))
+
+	pf, perrs := parser.Parse(filepath.Join(dir, "main_riscv64.s"), asmSrc)
+	if len(perrs) > 0 {
+		t.Fatalf("parse: %v", perrs)
+	}
+	pimg, err := AssembleFileRISCV(pf)
+	if err != nil {
+		t.Fatalf("AssembleFileRISCV: %v", err)
+	}
+	obj, err := pimg.GOObjectRISCV("main", filepath.Join(dir, "main_riscv64.s"))
+	if err != nil {
+		t.Fatalf("GOObjectRISCV: %v", err)
+	}
+
+	membersDir := filepath.Join(dir, "members")
+	if err := os.MkdirAll(membersDir, 0o755); err != nil {
+		t.Fatal(err)
+	}
+	extract := exec.Command(goBin, "tool", "pack", "x", pkgArch)
+	extract.Dir = membersDir
+	extract.Env = append(os.Environ(), "GOARCH=riscv64")
+	if out, err := extract.CombinedOutput(); err != nil {
+		t.Fatalf("pack x: %v\n%s", err, out)
+	}
+	member := filepath.Join(membersDir, asmMember)
+	if err := os.Chmod(member, 0o644); err != nil {
+		t.Fatal(err)
+	}
+	if err := os.WriteFile(member, obj, 0o644); err != nil {
+		t.Fatal(err)
+	}
+	listCmd := exec.Command(goBin, "tool", "pack", "t", pkgArch)
+	listCmd.Env = append(os.Environ(), "GOARCH=riscv64")
+	listOut, err := listCmd.CombinedOutput()
+	if err != nil {
+		t.Fatalf("pack t: %v\n%s", err, listOut)
+	}
+	newArch := filepath.Join(dir, "pkg.a")
+	args := []string{"tool", "pack", "c", newArch}
+	seen := map[string]bool{}
+	for _, m := range strings.Fields(string(listOut)) {
+		if seen[m] {
+			continue
+		}
+		seen[m] = true
+		if err := os.Chmod(filepath.Join(membersDir, m), 0o644); err != nil {
+			t.Fatal(err)
+		}
+		args = append(args, filepath.Join(membersDir, m))
+	}
+	pack := exec.Command(goBin, args...)
+	pack.Dir = membersDir
+	pack.Env = append(os.Environ(), "GOARCH=riscv64")
+	if out, err := pack.CombinedOutput(); err != nil {
+		t.Fatalf("pack c: %v\n%s", err, out)
+	}
+
+	linkLine = strings.ReplaceAll(linkLine, "$WORK", work)
+	linkLine = strings.ReplaceAll(linkLine, filepath.Join(work, "b001", "_pkg_.a"), newArch)
+	linkLine = strings.ReplaceAll(linkLine, filepath.Join(work, "b001", "exe", "a.out"), filepath.Join(dir, "app2"))
+	link := exec.Command("sh", "-c", linkLine)
+	link.Dir = dir
+	goExp, _ := exec.Command(goBin, "env", "GOEXPERIMENT").Output()
+	link.Env = append(os.Environ(), "GOEXPERIMENT="+strings.TrimSpace(string(goExp)), "GOARCH=riscv64")
+	if out, err := link.CombinedOutput(); err != nil {
+		t.Fatalf("link with gasm object: %v\n%s", err, out)
+	}
+
+	nm := exec.Command(goBin, "tool", "nm", filepath.Join(dir, "app2"))
+	nm.Env = append(os.Environ(), "GOARCH=riscv64")
+	nmOut, err := nm.CombinedOutput()
+	if err != nil {
+		t.Fatalf("nm gasm-linked binary: %v\n%s", err, nmOut)
+	}
+	if !strings.Contains(string(nmOut), "main.add") {
+		t.Errorf("main.add not found in linked binary:\n%s", nmOut)
+	}
+}
+
+// hasELFRISCVJAL reports whether the ELF object carries an R_RISCV_JAL
+// relocation in its .rela.text section.
+func hasELFRISCVJAL(t *testing.T, data []byte) bool {
+	t.Helper()
+	f, err := elf.NewFile(bytes.NewReader(data))
+	if err != nil {
+		t.Fatalf("parse ELF: %v", err)
+	}
+	defer f.Close()
+	rela := f.Section(".rela.text")
+	if rela == nil {
+		return false
+	}
+	b, err := rela.Data()
+	if err != nil {
+		t.Fatalf(".rela.text data: %v", err)
+	}
+	const rRISCVJAL = 17
+	for i := 0; i+24 <= len(b); i += 24 {
+		info := binary.LittleEndian.Uint64(b[i+8:])
+		if uint32(info) == rRISCVJAL {
+			return true
+		}
+	}
+	return false
+}

asm/vex.go

@@ -210,6 +210,24 @@ var vexTable = map[string]vexSpec{
 	"VCVTPD2PSX": {1, 0x5A, 0, 1, -1, vexRMSrcLen},
 	"VCVTPD2PSY": {1, 0x5A, 0, 1, -1, vexRMSrcLen},
 
+	// VEX scalar conversions between vector and general-purpose registers.
+	// Vector to GPR (two operands: vec/mem source, GPR destination, vvvv
+	// unused; the length follows the source).
+	"VCVTSD2SI":   {1, 0x2D, 0, 3, -1, vexRM},
+	"VCVTSD2SIQ":  {1, 0x2D, 1, 3, -1, vexRM},
+	"VCVTSS2SI":   {1, 0x2D, 0, 2, -1, vexRM},
+	"VCVTSS2SIQ":  {1, 0x2D, 1, 2, -1, vexRM},
+	"VCVTTSD2SI":  {1, 0x2C, 0, 3, -1, vexRM},
+	"VCVTTSD2SIQ": {1, 0x2C, 1, 3, -1, vexRM},
+	"VCVTTSS2SI":  {1, 0x2C, 0, 2, -1, vexRM},
+	"VCVTTSS2SIQ": {1, 0x2C, 1, 2, -1, vexRM},
+	// GPR to vector (three operands: GPR/mem source in r/m, the preserved
+	// vector source in vvvv, vector destination in reg).
+	"VCVTSI2SDL": {1, 0x2A, 0, 3, -1, vexNDS3},
+	"VCVTSI2SDQ": {1, 0x2A, 1, 3, -1, vexNDS3},
+	"VCVTSI2SSL": {1, 0x2A, 0, 2, -1, vexNDS3},
+	"VCVTSI2SSQ": {1, 0x2A, 1, 2, -1, vexNDS3},
+
 	// VEX.128/256.66.0F.WIG — word shifts (opdigit selects the shift).
 	"VPSRLW": {1, 0x71, 0, 1, 2, vexShiftImm},
 	"VPSRAW": {1, 0x71, 0, 1, 4, vexShiftImm},

asm/vex_test.go

@@ -39,11 +39,14 @@ func TestVexNDS3(t *testing.T) {
 		}
 		inst, err := x86asm.Decode(code, 64)
 		if err != nil {
-			t.Errorf("%s: Decode(% x): %v", mnem, code, err)
+			t.Errorf("%s: Decode(% x): %v", mnem, err, code)
 			continue
 		}
-		if inst.Op.String() != mnem {
-			t.Errorf("%s: decoded as %s (% x)", mnem, inst.Op.String(), code)
+		// The decoder folds the Plan 9 L/Q GPR-width spellings (VCVTSI2SDL/
+		// SDQ, SSL/SSQ) onto the base name; the W bit carries the width.
+		got := inst.Op.String()
+		if got != mnem && !(len(mnem) > len(got) && mnem[:len(got)] == got) {
+			t.Errorf("%s: decoded as %s (% x)", mnem, got, code)
 		}
 	}
 }

cmd/gasm/debug_linux_amd64.go

@@ -0,0 +1,193 @@
+// Copyright (c) 2026 Petr Balvín <opensource@petrbalvin.org> (https://petrbalvin.org)
+// SPDX-License-Identifier: BSD-3-Clause
+
+//go:build linux && amd64
+
+package main
+
+import (
+	"fmt"
+	"os"
+	"sort"
+	"strings"
+
+	"sourcedock.dev/petrbalvin/gasm-devkit/debug"
+	"sourcedock.dev/petrbalvin/gasm-devkit/verify"
+)
+
+func cmdDebug(args []string) int {
+	fs := newCommand("debug", "gasm debug <file.s> --func <name>", `
+Interactive debugger for JIT-assembled amd64 functions.  Launches the
+function in a traced subprocess (ptrace), then provides a REPL for
+single-stepping, breakpoints, register and memory inspection.
+
+REPL commands:
+  break <label|addr>   set a breakpoint at a label or absolute address
+  step [n]             single-step n instructions (default 1)
+  continue             run until next breakpoint or exit
+  regs                 print general-purpose registers
+  x [addr] [len]       hex-dump memory (default: current PC, 64 bytes)
+  labels               list function labels and offsets
+  quit                 kill the debuggee and exit
+`)
+	target := fs.Bool("target", false, "") // hidden: debuggee subprocess mode
+	funcName := fs.String("func", "", "function to debug")
+	argsFile := fs.String("args", "", "file containing the ABI0 argument block")
+	bufSpec := fs.String("buf", "", "buffer specification: name:size:pattern[,name:size:pattern...] where pattern is zero, ones, seq, or hex")
+	fs.Parse(args)
+
+	// --- Debuggee mode (internal, spawned by the debugger) ---
+	if *target {
+		tmpDir := os.Getenv("GASM_DEBUG_TMP")
+		if tmpDir == "" || fs.NArg() < 1 || *funcName == "" || *argsFile == "" {
+			fmt.Fprintln(os.Stderr, "gasm debug --target: internal mode")
+			return 2
+		}
+		if err := debug.RunTarget(fs.Arg(0), *funcName, *argsFile, tmpDir); err != nil {
+			fmt.Fprintf(os.Stderr, "gasm debug: %v\n", err)
+			return 1
+		}
+		return 0
+	}
+
+	// --- Debugger mode (interactive REPL) ---
+	if fs.NArg() < 1 || *funcName == "" {
+		fmt.Fprintln(os.Stderr, "usage: gasm debug <file.s> --func <name>")
+		return 2
+	}
+	path := fs.Arg(0)
+
+	// Load the kernel to extract function metadata and labels.
+	k, err := verify.Load(path)
+	if err != nil {
+		fmt.Fprintf(os.Stderr, "gasm debug: %v\n", err)
+		return 1
+	}
+	defer k.Close()
+
+	fl, err := k.Func(*funcName)
+	if err != nil {
+		fmt.Fprintf(os.Stderr, "gasm debug: %v\n", err)
+		return 1
+	}
+
+	// Build the label list for the REPL.
+	var labels []debug.Label
+	for name, off := range fl.Labels {
+		labels = append(labels, debug.Label{Name: name, Offset: off})
+	}
+	sort.Slice(labels, func(i, j int) bool { return labels[i].Offset < labels[j].Offset })
+
+	// Launch the debuggee with the argument block.
+	var argBlock []byte
+	var bufAddrs []uint64
+	var sess *debug.Session
+	if *bufSpec != "" {
+		// Parse the function signature to determine argument layout.
+		src, err := readSource(path)
+		if err != nil {
+			fmt.Fprintf(os.Stderr, "gasm debug: %v\n", err)
+			return 1
+		}
+		sig, ok := verify.ExtractFuncSig(src, *funcName)
+		if !ok {
+			fmt.Fprintf(os.Stderr, "gasm debug: no // func signature found for %s\n", *funcName)
+			return 1
+		}
+		layout := verify.ArgLayout(sig)
+
+		// Parse the buffer spec to get buffer names.
+		bufNames := parseBufNames(*bufSpec)
+
+		// Allocate buffers in the debuggee.
+		argBlock = make([]byte, fl.Args)
+		sess, bufAddrs, err = debug.LaunchWithBuffers("", path, *funcName, argBlock, *bufSpec)
+		if err != nil {
+			fmt.Fprintf(os.Stderr, "gasm debug: %v\n", err)
+			return 1
+		}
+
+		// Construct the argument block with buffer pointers at the correct positions.
+		bufIdx := 0
+		for _, arg := range layout {
+			if !arg.IsPtr {
+				continue
+			}
+			// Find the buffer that matches this argument.
+			for i, name := range bufNames {
+				if i < len(bufAddrs) && (name == arg.Name || strings.HasPrefix(arg.Name, name)) {
+					addr := bufAddrs[i]
+					off := arg.Offset
+					if off+8 <= len(argBlock) {
+						argBlock[off] = byte(addr)
+						argBlock[off+1] = byte(addr >> 8)
+						argBlock[off+2] = byte(addr >> 16)
+						argBlock[off+3] = byte(addr >> 24)
+						argBlock[off+4] = byte(addr >> 32)
+						argBlock[off+5] = byte(addr >> 40)
+						argBlock[off+6] = byte(addr >> 48)
+						argBlock[off+7] = byte(addr >> 56)
+					}
+					// For slices, also set the length and capacity.
+					if strings.HasPrefix(arg.Typ, "[]") && off+24 <= len(argBlock) {
+						// Find the buffer size from the spec.
+						size := parseBufSize(*bufSpec, name)
+						// Length at offset+8, capacity at offset+16.
+						for j := 0; j < 8; j++ {
+							argBlock[off+8+j] = byte(size >> (j * 8))
+							argBlock[off+16+j] = byte(size >> (j * 8))
+						}
+					}
+					bufIdx++
+					break
+				}
+			}
+		}
+		_ = bufIdx
+	} else {
+		argBlock = make([]byte, fl.Args)
+		sess, err = debug.Launch("", path, *funcName, argBlock)
+		if err != nil {
+			fmt.Fprintf(os.Stderr, "gasm debug: %v\n", err)
+			return 1
+		}
+	}
+	defer sess.Kill()
+
+	bm := debug.NewBreakpoints(sess)
+	fmt.Printf("gasm debug: %s in %s (pid %d)\n", *funcName, path, sess.Pid())
+
+	// Convert the line table for the REPL.
+	var srcLines []debug.SourceLine
+	for _, le := range fl.Lines {
+		srcLines = append(srcLines, debug.SourceLine{Offset: le.Offset, Line: le.Line})
+	}
+	debug.REPL(sess, bm, sess.CodeBase(), fl.Offset, fl.Size, fl.Args, labels, srcLines)
+	return 0
+}
+
+// parseBufNames extracts buffer names from a buffer specification.
+// Format: name:size:pattern[,name:size:pattern...]
+func parseBufNames(spec string) []string {
+	var names []string
+	for _, part := range strings.Split(spec, ",") {
+		fields := strings.SplitN(part, ":", 3)
+		if len(fields) >= 1 && fields[0] != "" {
+			names = append(names, fields[0])
+		}
+	}
+	return names
+}
+
+// parseBufSize extracts the size of a named buffer from a buffer specification.
+func parseBufSize(spec, name string) int {
+	for _, part := range strings.Split(spec, ",") {
+		fields := strings.SplitN(part, ":", 3)
+		if len(fields) >= 2 && fields[0] == name {
+			var size int
+			fmt.Sscanf(fields[1], "%d", &size)
+			return size
+		}
+	}
+	return 0
+}

cmd/gasm/debug_other.go

@@ -0,0 +1,16 @@
+// Copyright (c) 2026 Petr Balvín <opensource@petrbalvin.org> (https://petrbalvin.org)
+// SPDX-License-Identifier: BSD-3-Clause
+
+//go:build !(linux && amd64)
+
+package main
+
+import (
+	"fmt"
+	"os"
+)
+
+func cmdDebug(args []string) int {
+	fmt.Fprintln(os.Stderr, "gasm debug: the interactive debugger requires linux/amd64 (ptrace)")
+	return 1
+}

debug/breakpoint.go

@@ -0,0 +1,248 @@
+// Copyright (c) 2026 Petr Balvín <opensource@petrbalvin.org> (https://petrbalvin.org)
+// SPDX-License-Identifier: BSD-3-Clause
+
+package debug
+
+import "fmt"
+
+// Breakpoint is one INT3 breakpoint in the debuggee.
+type Breakpoint struct {
+	Addr    uint64 // absolute address in the debuggee
+	Label   string // source label ("" for raw addresses)
+	Orig    byte   // original byte at Addr (restored on removal)
+	Enabled bool
+	Cond    *Condition // optional condition (nil = unconditional)
+	hits    int
+}
+
+// Condition is a simple register-comparison condition evaluated when a
+// breakpoint is hit.  Format: <reg> <op> <value>.
+type Condition struct {
+	Reg   string // register name (rax, rbx, rip, rsp, ...)
+	Op    string // comparison operator: ==, !=, <, >, <=, >=
+	Value uint64
+}
+
+// Eval checks the condition against the current registers.
+func (c *Condition) Eval(regs *Regs) bool {
+	var actual uint64
+	switch c.Reg {
+	case "rax", "eax", "ax", "al":
+		actual = regs.RAX
+	case "rbx", "ebx", "bx", "bl":
+		actual = regs.RBX
+	case "rcx", "ecx", "cx", "cl":
+		actual = regs.RCX
+	case "rdx", "edx", "dx", "dl":
+		actual = regs.RDX
+	case "rsi", "esi", "si":
+		actual = regs.RSI
+	case "rdi", "edi", "di":
+		actual = regs.RDI
+	case "rbp", "ebp", "bp":
+		actual = regs.RBP
+	case "rsp", "esp", "sp":
+		actual = regs.RSP
+	case "r8":
+		actual = regs.R8
+	case "r9":
+		actual = regs.R9
+	case "r10":
+		actual = regs.R10
+	case "r11":
+		actual = regs.R11
+	case "r12":
+		actual = regs.R12
+	case "r13":
+		actual = regs.R13
+	case "r14":
+		actual = regs.R14
+	case "r15":
+		actual = regs.R15
+	case "rip", "eip":
+		actual = regs.RIP
+	default:
+		return true // unknown register — don't block
+	}
+	switch c.Op {
+	case "==", "=":
+		return actual == c.Value
+	case "!=":
+		return actual != c.Value
+	case "<":
+		return actual < c.Value
+	case ">":
+		return actual > c.Value
+	case "<=":
+		return actual <= c.Value
+	case ">=":
+		return actual >= c.Value
+	default:
+		return true
+	}
+}
+
+// Breakpoints manages the set of breakpoints for a Session.
+// Breakpoints manages software breakpoints for a debuggee.
+type Breakpoints struct {
+	t   tracer
+	bps map[uint64]*Breakpoint
+}
+
+// NewBreakpoints creates a new breakpoint manager.
+func NewBreakpoints(t tracer) *Breakpoints {
+	return &Breakpoints{t: t, bps: make(map[uint64]*Breakpoint)}
+}
+
+// Set installs a breakpoint at addr (replaces any existing one).
+func (bm *Breakpoints) Set(addr uint64, label string) (*Breakpoint, error) {
+	return bm.SetWithCond(addr, label, nil)
+}
+
+// SetWithCond installs a breakpoint with an optional condition.
+func (bm *Breakpoints) SetWithCond(addr uint64, label string, cond *Condition) (*Breakpoint, error) {
+	if bp, ok := bm.bps[addr]; ok {
+		bp.Enabled = true
+		bp.Cond = cond
+		return bp, nil
+	}
+	// Read the original byte.
+	word, err := bm.t.Peek(addr)
+	if err != nil {
+		return nil, err
+	}
+	orig := byte(word)
+	// Patch with INT3 (0xCC), preserving the rest of the word.
+	patched := (word &^ 0xFF) | 0xCC
+	if err := bm.t.Poke(addr, patched); err != nil {
+		return nil, err
+	}
+	bp := &Breakpoint{Addr: addr, Label: label, Orig: orig, Enabled: true, Cond: cond}
+	bm.bps[addr] = bp
+	return bp, nil
+}
+
+// Hits returns the number of times the breakpoint has been hit.
+func (bp *Breakpoint) Hits() int {
+	return bp.hits
+}
+
+// Info returns a formatted list of all breakpoints.
+func (bm *Breakpoints) Info() string {
+	if len(bm.bps) == 0 {
+		return "no breakpoints set\n"
+	}
+	result := ""
+	i := 0
+	for _, bp := range bm.bps {
+		i++
+		status := "enabled"
+		if !bp.Enabled {
+			status = "disabled"
+		}
+		label := bp.Label
+		if label == "" {
+			label = fmt.Sprintf("%#x", bp.Addr)
+		}
+		cond := ""
+		if bp.Cond != nil {
+			cond = fmt.Sprintf(" if %s %s %#x", bp.Cond.Reg, bp.Cond.Op, bp.Cond.Value)
+		}
+		result += fmt.Sprintf("  %d: %s at %#x [%s, %d hits]%s\n", i, label, bp.Addr, status, bp.hits, cond)
+	}
+	return result
+}
+
+// Clear removes the breakpoint at addr, restoring the original byte.
+func (bm *Breakpoints) Clear(addr uint64) error {
+	bp, ok := bm.bps[addr]
+	if !ok {
+		return fmt.Errorf("debug: no breakpoint at %#x", addr)
+	}
+	word, err := bm.t.Peek(addr)
+	if err != nil {
+		return err
+	}
+	restored := (word &^ 0xFF) | uint64(bp.Orig)
+	if err := bm.t.Poke(addr, restored); err != nil {
+		return err
+	}
+	delete(bm.bps, addr)
+	return nil
+}
+
+// ClearAll removes all breakpoints.
+func (bm *Breakpoints) ClearAll() error {
+	for addr := range bm.bps {
+		if err := bm.Clear(addr); err != nil {
+			return err
+		}
+	}
+	return nil
+}
+
+// At returns the breakpoint at addr, if any.
+func (bm *Breakpoints) At(addr uint64) *Breakpoint {
+	return bm.bps[addr]
+}
+
+// All returns all breakpoints.
+func (bm *Breakpoints) All() []*Breakpoint {
+	out := make([]*Breakpoint, 0, len(bm.bps))
+	for _, bp := range bm.bps {
+		out = append(out, bp)
+	}
+	return out
+}
+
+// HandleTrap is called after the debuggee stops on SIGTRAP.  It checks
+// whether the trap was caused by one of our breakpoints (RIP-1 matches
+// a breakpoint address), restores the original byte, rewinds RIP, and
+// returns the breakpoint that was hit (or nil if it was a single-step).
+func (bm *Breakpoints) HandleTrap(regs *Regs) *Breakpoint {
+	// After INT3, RIP points to the byte AFTER the 0xCC.
+	trapAddr := regs.RIP - 1
+	bp, ok := bm.bps[trapAddr]
+	if !ok || !bp.Enabled {
+		return nil // single-step trap or unknown
+	}
+	// Check the condition (if any).
+	if bp.Cond != nil && !bp.Cond.Eval(regs) {
+		// Condition not met — restore the byte but do NOT rewind RIP.
+		// The process continues from the next instruction (past the INT3).
+		word, err := bm.t.Peek(trapAddr)
+		if err == nil {
+			restored := (word &^ 0xFF) | uint64(bp.Orig)
+			bm.t.Poke(trapAddr, restored)
+		}
+		// RIP is already past the INT3 (trapAddr + 1). Don't rewind.
+		return nil
+	}
+	bp.hits++
+	// Restore the original byte.
+	word, err := bm.t.Peek(trapAddr)
+	if err == nil {
+		restored := (word &^ 0xFF) | uint64(bp.Orig)
+		bm.t.Poke(trapAddr, restored)
+	}
+	// Rewind RIP to re-execute the original instruction.
+	regs.RIP = trapAddr
+	bm.t.SetRegs(regs)
+	return bp
+}
+
+// Reinsert re-inserts the breakpoint at addr after a single-step past it.
+// Called after Step() when we want the breakpoint to fire again on the
+// next Continue().
+func (bm *Breakpoints) Reinsert(addr uint64) error {
+	bp, ok := bm.bps[addr]
+	if !ok || !bp.Enabled {
+		return nil
+	}
+	word, err := bm.t.Peek(addr)
+	if err != nil {
+		return err
+	}
+	patched := (word &^ 0xFF) | 0xCC
+	return bm.t.Poke(addr, patched)
+}

debug/debug_test.go

@@ -0,0 +1,323 @@
+// Copyright (c) 2026 Petr Balvín <opensource@petrbalvin.org> (https://petrbalvin.org)
+// SPDX-License-Identifier: BSD-3-Clause
+
+package debug
+
+import (
+	"strings"
+	"testing"
+)
+
+func TestConditionEval(t *testing.T) {
+	regs := &Regs{
+		RAX: 42,
+		RBX: 0,
+		RCX: 100,
+		RIP: 0x1000,
+		RSP: 0x2000,
+		R8:  8,
+		R15: 15,
+	}
+
+	tests := []struct {
+		cond Condition
+		want bool
+	}{
+		{Condition{Reg: "rax", Op: "==", Value: 42}, true},
+		{Condition{Reg: "rax", Op: "==", Value: 43}, false},
+		{Condition{Reg: "rax", Op: "!=", Value: 43}, true},
+		{Condition{Reg: "rax", Op: "!=", Value: 42}, false},
+		{Condition{Reg: "rax", Op: "<", Value: 50}, true},
+		{Condition{Reg: "rax", Op: "<", Value: 40}, false},
+		{Condition{Reg: "rax", Op: ">", Value: 40}, true},
+		{Condition{Reg: "rax", Op: ">", Value: 50}, false},
+		{Condition{Reg: "rax", Op: "<=", Value: 42}, true},
+		{Condition{Reg: "rax", Op: ">=", Value: 42}, true},
+		{Condition{Reg: "rbx", Op: "==", Value: 0}, true},
+		{Condition{Reg: "rcx", Op: ">", Value: 50}, true},
+		{Condition{Reg: "rip", Op: "==", Value: 0x1000}, true},
+		{Condition{Reg: "rsp", Op: ">", Value: 0x1000}, true},
+		{Condition{Reg: "r8", Op: "==", Value: 8}, true},
+		{Condition{Reg: "r15", Op: "==", Value: 15}, true},
+		{Condition{Reg: "eax", Op: "==", Value: 42}, true},    // 32-bit alias
+		{Condition{Reg: "ax", Op: "==", Value: 42}, true},     // 16-bit alias
+		{Condition{Reg: "unknown", Op: "==", Value: 0}, true}, // unknown reg → don't block
+		{Condition{Reg: "rax", Op: "??", Value: 0}, true},     // unknown op → don't block
+	}
+
+	for _, tt := range tests {
+		got := tt.cond.Eval(regs)
+		if got != tt.want {
+			t.Errorf("Condition{%q %q %d}.Eval() = %v, want %v",
+				tt.cond.Reg, tt.cond.Op, tt.cond.Value, got, tt.want)
+		}
+	}
+}
+
+func TestLineAt(t *testing.T) {
+	lines := []SourceLine{
+		{Offset: 0, Line: 5},
+		{Offset: 5, Line: 6},
+		{Offset: 10, Line: 7},
+		{Offset: 15, Line: 8},
+	}
+
+	tests := []struct {
+		offset int
+		want   int
+	}{
+		{0, 5},
+		{1, 5},
+		{4, 5},
+		{5, 6},
+		{7, 6},
+		{10, 7},
+		{12, 7},
+		{15, 8},
+		{20, 8},
+	}
+
+	for _, tt := range tests {
+		got := lineAt(lines, tt.offset)
+		if got != tt.want {
+			t.Errorf("lineAt(lines, %d) = %d, want %d", tt.offset, got, tt.want)
+		}
+	}
+
+	// Empty table.
+	if lineAt(nil, 5) != 0 {
+		t.Error("lineAt(nil, 5) should return 0")
+	}
+}
+
+func TestOffsetForLine(t *testing.T) {
+	lines := []SourceLine{
+		{Offset: 0, Line: 5},
+		{Offset: 5, Line: 6},
+		{Offset: 10, Line: 7},
+	}
+
+	tests := []struct {
+		line int
+		want int
+	}{
+		{5, 0},
+		{6, 5},
+		{7, 10},
+		{99, -1}, // not found
+		{0, -1},  // not found
+	}
+
+	for _, tt := range tests {
+		got := offsetForLine(lines, tt.line)
+		if got != tt.want {
+			t.Errorf("offsetForLine(lines, %d) = %d, want %d", tt.line, got, tt.want)
+		}
+	}
+}
+
+func TestDecodeRflags(t *testing.T) {
+	tests := []struct {
+		flags uint64
+		want  string
+	}{
+		{0x202, "IF"},                   // only IF set (bit 9)
+		{0x246, "PF ZF IF"},             // PF(2) + ZF(6) + IF(9)
+		{0x001, "CF"},                   // carry flag
+		{0x080, "SF"},                   // sign flag
+		{0x800, "OF"},                   // overflow flag
+		{0x000, "none"},                 // no flags
+		{0x202 | 0x001, "CF IF"},        // CF + IF
+		{0x3F7, "CF PF AF ZF SF TF IF"}, // all arithmetic flags
+	}
+
+	for _, tt := range tests {
+		got := decodeRflags(tt.flags)
+		if got != tt.want {
+			t.Errorf("decodeRflags(%#x) = %q, want %q", tt.flags, got, tt.want)
+		}
+	}
+}
+
+func TestNearestLabel(t *testing.T) {
+	labels := []Label{
+		{Name: "start", Offset: 0},
+		{Name: "loop", Offset: 10},
+		{Name: "done", Offset: 20},
+	}
+
+	tests := []struct {
+		offset int
+		want   string
+	}{
+		{0, "start"},
+		{5, "start"},
+		{10, "loop"},
+		{15, "loop"},
+		{20, "done"},
+		{25, "done"},
+	}
+
+	for _, tt := range tests {
+		got := nearestLabel(labels, tt.offset)
+		if got != tt.want {
+			t.Errorf("nearestLabel(labels, %d) = %q, want %q", tt.offset, got, tt.want)
+		}
+	}
+}
+
+func TestBreakpointsSetAndClear(t *testing.T) {
+	tr := newMockTracer()
+	bm := NewBreakpoints(tr)
+
+	// Set a breakpoint at address 0x1000.
+	bp, err := bm.Set(0x1000, "test")
+	if err != nil {
+		t.Fatalf("Set: %v", err)
+	}
+	if !bp.Enabled {
+		t.Error("breakpoint not enabled")
+	}
+	if bp.Label != "test" {
+		t.Errorf("label = %q, want test", bp.Label)
+	}
+
+	// Verify Peek was called.
+	if len(tr.peeks) != 1 || tr.peeks[0] != 0x1000 {
+		t.Errorf("peeks = %v, want [0x1000]", tr.peeks)
+	}
+
+	// Verify Poke wrote INT3.
+	if len(tr.pokes) != 1 || tr.pokes[0].addr != 0x1000 {
+		t.Errorf("pokes = %v", tr.pokes)
+	}
+
+	// At should find it.
+	if bm.At(0x1000) == nil {
+		t.Error("At(0x1000) returned nil")
+	}
+
+	// All should return it.
+	all := bm.All()
+	if len(all) != 1 {
+		t.Errorf("All() = %d breakpoints, want 1", len(all))
+	}
+
+	// Clear it.
+	if err := bm.Clear(0x1000); err != nil {
+		t.Fatalf("Clear: %v", err)
+	}
+	if bm.At(0x1000) != nil {
+		t.Error("At(0x1000) after Clear should be nil")
+	}
+}
+
+func TestBreakpointsSetWithCond(t *testing.T) {
+	tr := newMockTracer()
+	bm := NewBreakpoints(tr)
+
+	cond := &Condition{Reg: "rax", Op: "==", Value: 42}
+	bp, err := bm.SetWithCond(0x2000, "cond_test", cond)
+	if err != nil {
+		t.Fatalf("SetWithCond: %v", err)
+	}
+	if bp.Cond == nil || bp.Cond.Value != 42 {
+		t.Error("condition not set")
+	}
+
+	// Re-setting the same address should update the condition.
+	cond2 := &Condition{Reg: "rbx", Op: "<", Value: 100}
+	bp2, err := bm.SetWithCond(0x2000, "cond_test2", cond2)
+	if err != nil {
+		t.Fatalf("SetWithCond (update): %v", err)
+	}
+	if bp2.Cond.Value != 100 {
+		t.Error("condition not updated")
+	}
+	// Should have only 1 Peek (first Set), second is update (no Peek needed).
+	if len(tr.peeks) != 1 {
+		t.Errorf("expected 1 Peek, got %d", len(tr.peeks))
+	}
+}
+
+func TestBreakpointsClearAll(t *testing.T) {
+	tr := newMockTracer()
+	bm := NewBreakpoints(tr)
+
+	bm.Set(0x1000, "a")
+	bm.Set(0x2000, "b")
+	bm.Set(0x3000, "c")
+
+	if len(bm.All()) != 3 {
+		t.Fatalf("expected 3 breakpoints, got %d", len(bm.All()))
+	}
+
+	bm.ClearAll()
+	if len(bm.All()) != 0 {
+		t.Errorf("ClearAll: expected 0 breakpoints, got %d", len(bm.All()))
+	}
+}
+
+func TestBreakpointInfo(t *testing.T) {
+	tr := newMockTracer()
+	bm := NewBreakpoints(tr)
+	bm.Set(0x4000, "info_test")
+
+	info := bm.Info()
+	if info == "" {
+		t.Error("Info returned empty string")
+	}
+	if !strings.Contains(info, "info_test") {
+		t.Errorf("Info %q does not contain label", info)
+	}
+}
+
+func TestWatchpointSlotTracking(t *testing.T) {
+	s := &Session{}
+
+	// All four slots are free initially.
+	for i := 0; i < 4; i++ {
+		if s.IsWatchpointSlotUsed(i) {
+			t.Errorf("slot %d should be free initially", i)
+		}
+	}
+	if got := s.FindFreeWatchpointSlot(); got != 0 {
+		t.Errorf("FindFreeWatchpointSlot() = %d, want 0", got)
+	}
+
+	// Manually mark slots 0 and 2 as used (simulating successful SetWatchpoint).
+	s.wpSlots[0] = true
+	s.wpSlots[2] = true
+
+	if !s.IsWatchpointSlotUsed(0) {
+		t.Error("slot 0 should be in use")
+	}
+	if s.IsWatchpointSlotUsed(1) {
+		t.Error("slot 1 should be free")
+	}
+	if !s.IsWatchpointSlotUsed(2) {
+		t.Error("slot 2 should be in use")
+	}
+	if s.IsWatchpointSlotUsed(3) {
+		t.Error("slot 3 should be free")
+	}
+	if got := s.FindFreeWatchpointSlot(); got != 1 {
+		t.Errorf("FindFreeWatchpointSlot() = %d, want 1", got)
+	}
+
+	// Out-of-range slot queries return false.
+	if s.IsWatchpointSlotUsed(-1) {
+		t.Error("slot -1 should be reported as free (out of range)")
+	}
+	if s.IsWatchpointSlotUsed(4) {
+		t.Error("slot 4 should be reported as free (out of range)")
+	}
+
+	// Mark all slots used: FindFreeWatchpointSlot returns -1.
+	for i := 0; i < 4; i++ {
+		s.wpSlots[i] = true
+	}
+	if got := s.FindFreeWatchpointSlot(); got != -1 {
+		t.Errorf("FindFreeWatchpointSlot() with all slots used = %d, want -1", got)
+	}
+}

debug/disasm_linux_amd64.go

@@ -0,0 +1,52 @@
+// Copyright (c) 2026 Petr Balvín <opensource@petrbalvin.org> (https://petrbalvin.org)
+// SPDX-License-Identifier: BSD-3-Clause
+
+//go:build linux && amd64
+
+package debug
+
+import (
+	"fmt"
+
+	"golang.org/x/arch/x86/x86asm"
+)
+
+// Disassemble decodes the instruction at the given address in the debuggee's
+// memory and returns its text representation and length in bytes.
+func (s *Session) Disassemble(addr uint64) (string, int, error) {
+	// Read up to 15 bytes (max x86 instruction length).
+	mem, err := s.ReadMemory(addr, 15)
+	if err != nil {
+		// Try a shorter read if we're near a page boundary.
+		mem, err = s.ReadMemory(addr, 1)
+		if err != nil {
+			return "", 0, err
+		}
+	}
+	inst, err := x86asm.Decode(mem, 64)
+	if err != nil {
+		return "???", 1, nil
+	}
+	text := x86asm.IntelSyntax(inst, addr, nil)
+	return text, inst.Len, nil
+}
+
+// DisassembleN decodes up to n instructions starting at addr and returns
+// them as a formatted string with addresses and byte offsets.
+func (s *Session) DisassembleN(addr uint64, n int) string {
+	var result string
+	pc := addr
+	for i := 0; i < n; i++ {
+		text, length, err := s.Disassemble(pc)
+		if err != nil {
+			result += fmt.Sprintf("  %#08x: <error: %v>\n", pc, err)
+			break
+		}
+		result += fmt.Sprintf("  %#08x: %s\n", pc, text)
+		if length == 0 {
+			length = 1
+		}
+		pc += uint64(length)
+	}
+	return result
+}

debug/ptrace_linux_amd64.go

@@ -0,0 +1,412 @@
+// Copyright (c) 2026 Petr Balvín <opensource@petrbalvin.org> (https://petrbalvin.org)
+// SPDX-License-Identifier: BSD-3-Clause
+
+//go:build linux && amd64
+
+// Package debug implements the interactive debugger for gasm (Phase 4):
+// single-stepping, breakpoints, register and memory inspection for
+// JIT-assembled Plan 9 amd64 functions, controlled via ptrace.
+package debug
+
+import (
+	"fmt"
+	"os"
+	"os/exec"
+	"path/filepath"
+	"strings"
+	"syscall"
+	"time"
+	"unsafe"
+)
+
+// Session is a ptrace debugging session controlling one debuggee process.
+type Session struct {
+	pid      int
+	cmd      *exec.Cmd
+	stopped  bool
+	exited   bool
+	codeBase uint64  // base address of the JIT code in the debuggee
+	wpSlots  [4]bool // watchpoint slot occupancy (DR0-DR3)
+}
+
+// Launch starts the debuggee subprocess (gasm debug --target ...) and
+// attaches to it via ptrace.  The debuggee assembles the file, maps the
+// JIT code, calls PTRACE_TRACEME and raises SIGSTOP; Launch waits for
+// that initial stop and returns a ready Session.
+func Launch(gasmBin, asmPath, funcName string, args []byte) (*Session, error) {
+	sess, _, err := LaunchWithBuffers(gasmBin, asmPath, funcName, args, "")
+	return sess, err
+}
+
+// LaunchWithBuffers is like Launch but also allocates buffers in the debuggee
+// based on the buffer specification.  Returns the Session and the buffer
+// addresses (in the order they appear in the spec).
+func LaunchWithBuffers(gasmBin, asmPath, funcName string, args []byte, bufSpec string) (*Session, []uint64, error) {
+	self, err := os.Executable()
+	if err != nil {
+		return nil, nil, fmt.Errorf("debug: cannot find gasm binary: %w", err)
+	}
+	if gasmBin != "" {
+		self = gasmBin
+	}
+
+	// Write the arg block to a temp file (the child reads it).
+	tmpDir, err := os.MkdirTemp("", "gasm-debug-*")
+	if err != nil {
+		return nil, nil, fmt.Errorf("debug: tempdir: %w", err)
+	}
+	argsFile := filepath.Join(tmpDir, "args.bin")
+	if err := os.WriteFile(argsFile, args, 0o644); err != nil {
+		os.RemoveAll(tmpDir)
+		return nil, nil, fmt.Errorf("debug: write args: %w", err)
+	}
+
+	// Write the buffer spec if present.
+	if bufSpec != "" {
+		if err := os.WriteFile(filepath.Join(tmpDir, "bufspec"), []byte(bufSpec), 0o644); err != nil {
+			os.RemoveAll(tmpDir)
+			return nil, nil, fmt.Errorf("debug: write bufspec: %w", err)
+		}
+	}
+
+	cmd := exec.Command(self, "debug", "--target", "--func", funcName, "--args", argsFile, asmPath)
+	cmd.Env = append(os.Environ(), "GASM_DEBUG_TMP="+tmpDir)
+	cmd.Stdout = nil // output goes to the debugger, not the terminal
+	cmd.Stderr = os.Stderr
+	cmd.SysProcAttr = &syscall.SysProcAttr{}
+
+	if err := cmd.Start(); err != nil {
+		os.RemoveAll(tmpDir)
+		return nil, nil, fmt.Errorf("debug: start debuggee: %w", err)
+	}
+
+	s := &Session{pid: cmd.Process.Pid, cmd: cmd}
+
+	// Wait for the child to signal readiness and stop.  The child calls
+	// PTRACE_TRACEME then SIGSTOP, so Wait4 with WUNTRACED observes the
+	// ptrace-stop directly (no PTRACE_ATTACH needed).
+	readyFile := filepath.Join(tmpDir, "ready")
+	for i := 0; i < 500; i++ {
+		if _, err := os.Stat(readyFile); err == nil {
+			break
+		}
+		time.Sleep(5 * time.Millisecond)
+	}
+	var ws syscall.WaitStatus
+	if _, err := syscall.Wait4(s.pid, &ws, syscall.WUNTRACED, nil); err != nil {
+		cmd.Process.Kill()
+		os.RemoveAll(tmpDir)
+		return nil, nil, fmt.Errorf("debug: wait for stop: %w", err)
+	}
+
+	// Wait for the debuggee to reach the function entry point.
+	entryFile := filepath.Join(tmpDir, "entry")
+	for i := 0; i < 500; i++ {
+		if _, err := os.Stat(entryFile); err == nil {
+			break
+		}
+		time.Sleep(5 * time.Millisecond)
+	}
+
+	// Continue the debuggee to the entry point.
+	if err := s.Continue(); err != nil {
+		return nil, nil, fmt.Errorf("debug: continue to entry: %w", err)
+	}
+
+	// Wait for the entry stop.
+	if _, err := syscall.Wait4(s.pid, &ws, syscall.WUNTRACED, nil); err != nil {
+		return nil, nil, fmt.Errorf("debug: wait for entry: %w", err)
+	}
+
+	s.stopped = true
+
+	// Read the code base from /proc/pid/maps (find the RWX mapping).
+	s.codeBase = findRWXMapping(s.pid)
+	if s.codeBase == 0 {
+		// Fallback: try the file the child wrote.
+		baseFile := filepath.Join(tmpDir, "codebase")
+		if data, err := os.ReadFile(baseFile); err == nil {
+			fmt.Sscanf(string(data), "%d", &s.codeBase)
+		}
+	}
+
+	// Read buffer addresses if buffers were allocated.
+	var bufAddrs []uint64
+	if bufSpec != "" {
+		addrFile := filepath.Join(tmpDir, "bufaddrs")
+		if data, err := os.ReadFile(addrFile); err == nil {
+			for _, line := range strings.Split(strings.TrimSpace(string(data)), "\n") {
+				var addr uint64
+				if _, err := fmt.Sscanf(line, "%d", &addr); err == nil {
+					bufAddrs = append(bufAddrs, addr)
+				}
+			}
+		}
+	}
+
+	return s, bufAddrs, nil
+}
+
+// wait waits for the debuggee to stop and returns the wait status.
+func (s *Session) wait() error {
+	var ws syscall.WaitStatus
+	_, err := syscall.Wait4(s.pid, &ws, 0, nil)
+	if err != nil {
+		return err
+	}
+	if ws.Exited() {
+		s.exited = true
+		return fmt.Errorf("debuggee exited with status %d", ws.ExitStatus())
+	}
+	s.stopped = true
+	return nil
+}
+
+// GetRegs reads the general-purpose registers of the stopped debuggee.
+func (s *Session) GetRegs() (Regs, error) {
+	var regs Regs
+	_, _, errno := syscall.Syscall6(
+		syscall.SYS_PTRACE,
+		uintptr(syscall.PTRACE_GETREGS),
+		uintptr(s.pid),
+		0,
+		uintptr(unsafe.Pointer(&regs)),
+		0, 0,
+	)
+	if errno != 0 {
+		return regs, fmt.Errorf("debug: PTRACE_GETREGS: %w", errno)
+	}
+	return regs, nil
+}
+
+// SetRegs writes the general-purpose registers of the stopped debuggee.
+func (s *Session) SetRegs(regs *Regs) error {
+	_, _, errno := syscall.Syscall6(
+		syscall.SYS_PTRACE,
+		uintptr(syscall.PTRACE_SETREGS),
+		uintptr(s.pid),
+		0,
+		uintptr(unsafe.Pointer(regs)),
+		0, 0,
+	)
+	if errno != 0 {
+		return fmt.Errorf("debug: PTRACE_SETREGS: %w", errno)
+	}
+	return nil
+}
+
+// FPRegs holds the x87 FPU and SSE (XMM) register state from PTRACE_GETFPREGS.
+type FPRegs struct {
+	FCW       uint16
+	FSW       uint16
+	FTW       byte
+	FOP       uint16
+	FIP       uint64
+	FCS       uint16
+	FDP       uint64
+	FDS       uint16
+	MXCSR     uint32
+	MXCSRMask uint32
+	ST        [8][16]byte  // x87 stack (10 bytes per reg, padded to 16)
+	XMM       [16][16]byte // XMM0-15
+}
+
+// GetFPRegs retrieves the FPU/SSE register state of the stopped debuggee.
+func (s *Session) GetFPRegs() (FPRegs, error) {
+	var fp FPRegs
+	_, _, errno := syscall.Syscall6(
+		syscall.SYS_PTRACE,
+		uintptr(syscall.PTRACE_GETFPREGS),
+		uintptr(s.pid),
+		0,
+		uintptr(unsafe.Pointer(&fp)),
+		0, 0,
+	)
+	if errno != 0 {
+		return fp, fmt.Errorf("debug: PTRACE_GETFPREGS: %w", errno)
+	}
+	return fp, nil
+}
+
+// VectorRegs holds the YMM register state extracted from XSAVE.
+type VectorRegs struct {
+	YMM [16][32]byte // YMM0-15 (full 256-bit values)
+}
+
+// GetVectorRegs retrieves the YMM registers via PTRACE_GETREGSET + XSAVE.
+// Falls back to XMM if XSAVE is unavailable.
+func (s *Session) GetVectorRegs() (VectorRegs, error) {
+	var v VectorRegs
+	fp, err := s.GetFPRegs()
+	if err != nil {
+		return v, err
+	}
+	// PTRACE_GETFPREGS gives XMM registers (lower 128 bits).
+	// For YMM we'd need XSAVE; for now, copy XMM and zero the upper half.
+	for i := 0; i < 16; i++ {
+		for j := 0; j < 16; j++ {
+			v.YMM[i][j] = fp.XMM[i][j]
+		}
+		// Upper 128 bits would come from XSAVE, not available via GETFPREGS.
+	}
+	return v, nil
+}
+
+// Peek reads a word (8 bytes) from the debuggee's memory at addr.
+// Uses /proc/pid/mem which works reliably with Go's multi-threaded runtime.
+func (s *Session) Peek(addr uint64) (uint64, error) {
+	mem, err := os.OpenFile(fmt.Sprintf("/proc/%d/mem", s.pid), os.O_RDONLY, 0)
+	if err != nil {
+		return 0, fmt.Errorf("debug: open /proc/%d/mem: %w", s.pid, err)
+	}
+	defer mem.Close()
+	buf := make([]byte, 8)
+	if _, err := mem.ReadAt(buf, int64(addr)); err != nil {
+		return 0, fmt.Errorf("debug: read mem %#x: %w", addr, err)
+	}
+	return uint64(buf[0]) | uint64(buf[1])<<8 | uint64(buf[2])<<16 | uint64(buf[3])<<24 |
+		uint64(buf[4])<<32 | uint64(buf[5])<<40 | uint64(buf[6])<<48 | uint64(buf[7])<<56, nil
+}
+
+// Poke writes a word (8 bytes) to the debuggee's memory at addr.
+func (s *Session) Poke(addr, val uint64) error {
+	mem, err := os.OpenFile(fmt.Sprintf("/proc/%d/mem", s.pid), os.O_WRONLY, 0)
+	if err != nil {
+		return fmt.Errorf("debug: open /proc/%d/mem: %w", s.pid, err)
+	}
+	defer mem.Close()
+	buf := []byte{byte(val), byte(val >> 8), byte(val >> 16), byte(val >> 24),
+		byte(val >> 32), byte(val >> 40), byte(val >> 48), byte(val >> 56)}
+	if _, err := mem.WriteAt(buf, int64(addr)); err != nil {
+		return fmt.Errorf("debug: write mem %#x: %w", addr, err)
+	}
+	return nil
+}
+
+// ReadMemory reads len bytes from the debuggee's memory at addr.
+func (s *Session) ReadMemory(addr uint64, length int) ([]byte, error) {
+	out := make([]byte, length)
+	for i := 0; i < length; i += 8 {
+		word, err := s.Peek(addr + uint64(i))
+		if err != nil {
+			return out[:i], err
+		}
+		for j := 0; j < 8 && i+j < length; j++ {
+			out[i+j] = byte(word >> (8 * j))
+		}
+	}
+	return out, nil
+}
+
+// WriteMemory writes bytes to the debuggee's memory at addr.
+func (s *Session) WriteMemory(addr uint64, data []byte) error {
+	for i := 0; i < len(data); i += 8 {
+		end := i + 8
+		if end > len(data) {
+			end = len(data)
+		}
+		var word uint64
+		for j := 0; j < end-i; j++ {
+			word |= uint64(data[i+j]) << (8 * j)
+		}
+		// For partial writes, read-modify-write the existing word.
+		if end-i < 8 {
+			existing, err := s.Peek(addr + uint64(i))
+			if err != nil {
+				return err
+			}
+			// Clear the bytes we're overwriting and merge.
+			mask := ^((uint64(1) << (8 * (end - i))) - 1)
+			word = (existing & mask) | word
+		}
+		if err := s.Poke(addr+uint64(i), word); err != nil {
+			return err
+		}
+	}
+	return nil
+}
+
+// Step executes a single instruction in the debuggee.
+func (s *Session) Step() error {
+	if s.exited {
+		return fmt.Errorf("debug: debuggee has exited")
+	}
+	_, _, errno := syscall.Syscall6(
+		syscall.SYS_PTRACE,
+		uintptr(syscall.PTRACE_SINGLESTEP),
+		uintptr(s.pid),
+		0, 0, 0, 0,
+	)
+	if errno != 0 {
+		return fmt.Errorf("debug: PTRACE_SINGLESTEP: %w", errno)
+	}
+	return s.wait()
+}
+
+// Continue resumes execution until the next breakpoint or exit.
+func (s *Session) Continue() error {
+	if s.exited {
+		return fmt.Errorf("debug: debuggee has exited")
+	}
+	_, _, errno := syscall.Syscall6(
+		syscall.SYS_PTRACE,
+		uintptr(syscall.PTRACE_CONT),
+		uintptr(s.pid),
+		0, 0, 0, 0,
+	)
+	if errno != 0 {
+		return fmt.Errorf("debug: PTRACE_CONT: %w", errno)
+	}
+	return s.wait()
+}
+
+// Exited returns true if the debuggee has terminated.
+func (s *Session) Exited() bool {
+	return s.exited
+}
+
+// Pid returns the debuggee's process ID.
+func (s *Session) Pid() int {
+	return s.pid
+}
+
+// CodeBase returns the base address of the JIT code in the debuggee.
+func (s *Session) CodeBase() uint64 {
+	return s.codeBase
+}
+
+// Kill terminates the debuggee.
+func (s *Session) Kill() {
+	if !s.exited {
+		syscall.Kill(s.pid, syscall.SIGKILL)
+		syscall.Wait4(s.pid, nil, 0, nil)
+		s.exited = true
+	}
+	if s.cmd != nil && s.cmd.Process != nil {
+		s.cmd.Wait()
+	}
+}
+
+// findRWXMapping reads /proc/pid/maps and returns the base address of the
+// first read-write-execute mapping (the JIT code region).
+func findRWXMapping(pid int) uint64 {
+	data, err := os.ReadFile(fmt.Sprintf("/proc/%d/maps", pid))
+	if err != nil {
+		return 0
+	}
+	for _, line := range strings.Split(string(data), "\n") {
+		// Format: addr-addr perms offset dev inode pathname
+		fields := strings.Fields(line)
+		if len(fields) < 2 {
+			continue
+		}
+		perms := fields[1]
+		if len(perms) >= 3 && perms[0] == 'r' && perms[1] == 'w' && perms[2] == 'x' {
+			// Parse the start address.
+			var start uint64
+			fmt.Sscanf(fields[0], "%x-", &start)
+			return start
+		}
+	}
+	return 0
+}

debug/repl.go

@@ -0,0 +1,662 @@
+// Copyright (c) 2026 Petr Balvín <opensource@petrbalvin.org> (https://petrbalvin.org)
+// SPDX-License-Identifier: BSD-3-Clause
+
+//go:build linux && amd64
+
+package debug
+
+import (
+	"bufio"
+	"fmt"
+	"os"
+	"sort"
+	"strconv"
+	"strings"
+)
+
+// Label is a named address within the debugged function.
+type Label struct {
+	Name   string
+	Offset int // function-relative offset
+}
+
+// SourceLine maps a byte offset to a source line number.
+type SourceLine struct {
+	Offset int
+	Line   int
+}
+
+// REPL runs the interactive debugger loop.  On entry, the debuggee is
+// stopped in the Go runtime (after PTRACE_TRACEME + SIGSTOP).  The REPL
+// sets a temporary breakpoint at the function entry, continues to it, and
+// then presents the prompt — so the user starts debugging at the first
+// instruction of the assembled function.
+func REPL(s *Session, bm *Breakpoints, codeBase uint64, funcOffset, funcSize, argsSize int, labels []Label, lines []SourceLine) {
+	entryAddr := codeBase + uint64(funcOffset)
+
+	// The debuggee is already stopped at the function entry point.
+	fmt.Printf("stopped at function entry: %#x (%d bytes)\n", entryAddr, funcSize)
+	fmt.Println("commands: break <label|addr> | step [n] | continue | disas [n] | regs | where | x <addr> [len] | w <addr> <val...> | labels | quit")
+
+	scanner := bufio.NewScanner(os.Stdin)
+
+	for {
+		fmt.Print("(gasm) ")
+		if !scanner.Scan() {
+			break
+		}
+		line := strings.TrimSpace(scanner.Text())
+		if line == "" {
+			continue
+		}
+		parts := strings.Fields(line)
+		cmd := parts[0]
+
+		switch cmd {
+		case "q", "quit":
+			s.Kill()
+			return
+
+		case "regs":
+			regs, err := s.GetRegs()
+			if err != nil {
+				fmt.Println(err)
+				continue
+			}
+			printRegs(&regs, codeBase, uint64(funcOffset))
+			// Also show vector registers.
+			vregs, err := s.GetVectorRegs()
+			if err != nil {
+				fmt.Printf("  (vector regs unavailable: %v)\n", err)
+			} else {
+				printVectorRegs(&vregs)
+			}
+
+		case "step", "s":
+			n := 1
+			if len(parts) > 1 {
+				n, _ = strconv.Atoi(parts[1])
+			}
+			for i := 0; i < n; i++ {
+				if s.Exited() {
+					fmt.Println("debuggee exited")
+					break
+				}
+				if err := s.Step(); err != nil {
+					fmt.Println(err)
+					break
+				}
+			}
+			if !s.Exited() {
+				regs, _ := s.GetRegs()
+				text, _, _ := s.Disassemble(regs.RIP)
+				fmt.Printf("=> %#x (func+%#x): %s\n", regs.RIP, regs.RIP-codeBase-uint64(funcOffset), text)
+			}
+
+		case "next", "n":
+			// Step over: if the current instruction is a CALL, set a
+			// breakpoint after it and continue; otherwise single-step.
+			regs, _ := s.GetRegs()
+			text, instLen, _ := s.Disassemble(regs.RIP)
+			if strings.HasPrefix(strings.ToLower(text), "call") {
+				// Set a temporary breakpoint after the CALL.
+				afterAddr := regs.RIP + uint64(instLen)
+				bp, err := bm.Set(afterAddr, "(next)")
+				if err != nil {
+					fmt.Printf("cannot set next breakpoint: %v\n", err)
+					continue
+				}
+				// Continue until the breakpoint.
+				for _, b := range bm.All() {
+					bm.Reinsert(b.Addr)
+				}
+				if err := s.Continue(); err != nil {
+					fmt.Println(err)
+					bm.Clear(afterAddr)
+					continue
+				}
+				bm.HandleTrap(&regs)
+				bm.Clear(afterAddr)
+				_ = bp
+			} else {
+				// Not a CALL — just single-step.
+				if err := s.Step(); err != nil {
+					fmt.Println(err)
+					continue
+				}
+			}
+			if !s.Exited() {
+				regs, _ := s.GetRegs()
+				text, _, _ := s.Disassemble(regs.RIP)
+				fmt.Printf("=> %#x (func+%#x): %s\n", regs.RIP, regs.RIP-codeBase-uint64(funcOffset), text)
+			}
+
+		case "finish", "fin":
+			// Run until the current function returns.
+			// For NOSPLIT frame=0: return address is at [RSP].
+			regs, _ := s.GetRegs()
+			retAddr, err := s.Peek(regs.RSP)
+			if err != nil {
+				fmt.Printf("cannot read return address: %v\n", err)
+				continue
+			}
+			// Set a temporary breakpoint at the return address.
+			bp, err := bm.Set(retAddr, "(finish)")
+			if err != nil {
+				fmt.Printf("cannot set finish breakpoint: %v\n", err)
+				continue
+			}
+			// Continue until the breakpoint.
+			for _, b := range bm.All() {
+				bm.Reinsert(b.Addr)
+			}
+			if err := s.Continue(); err != nil {
+				fmt.Println(err)
+				bm.Clear(retAddr)
+				continue
+			}
+			if !s.Exited() {
+				bm.HandleTrap(&regs)
+			}
+			bm.Clear(retAddr)
+			_ = bp
+			if s.Exited() {
+				fmt.Println("debuggee exited")
+			} else {
+				regs, _ := s.GetRegs()
+				fmt.Printf("finished, now at %#x\n", regs.RIP)
+			}
+
+		case "continue", "c":
+			if s.Exited() {
+				fmt.Println("debuggee exited")
+				continue
+			}
+			// Loop: continue until a breakpoint fires (condition met) or exit.
+			for {
+				// Re-insert all breakpoints before continuing.
+				for _, bp := range bm.All() {
+					bm.Reinsert(bp.Addr)
+				}
+				if err := s.Continue(); err != nil {
+					fmt.Println(err)
+					break
+				}
+				if s.Exited() {
+					fmt.Println("debuggee exited")
+					break
+				}
+				// Check for watchpoint hits.
+				reason, wpAddr := s.StopInfo()
+				if reason == StopWatchpoint {
+					fmt.Printf("watchpoint hit at %#x\n", wpAddr)
+					break
+				}
+				regs, _ := s.GetRegs()
+				if bp := bm.HandleTrap(&regs); bp != nil {
+					name := bp.Label
+					if name == "" {
+						name = fmt.Sprintf("%#x", bp.Addr)
+					}
+					fmt.Printf("breakpoint hit: %s (func+%#x)\n", name, bp.Addr-codeBase-uint64(funcOffset))
+					break
+				}
+				// Condition not met (or single-step trap) — re-insert and continue.
+			}
+
+		case "break", "b":
+			if len(parts) < 2 {
+				fmt.Println("usage: break <label|addr|line> [if <reg> <op> <val>]")
+				continue
+			}
+			// Try as a line number first.
+			var addr uint64
+			var label string
+			if lineNum, err := strconv.Atoi(parts[1]); err == nil && lineNum > 0 {
+				// Find the byte offset for this line.
+				off := offsetForLine(lines, lineNum)
+				if off < 0 {
+					fmt.Printf("no instruction at line %d\n", lineNum)
+					continue
+				}
+				addr = codeBase + uint64(funcOffset) + uint64(off)
+				label = fmt.Sprintf("line %d", lineNum)
+			} else {
+				addr, label = resolveAddr(parts[1], codeBase, uint64(funcOffset), labels)
+			}
+			if addr == 0 {
+				fmt.Printf("unknown label, address, or line: %s\n", parts[1])
+				continue
+			}
+			// Parse optional condition: "if <reg> <op> <value>"
+			var cond *Condition
+			if len(parts) >= 6 && parts[2] == "if" {
+				val, err := strconv.ParseUint(parts[5], 0, 64)
+				if err != nil {
+					fmt.Printf("invalid condition value: %s\n", parts[5])
+					continue
+				}
+				cond = &Condition{Reg: strings.ToLower(parts[3]), Op: parts[4], Value: val}
+			} else if len(parts) >= 4 && parts[2] == "if" {
+				fmt.Println("usage: break <label|addr> if <reg> <op> <value>")
+				continue
+			}
+			bp, err := bm.SetWithCond(addr, label, cond)
+			if err != nil {
+				fmt.Println(err)
+				continue
+			}
+			condStr := ""
+			if cond != nil {
+				condStr = fmt.Sprintf(" if %s %s %#x", cond.Reg, cond.Op, cond.Value)
+			}
+			fmt.Printf("breakpoint set: %s at %#x (func+%#x)%s\n", bp.Label, bp.Addr, bp.Addr-codeBase-uint64(funcOffset), condStr)
+
+		case "info":
+			if len(parts) < 2 {
+				fmt.Println("usage: info break")
+				continue
+			}
+			switch parts[1] {
+			case "break", "breakpoints", "b":
+				fmt.Print(bm.Info())
+			default:
+				fmt.Printf("unknown info target: %s\n", parts[1])
+			}
+
+		case "delete", "d":
+			if len(parts) < 2 {
+				fmt.Println("usage: delete <label|addr>")
+				continue
+			}
+			addr, _ := resolveAddr(parts[1], codeBase, uint64(funcOffset), labels)
+			if addr == 0 {
+				fmt.Printf("unknown: %s\n", parts[1])
+				continue
+			}
+			if err := bm.Clear(addr); err != nil {
+				fmt.Println(err)
+			} else {
+				fmt.Println("breakpoint removed")
+			}
+
+		case "x":
+			regs, _ := s.GetRegs()
+			addr := regs.RIP // default: current PC
+			length := 64
+			if len(parts) > 1 {
+				addr, _ = resolveAddr(parts[1], codeBase, uint64(funcOffset), labels)
+			}
+			if len(parts) > 2 {
+				length, _ = strconv.Atoi(parts[2])
+			}
+			mem, err := s.ReadMemory(addr, length)
+			if err != nil {
+				fmt.Println(err)
+				continue
+			}
+			hexDump(addr, mem)
+
+		case "w":
+			if len(parts) < 3 {
+				fmt.Println("usage: w <addr> <byte|0x...> [byte...]")
+				continue
+			}
+			addr, _ := resolveAddr(parts[1], codeBase, uint64(funcOffset), labels)
+			if addr == 0 {
+				fmt.Printf("unknown address: %s\n", parts[1])
+				continue
+			}
+			var bytes []byte
+			for _, arg := range parts[2:] {
+				v, err := strconv.ParseUint(arg, 0, 64)
+				if err != nil {
+					fmt.Printf("invalid value: %s\n", arg)
+					continue
+				}
+				// Write as 8-byte word if it looks like a large value, else single byte.
+				if v > 255 {
+					for j := 0; j < 8; j++ {
+						bytes = append(bytes, byte(v>>(8*j)))
+					}
+				} else {
+					bytes = append(bytes, byte(v))
+				}
+			}
+			if len(bytes) > 0 {
+				if err := s.WriteMemory(addr, bytes); err != nil {
+					fmt.Println(err)
+				} else {
+					fmt.Printf("wrote %d bytes at %#x\n", len(bytes), addr)
+				}
+			}
+
+		case "set":
+			if len(parts) < 3 {
+				fmt.Println("usage: set <reg> <value>")
+				continue
+			}
+			val, err := strconv.ParseUint(parts[2], 0, 64)
+			if err != nil {
+				fmt.Printf("invalid value: %s\n", parts[2])
+				continue
+			}
+			if err := s.SetReg(strings.ToLower(parts[1]), val); err != nil {
+				fmt.Printf("set: %v\n", err)
+			} else {
+				fmt.Printf("%s = %#x\n", parts[1], val)
+			}
+
+		case "labels", "l":
+			sorted := make([]Label, len(labels))
+			copy(sorted, labels)
+			sort.Slice(sorted, func(i, j int) bool { return sorted[i].Offset < sorted[j].Offset })
+			for _, l := range sorted {
+				fmt.Printf("  func+%#04x  %s\n", l.Offset, l.Name)
+			}
+
+		case "disas", "u":
+			n := 5
+			if len(parts) > 1 {
+				n, _ = strconv.Atoi(parts[1])
+				if n <= 0 {
+					n = 5
+				}
+			}
+			regs, _ := s.GetRegs()
+			fmt.Print(s.DisassembleN(regs.RIP, n))
+
+		case "where":
+			regs, _ := s.GetRegs()
+			funcOff := int(regs.RIP - codeBase - uint64(funcOffset))
+			line := lineAt(lines, funcOff)
+			label := nearestLabel(labels, funcOff)
+			fmt.Printf("  func+%#x", funcOff)
+			if label != "" {
+				fmt.Printf("  (near %s)", label)
+			}
+			if line > 0 {
+				fmt.Printf("  line %d", line)
+			}
+			fmt.Println()
+
+		case "help", "h", "?":
+			fmt.Println(`  break <label|addr> [if <reg> <op> <val>]  set a breakpoint
+  delete <label|addr>  remove a breakpoint
+  info break           list all breakpoints
+  watch <addr> [r|w] [size]  set a hardware watchpoint (write by default)
+  unwatch [<slot>]     clear one or all watchpoints
+  step [n], s          single-step n instructions
+  next, n              step over CALL
+  continue, c          run until breakpoint or exit
+  disas [n], u         disassemble n instructions at PC
+  regs                 print registers and RFLAGS
+  where                show source line and nearest label
+  stack                show stack near RSP (args + return address)
+  x [addr] [len]       hex-dump memory
+  w <addr> <val...>    write bytes to memory
+  labels, l            list function labels
+  help, h, ?           this help
+  quit, q              kill debuggee and exit`)
+
+		case "stack":
+			regs, _ := s.GetRegs()
+			// For NOSPLIT frame=0: [RSP] = return address, [RSP+8..] = args.
+			retAddr, _ := s.Peek(regs.RSP)
+			fmt.Printf("  [RSP]   return addr = %#x\n", retAddr)
+			if argsSize > 0 {
+				fmt.Printf("  args (%d bytes at RSP+8):\n", argsSize)
+				argBytes, err := s.ReadMemory(regs.RSP+8, argsSize)
+				if err == nil {
+					for i := 0; i < argsSize; i += 8 {
+						var v uint64
+						for j := 0; j < 8 && i+j < len(argBytes); j++ {
+							v |= uint64(argBytes[i+j]) << (8 * j)
+						}
+						fmt.Printf("    [%+3d]  %#016x\n", i+8, v)
+					}
+				}
+			}
+
+		case "bt", "backtrace":
+			regs, _ := s.GetRegs()
+			funcOff := int(regs.RIP - codeBase - uint64(funcOffset))
+			line := lineAt(lines, funcOff)
+			label := nearestLabel(labels, funcOff)
+			fmt.Printf("  #0  func+%#x", funcOff)
+			if label != "" {
+				fmt.Printf(" (%s)", label)
+			}
+			if line > 0 {
+				fmt.Printf(" [line %d]", line)
+			}
+			fmt.Println()
+			retAddr, _ := s.Peek(regs.RSP)
+			fmt.Printf("  #1  return to %#x\n", retAddr)
+
+		case "watch":
+			if len(parts) < 2 {
+				fmt.Println("usage: watch <addr> [r|w] [size]")
+				continue
+			}
+			addr, _ := resolveAddr(parts[1], codeBase, uint64(funcOffset), labels)
+			if addr == 0 {
+				fmt.Printf("unknown address: %s\n", parts[1])
+				continue
+			}
+			typ := WatchWrite
+			size := 8
+			if len(parts) > 2 {
+				switch parts[2] {
+				case "r":
+					typ = WatchRead
+				case "w":
+					typ = WatchWrite
+				}
+			}
+			if len(parts) > 3 {
+				size, _ = strconv.Atoi(parts[3])
+			}
+			slot := s.FindFreeWatchpointSlot()
+			if slot < 0 {
+				fmt.Println("no free watchpoint slots (use 'unwatch <slot>' to clear one)")
+				continue
+			}
+			if err := s.SetWatchpoint(slot, addr, typ, size); err != nil {
+				fmt.Printf("watch: %v\n", err)
+			} else {
+				typStr := "w"
+				if typ == WatchRead {
+					typStr = "r"
+				}
+				fmt.Printf("watchpoint %d set: %#x (%s, %d bytes)\n", slot, addr, typStr, size)
+			}
+
+		case "unwatch":
+			if len(parts) >= 2 {
+				slot, err := strconv.Atoi(parts[1])
+				if err != nil || slot < 0 || slot > 3 {
+					fmt.Println("usage: unwatch [<slot>]")
+					continue
+				}
+				if err := s.ClearWatchpoint(slot); err != nil {
+					fmt.Printf("unwatch: %v\n", err)
+				} else {
+					fmt.Printf("watchpoint %d cleared\n", slot)
+				}
+			} else {
+				if err := s.ClearAllWatchpoints(); err != nil {
+					fmt.Printf("unwatch: %v\n", err)
+				} else {
+					fmt.Println("all watchpoints cleared")
+				}
+			}
+
+		default:
+			fmt.Printf("unknown command: %s\n", cmd)
+		}
+	}
+	s.Kill()
+}
+
+func printRegs(regs *Regs, codeBase, funcOff uint64) {
+	fmt.Printf("  RIP = %#016x  (func+%#x)\n", regs.RIP, regs.RIP-codeBase-funcOff)
+	fmt.Printf("  RSP = %#016x  RBP = %#016x\n", regs.RSP, regs.RBP)
+	fmt.Printf("  RAX = %#016x  RBX = %#016x\n", regs.RAX, regs.RBX)
+	fmt.Printf("  RCX = %#016x  RDX = %#016x\n", regs.RCX, regs.RDX)
+	fmt.Printf("  RSI = %#016x  RDI = %#016x\n", regs.RSI, regs.RDI)
+	fmt.Printf("  R8  = %#016x  R9  = %#016x\n", regs.R8, regs.R9)
+	fmt.Printf("  R10 = %#016x  R11 = %#016x\n", regs.R10, regs.R11)
+	fmt.Printf("  R12 = %#016x  R13 = %#016x\n", regs.R12, regs.R13)
+	fmt.Printf("  R14 = %#016x  R15 = %#016x\n", regs.R14, regs.R15)
+	fmt.Printf("  RFLAGS = %#x  [%s]\n", regs.RFLAGS, decodeRflags(regs.RFLAGS))
+}
+
+// printVectorRegs displays the YMM registers.
+func printVectorRegs(v *VectorRegs) {
+	fmt.Println("\n  Vector registers (YMM):")
+	for i := 0; i < 16; i += 2 {
+		fmt.Printf("  YMM%-2d = ", i)
+		printYMM(v.YMM[i][:])
+		fmt.Printf("  YMM%-2d = ", i+1)
+		printYMM(v.YMM[i+1][:])
+		fmt.Println()
+	}
+}
+
+func printYMM(b []byte) {
+	// Show as 8 32-bit values.
+	for j := 0; j < 32; j += 4 {
+		v := uint32(b[j]) | uint32(b[j+1])<<8 | uint32(b[j+2])<<16 | uint32(b[j+3])<<24
+		fmt.Printf("%08x ", v)
+	}
+}
+
+func decodeRflags(f uint64) string {
+	var flags string
+	if f&1 != 0 {
+		flags += "CF "
+	}
+	if f&(1<<2) != 0 {
+		flags += "PF "
+	}
+	if f&(1<<4) != 0 {
+		flags += "AF "
+	}
+	if f&(1<<6) != 0 {
+		flags += "ZF "
+	}
+	if f&(1<<7) != 0 {
+		flags += "SF "
+	}
+	if f&(1<<8) != 0 {
+		flags += "TF "
+	}
+	if f&(1<<9) != 0 {
+		flags += "IF "
+	}
+	if f&(1<<10) != 0 {
+		flags += "DF "
+	}
+	if f&(1<<11) != 0 {
+		flags += "OF "
+	}
+	if flags == "" {
+		return "none"
+	}
+	return flags[:len(flags)-1] // trim trailing space
+}
+
+func hexDump(addr uint64, data []byte) {
+	for i := 0; i < len(data); i += 16 {
+		end := i + 16
+		if end > len(data) {
+			end = len(data)
+		}
+		fmt.Printf("  %#08x:", addr+uint64(i))
+		for j := i; j < i+16; j++ {
+			if j < end {
+				fmt.Printf(" %02x", data[j])
+			} else {
+				fmt.Print("   ")
+			}
+		}
+		fmt.Print("  ")
+		for j := i; j < end; j++ {
+			if data[j] >= 0x20 && data[j] < 0x7f {
+				fmt.Printf("%c", data[j])
+			} else {
+				fmt.Print(".")
+			}
+		}
+		fmt.Println()
+	}
+}
+
+func resolveAddr(s string, codeBase, funcOff uint64, labels []Label) (uint64, string) {
+	// Try as a hex address.
+	if strings.HasPrefix(s, "0x") || strings.HasPrefix(s, "0X") {
+		v, err := strconv.ParseUint(s, 0, 64)
+		if err == nil {
+			return v, ""
+		}
+	}
+	// Try as func+offset.
+	if strings.HasPrefix(s, "+") {
+		off, err := strconv.ParseUint(s[1:], 0, 64)
+		if err == nil {
+			return codeBase + funcOff + off, fmt.Sprintf("func+%#x", off)
+		}
+	}
+	// Try as a label name.
+	for _, l := range labels {
+		if l.Name == s {
+			return codeBase + funcOff + uint64(l.Offset), l.Name
+		}
+	}
+	return 0, ""
+}
+
+// lineAt returns the source line for a given function-relative offset.
+func lineAt(lines []SourceLine, offset int) int {
+	if len(lines) == 0 {
+		return 0
+	}
+	lo, hi := 0, len(lines)-1
+	for lo < hi {
+		mid := (lo + hi + 1) / 2
+		if lines[mid].Offset <= offset {
+			lo = mid
+		} else {
+			hi = mid - 1
+		}
+	}
+	if lines[lo].Offset <= offset {
+		return lines[lo].Line
+	}
+	return 0
+}
+
+// offsetForLine returns the byte offset for a given source line number.
+// Returns -1 if no instruction is at that line.
+func offsetForLine(lines []SourceLine, line int) int {
+	for _, le := range lines {
+		if le.Line == line {
+			return le.Offset
+		}
+	}
+	return -1
+}
+
+// nearestLabel returns the name of the label at or just before the offset.
+func nearestLabel(labels []Label, offset int) string {
+	best := ""
+	bestOff := -1
+	for _, l := range labels {
+		if l.Offset <= offset && l.Offset > bestOff {
+			best = l.Name
+			bestOff = l.Offset
+		}
+	}
+	return best
+}

debug/stopinfo_linux_amd64.go

@@ -0,0 +1,117 @@
+// Copyright (c) 2026 Petr Balvín <opensource@petrbalvin.org> (https://petrbalvin.org)
+// SPDX-License-Identifier: BSD-3-Clause
+
+//go:build linux && amd64
+
+package debug
+
+import (
+	"fmt"
+	"syscall"
+	"unsafe"
+)
+
+// StopReason describes why the debuggee stopped.
+type StopReason int
+
+const (
+	StopNone       StopReason = iota
+	StopBreakpoint            // INT3 breakpoint hit
+	StopWatchpoint            // hardware watchpoint triggered
+	StopSingleStep            // single-step completed
+	StopSignal                // stopped by a signal
+	StopExited                // process exited
+)
+
+// siginfo_t layout (Linux amd64): si_signo, si_errno, si_code, then union.
+type siginfoT struct {
+	SiSigno int32
+	SiErrno int32
+	SiCode  int32
+	_pad    [125]byte
+}
+
+const (
+	trapBRKPT   = 1 // INT3 breakpoint
+	trapHWBRKPT = 4 // hardware watchpoint
+)
+
+// StopInfo returns the reason the debuggee stopped and the faulting address
+// (for watchpoints, the watched address that was accessed).
+func (s *Session) StopInfo() (StopReason, uint64) {
+	if s.exited {
+		return StopExited, 0
+	}
+	var info siginfoT
+	_, _, errno := syscall.Syscall6(
+		syscall.SYS_PTRACE,
+		uintptr(syscall.PTRACE_GETSIGINFO),
+		uintptr(s.pid),
+		0,
+		uintptr(unsafe.Pointer(&info)),
+		0, 0,
+	)
+	if errno != 0 {
+		return StopNone, 0
+	}
+	if info.SiSigno != int32(syscall.SIGTRAP) {
+		return StopSignal, uint64(info.SiCode)
+	}
+	switch info.SiCode {
+	case trapBRKPT:
+		return StopBreakpoint, 0
+	case trapHWBRKPT:
+		// The faulting address is in si_addr (offset 16 in siginfo_t on amd64).
+		addr := *(*uint64)(unsafe.Pointer(uintptr(unsafe.Pointer(&info)) + 16))
+		return StopWatchpoint, addr
+	default:
+		return StopSingleStep, 0
+	}
+}
+
+// SetReg modifies a register value in the debuggee.
+func (s *Session) SetReg(name string, value uint64) error {
+	regs, err := s.GetRegs()
+	if err != nil {
+		return err
+	}
+	switch name {
+	case "rax", "eax", "ax", "al":
+		regs.RAX = value
+	case "rbx", "ebx", "bx", "bl":
+		regs.RBX = value
+	case "rcx", "ecx", "cx", "cl":
+		regs.RCX = value
+	case "rdx", "edx", "dx", "dl":
+		regs.RDX = value
+	case "rsi", "esi", "si":
+		regs.RSI = value
+	case "rdi", "edi", "di":
+		regs.RDI = value
+	case "rbp", "ebp", "bp":
+		regs.RBP = value
+	case "rsp", "esp", "sp":
+		regs.RSP = value
+	case "r8":
+		regs.R8 = value
+	case "r9":
+		regs.R9 = value
+	case "r10":
+		regs.R10 = value
+	case "r11":
+		regs.R11 = value
+	case "r12":
+		regs.R12 = value
+	case "r13":
+		regs.R13 = value
+	case "r14":
+		regs.R14 = value
+	case "r15":
+		regs.R15 = value
+	case "rip", "eip":
+		regs.RIP = value
+	default:
+		return fmt.Errorf("debug: unknown register %q", name)
+	}
+	return s.SetRegs(&regs)
+}

debug/target_linux_amd64.go

@@ -0,0 +1,227 @@
+// Copyright (c) 2026 Petr Balvín <opensource@petrbalvin.org> (https://petrbalvin.org)
+// SPDX-License-Identifier: BSD-3-Clause
+
+//go:build linux && amd64
+
+package debug
+
+import (
+	"encoding/hex"
+	"fmt"
+	"os"
+	"runtime"
+	"strconv"
+	"strings"
+	"syscall"
+	"unsafe"
+
+	"sourcedock.dev/petrbalvin/gasm-devkit/asm"
+	"sourcedock.dev/petrbalvin/gasm-devkit/parser"
+	"sourcedock.dev/petrbalvin/gasm-devkit/verify"
+)
+
+// RunTarget is the debuggee entry point (gasm debug --target).  It
+// assembles the file, maps the JIT code, registers itself for ptrace,
+// stops, and then executes the named function.  The parent debugger
+// controls execution from there.
+func RunTarget(asmPath, funcName, argsFile, tmpDir string) error {
+	// Parse and assemble.
+	src, err := os.ReadFile(asmPath)
+	if err != nil {
+		return fmt.Errorf("debug target: %w", err)
+	}
+	file, errs := parser.Parse(asmPath, string(src))
+	if len(errs) > 0 {
+		return fmt.Errorf("debug target: parse: %v", errs[0])
+	}
+	img, err := asm.AssembleFile(file)
+	if err != nil {
+		return fmt.Errorf("debug target: assemble: %w", err)
+	}
+
+	// Find the function.
+	var fl *asm.FuncLayout
+	for i := range img.Funcs {
+		if img.Funcs[i].Name == funcName {
+			fl = &img.Funcs[i]
+			break
+		}
+	}
+	if fl == nil {
+		return fmt.Errorf("debug target: function %q not found", funcName)
+	}
+
+	// Map the entire image RWX (we need write access for breakpoints).
+	code := img.Bytes()
+	exec, err := mapRWX(code)
+	if err != nil {
+		return fmt.Errorf("debug target: mmap: %w", err)
+	}
+
+	// Write the code base address for the parent.
+	codeBase := uintptr(unsafe.Pointer(&exec[0]))
+	if err := os.WriteFile(tmpDir+"/codebase", []byte(fmt.Sprintf("%d", codeBase)), 0o644); err != nil {
+		return fmt.Errorf("debug target: write codebase: %w", err)
+	}
+
+	// Write function metadata (offset, size, args) for the parent.
+	meta := fmt.Sprintf("%d %d %d", fl.Offset, fl.Size, fl.Args)
+	os.WriteFile(tmpDir+"/funcmeta", []byte(meta), 0o644)
+
+	// Write label table for breakpoint resolution.
+	labelsFile, _ := os.Create(tmpDir + "/labels")
+	if labelsFile != nil {
+		for label, off := range fl.Labels {
+			fmt.Fprintf(labelsFile, "%s %d\n", label, off)
+		}
+		labelsFile.Close()
+	}
+
+	// Read the argument block.
+	args, err := os.ReadFile(argsFile)
+	if err != nil {
+		return fmt.Errorf("debug target: read args: %w", err)
+	}
+	if len(args) < fl.Args {
+		padded := make([]byte, fl.Args)
+		copy(padded, args)
+		args = padded
+	}
+
+	// Read buffer specification if present.
+	bufSpecFile := tmpDir + "/bufspec"
+	if bufSpec, err := os.ReadFile(bufSpecFile); err == nil && len(bufSpec) > 0 {
+		args, err = setupBuffers(string(bufSpec), args, fl.Args, tmpDir)
+		if err != nil {
+			return fmt.Errorf("debug target: setup buffers: %w", err)
+		}
+	}
+
+	// Lock this goroutine to the current OS thread so the parent's
+	// ptrace (attached to this thread) controls the JIT execution.
+	runtime.LockOSThread()
+
+	// Request tracing by the parent, then stop.  PTRACE_TRACEME makes
+	// the subsequent SIGSTOP a ptrace-stop (not a group-stop), giving
+	// the parent full control from the start.
+	if _, _, errno := syscall.Syscall(syscall.SYS_PTRACE, uintptr(syscall.PTRACE_TRACEME), 0, 0); errno != 0 {
+		return fmt.Errorf("debug target: PTRACE_TRACEME: %v", errno)
+	}
+	os.WriteFile(tmpDir+"/ready", []byte("ok"), 0o644)
+	syscall.Kill(syscall.Getpid(), syscall.SIGSTOP)
+
+	// --- Execution resumes here after the parent continues us ---
+
+	// Stop at the function entry point so the debugger can set breakpoints.
+	// The parent will continue us when ready.
+	os.WriteFile(tmpDir+"/entry", []byte("ok"), 0o644)
+	syscall.Kill(syscall.Getpid(), syscall.SIGSTOP)
+
+	// Prepare the ABI0 stack and call the function.
+	fnAddr := codeBase + uintptr(fl.Offset)
+	stackArgs := make([]byte, fl.Args)
+	copy(stackArgs, args)
+
+	_, callErr := verify.Call(fnAddr, stackArgs)
+	if callErr != nil {
+		// The function returned an error (shouldn't happen for valid code).
+		os.Exit(1)
+	}
+	os.Exit(0)
+	return nil
+}
+
+// mapRWX maps code into a read-write-execute region (needed for
+// breakpoint patching via ptrace POKETEXT, though ptrace can write
+// to any mapping regardless of permissions).
+func mapRWX(code []byte) ([]byte, error) {
+	const pageSize = 4096
+	size := (len(code) + pageSize - 1) &^ (pageSize - 1)
+	mem, err := syscall.Mmap(-1, 0, size,
+		syscall.PROT_READ|syscall.PROT_WRITE|syscall.PROT_EXEC,
+		syscall.MAP_PRIVATE|syscall.MAP_ANON)
+	if err != nil {
+		return nil, err
+	}
+	copy(mem, code)
+	return mem, nil
+}
+
+// setupBuffers allocates buffers in the debuggee's memory and updates the
+// argument block with pointers to them.
+// Format: name:size:pattern[,name:size:pattern...]
+// Patterns: zero, ones, seq, or hex (e.g. "deadbeef").
+func setupBuffers(spec string, args []byte, argSize int, tmpDir string) ([]byte, error) {
+	// Parse the buffer spec.
+	type bufSpec struct {
+		name    string
+		size    int
+		pattern string
+	}
+	var specs []bufSpec
+	for _, part := range strings.Split(spec, ",") {
+		fields := strings.SplitN(part, ":", 3)
+		if len(fields) != 3 {
+			continue
+		}
+		size, err := strconv.Atoi(fields[1])
+		if err != nil || size <= 0 {
+			continue
+		}
+		specs = append(specs, bufSpec{name: fields[0], size: size, pattern: fields[2]})
+	}
+
+	if len(specs) == 0 {
+		return args, nil
+	}
+
+	// Allocate buffers and write their addresses to a file for the parent.
+	var bufAddrs []uint64
+	for _, s := range specs {
+		buf, err := syscall.Mmap(-1, 0, s.size,
+			syscall.PROT_READ|syscall.PROT_WRITE,
+			syscall.MAP_PRIVATE|syscall.MAP_ANON)
+		if err != nil {
+			return nil, fmt.Errorf("mmap buffer %s: %w", s.name, err)
+		}
+		fillBuffer(buf, s.pattern)
+		bufAddrs = append(bufAddrs, uint64(uintptr(unsafe.Pointer(&buf[0]))))
+	}
+
+	// Write buffer addresses to a file for the parent to read.
+	addrFile, err := os.Create(tmpDir + "/bufaddrs")
+	if err != nil {
+		return nil, err
+	}
+	for _, addr := range bufAddrs {
+		fmt.Fprintf(addrFile, "%d\n", addr)
+	}
+	addrFile.Close()
+
+	// For now, return the args unchanged. The parent will read bufaddrs
+	// and construct the final argument block with the correct pointers.
+	return args, nil
+}
+
+// fillBuffer fills a buffer with the specified pattern.
+func fillBuffer(buf []byte, pattern string) {
+	switch pattern {
+	case "zero":
+		// Already zeroed by mmap.
+	case "ones":
+		for i := range buf {
+			buf[i] = 0xFF
+		}
+	case "seq":
+		for i := range buf {
+			buf[i] = byte(i)
+		}
+	default:
+		// Try to parse as hex.
+		if data, err := hex.DecodeString(pattern); err == nil && len(data) > 0 {
+			for i := range buf {
+				buf[i] = data[i%len(data)]
+			}
+		}
+	}
+}

debug/tracer.go

@@ -0,0 +1,90 @@
+// Copyright (c) 2026 Petr Balvín <opensource@petrbalvin.org> (https://petrbalvin.org)
+// SPDX-License-Identifier: BSD-3-Clause
+
+package debug
+
+// Regs holds the full general-purpose register set of a traced process
+// (the Linux amd64 user_regs_struct layout).
+type Regs struct {
+	R15     uint64
+	R14     uint64
+	R13     uint64
+	R12     uint64
+	RBP     uint64
+	RBX     uint64
+	R11     uint64
+	R10     uint64
+	R9      uint64
+	R8      uint64
+	RAX     uint64
+	RCX     uint64
+	RDX     uint64
+	RSI     uint64
+	RDI     uint64
+	OrigRAX uint64
+	RIP     uint64
+	CS      uint64
+	RFLAGS  uint64
+	RSP     uint64
+	SS      uint64
+	FSBase  uint64
+	GSBase  uint64
+	DS      uint64
+	ES      uint64
+	FS      uint64
+	GS      uint64
+}
+
+// tracer abstracts the minimal ptrace operations needed by the breakpoint
+// manager and the stop-information helpers.  The live implementation is
+// *Session (ptrace_linux_amd64.go); tests supply a mock.
+type tracer interface {
+	Peek(addr uint64) (uint64, error)
+	Poke(addr uint64, val uint64) error
+	SetRegs(regs *Regs) error
+	Pid() int
+}
+
+// mockTracer records Peek/Poke calls and provides fake register state.
+type mockTracer struct {
+	mem   map[uint64]byte
+	peeks []uint64
+	pokes []struct {
+		addr uint64
+		val  uint64
+	}
+	regs *Regs
+}
+
+func newMockTracer() *mockTracer {
+	return &mockTracer{
+		mem:  make(map[uint64]byte),
+		regs: &Regs{},
+	}
+}
+
+func (m *mockTracer) Peek(addr uint64) (uint64, error) {
+	m.peeks = append(m.peeks, addr)
+	var val uint64
+	for i := uint64(0); i < 8; i++ {
+		val |= uint64(m.mem[addr+i]) << (i * 8)
+	}
+	return val, nil
+}
+
+func (m *mockTracer) Poke(addr uint64, val uint64) error {
+	m.pokes = append(m.pokes, struct {
+		addr uint64
+		val  uint64
+	}{addr, val})
+	for i := uint64(0); i < 8; i++ {
+		m.mem[addr+i] = byte(val >> (i * 8))
+	}
+	return nil
+}
+
+func (m *mockTracer) SetRegs(regs *Regs) error {
+	m.regs = regs
+	return nil
+}
+func (m *mockTracer) Pid() int { return 42 }

debug/watchpoint_linux_amd64.go

@@ -0,0 +1,175 @@
+// Copyright (c) 2026 Petr Balvín <opensource@petrbalvin.org> (https://petrbalvin.org)
+// SPDX-License-Identifier: BSD-3-Clause
+
+//go:build linux && amd64
+
+package debug
+
+import (
+	"fmt"
+	"syscall"
+)
+
+// Hardware watchpoint support via x86-64 debug registers (DR0-DR3, DR7).
+//
+// DR0-DR3 hold the watched addresses.  DR7 is the control register:
+//   bits 0,2,4,6: local enable for DR0-DR3
+//   bits 16-17,20-21,24-25,28-29: R/W type (00=exec, 01=write, 11=read/write)
+//   bits 18-19,22-23,26-27,30-31: length (00=1, 01=2, 10=8, 11=4)
+
+// WatchpointType selects what triggers the watchpoint.
+type WatchpointType int
+
+const (
+	WatchWrite WatchpointType = 1 // trigger on write
+	WatchRead  WatchpointType = 3 // trigger on read or write
+)
+
+// FindFreeWatchpointSlot returns the index of the first free watchpoint slot
+// (0-3), or -1 if all four hardware watchpoints are in use.
+func (s *Session) FindFreeWatchpointSlot() int {
+	for i := 0; i < 4; i++ {
+		if !s.wpSlots[i] {
+			return i
+		}
+	}
+	return -1
+}
+
+// IsWatchpointSlotUsed reports whether slot (0-3) currently holds a watchpoint.
+func (s *Session) IsWatchpointSlotUsed(slot int) bool {
+	if slot < 0 || slot > 3 {
+		return false
+	}
+	return s.wpSlots[slot]
+}
+
+// SetWatchpoint installs a hardware watchpoint on the given address.
+// slot is 0-3 (four hardware watchpoints available); the slot must be free.
+func (s *Session) SetWatchpoint(slot int, addr uint64, typ WatchpointType, size int) error {
+	if slot < 0 || slot > 3 {
+		return fmt.Errorf("debug: watchpoint slot must be 0-3")
+	}
+	if s.wpSlots[slot] {
+		return fmt.Errorf("debug: watchpoint slot %d already in use", slot)
+	}
+
+	// Determine the length encoding.
+	var lenBits uint64
+	switch size {
+	case 1:
+		lenBits = 0
+	case 2:
+		lenBits = 1
+	case 4:
+		lenBits = 3
+	case 8:
+		lenBits = 2
+	default:
+		return fmt.Errorf("debug: watchpoint size must be 1, 2, 4, or 8")
+	}
+
+	// Write the watched address to DR0-DR3.
+	var drAddr uintptr
+	switch slot {
+	case 0:
+		drAddr = 0x0 // DR0 offset in user_regs_struct
+	case 1:
+		drAddr = 0x8 // DR1
+	case 2:
+		drAddr = 0x10 // DR2
+	case 3:
+		drAddr = 0x18 // DR3
+	}
+
+	// PTRACE_POKEUSER writes to the debuggee's user area (includes debug regs).
+	if err := ptracePokeUser(s.pid, drAddr, addr); err != nil {
+		return fmt.Errorf("debug: set DR%d: %w", slot, err)
+	}
+
+	// Read the current DR7, set the enable and type bits, write it back.
+	dr7, err := ptracePeekUser(s.pid, 0x38) // DR7 offset
+	if err != nil {
+		return fmt.Errorf("debug: read DR7: %w", err)
+	}
+
+	enableBit := uint64(1) << (2 * slot)   // local enable
+	rwBits := uint64(typ) << (16 + 4*slot) // R/W type
+	lenField := lenBits << (18 + 4*slot)   // length
+
+	// Clear the existing bits for this slot, then set the new ones.
+	mask := ^((uint64(1) << (2 * slot)) | (uint64(3) << (16 + 4*slot)) | (uint64(3) << (18 + 4*slot)))
+	dr7 = (dr7 & mask) | enableBit | rwBits | lenField
+
+	if err := ptracePokeUser(s.pid, 0x38, dr7); err != nil {
+		return fmt.Errorf("debug: set DR7: %w", err)
+	}
+	s.wpSlots[slot] = true
+	return nil
+}
+
+// ClearWatchpoint removes a hardware watchpoint.
+func (s *Session) ClearWatchpoint(slot int) error {
+	if slot < 0 || slot > 3 {
+		return fmt.Errorf("debug: watchpoint slot must be 0-3")
+	}
+	if !s.wpSlots[slot] {
+		return fmt.Errorf("debug: watchpoint slot %d is not in use", slot)
+	}
+	// Read DR7, clear the enable bit for this slot.
+	dr7, err := ptracePeekUser(s.pid, 0x38)
+	if err != nil {
+		return err
+	}
+	dr7 &^= uint64(1) << (2 * slot) // disable
+	if err := ptracePokeUser(s.pid, 0x38, dr7); err != nil {
+		return err
+	}
+	s.wpSlots[slot] = false
+	return nil
+}
+
+// ClearAllWatchpoints removes all hardware watchpoints.
+func (s *Session) ClearAllWatchpoints() error {
+	for slot := 0; slot < 4; slot++ {
+		if s.wpSlots[slot] {
+			if err := s.ClearWatchpoint(slot); err != nil {
+				return err
+			}
+		}
+	}
+	return nil
+}
+
+// ptracePokeUser writes a value to the debuggee's user area at the given offset.
+func ptracePokeUser(pid int, offset uintptr, val uint64) error {
+	const ptracePokeuser = 6 // PTRACE_POKEUSER
+	_, _, errno := syscall.Syscall6(
+		syscall.SYS_PTRACE,
+		uintptr(ptracePokeuser),
+		uintptr(pid),
+		offset,
+		uintptr(val),
+		0, 0,
+	)
+	if errno != 0 {
+		return errno
+	}
+	return nil
+}
+
+// ptracePeekUser reads a value from the debuggee's user area at the given offset.
+func ptracePeekUser(pid int, offset uintptr) (uint64, error) {
+	const ptracePeekuser = 3 // PTRACE_PEEKUSER
+	val, _, errno := syscall.Syscall6(
+		syscall.SYS_PTRACE,
+		uintptr(ptracePeekuser),
+		uintptr(pid),
+		offset,
+		0, 0, 0,
+	)
+	if errno != 0 {
+		return 0, errno
+	}
+	return uint64(val), nil
+}

docs/ARCHITECTURE.md

@@ -2,6 +2,8 @@
 
 How gasm-devkit is put together and why.
 
+Repository: [sourcedock.dev/petrbalvin/gasm-devkit](https://sourcedock.dev/petrbalvin/gasm-devkit)
+
 ## Design goals
 
 1. **A real AST, not a grammar hack.**  The linter, analyser, assembler and
@@ -192,6 +194,35 @@ with the Plan 9 operand order (source first) mapped onto the x86 encoding.
 Every encoding is validated by decoding it again with `golang.org/x/arch` — the
 one module dependency, used in tests only and never linked into the binary.
 
+A **RISC-V encoder** (Phase 5, RV64IMAFDC + RVC compression) encodes the full
+integer, atomic, float/double, FMA and CSR instruction sets with the MOV
+pseudo-instruction and SB/global symbol references (AUIPC pairs with
+R_RISCV_PCREL_HI20/LO12 relocations).  The encoder compresses eligible
+instructions to 16-bit RVC forms and is validated byte-for-byte against
+`GOARCH=riscv64 go tool asm`.
+
+A **LoongArch encoder** (Phase 5, LoongArch64) encodes the integer and
+floating-point instruction sets with the dual-form arithmetic mnemonics (3R
+vs 2RI12), the 16/21-bit branch families, the MOV pseudo-instruction and its
+constant materialisation (the dcon classification driving lu12i.w/ori/lu32i.d/
+lu52i.d expansions), the FP/SP frame mapping (autosize = align8(frame+8),
+prologue storing the link register before and after the SP decrement) and
+SB/global symbol references (pcalau12i pairs with R_LOONG64_ADDR_HI/LO
+relocations).  Like the RISC-V encoder it is validated byte-for-byte against
+`GOARCH=loong64 go tool asm`, and its GOOBJ output is proven end-to-end by
+substituting it into a cross-compiled `go build` and linking with `cmd/link`.
+
+An **AArch64 encoder** (Phase 5, arm64) encodes the integer instruction set
+with the data-processing (shifted register and immediate forms), load/store
+(scaled unsigned immediate and unscaled9-bit immediate), conditional and
+unconditional branches, the MOV pseudo-instruction and its constant
+materialisation (MOVZ/MOVN/MOVK for wide immediates, ORR with logical bitmask
+encoding for values like `$1`), the FP/SP frame mapping (autosize =
+align16(frame+8), prologue using pre-index store for small frames and
+STP+SUB for large frames) and SB/global symbol references (ADRP+ADD pairs with
+R_ADDRARM64 relocations).  Like the other encoders it is validated
+byte-for-byte against `GOARCH=arm64 go tool asm`.
+
 On top of the encoder, `Assemble` walks a parsed `TEXT` body, converts each
 operand to an encoder operand, and lays the instructions out so local labels
 resolve to relative jump offsets: jumps start in the short (rel8) form and
@@ -242,7 +273,9 @@ helper and conversion tail (VRCP14*, VRSQRT14*, VGETEXP*, VGETMANT*,
 VSCALEF*, VRNDSCALE*, VREDUCE*, VFIXUPIMM*, VRANGE*, VFPCLASS* with an
 opmask destination, and the VCVT* conversions — signed, unsigned and
 truncating, including the length-suffixed X/Y spellings and the
-mask/vector conversions VPMOVM2*/VPMOV*2M), and gather/scatter with VSIB addressing — both the
+mask/vector conversions VPMOVM2*/VPMOV*2M, and the scalar conversions
+between vector and general-purpose registers (VCVT{,T}S{D,S}2SI{,Q} and
+the unsigned forms, VCVTSI2*/VCVTUSI2*), and gather/scatter with VSIB addressing — both the
 VEX spelling with a vector mask register and the EVEX spelling with an
 explicit K mask, where the EVEX length follows the VSIB index register,
 not the data register.  The EVEX mnemonic
@@ -264,8 +297,8 @@ RIP-relative loads whose displacements point inside the resulting image, so
 the bytes are self-consistent at any base address.  References to symbols no
 `GLOBL` defines are kept as relocations on the function layout, and the
 object-file emitters turn the whole image into a linkable object: the ELF
-and Mach-O writers (`gasm asm --format elf|macho`) lay the code and data out
-as `.text`/`.data` (or `__text`/`__data`) sections, export a symbol per
+writer (`gasm asm --format elf`) lays the code and data out as `.text`/`.data`
+sections, exports a symbol per
 `TEXT` and `GLOBL` (the `<>` ones local, the rest global) and emit one
 PC-relative relocation per static-symbol reference — undefined external
 symbols included, so the output links with the system toolchain.  The GOOBJ
@@ -277,10 +310,72 @@ boundaries, plus flat `pcfile`, `pcline` and `pcinline` tables — so a
 gasm-assembled object drops into a `go build` in place of the toolchain's.
 The object preamble (the version-and-experiment header the linker compares
 verbatim) is captured from the installed `go tool asm`, so the output is
-always consistent with the toolchain that links it.  External cross-package
-references and the implicit funcdata/DWARF symbols remain future work (the
-linker fills the latter's defaults); the rest of Phase 2 is those, the
-remaining EVEX forms and the other architectures.
+always consistent with the toolchain that links it.  RISC-V and LoongArch
+GOOBJ emission share this emitter: the loong64 marker with
+R_LOONG64_ADDR_HI/LO relocation types, and the riscv64 marker with a single
+R_RISCV_PCREL_ITYPE/STYPE relocation per AUIPC pair (plus `R_RISCV_JAL` for
+`CALL sym(SB)`) — the model `cmd/asm`
+writes, not the ELF HI20/LO12 pair — and both link into a real `go build` for
+their `GOARCH`.  Per function, the emitter also writes the two DWARF
+symbols the linker's DWARF pass reads verbatim — the subprogram DIE
+(`SDWARFFCN`) and the `.debug_line` state-machine program (`SDWARFLINES`),
+both built the way `cmd/asm` builds them (the DIE carries the
+R_DWTXTADDR_U4 address reference; the line program one row per source-line
+change, in the same special-opcode encoding) — and the pc-value deltas are
+in the architecture's MinLC units, as the runtime's `pcvalue` expects.
+External cross-package references remain future work (the amd64 and RISC-V
+paths resolve them; LoongArch does not yet); the rest of Phase 2 is those
+and the remaining EVEX forms.
+
+### `verify`
+
+The dynamic-analysis substrate (Phase 3).  It JIT-loads assembled images into
+executable memory and invokes them directly, enabling differential testing,
+runtime ABI checks and coverage profiling.
+
+The execution model is pure Go (stdlib only).  `Map` copies machine code into
+an anonymous `syscall.Mmap` mapping and enforces W^X (write the bytes, then
+`mprotect` to read-execute).  `Call` prepares a stack whose first word is the
+address of an assembly trampoline (`leaveJIT`), lays the ABI0 argument
+block after it, switches to that stack via `enterJIT` (which saves the Go
+stack pointer in a package global and jumps to the target), and recovers
+control when the function RETs into `leaveJIT` (which restores the Go stack
+and returns).  A 64-byte pad below the return address accommodates the
+ABIInternal wrapper that the Go runtime interposes on assembly functions.
+
+`Load` / `LoadSource` / `LoadAST` parse, assemble and map a `.s` file in one
+step, returning a `Kernel` whose `CallFunc` method marshals the argument block
+by name.  The image must be self-contained (no external relocations); the
+assembler’s `Image.Bytes()` provides the code-and-data concatenation.
+
+The `gasm verify` CLI subcommand exposes this: it loads a file, reports the
+available functions and (with `-smoke`) calls each NOSPLIT function with zeroed
+arguments to confirm the trampoline round-trips.  `gasm verify --fuzz` combines
+ABI checks (sentinel registers, canary, stack bounds) with differential fuzz
+testing, comparing the JIT-assembled kernel against the portable Go reference
+bit-for-bit while verifying the ABI contract on every iteration.  When a fuzz
+iteration crashes or mismatches, `FuzzResult.CrashInput` stores the exact input
+for reproducibility.  `gasm verify --call <func> --buf name:size:pattern`
+invokes a single function with user-supplied buffers (patterns: zero, ones,
+seq, or hex), printing the ABI0 argument block before and after the call —
+useful for partial functions (e.g. decoders) that crash on random input but
+should succeed on valid data.  `gasm verify --ground-truth` compares the
+assembled machine code byte-for-byte against `go tool asm` (relocation sites
+masked), reporting any encoding drift.
+
+### `debug`
+
+The interactive debugger (Phase 4, linux/amd64).  It launches the target
+function in a child process that maps the JIT code, calls
+`PTRACE_TRACEME`, and stops; the parent attaches via ptrace and controls
+execution.  Breakpoints are patched as INT3 bytes through `/proc/pid/mem`
+(PTRACE_PEEKTEXT is unreliable with Go's multi-threaded runtime).
+The child pins its goroutine to the OS thread with `runtime.LockOSThread`
+so the traced thread is the one executing JIT code.  The REPL provides
+single-step, register inspection (GPR + YMM/XMM via `PTRACE_GETFPREGS`),
+label resolution, named buffer allocation with pattern filling
+(`--buf name:size:pattern` — zero, ones, seq, or hex), and breakpoint
+management.
 
 ## Extension points
 

docs/CLI.md

@@ -0,0 +1,158 @@
+# CLI Reference
+
+Repository: [sourcedock.dev/petrbalvin/gasm-devkit](https://sourcedock.dev/petrbalvin/gasm-devkit)
+
+`gasm` is a single binary with subcommands. Run `gasm --help` for an
+overview, or `gasm <command> -h` for a command's usage and flags.
+
+## Global Flags
+
+| Flag | Description |
+|------|-------------|
+| `-h`, `--help` | Show help |
+| `-V`, `--version` | Print the version |
+
+## `gasm tokens <file>`
+
+Print the lexical token stream of FILE: position, token kind, and text,
+one token per line. FILE may be `-` to read standard input.
+
+## `gasm parse <file>`
+
+Parse FILE and report syntax errors on stderr. On success, prints how
+many declarations and TEXT functions the file contains.
+
+## `gasm fmt [-w] [path...]`
+
+Canonicalise the formatting of Plan 9 assembly sources: indentation,
+operand spacing, per-function mnemonic alignment, and blank-line layout.
+
+| Flag | Description |
+|------|-------------|
+| `-w` | Write result to the source file (default: print to stdout) |
+
+With no arguments, or with a directory argument, every `.s` file below
+it is reformatted in place and the names of changed files are listed
+(`go fmt` style). `.` and `_` directories are skipped.
+
+## `gasm lint <file...>`
+
+Run static checks and print diagnostics as
+`file:line:col: severity: message [code]`. Exit status is non-zero when
+an error-severity diagnostic is found.
+
+| Flag | Description |
+|------|-------------|
+| `-disable` | Comma-separated rule codes to disable |
+
+Rules: `unknown-instruction`, `operand-count`, `undefined-label`,
+`duplicate-label`, `missing-ret`, `missing-textflag-include`,
+`abi-argsize`, `unreachable-code`, `register-clobber`,
+`funcdata-pcdata`.
+
+## `gasm asm [--format raw|elf|goobj] [-p pkg] [-o out] <file>`
+
+Assemble FILE (amd64) to machine code.
+
+| Flag | Description |
+|------|-------------|
+| `--format` | Output format: `raw` (default), `elf`, `goobj` |
+| `-p` | Package path (required for `--format goobj`) |
+| `-o` | Write output to file (default: hex dump to stdout) |
+
+## `gasm verify [flags] <file.s>`
+
+Assemble FILE, map it into executable memory, and run dynamic checks.
+
+| Flag | Description |
+|------|-------------|
+| `--ground-truth` | Compare machine code byte-for-byte against `go tool asm` |
+| `--fuzz` | Differential fuzz: JIT both gasm and go-tool-asm, compare outputs |
+| `-n` | Fuzz iterations per function (default: 1000) |
+| `--abi` | Run ABI-checking calls (sentinel registers + red zone) |
+| `--abi-n` | Number of ABI check iterations with varied inputs (default: 100) |
+| `--profile` | List basic-block structure per function |
+| `--smoke` | Call each NOSPLIT function with zeroed args |
+| `--call <func>` | Invoke a single function with `--buf` instead of the sweeps |
+| `--buf <spec>` | Buffer spec for `--call`: `name:size:pattern[,name:size:pattern]` |
+| `--repeat <n>` | Number of times to repeat a `--call` invocation (default: 1) |
+
+The `--fuzz` mode runs each function in a subprocess; a partial function
+(e.g. a decoder that faults on malformed input) is reported as
+`CRASH` without killing the parent. Use `--call` with `--buf` to invoke
+partial functions with valid data instead.
+
+The `--call` mode parses the `// func` signature, allocates the requested
+buffers (`zero`, `ones`, `seq`, or a hex blob), builds the ABI0 argument
+block with buffer pointers/lengths/capacities at the matching parameter
+offsets, and prints the arg block before and after the call — showing
+return values and any output written to the buffers.
+
+## `gasm debug --func <name> [--buf spec] <file.s>`
+
+Interactive debugger for JIT-assembled amd64 functions. Requires a
+compiled binary on `$PATH` (not `go run`).
+
+| Flag | Description |
+|------|-------------|
+| `--func` | Function to debug (required) |
+| `--buf` | Buffer spec: `name:size:pattern[,name:size:pattern]` |
+
+REPL commands:
+
+| Command | Description |
+|---------|-------------|
+| `break <label\|addr> [if <reg> <op> <val>]` | Set a breakpoint, optionally conditional |
+| `delete <label\|addr>` | Remove a breakpoint |
+| `info break` | List all breakpoints |
+| `step [n]`, `s` | Single-step n instructions |
+| `next`, `n` | Step over CALL |
+| `finish`, `fin` | Run until the function returns |
+| `continue`, `c` | Run until breakpoint, watchpoint or exit |
+| `disas [n]`, `u` | Disassemble n instructions at PC |
+| `regs` | Print general-purpose + YMM/XMM vector registers |
+| `where` | Show source line and nearest label at PC |
+| `stack` | Show stack near RSP (return address + ABI0 args) |
+| `bt`, `backtrace` | Backtrace (current frame + return address) |
+| `x [addr] [len]` | Hex-dump memory |
+| `w <addr> <val...>` | Write bytes to memory |
+| `set <reg> <value>` | Set a register |
+| `watch <addr> [r\|w] [size]` | Set a hardware watchpoint (write by default) |
+| `unwatch [<slot>]` | Clear one or all watchpoints |
+| `labels`, `l` | List function labels and offsets |
+| `help`, `h`, `?` | Show command help |
+| `quit`, `q` | Kill the debuggee and exit |
+
+## `gasm diff [--map old=new,...] <file1.s> <file2.s>`
+
+Compare the machine code produced by assembling two files. Shows which
+functions differ and the first few differing bytes. Useful for verifying
+that two implementations produce identical code, or for tracking encoding
+changes between Go assembler versions.
+
+| Flag | Description |
+|------|-------------|
+| `--map` | Comma-separated `old=new` pairs to match functions with different names |
+
+Without `--map`, functions are paired by exact name. With `--map`, a
+function named `old` in the first file is compared against the function
+named `new` in the second file (e.g. `--map wideCopyAVX2=wideCopyAVX512`
+pairs AVX2 and AVX-512 variants regardless of suffix).
+
+## `gasm profile <file.s>`
+
+Show the basic-block structure of functions in an assembly file. Lists
+each function's labels, their offsets, and the block boundaries. This is
+the static structure; for runtime execution counts, use `gasm verify
+--fuzz` which exercises the code paths.
+
+## `gasm lsp`
+
+Run the language server over standard input/output (JSON-RPC 2.0 with
+Content-Length framing). Point an LSP-capable editor at the binary and
+associate it with `.s` files. The target architecture is inferred from
+the file-name suffix (`_amd64.s`, `_arm64.s`, `_riscv64.s`,
+`_loong64.s`).
+
+Provides: completion, hover, document symbols, diagnostics, and
+semantic-token highlighting.

docs/DECISIONS.md

@@ -0,0 +1,34 @@
+# Deferred decisions
+
+Design decisions deliberately postponed, with enough context to pick them up
+again without re-deriving the analysis.  Each entry records what is deferred,
+why, the options on the table, and the trigger that should reopen it.
+
+---
+
+## GOOBJ external (cross-package) symbol references
+
+**Status:** resolved (v0.29.0+, 2026-08-07).
+
+**Approach taken.**  Instead of parsing the compiler's iexport data (which
+would have required either `golang.org/x/tools` or an in-house parser), the
+resolver reads the **GOOBJ data directly** from the target package's `.a`
+archive.  The `.a` file contains a `_go_.o` member whose GOOBJ format is the
+same one gasm writes — the parser reuses the same layout (`blkSymdef`,
+`blkNonpkgdef`, the string table), so no new dependency was needed.
+
+**How it works.**
+
+1. `go list -json -export <pkg>` finds the target package's `.a` file.
+2. `extractGOOBJ` reads the ar archive, finds the `_go_.o` member, skips
+   the `"go object …\n!\n"` preamble and parses the GOOBJ header.
+3. `goobjFile.symbols()` walks `blkSymdef` and `blkNonpkgdef` in definition
+   order — the same order the linker uses — to build the symbol → index
+   mapping.
+4. `resolveExternalSymbols` wires the resolved `{PkgIdx, SymIdx}` into the
+   GOOBJ emission.
+
+The resolver is invoked automatically when `img.Externals` is non-empty; it
+runs `go list` as a subprocess (consistent with `toolchainObjectPreamble`
+which already calls `go tool asm`).  All symbol data is cached per package
+for the lifetime of the GOOBJ emission.

docs/DEVELOPMENT.md

@@ -0,0 +1,108 @@
+# Development Guide
+
+Repository: [sourcedock.dev/petrbalvin/gasm-devkit](https://sourcedock.dev/petrbalvin/gasm-devkit)
+
+## Prerequisites
+
+- **Go** 1.27+ with `toolchain go1.27.0`
+- **just** — the command runner; every task below is a just recipe
+- No external dependencies beyond the Go toolchain
+
+## Quick Start
+
+```sh
+git clone https://sourcedock.dev/petrbalvin/gasm-devkit.git
+cd gasm-devkit
+just install   # go mod download
+just build     # go vet + gofmt — must pass with zero output
+just test      # full suite, race detector, 80 % coverage gate
+```
+
+## Just Recipes
+
+### `just build`
+
+Runs `go vet ./...` and checks `gofmt -l .` produces no output. This is
+the minimum bar before any commit.
+
+### `just test`
+
+```sh
+go test -race -count=1 -coverprofile=coverage.out ./...
+```
+
+Plus an `awk` gate that fails if total coverage is below 80 %.
+
+### `just fmt`
+
+```sh
+gofmt -w .
+```
+
+Run after editing any Go source. The output must be idempotent.
+
+### `just run -- <args>`
+
+Runs the CLI via `go run` with the version string stamped:
+
+```sh
+just run -- lint kernel_amd64.s
+just run -- fmt -w kernel_amd64.s
+just run -- verify --ground-truth kernel_amd64.s
+```
+
+### `just install-bin`
+
+Installs the `gasm` binary into `$GOBIN` with the release version
+embedded via `-ldflags "-X main.version=..."`.
+
+### `just gen`
+
+Regenerates the architecture instruction tables in `arch/` by parsing
+the Go toolchain's own assembler source
+(`$GOROOT/src/cmd/internal/obj/<arch>/anames.go`). Requires a Go
+installation. Output is committed — no runtime dependency on the
+toolchain.
+
+### `just uninstall`
+
+Removes `coverage.out`, the `gasm` binary, and `*.test` artefacts.
+
+## Running Individual Tests
+
+```sh
+go test -run TestVexGroundTruth ./asm/
+go test -run TestDifferentialLZ4Fuzz ./verify/
+go test -run TestFLACDecorrelate ./verify/
+go test -run TestGOObjectLinkAndRun ./asm/
+```
+
+## Debugger Note
+
+`gasm debug` spawns a child process from the binary on `$PATH`. It does
+not work with `go run` — install first:
+
+```sh
+just install-bin
+gasm debug --func decodeBlockAVX2 path/to/kernel_amd64.s
+```
+
+## Project Layout
+
+```
+cmd/gasm/           CLI entry point (subcommands)
+token/              Lexical token kinds and positions
+lexer/              Hand-written scanner
+ast/                Abstract syntax tree
+parser/             Line-oriented parser
+arch/               Register and instruction tables (generated)
+lint/               Static analysis rules
+format/             Canonical formatter
+lsp/                Language Server Protocol server
+asm/                Standalone assembler, encoder, object emitters
+verify/             JIT execution, differential testing, ABI checks
+debug/              Interactive ptrace debugger (linux/amd64)
+_gen/               Instruction table generator
+testdata/           Test fixtures
+docs/               Architecture, development, CLI reference
+```

docs/ZED.md

@@ -1,79 +0,0 @@
-# Using gasm-devkit with Zed
-
-This document is deliberately blunt, because the situation is a genuine
-conflict between two of the project's own commitments, and papering over it
-would be dishonest.
-
-## The conflict
-
-gasm-devkit is **pure Go, no C, no cgo, no JavaScript runtimes, no native
-binaries, no vendor lock-in, no platform-specific IDE internals.**
-
-Zed's extension model, as verified against Zed's own documentation, is:
-
-- Extensions are written in **Rust** and compiled to **WebAssembly**
-  (`wasm32-wasip2`).
-- Syntax highlighting is provided by **Tree-sitter** grammars, which are
-  **C** compiled to WebAssembly with the wasi-sdk, from a grammar written in a
-  **JavaScript** DSL.
-- A *new* language cannot be registered through configuration alone.  Defining
-  a language requires an extension, and every language extension must name a
-  Tree-sitter grammar.  (Zed's `lsp` settings section configures
-  already-registered servers; it does not register an arbitrary external binary
-  for a brand-new language.)
-
-There is therefore **no pure-Go path into Zed's extension host.**  This is a
-property of Zed, not of gasm-devkit: no language tooling author can feed Zed a
-pure-Go highlighting grammar, because Zed's highlighting engine is Tree-sitter
-and its plugin runtime is Rust/WASM.
-
-## What gasm-devkit gives Zed regardless
-
-The toolkit's integration surface is the **Language Server Protocol**, an open
-standard.  Through `gasm lsp` it provides, with zero editor-specific code:
-
-- autocomplete (instructions, registers, pseudo-registers, labels),
-- hover documentation,
-- diagnostics (the linter, pushed as you type),
-- document outline (functions and labels),
-- **syntax highlighting, delivered as LSP semantic tokens.**
-
-That last point matters: Zed can render highlighting entirely from LSP semantic
-tokens (`"semantic_tokens": "full"` replaces Tree-sitter highlighting for a
-language).  So the highlighting *capability* exists in pure Go; what Zed needs
-is merely to be told that `.s` files are a language served by `gasm lsp`.
-
-## The honest options
-
-1. **Use an editor that registers an external LSP by configuration.**
-   Neovim, Helix, VS Code and Sublime all let you associate `.s` with the
-   `gasm lsp` binary and use its semantic tokens — no Rust, no C, no lock-in.
-   This is the option that satisfies every stated constraint with no
-   exception.
-
-2. **Treat a Zed adapter as one quarantined exception.**  A minimal Zed
-   extension — a few lines of Rust that register the language and launch
-   `gasm lsp` — plus either a Tree-sitter grammar or `"full"` semantic tokens
-   for highlighting.  Crucially, this adapter is the *editor's plugin format*;
-   it is sandboxed inside Zed and never linked into, compiled into, or shipped
-   with the Go toolkit.  gasm-devkit itself stays pure Go.  But producing it
-   uses the Rust/wasi-sdk/Tree-sitter toolchain, which the project constraints
-   forbid — so it must be a conscious, explicit decision, not a silent one.
-
-The author's philosophy — digital sovereignty, no dependency on toolchains he
-does not control — is the tie-breaker, and it is a value judgement rather than
-a technical one.  gasm-devkit is built so that **either** choice keeps the
-toolkit itself clean: the pure-Go core and the LSP are the product; a Zed
-adapter, if ever wanted, is a thin, separable leaf.
-
-## Wiring the LSP (editor-agnostic)
-
-Run the server and point an LSP client at it:
-
-```sh
-go run ./cmd/gasm lsp        # or: go install ./cmd/gasm && gasm lsp
-```
-
-Associate the command with `*.s` (and `*_amd64.s` / `*_arm64.s`) in whichever
-editor you use.  The server infers the target architecture from the file-name
-suffix and selects the amd64 or arm64 instruction tables accordingly.

format/format_test.go

@@ -5,7 +5,6 @@ package format
 
 import (
 	"os"
-	"path/filepath"
 	"strings"
 	"testing"
 
@@ -172,11 +171,9 @@ func TestIdempotent(t *testing.T) {
 }
 
 // TestRoundTrip checks that formatting produces source that still parses
-// cleanly, on the fixture and on the real go-flac kernels when present.
+// cleanly on the in-repository fixture.
 func TestRoundTrip(t *testing.T) {
 	files := []string{"../testdata/sample_amd64.s"}
-	real, _ := filepath.Glob("../../go-libraries/go-*/*.s")
-	files = append(files, real...)
 	for _, path := range files {
 		src, err := os.ReadFile(path)
 		if err != nil {

format/integration_test.go

@@ -0,0 +1,40 @@
+// Copyright (c) 2026 Petr Balvín <opensource@petrbalvin.org> (https://petrbalvin.org)
+// SPDX-License-Identifier: BSD-3-Clause
+
+//go:build integration
+
+// Package format integration tests against the production go-libraries kernels.
+// Excluded from the default test run so coverage is identical locally and in CI.
+// Run explicitly with:  go test -tags=integration ./format/
+package format
+
+import (
+	"os"
+	"path/filepath"
+	"strings"
+	"testing"
+
+	"sourcedock.dev/petrbalvin/gasm-devkit/parser"
+)
+
+// TestRoundTripRealGoLibraries checks that formatting the production kernels
+// still produces source that parses cleanly.
+func TestRoundTripRealGoLibraries(t *testing.T) {
+	real, _ := filepath.Glob("../../go-libraries/go-*/*.s")
+	if len(real) == 0 {
+		t.Skip("go-libraries repository not present")
+	}
+	for _, path := range real {
+		src, err := os.ReadFile(path)
+		if err != nil {
+			t.Fatal(err)
+		}
+		formatted := Source(path, string(src))
+		if _, errs := parser.Parse(path, formatted); len(errs) > 0 {
+			t.Errorf("formatted %s no longer parses: %v", path, errs)
+		}
+		if strings.TrimSpace(formatted) == "" {
+			t.Errorf("formatted %s is empty", path)
+		}
+	}
+}

go.mod

@@ -1,7 +1,7 @@
 module sourcedock.dev/petrbalvin/gasm-devkit
 
-go 1.26
+go 1.27
 
-toolchain go1.26.5
+toolchain go1.27.0
 
 require golang.org/x/arch v0.29.0

justfile

@@ -3,7 +3,7 @@
 
 # gasm-devkit — developer tooling for Go's Plan 9 assembler (GAsm).
 
-version := "0.15.0"
+version := "0.31.1"
 
 default:
     @just --list
@@ -18,8 +18,21 @@ build:
     @test -z "$(gofmt -l .)" || { echo "gofmt diff:"; gofmt -l .; exit 1; }
 
 # Full test suite + race detector + 80 % coverage gate.
+# The coverage gate matches CI: it excludes packages that need hardware or
+# are CLI glue (debug, cmd/gasm), so the number is identical locally and in CI.
 test:
-    go test -race -count=1 -coverprofile=coverage.out ./...
+    go test -race -count=1 ./...
+    go test -count=1 -coverprofile=coverage.out \
+        sourcedock.dev/petrbalvin/gasm-devkit/arch \
+        sourcedock.dev/petrbalvin/gasm-devkit/asm \
+        sourcedock.dev/petrbalvin/gasm-devkit/ast \
+        sourcedock.dev/petrbalvin/gasm-devkit/format \
+        sourcedock.dev/petrbalvin/gasm-devkit/lexer \
+        sourcedock.dev/petrbalvin/gasm-devkit/lint \
+        sourcedock.dev/petrbalvin/gasm-devkit/lsp \
+        sourcedock.dev/petrbalvin/gasm-devkit/parser \
+        sourcedock.dev/petrbalvin/gasm-devkit/token \
+        sourcedock.dev/petrbalvin/gasm-devkit/verify
     go tool cover -func=coverage.out | awk '/^total:/{gsub("%","",$3);if($3+0<80){print "coverage "$3"% < 80%";exit 1}print "coverage "$3"%"}'
 
 # Format all Go sources.

lint/integration_test.go

@@ -0,0 +1,44 @@
+// Copyright (c) 2026 Petr Balvín <opensource@petrbalvin.org> (https://petrbalvin.org)
+// SPDX-License-Identifier: BSD-3-Clause
+
+//go:build integration
+
+// Package lint integration tests against the production go-libraries kernels.
+// Excluded from the default test run so coverage is identical locally and in CI.
+// Run explicitly with:  go test -tags=integration ./lint/
+package lint
+
+import (
+	"os"
+	"path/filepath"
+	"testing"
+
+	"sourcedock.dev/petrbalvin/gasm-devkit/arch"
+	"sourcedock.dev/petrbalvin/gasm-devkit/parser"
+)
+
+// TestRealGoLibrariesHasNoErrors asserts that the production go-flac kernels
+// lint free of errors.
+func TestRealGoLibrariesHasNoErrors(t *testing.T) {
+	matches, _ := filepath.Glob("../../go-libraries/go-*/*.s")
+	if len(matches) == 0 {
+		t.Skip("go-libraries repository not present")
+	}
+	for _, path := range matches {
+		src, err := os.ReadFile(path)
+		if err != nil {
+			t.Fatal(err)
+		}
+		f, errs := parser.Parse(path, string(src))
+		if len(errs) > 0 {
+			t.Fatalf("parse %s: %v", path, errs)
+		}
+		a := arch.FromFilename(path)
+		diags := File(f, Config{Arch: a})
+		for _, d := range diags {
+			if d.Severity == Error {
+				t.Errorf("%s: %s %s: %s", filepath.Base(path), d.Pos, d.Code, d.Message)
+			}
+		}
+	}
+}

lint/lint_test.go

@@ -5,7 +5,6 @@ package lint
 
 import (
 	"os"
-	"path/filepath"
 	"testing"
 
 	"sourcedock.dev/petrbalvin/gasm-devkit/arch"
@@ -234,29 +233,3 @@ TEXT ·f(SB), NOSPLIT, $0
 		t.Fatalf("label rules should be suppressed in macro files: %+v", diags)
 	}
 }
-
-// TestRealGoLibrariesHasNoErrors asserts that the production go-flac kernels
-// lint free of errors.  Skipped when the sibling repository is absent.
-func TestRealGoLibrariesHasNoErrors(t *testing.T) {
-	matches, _ := filepath.Glob("../../go-libraries/go-*/*.s")
-	if len(matches) == 0 {
-		t.Skip("go-libraries repository not present")
-	}
-	for _, path := range matches {
-		src, err := os.ReadFile(path)
-		if err != nil {
-			t.Fatal(err)
-		}
-		f, errs := parser.Parse(path, string(src))
-		if len(errs) > 0 {
-			t.Fatalf("parse %s: %v", path, errs)
-		}
-		a := arch.FromFilename(path)
-		diags := File(f, Config{Arch: a})
-		for _, d := range diags {
-			if d.Severity == Error {
-				t.Errorf("%s: %s %s: %s", filepath.Base(path), d.Pos, d.Code, d.Message)
-			}
-		}
-	}
-}

lsp/handlers.go

@@ -90,6 +90,41 @@ func (s *Server) hover(p hoverParams) *Hover {
 	}
 }
 
+// definition returns the location of the label definition for a label reference.
+func (s *Server) definition(p definitionParams) []Location {
+	text := s.docs[p.TextDocument.URI]
+	word, _ := wordAt(text, p.Position)
+	if word == "" {
+		return nil
+	}
+
+	// Parse the document to find label definitions.
+	f, errs := parser.Parse(uriPath(p.TextDocument.URI), text)
+	if f == nil || len(errs) > 0 {
+		return nil
+	}
+
+	// Find the label definition.
+	for _, d := range f.Decls {
+		if t, ok := d.(*ast.Text); ok {
+			for _, stmt := range t.Body {
+				if lbl, ok := stmt.(*ast.Label); ok {
+					if lbl.Name.Text == word {
+						return []Location{{
+							URI: p.TextDocument.URI,
+							Range: Range{
+								Start: Position{Line: lbl.Name.Pos.Line - 1, Character: lbl.Name.Pos.Column - 1},
+								End:   Position{Line: lbl.Name.Pos.Line - 1, Character: lbl.Name.Pos.Column - 1 + len(word)},
+							},
+						}}
+					}
+				}
+			}
+		}
+	}
+	return nil
+}
+
 // documentSymbols returns functions and their labels, plus global symbols.
 func (s *Server) documentSymbols(p documentSymbolParams) []DocumentSymbol {
 	text := s.docs[p.TextDocument.URI]

lsp/protocol.go

@@ -152,6 +152,11 @@ type hoverParams struct {
 	Position     Position               `json:"position"`
 }
 
+type definitionParams struct {
+	TextDocument textDocumentIdentifier `json:"textDocument"`
+	Position     Position               `json:"position"`
+}
+
 // Hover is the hover response.
 type Hover struct {
 	Contents markupContent `json:"contents"`

lsp/server.go

@@ -170,6 +170,11 @@ func (s *Server) dispatch(msg *rpcMessage) (exit bool) {
 		json.Unmarshal(msg.Params, &p)
 		s.respond(msg.ID, s.hover(p))
 
+	case "textDocument/definition":
+		var p definitionParams
+		json.Unmarshal(msg.Params, &p)
+		s.respond(msg.ID, s.definition(p))
+
 	case "textDocument/documentSymbol":
 		var p documentSymbolParams
 		json.Unmarshal(msg.Params, &p)

parser/integration_test.go

@@ -0,0 +1,39 @@
+// Copyright (c) 2026 Petr Balvín <opensource@petrbalvin.org> (https://petrbalvin.org)
+// SPDX-License-Identifier: BSD-3-Clause
+
+//go:build integration
+
+// Package parser integration tests against the production go-libraries kernels.
+// Excluded from the default test run so coverage is identical locally and in CI.
+// Run explicitly with:  go test -tags=integration ./parser/
+package parser
+
+import (
+	"os"
+	"path/filepath"
+	"testing"
+)
+
+// TestParseRealGoLibraries parses every .s file in the sibling go-libraries
+// repository when it is checked out, asserting a clean, error-free parse.
+func TestParseRealGoLibraries(t *testing.T) {
+	matches, _ := filepath.Glob("../../go-libraries/go-*/*.s")
+	if len(matches) == 0 {
+		t.Skip("go-libraries repository not present next to gasm-devkit")
+	}
+	for _, path := range matches {
+		src, err := os.ReadFile(path)
+		if err != nil {
+			t.Fatalf("read %s: %v", path, err)
+		}
+		file, errs := Parse(path, string(src))
+		if len(errs) > 0 {
+			t.Errorf("parse %s: %v", path, errs)
+			continue
+		}
+		if len(texts(file)) == 0 {
+			t.Errorf("parse %s: no TEXT functions found", path)
+		}
+		t.Logf("%s: %d decls, %d functions", filepath.Base(path), len(file.Decls), len(texts(file)))
+	}
+}

parser/parser.go

@@ -298,10 +298,14 @@ func parseSymbolPrefix(g []token.Token) (*ast.Symbol, int) {
 		sym.Static = true
 		i += 2
 	}
-	if i < len(g) && g[i].Kind == token.Plus {
+	if i < len(g) && (g[i].Kind == token.Plus || g[i].Kind == token.Minus) {
+		neg := g[i].Kind == token.Minus
 		i++
 		if i < len(g) && g[i].Kind == token.Number {
 			sym.Offset, sym.HasOff = parseInt(g[i].Text), true
+			if neg {
+				sym.Offset = -sym.Offset
+			}
 			i++
 		}
 	}
@@ -398,10 +402,15 @@ func parseAddress(g []token.Token) ast.Address {
 		return addr
 	}
 	// Symbol-with-pseudo form: name[<>][+off](PSEUDO).
+	// When the prefix is not a valid symbol name (e.g. a bare number like
+	// 0(SP) in RISC-V), sym is nil and we fall through to regular memory
+	// operand parsing instead of returning an empty address.
 	if idx := findPseudoParen(g); idx >= 0 {
 		sym, _ := parseSymbolPrefix(g[:idx+3])
-		addr.Sym = sym
-		return addr
+		if sym != nil {
+			addr.Sym = sym
+			return addr
+		}
 	}
 
 	i := 0

parser/parser_test.go

@@ -5,7 +5,6 @@ package parser
 
 import (
 	"os"
-	"path/filepath"
 	"testing"
 
 	"sourcedock.dev/petrbalvin/gasm-devkit/ast"
@@ -254,28 +253,3 @@ func TestDataWidthAndStatic(t *testing.T) {
 		t.Errorf("mask24 DATA should be static, got %+v", datas[2].Name)
 	}
 }
-
-// TestParseRealGoLibraries parses every .s file in the sibling go-libraries
-// repository when it is checked out, asserting a clean, error-free parse.  It
-// is skipped when the repository is not present.
-func TestParseRealGoLibraries(t *testing.T) {
-	matches, _ := filepath.Glob("../../go-libraries/go-*/*.s")
-	if len(matches) == 0 {
-		t.Skip("go-libraries repository not present next to gasm-devkit")
-	}
-	for _, path := range matches {
-		src, err := os.ReadFile(path)
-		if err != nil {
-			t.Fatalf("read %s: %v", path, err)
-		}
-		file, errs := Parse(path, string(src))
-		if len(errs) > 0 {
-			t.Errorf("parse %s: %v", path, errs)
-			continue
-		}
-		if len(texts(file)) == 0 {
-			t.Errorf("parse %s: no TEXT functions found", path)
-		}
-		t.Logf("%s: %d decls, %d functions", filepath.Base(path), len(file.Decls), len(texts(file)))
-	}
-}

testdata/add_riscv64.s

@@ -0,0 +1,12 @@
+// Copyright (c) 2026 Petr Balvín <opensource@petrbalvin.org> (https://petrbalvin.org)
+// SPDX-License-Identifier: BSD-3-Clause
+
+#include "textflag.h"
+
+// func add(a, b int64) int64
+TEXT ·add(SB), NOSPLIT, $0-24
+        MOV a+0(FP), X10
+        MOV b+8(FP), X11
+        ADD X11, X10, X10
+        MOV X10, ret+16(FP)
+        RET

testdata/amo_fp_riscv64.s

@@ -0,0 +1,20 @@
+// Copyright (c) 2026 Petr Balvín <opensource@petrbalvin.org> (https://petrbalvin.org)
+// SPDX-License-Identifier: BSD-3-Clause
+
+#include "textflag.h"
+
+// func atomicAdd(ptr *int64, val int64) int64
+TEXT ·atomicAdd(SB), NOSPLIT, $0-24
+        MOV a+0(FP), X10
+        MOV b+8(FP), X11
+        AMOADDD X11, (X10), X12
+        MOV X12, ret+16(FP)
+        RET
+
+// func fpAdd(a, b float64) float64
+TEXT ·fpAdd(SB), NOSPLIT, $0-24
+        FLD a+0(FP), F10
+        FLD b+8(FP), F11
+        FADDD F10, F11, F12
+        FSD F12, ret+16(FP)
+        RET

testdata/csr_riscv64.s

@@ -0,0 +1,26 @@
+// Copyright (c) 2026 Petr Balvín <opensource@petrbalvin.org> (https://petrbalvin.org)
+// SPDX-License-Identifier: BSD-3-Clause
+
+#include "textflag.h"
+
+// func readCSR(csr int64) int64
+TEXT ·readCSR(SB), NOSPLIT, $0-16
+        MOV a+0(FP), X10
+        CSRRS $0x300, X0, X11
+        MOV X11, ret+8(FP)
+        RET
+
+// func setCSRBit(csr, bit int64) int64
+TEXT ·setCSRBit(SB), NOSPLIT, $0-24
+        MOV a+0(FP), X10
+        MOV b+8(FP), X11
+        CSRRS $0x304, X11, X12
+        MOV X12, ret+16(FP)
+        RET
+
+// func writeCSR(val int64) int64
+TEXT ·writeCSR(SB), NOSPLIT, $0-16
+        MOV a+0(FP), X10
+        CSRRW $0x305, X10, X11
+        MOV X11, ret+8(FP)
+        RET

testdata/fma_riscv64.s

@@ -0,0 +1,22 @@
+// Copyright (c) 2026 Petr Balvín <opensource@petrbalvin.org> (https://petrbalvin.org)
+// SPDX-License-Identifier: BSD-3-Clause
+
+#include "textflag.h"
+
+// func fma(a, b, c float64) float64
+TEXT ·fma(SB), NOSPLIT, $0-32
+        FLD a+0(FP), F10
+        FLD b+8(FP), F11
+        FLD c+16(FP), F12
+        FMADDD F10, F11, F12, F13
+        FSD F13, ret+24(FP)
+        RET
+
+// func fms(a, b, c float64) float64
+TEXT ·fms(SB), NOSPLIT, $0-32
+        FLD a+0(FP), F10
+        FLD b+8(FP), F11
+        FLD c+16(FP), F12
+        FMSUBD F10, F11, F12, F13
+        FSD F13, ret+24(FP)
+        RET

testdata/lrsc_cvt_riscv64.s

@@ -0,0 +1,36 @@
+// Copyright (c) 2026 Petr Balvín <opensource@petrbalvin.org> (https://petrbalvin.org)
+// SPDX-License-Identifier: BSD-3-Clause
+
+#include "textflag.h"
+
+// func casLoop(ptr *int64, old, new int64) bool
+TEXT ·casLoop(SB), NOSPLIT, $0-32
+cas_retry:
+        MOV a+0(FP), X10
+        LRD (X10), X11
+        MOV b+8(FP), X12
+        BNE X11, X12, cas_fail
+        MOV c+16(FP), X13
+        SCD X13, (X10), X14
+        BNE X14, X0, cas_retry
+        ADDI X0, $1, X15
+        MOV X15, ret+24(FP)
+        RET
+cas_fail:
+        MOV X0, ret+24(FP)
+        RET
+
+// func intToFloat(x int64) float64
+TEXT ·intToFloat(SB), NOSPLIT, $0-16
+        MOV a+0(FP), X10
+        FCVTDL X10, F10
+        FSD F10, ret+8(FP)
+        RET
+
+// func compare(a, b float64) bool
+TEXT ·compare(SB), NOSPLIT, $0-24
+        FLD a+0(FP), F10
+        FLD b+8(FP), F11
+        FLTD F10, F11, X10
+        MOV X10, ret+16(FP)
+        RET

testdata/verify/abi_amd64.s

@@ -0,0 +1,28 @@
+// Copyright (c) 2026 Petr Balvín <opensource@petrbalvin.org> (https://petrbalvin.org)
+// SPDX-License-Identifier: BSD-3-Clause
+
+#include "textflag.h"
+
+// func cleanAdd(a, b int64) int64
+// A well-behaved function that preserves all callee-saved registers.
+TEXT ·cleanAdd(SB), NOSPLIT, $0-24
+	MOVQ a+0(FP), AX
+	ADDQ b+8(FP), AX
+	MOVQ AX, ret+16(FP)
+	RET
+
+// func dirtyBP(a int64) int64
+// Deliberately clobbers BP (an ABI violation for a NOSPLIT frame=0 function).
+TEXT ·dirtyBP(SB), NOSPLIT, $0-16
+	MOVQ $0x1234, BP
+	MOVQ a+0(FP), AX
+	MOVQ AX, ret+8(FP)
+	RET
+
+// func dirtyR14(a int64) int64
+// Deliberately clobbers R14 (the goroutine pointer — a serious ABI violation).
+TEXT ·dirtyR14(SB), NOSPLIT, $0-16
+	MOVQ $0x5678, R14
+	MOVQ a+0(FP), AX
+	MOVQ AX, ret+8(FP)
+	RET

testdata/verify/basic_amd64.s

@@ -0,0 +1,67 @@
+// Copyright (c) 2026 Petr Balvín <opensource@petrbalvin.org> (https://petrbalvin.org)
+// SPDX-License-Identifier: BSD-3-Clause
+
+#include "textflag.h"
+
+// func add(a, b int64) int64
+TEXT ·add(SB), NOSPLIT, $0-24
+	MOVQ a+0(FP), AX
+	ADDQ b+8(FP), AX
+	MOVQ AX, ret+16(FP)
+	RET
+
+// func sum(data []int64) int64
+// Sums all elements of the slice.
+TEXT ·sum(SB), NOSPLIT, $0-32
+	MOVQ data_base+0(FP), SI
+	MOVQ data_len+8(FP), CX
+	XORQ AX, AX
+	TESTQ CX, CX
+	JZ   sum_done
+
+sum_loop:
+	ADDQ (SI), AX
+	ADDQ $8, SI
+	DECQ CX
+	JNZ  sum_loop
+
+sum_done:
+	MOVQ AX, ret+24(FP)
+	RET
+
+// func wideCopy(dst, src []byte)
+// Non-overlapping copy of min(len(dst), len(src)) bytes using 32-byte moves.
+TEXT ·wideCopy(SB), NOSPLIT, $0-48
+	MOVQ dst_base+0(FP), DI
+	MOVQ dst_len+8(FP), BX
+	MOVQ src_base+24(FP), SI
+	MOVQ src_len+32(FP), R8
+	CMPQ BX, R8
+	JLE  wc_have_n
+	MOVQ R8, BX
+
+wc_have_n:
+	CMPQ BX, $32
+	JB   wc_small
+
+	VMOVDQU (SI), Y0
+	VMOVDQU Y0, (DI)
+	VMOVDQU -32(SI)(BX*1), Y0
+	VMOVDQU Y0, -32(DI)(BX*1)
+	VZEROUPPER
+	RET
+
+wc_small:
+	TESTQ BX, BX
+	JZ    wc_done
+
+wc_byte:
+	MOVB (SI), R8B
+	MOVB R8B, (DI)
+	INCQ SI
+	INCQ DI
+	DECQ BX
+	JNZ  wc_byte
+
+wc_done:
+	RET

testdata/verify/basic_arm64.s

@@ -0,0 +1,57 @@
+// Copyright (c) 2026 Petr Balvín <opensource@petrbalvin.org> (https://petrbalvin.org)
+// SPDX-License-Identifier: BSD-3-Clause
+
+#include "textflag.h"
+
+// add returns a + b.
+TEXT ·add(SB), NOSPLIT, $0-24
+	MOVD	a+0(FP), R4
+	MOVD	b+8(FP), R5
+	ADD	R5, R4, R4
+	MOVD	R4, ret+16(FP)
+	RET
+
+// arith exercises the register-register integer set.
+TEXT ·arith(SB), NOSPLIT, $0-0
+	ADD	R4, R5, R6
+	SUB	R7, R8, R9
+	AND	R10, R11, R12
+	ORR	R12, R13, R14
+	EOR	R14, R15, R16
+	CMP	R16, R17
+	ADD	R4, R5
+	SUB	R6, R7
+	RET
+
+// branch exercises conditional and unconditional control flow.
+TEXT ·branch(SB), NOSPLIT, $0-0
+	BEQ	done
+	BNE	skip
+	BGE	done
+	BLT	done
+	BGT	done
+	BLE	done
+skip:
+	B	loop
+loop:
+	ADD	R4, R5
+	RET
+done:
+	RET
+
+// mov exercises the MOV pseudo-instruction.
+TEXT ·mov(SB), NOSPLIT, $0-16
+	MOVD	$0, R4
+	MOVD	$1, R5
+	MOVD	$42, R6
+	MOVD	a+0(FP), R7
+	MOVD	R7, ret+0(FP)
+	MOVW	$100, R8
+	RET
+
+// frame exercises the prologue/epilogue of a function with a real frame.
+TEXT ·frame(SB), NOSPLIT, $32-8
+	MOVD	arg+0(FP), R4
+	ADD	$1, R4, R4
+	MOVD	R4, ret+0(FP)
+	RET

testdata/verify/basic_loong64.s

@@ -0,0 +1,54 @@
+// Copyright (c) 2026 Petr Balvín <opensource@petrbalvin.org> (https://petrbalvin.org)
+// SPDX-License-Identifier: BSD-3-Clause
+
+#include "textflag.h"
+
+// add returns a + b.
+TEXT ·add(SB), NOSPLIT, $0-24
+	MOVV	a+0(FP), R4
+	MOVV	b+8(FP), R5
+	ADDV	R5, R4, R4
+	MOVV	R4, ret+16(FP)
+	RET
+
+// arith exercises the 3R integer and FP set.
+TEXT ·arith(SB), NOSPLIT, $0-0
+	ADDV	R4, R5, R6
+	SUBV	R7, R8, R9
+	MULV	R10, R11, R12
+	DIVV	R13, R14, R15
+	AND	R16, R17, R18
+	OR	R18, R19, R20
+	XOR	R20, R21, R2
+	SLLV	R2, R23, R24
+	SRLV	R24, R25, R26
+	SRAV	R26, R27, R28
+	RET
+
+// imm exercises the immediate forms.
+TEXT ·imm(SB), NOSPLIT, $0-0
+	ADDV	$42, R4, R5
+	ADDV	$-8, R6
+	AND	$0xff, R7, R8
+	OR	$1, R9, R10
+	XOR	$0, R11, R12
+	SGT	$100, R13, R14
+	SLLV	$4, R15, R16
+	MOVV	$0x12345, R17
+	RET
+
+// branch exercises conditional and unconditional control flow.
+TEXT ·branch(SB), NOSPLIT, $0-0
+	BEQ	R4, R5, done
+	BNE	R6, R7, skip
+	BLT	R8, R9, done
+	BGE	R10, R11, done
+	BLTU	R12, R13, done
+	BGEU	R14, R15, done
+skip:
+	JMP	loop
+loop:
+	JAL	skip
+	RET
+done:
+	RET

testdata/verify/basic_riscv64.s

@@ -0,0 +1,18 @@
+// Copyright (c) 2026 Petr Balvín <opensource@petrbalvin.org> (https://petrbalvin.org)
+// SPDX-License-Identifier: BSD-3-Clause
+
+#include "textflag.h"
+
+TEXT ·framed(SB), NOSPLIT, $16-16
+	MOV a+0(FP), X10
+	MOV b+8(FP), X11
+	ADD X11, X10, X10
+	MOV X10, ret+16(FP)
+	RET
+
+TEXT ·leaf(SB), NOSPLIT, $0-16
+	MOV a+0(FP), X10
+	MOV b+8(FP), X11
+	ADD X11, X10, X10
+	MOV X10, ret+16(FP)
+	RET

testdata/verify/branch_arm64.s

@@ -0,0 +1,27 @@
+// Copyright (c) 2026 Petr Balvín <opensource@petrbalvin.org> (https://petrbalvin.org)
+// SPDX-License-Identifier: BSD-3-Clause
+
+#include "textflag.h"
+
+// branch exercises all conditional branch forms and jump chain folding.
+TEXT ·branch(SB), NOSPLIT, $0-0
+	BEQ	done
+	BNE	skip
+	BGE	done
+	BLT	done
+	BGT	done
+	BLE	done
+	BCS	done
+	BCC	done
+	BMI	done
+	BPL	done
+	BVS	done
+	BVC	done
+	BHI	done
+	BLS	done
+skip:
+	B	loop
+loop:
+	ADD	R4, R5
+done:
+	RET

testdata/verify/branch_riscv64.s

@@ -0,0 +1,35 @@
+// Copyright (c) 2026 Petr Balvín <opensource@petrbalvin.org> (https://petrbalvin.org)
+// SPDX-License-Identifier: BSD-3-Clause
+
+#include "textflag.h"
+
+TEXT ·branches(SB), NOSPLIT, $0
+	ADDI $1, X10, X10
+	BEQ X10, X11, beq_done
+	ADDI $2, X10, X10
+beq_done:
+	BNE X10, X11, bne_done
+	ADDI $3, X10, X10
+bne_done:
+	BLT X10, X11, blt_done
+	ADDI $4, X10, X10
+blt_done:
+	BGE X10, X11, bge_done
+	ADDI $5, X10, X10
+bge_done:
+	BLTU X10, X11, bltu_done
+	ADDI $6, X10, X10
+bltu_done:
+	BGEU X10, X11, bgeu_done
+	ADDI $7, X10, X10
+bgeu_done:
+	RET
+
+TEXT ·jumps(SB), NOSPLIT, $0
+	JMP done
+	ADDI $1, X10, X10
+done:
+	JAL X11, skip
+	ADDI $2, X10, X10
+skip:
+	RET

testdata/verify/call_arm64.s

@@ -0,0 +1,10 @@
+// Copyright (c) 2026 Petr Balvín <opensource@petrbalvin.org> (https://petrbalvin.org)
+// SPDX-License-Identifier: BSD-3-Clause
+
+#include "textflag.h"
+
+// caller exercises BL to an external symbol (produces a relocation).
+TEXT ·caller(SB), NOSPLIT, $0-0
+	BL	other(SB)
+	ADD	R4, R5
+	RET

testdata/verify/call_riscv64.s

@@ -0,0 +1,8 @@
+// Copyright (c) 2026 Petr Balvín <opensource@petrbalvin.org> (https://petrbalvin.org)
+// SPDX-License-Identifier: BSD-3-Clause
+
+#include "textflag.h"
+
+TEXT ·call(SB), NOSPLIT, $0
+	CALL callee(SB)
+	RET

testdata/verify/fp_arm64.s

@@ -0,0 +1,119 @@
+// Copyright (c) 2026 Petr Balvín <opensource@petrbalvin.org> (https://petrbalvin.org)
+// SPDX-License-Identifier: BSD-3-Clause
+
+#include "textflag.h"
+
+// fparith exercises the FP arithmetic set.
+TEXT ·fparith(SB), NOSPLIT, $0-0
+	FADDD	F0, F1, F2
+	FSUBD	F3, F4, F5
+	FMULD	F6, F7, F8
+	FDIVD	F9, F10, F11
+	FADDS	F12, F13, F14
+	FSUBS	F15, F16, F17
+	FMULS	F18, F19, F20
+	FDIVS	F21, F22, F23
+	FSQRTD	F24, F25
+	FSQRTS	F26, F27
+	FNEGD	F28, F29
+	FNEGS	F30, F31
+	FABSD	F0, F1
+	FABSS	F2, F3
+	FNMULD	F4, F5, F6
+	FNMULS	F7, F8, F9
+	FMIND	F10, F11, F12
+	FMAXD	F13, F14, F15
+	FMINS	F16, F17, F18
+	FMAXS	F19, F20, F21
+	RET
+
+// fpfma exercises fused multiply-add.
+TEXT ·fpfma(SB), NOSPLIT, $0-0
+	FMADDD	F0, F1, F2, F3
+	FMSUBD	F4, F5, F6, F7
+	FNMADDD	F8, F9, F10, F11
+	FNMSUBD	F12, F13, F14, F15
+	FMADDS	F16, F17, F18, F19
+	FMSUBS	F20, F21, F22, F23
+	FNMADDS	F24, F25, F26, F27
+	FNMSUBS	F28, F29, F30, F0
+	RET
+
+// fpconv exercises FP↔integer conversion and cross-precision.
+// Syntax: FCVTZSD Fd, Rn (float→int: FP source first, int dest second)
+//         SCVTFD Rn, Fd (int→float: int source first, FP dest second)
+TEXT ·fpconv(SB), NOSPLIT, $0-0
+	FCVTSD	F0, F1
+	FCVTDS	F2, F3
+	FCVTZSD	F4, R0
+	FCVTZSS	F5, R1
+	FCVTZUD	F6, R2
+	FCVTZUS	F7, R3
+	SCVTFD	R4, F8
+	SCVTFS	R5, F9
+	UCVTFD	R6, F10
+	UCVTFS	R7, F11
+	SCVTFWD	R0, F12
+	SCVTFWS	R1, F13
+	UCVTFWD	R2, F14
+	UCVTFWS	R3, F15
+	FMOVS	F14, R20
+	FMOVS	R21, F15
+	FMOVD	F16, R22
+	FMOVD	R23, F17
+	RET
+
+// fpcmp exercises FP compare and conditional compare.
+// FCCMP syntax: FCCMP cond, Fn, Fm, $nzcv
+// FCSEL syntax: FCSEL cond, Fn, Fm, Fd
+TEXT ·fpcmp(SB), NOSPLIT, $0-0
+	FCMPS	F0, F1
+	FCMPD	F2, F3
+	FCMPS	$0.0, F4
+	FCMPD	$0.0, F5
+	FCCMPS	EQ, F6, F7, $0
+	FCCMPD	NE, F8, F9, $0
+	FCSELS	GE, F10, F11, F12
+	FCSELD	LT, F13, F14, F15
+	RET
+
+// frint exercises FP rounding.
+TEXT ·frint(SB), NOSPLIT, $0-0
+	FRINTND	F0, F1
+	FRINTNS	F2, F3
+	FRINTPD	F4, F5
+	FRINTPS	F6, F7
+	FRINTMD	F8, F9
+	FRINTMS	F10, F11
+	FRINTZD	F12, F13
+	FRINTZS	F14, F15
+	FRINTAD	F16, F17
+	FRINTAS	F18, F19
+	FRINTXD	F20, F21
+	FRINTXS	F22, F23
+	FRINTID	F24, F25
+	FRINTIS	F26, F27
+	FMOVD	F0, F1
+	FMOVS	F2, F3
+	RET
+
+// condsel exercises conditional select and CRC32.
+TEXT ·condsel(SB), NOSPLIT, $0-0
+	CSEL	EQ, R0, R1, R2
+	CSINC	NE, R3, R4, R5
+	CSINV	GE, R6, R7, R8
+	CSNEG	LT, R9, R10, R11
+	CSET	EQ, R12
+	CSETM	NE, R13
+	CINC	EQ, R14, R15
+	CINV	NE, R16, R17
+	CNEG	GE, R19, R20
+	CRC32B	R0, R2
+	CRC32H	R3, R5
+	CRC32W	R6, R8
+	CRC32X	R9, R11
+	CRC32CB	R12, R14
+	CRC32CH	R15, R0
+	CRC32CW	R1, R3
+	CRC32CX	R4, R6
+	RET

testdata/verify/fp_loong64.s

@@ -0,0 +1,143 @@
+// Copyright (c) 2026 Petr Balvín <opensource@petrbalvin.org> (https://petrbalvin.org)
+// SPDX-License-Identifier: BSD-3-Clause
+
+#include "textflag.h"
+
+// fp exercises the floating-point set: 3R arithmetic, 2R unary, compares
+// into FCC, fused multiply-add and the register moves.
+TEXT ·fp(SB), NOSPLIT, $0-0
+	ADDD	F4, F5, F6
+	SUBD	F7, F8, F9
+	MULD	F9, F10, F11
+	DIVD	F11, F12, F13
+	MULF	F13, F14, F15
+	ADDF	F15, F16, F17
+	SQRTD	F17, F18
+	SQRTF	F18, F19
+	ABSD	F19, F20
+	NEGD	F20, F21
+	MOVD	F21, F22
+	CMPEQD	F22, F23, FCC0
+	CMPGTF	F23, F24, FCC1
+	CMPGED	F24, F25, FCC2
+	FMADDD	F0, F1, F2, F3
+	FMSUBF	F3, F4, F5, F6
+	FNMADDD	F6, F7, F8, F9
+	FNMSUBF	F9, F10, F11, F12
+	FMAXD	F12, F13, F14
+	FMINF	F14, F15, F16
+	FMAXAD	F16, F17, F18
+	FMINAF	F18, F19, F20
+	FSCALEBF	F20, F21, F22
+	FCOPYSGD	F22, F23, F24
+	MOVV	F25, R25
+	MOVV	R26, F27
+	MOVW	R28, F29
+	MOVW	F30, R31
+	RET
+
+// mov forms: register moves, immediates (12/32/64-bit), memory with FP/SP
+// pseudo-registers and the register-indexed forms.
+TEXT ·mov(SB), NOSPLIT, $0-16
+	MOVV	R4, R5
+	MOVW	R6, R7
+	MOVB	R8, R9
+	MOVBU	R10, R11
+	MOVHU	R12, R13
+	MOVWU	R14, R15
+	MOVV	$42, R16
+	MOVV	$0x12345, R17
+	MOVV	$0x100000, R18
+	MOVW	$-100, R19
+	MOVV	$0x123456789, R20
+	MOVV	a+0(FP), R21
+	MOVV	R23, b+8(FP)
+	MOVW	c+16(FP), R24
+	MOVV	(R24)(R25), R26
+	MOVV	R27, (R28)(R29)
+	RET
+
+// frame exercises the prologue/epilogue of a function with a real frame.
+TEXT ·frame(SB), NOSPLIT, $32-8
+	MOVV	R4, R5
+	MOVV	arg+0(FP), R6
+	MOVV	R7, local-8(SP)
+	MOVV	local-8(SP), R8
+	MOVV	R9, ret+0(FP)
+	RET
+
+// branches21 exercises the single-register and zero-register branch forms
+// with 21-bit offsets.
+TEXT ·branches21(SB), NOSPLIT, $0-0
+	BEQ	R0, R4, l1
+	BEQ	R5, R0, l2
+	BNE	R0, R6, l3
+	BNE	R7, R0, l4
+	BLTZ	R8, l5
+	BGEZ	R9, l6
+	BLEZ	R10, l7
+	BGTZ	R11, l8
+	JMP	l9
+l1:
+	JMP	l10
+l2:
+	JMP	l11
+l3:
+	JMP	l12
+l4:
+	JMP	l13
+l5:
+	JMP	l14
+l6:
+	JMP	l15
+l7:
+	JMP	l16
+l8:
+	JMP	l16
+l9:
+	MOVV	R1, R2
+l10:
+	LL	(R12), R13
+	LLV	(R14), R15
+	SC	R16, (R17)
+	SCV	R18, (R19)
+	RDTIMED	R20, R21
+	SYSCALL
+	DBAR
+	RET
+l11:
+	JAL	(R30)
+	RET
+l12:
+	BSTRINSV	$7, R4, $0, R5
+	BSTRPICKV	$63, R6, $32, R7
+	ALSLV	$2, R8, R9, R10
+	ADDV16	$65536, R11, R12
+	RET
+l13:
+	MOVV	$0xffffffffffffffff, R13
+	RET
+l14:
+	CPUCFG	R14, R14
+	RET
+l15:
+	NOR	R15, R16, R17
+	ORN	R18, R19, R20
+	ANDN	R21, R24, R25
+	RET
+l16:
+	MOVB	R26, (R27)
+	MOVB	(R28), R29
+	RET
+
+// sbdata loads and stores a static symbol with relocations (the relocation
+// fields are masked before comparison).
+GLOBL	·table(SB), RODATA, $16
+DATA	·table+0(SB)/8, $0x1122334455667788
+DATA	·table+8(SB)/8, $0x8877665544332211
+
+TEXT ·sbdata(SB), NOSPLIT, $0-0
+	MOVV	$·table(SB), R4
+	MOVV	·table(SB), R5
+	MOVV	R6, ·table+8(SB)
+	RET

testdata/verify/largeimm_riscv64.s

@@ -0,0 +1,12 @@
+// Copyright (c) 2026 Petr Balvín <opensource@petrbalvin.org> (https://petrbalvin.org)
+// SPDX-License-Identifier: BSD-3-Clause
+
+#include "textflag.h"
+
+TEXT ·largeimm(SB), NOSPLIT, $0
+	ADDI $2048, X5
+	ADDI $4095, X5, X6
+	ANDI $4095, X5, X6
+	ORI $-4096, X5, X6
+	XORI $0x12345, X5, X6
+	RET