style: modernize to splitseq, cut, min, maps.copy and range-over-int

AGENTS.md

@@ -1,119 +0,0 @@
-# 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
-```

asm/aarch64_goobj_test.go

@@ -110,7 +110,7 @@ func main() {
 		t.Fatalf("baseline build: %v\n%s", err, buildLog)
 	}
 	var work, linkLine, asmObj string
-	for _, line := range strings.Split(string(buildLog), "\n") {
+	for line := range strings.SplitSeq(string(buildLog), "\n") {
 		switch {
 		case strings.HasPrefix(line, "WORK="):
 			work = strings.TrimPrefix(line, "WORK=")

asm/arm64_assemble.go

@@ -638,7 +638,7 @@ func encodeARM64LoadImm(rd int, v int64, mnem string) ([]byte, error) {
 	// Multi-instruction: MOVZ + MOVK for each non-zero16-bit chunk.
 	var ws []uint32
 	first := true
-	for i := 0; i < 4; i++ {
+	for i := range 4 {
 		chunk := (d >> uint(i*16)) & 0xFFFF
 		if chunk == 0 {
 			continue
@@ -679,7 +679,7 @@ func arm64Bitmask(v uint64, sf int) (N, immr, imms uint32, ok bool) {
 		}
 
 		// Check each rotation: is the rotated pattern a contiguous block of 1s at the LSB?
-		for r := uint(0); r < esize; r++ {
+		for r := range esize {
 			rotated := (pattern >> r) | ((pattern << (esize - r)) & emask)
 			if rotated == 0 {
 				continue

asm/elf_test.go

@@ -187,7 +187,7 @@ func TestELFObject(t *testing.T) {
 		end := bytes.IndexByte(strtabRaw[stName:], 0)
 		return string(strtabRaw[stName : int(stName)+end])
 	}
-	for i := 0; i < 2; i++ {
+	for i := range 2 {
 		e := raw[i*24 : (i+1)*24]
 		off := binary.LittleEndian.Uint64(e[0:])
 		info := binary.LittleEndian.Uint64(e[8:])

asm/elfloong64_test.go

@@ -139,7 +139,7 @@ DATA answer<>+0(SB)/8, $42
 		t.Fatalf(".rela.text has %d bytes, want two 24-byte entries", len(raw))
 	}
 	le := binary.LittleEndian
-	for i := 0; i < 2; i++ {
+	for i := range 2 {
 		e := raw[i*24 : (i+1)*24]
 		off := le.Uint64(e[0:])
 		info := le.Uint64(e[8:])

asm/encode.go

@@ -419,7 +419,7 @@ func le16(v int64) []byte {
 func le64(v int64) []byte {
 	u := uint64(v)
 	b := make([]byte, 8)
-	for i := 0; i < 8; i++ {
+	for i := range 8 {
 		b[i] = byte(u >> (8 * i))
 	}
 	return b

asm/evex.go

@@ -603,12 +603,12 @@ func (s evexSuffix) evexOnly() bool {
 // broadcast together with rounding/SAE.
 func parseEvexSuffix(mnem string) (string, evexSuffix, error) {
 	sfx := evexSuffix{rounding: -1}
-	i := strings.IndexByte(mnem, '.')
+	before, after, ok := strings.Cut(mnem, ".")
-	if i < 0 {
+	if !ok {
 		return mnem, sfx, nil
 	}
-	base := mnem[:i]
+	base := before
-	parts := strings.Split(mnem[i+1:], ".")
+	parts := strings.Split(after, ".")
 	seen := map[string]bool{}
 	for j, p := range parts {
 		if seen[p] {
@@ -618,7 +618,7 @@ func parseEvexSuffix(mnem string) (string, evexSuffix, error) {
 		switch p {
 		case "Z":
 			if j != len(parts)-1 {
-				return "", sfx, fmt.Errorf("the .Z suffix must come last in %q", mnem[i+1:])
+				return "", sfx, fmt.Errorf("the .Z suffix must come last in %q", after)
 			}
 			sfx.zeroing = true
 		case "SAE":
@@ -638,7 +638,7 @@ func parseEvexSuffix(mnem string) (string, evexSuffix, error) {
 		}
 	}
 	if sfx.bcst && (sfx.sae || sfx.rounding >= 0) {
-		return "", sfx, fmt.Errorf("cannot combine .BCST with rounding or SAE in %q", mnem[i+1:])
+		return "", sfx, fmt.Errorf("cannot combine .BCST with rounding or SAE in %q", after)
 	}
 	return base, sfx, nil
 }

asm/goobj.go

@@ -464,7 +464,7 @@ func (img *Image) emitGOObject(pkgPath, srcPath string, pre []byte, minLC int, r
 	auxIdxBlk := make([]byte, 0, 4*(nsyms+1))
 	dataIdxBlk := make([]byte, 0, 4*(nsyms+1))
 	var nr, na, nd uint32
-	for si := 0; si < nsyms; si++ {
+	for si := range nsyms {
 		relocIdxBlk = binary.LittleEndian.AppendUint32(relocIdxBlk, nr)
 		auxIdxBlk = binary.LittleEndian.AppendUint32(auxIdxBlk, na)
 		dataIdxBlk = binary.LittleEndian.AppendUint32(dataIdxBlk, nd)

asm/goobj_dwarf.go

@@ -139,10 +139,7 @@ func dwSelectOpcode(deltaPC uint64, deltaLC int64) int64 {
 		return int64(dwOpcodeBase) + (deltaLC - dwLineBase) + dwLineRange*int64(deltaPC)
 	default:
 		if deltaPC <= uint64(dwPCRange) {
-			op := int64(dwOpcodeBase) + (dwLineRange - 1) + dwLineRange*int64(deltaPC)
+			op := min(int64(dwOpcodeBase)+(dwLineRange-1)+dwLineRange*int64(deltaPC), 255)
-			if op > 255 {
-				op = 255
-			}
 			return op
 		}
 		switch deltaPC - uint64(dwPCRange) {

asm/goobj_resolve.go

@@ -323,8 +323,8 @@ 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 {
+	if before, after, ok := strings.Cut(full, "."); ok {
-		return full[:idx], full[idx+1:]
+		return before, after
 	}
 	return "", full
 }

asm/goobj_test.go

@@ -393,7 +393,7 @@ func main() {
 	}
 	var work string
 	var asmObj, pkgArch, linkLine string
-	for _, line := range strings.Split(string(buildLog), "\n") {
+	for line := range strings.SplitSeq(string(buildLog), "\n") {
 		switch {
 		case strings.HasPrefix(line, "WORK="):
 			work = strings.TrimPrefix(line, "WORK=")
@@ -461,7 +461,7 @@ func main() {
 	newArch := filepath.Join(dir, "pkg.a")
 	args := []string{"tool", "pack", "c", newArch}
 	seen := map[string]bool{}
-	for _, m := range strings.Fields(string(listOut)) {
+	for m := range strings.FieldsSeq(string(listOut)) {
 		if seen[m] {
 			continue
 		}

asm/l64_goobj_test.go

@@ -214,7 +214,7 @@ func main() {
 		t.Fatalf("baseline build: %v\n%s", err, buildLog)
 	}
 	var pkgArch, work, linkLine, asmObj string
-	for _, line := range strings.Split(string(buildLog), "\n") {
+	for line := range strings.SplitSeq(string(buildLog), "\n") {
 		switch {
 		case strings.HasPrefix(line, "WORK="):
 			work = strings.TrimPrefix(line, "WORK=")
@@ -278,7 +278,7 @@ func main() {
 	newArch := filepath.Join(dir, "pkg.a")
 	args := []string{"tool", "pack", "c", newArch}
 	seen := map[string]bool{}
-	for _, m := range strings.Fields(string(listOut)) {
+	for m := range strings.FieldsSeq(string(listOut)) {
 		if seen[m] {
 			continue
 		}

asm/link.go

@@ -488,7 +488,7 @@ func collectData(f *ast.File) ([]dataSym, error) {
 			if dd.Value.Imm.Neg {
 				v = -v
 			}
-			for j := 0; j < w; j++ {
+			for j := range w {
 				buf[off+int64(j)] = byte(v >> (8 * j))
 			}
 		}

asm/loong64_encode.go

@@ -30,6 +30,8 @@ package asm
 // of the immediate and register fields), mirroring the toolchain's OP_*
 // helpers, so each l64* function only ORs its fields in.
 
+import "maps"
+
 // 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
@@ -368,7 +370,7 @@ func init() {
 	// 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{
+	maps.Copy(l64DualTable, map[string]l64DualEnc{
 		"ADD":   {rrr: 0x20 << 15, imm: 0x00a << 22},
 		"ADDW":  {rrr: 0x20 << 15, imm: 0x00a << 22},
 		"ADDV":  {rrr: 0x21 << 15, imm: 0x00b << 22},
@@ -386,9 +388,7 @@ func init() {
 		"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}

asm/reg.go

@@ -7,6 +7,8 @@
 // by round-tripping through golang.org/x/arch's decoder in the tests.
 package asm
 
+import "maps"
+
 import "strings"
 
 // Reg is an x86-64 register.  In Plan 9 assembly the classic names (AX, BX, …)
@@ -121,13 +123,11 @@ func buildRegByName() map[string]Reg {
 	}
 
 	// 8-bit: AL..BH, SPL..DIL, R8B..R15B.
-	for n, r := range map[string]Reg{
+	maps.Copy(m, map[string]Reg{
 		"AL": AL, "CL": CL, "DL": DL, "BL": BL,
 		"AH": AH, "CH": CH, "DH": DH, "BH": BH,
 		"SPL": SPL, "BPL": BPL, "SIL": SIL, "DIL": DIL,
-	} {
+	})
-		m[n] = r
-	}
 	for i := 8; i <= 15; i++ {
 		m["R"+itoa(i)+"B"] = Reg{idx: i, size: 1}
 	}

asm/riscv_goobj_test.go

@@ -141,7 +141,7 @@ DATA answer<>+0(SB)/8, $42
 	first := int(le.Uint32(relocIdx[4*(4+4):]))
 	wantType := []uint16{relocRISCVPcrelItype, relocRISCVPcrelItype, relocRISCVPcrelStype}
 	wantOffAbs := []int{0, 8, 16}
-	for i := 0; i < 3; i++ {
+	for i := range 3 {
 		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 {
@@ -221,7 +221,7 @@ func main() {
 		t.Fatalf("baseline build: %v\n%s", err, buildLog)
 	}
 	var pkgArch, work, linkLine, asmObj string
-	for _, line := range strings.Split(string(buildLog), "\n") {
+	for line := range strings.SplitSeq(string(buildLog), "\n") {
 		switch {
 		case strings.HasPrefix(line, "WORK="):
 			work = strings.TrimPrefix(line, "WORK=")
@@ -279,7 +279,7 @@ func main() {
 	newArch := filepath.Join(dir, "pkg.a")
 	args := []string{"tool", "pack", "c", newArch}
 	seen := map[string]bool{}
-	for _, m := range strings.Fields(string(listOut)) {
+	for m := range strings.FieldsSeq(string(listOut)) {
 		if seen[m] {
 			continue
 		}

cmd/gasm/audit.go

@@ -171,7 +171,7 @@ func probeGoAsm(names []string) (map[string]bool, error) {
 		result[name] = true // no news = the name parsed fine
 	}
 	reParse := regexp.MustCompile(`probe\.s:(\d+):`)
-	for _, l := range strings.Split(string(out), "\n") {
+	for l := range strings.SplitSeq(string(out), "\n") {
 		m := reParse.FindStringSubmatch(l)
 		if m == nil {
 			continue

cmd/gasm/debug_linux.go

@@ -150,7 +150,7 @@ REPL commands:
 						// 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++ {
+						for j := range 8 {
 							argBlock[off+8+j] = byte(size >> (j * 8))
 							argBlock[off+16+j] = byte(size >> (j * 8))
 						}
@@ -260,7 +260,7 @@ REPL commands:
 // Format: name:size:pattern[,name:size:pattern...]
 func parseBufNames(spec string) []string {
 	var names []string
-	for _, part := range strings.Split(spec, ",") {
+	for part := range strings.SplitSeq(spec, ",") {
 		fields := strings.SplitN(part, ":", 3)
 		if len(fields) >= 1 && fields[0] != "" {
 			names = append(names, fields[0])
@@ -271,7 +271,7 @@ func parseBufNames(spec string) []string {
 
 // parseBufSize extracts the size of a named buffer from a buffer specification.
 func parseBufSize(spec, name string) int {
-	for _, part := range strings.Split(spec, ",") {
+	for part := range strings.SplitSeq(spec, ",") {
 		fields := strings.SplitN(part, ":", 3)
 		if len(fields) >= 2 && fields[0] == name {
 			var size int

cmd/gasm/main.go

@@ -359,7 +359,7 @@ unreachable-code, register-clobber and funcdata-pcdata.
 		return 2
 	}
 	disabled := map[string]bool{}
-	for _, code := range strings.Split(*disable, ",") {
+	for code := range strings.SplitSeq(*disable, ",") {
 		if code = strings.TrimSpace(code); code != "" {
 			disabled[code] = true
 		}
@@ -460,10 +460,7 @@ requires -p, the package path, and the installed Go toolchain).
 		code := img.Code[fn.Offset : fn.Offset+fn.Size]
 		fmt.Printf("%s: %d bytes\n", fn.Name, fn.Size)
 		for i := 0; i < len(code); i += 16 {
-			end := i + 16
+			end := min(i+16, len(code))
-			if end > len(code) {
-				end = len(code)
-			}
 			fmt.Printf("  %04x:", i)
 			for _, b := range code[i:end] {
 				fmt.Printf(" %02x", b)
@@ -485,10 +482,7 @@ requires -p, the package path, and the installed Go toolchain).
 			fmt.Printf("  %s: %d bytes at 0x%x\n", g.Name.Name, size, img.Symbols[g.Name.Name])
 		}
 		for i := 0; i < len(img.Data); i += 16 {
-			end := i + 16
+			end := min(i+16, len(img.Data))
-			if end > len(img.Data) {
-				end = len(img.Data)
-			}
 			fmt.Printf("  %04x:", len(img.Code)+i)
 			for _, b := range img.Data[i:end] {
 				fmt.Printf(" %02x", b)
@@ -570,7 +564,7 @@ e.g. --map wideCopyAVX2=wideCopyAVX512 pairs the two regardless of suffix.
 	// Parse the name mapping (file1 name → file2 name).
 	nameMap := make(map[string]string)
 	if *mapSpec != "" {
-		for _, pair := range strings.Split(*mapSpec, ",") {
+		for pair := range strings.SplitSeq(*mapSpec, ",") {
 			old, new, ok := strings.Cut(pair, "=")
 			if !ok || old == "" || new == "" {
 				fmt.Fprintf(os.Stderr, "gasm diff: invalid --map pair %q (expected old=new)\n", pair)
@@ -679,10 +673,7 @@ func assemblePath(path string) (*asm.Image, error) {
 
 // printByteDiff shows the first few byte differences between two code blocks.
 func printByteDiff(a, b []byte) {
-	maxLen := len(a)
+	maxLen := min(len(b), len(a))
-	if len(b) < maxLen {
-		maxLen = len(b)
-	}
 	shown := 0
 	for i := 0; i < maxLen && shown < 8; i++ {
 		if a[i] != b[i] {
@@ -1344,8 +1335,8 @@ func fuzzInSubprocess(path, funcName string, n int) string {
 			}
 		}
 		// Non-zero exit without a signal: the fuzz reported mismatches.
-		lines := strings.Split(strings.TrimSpace(string(out)), "\n")
+		lines := strings.SplitSeq(strings.TrimSpace(string(out)), "\n")
-		for _, l := range lines {
+		for l := range lines {
 			if strings.Contains(l, funcName) {
 				return strings.TrimSpace(l)
 			}
@@ -1353,8 +1344,8 @@ func fuzzInSubprocess(path, funcName string, n int) string {
 		return fmt.Sprintf("%s: FAIL (exit %v)", funcName, err)
 	}
 	// Success: extract the result line.
-	lines := strings.Split(strings.TrimSpace(string(out)), "\n")
+	lines := strings.SplitSeq(strings.TrimSpace(string(out)), "\n")
-	for _, l := range lines {
+	for l := range lines {
 		if strings.Contains(l, funcName) {
 			return strings.TrimSpace(l)
 		}
@@ -1400,7 +1391,7 @@ func sweepInSubprocess(path, funcName string, smoke, abi bool, abiN int) (string
 // dropping the child's own file/function banners (the parent prints those).
 func sweepCheckLines(out []byte) string {
 	var lines []string
-	for _, l := range strings.Split(string(out), "\n") {
+	for l := range strings.SplitSeq(string(out), "\n") {
 		t := strings.TrimSpace(l)
 		if strings.HasPrefix(t, "smoke:") || strings.HasPrefix(t, "abi:") {
 			lines = append(lines, "    "+t)
@@ -1570,10 +1561,7 @@ func formatResults(rs []verify.Param) string {
 // hexDump returns a one-line hex dump of buf, truncated to 64 bytes.
 func hexDump(buf []byte) string {
 	const max = 64
-	n := len(buf)
+	n := min(len(buf), max)
-	if n > max {
-		n = max
-	}
 	var sb strings.Builder
 	for i := range n {
 		if i > 0 {

cmd/gasm/scaffold.go

@@ -136,7 +136,7 @@ type sigResult struct {
 // parseSig parses the // func signature of a doc comment.
 func parseSig(doc string) ([]sigParam, []sigResult, bool) {
 	var line string
-	for _, l := range strings.Split(doc, "\n") {
+	for l := range strings.SplitSeq(doc, "\n") {
 		if t := strings.TrimSpace(l); strings.HasPrefix(t, "func ") {
 			line = t
 			break

debug/breakpoint.go

@@ -5,6 +5,8 @@
 
 package debug
 
+import "strings"
+
 import "fmt"
 
 // Breakpoint is one INT3 breakpoint in the debuggee.
@@ -119,7 +121,7 @@ func (bm *Breakpoints) Info() string {
 	if len(bm.bps) == 0 {
 		return "no breakpoints set\n"
 	}
-	result := ""
+	var result strings.Builder
 	i := 0
 	for _, bp := range bm.bps {
 		i++
@@ -135,9 +137,9 @@ func (bm *Breakpoints) Info() string {
 		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)
+		result.WriteString(fmt.Sprintf("  %d: %s at %#x [%s, %d hits]%s\n", i, label, bp.Addr, status, bp.hits, cond))
 	}
-	return result
+	return result.String()
 }
 
 // Clear removes the breakpoint at addr, restoring the original byte.

debug/debug_test.go

@@ -279,7 +279,7 @@ func TestWatchpointSlotTracking(t *testing.T) {
 	s := &Session{}
 
 	// All four slots are free initially.
-	for i := 0; i < 4; i++ {
+	for i := range 4 {
 		if s.IsWatchpointSlotUsed(i) {
 			t.Errorf("slot %d should be free initially", i)
 		}
@@ -317,7 +317,7 @@ func TestWatchpointSlotTracking(t *testing.T) {
 	}
 
 	// Mark all slots used: FindFreeWatchpointSlot returns -1.
-	for i := 0; i < 4; i++ {
+	for i := range 4 {
 		wpSlots[i] = true
 	}
 	if got := s.FindFreeWatchpointSlot(); got != -1 {

debug/disasm_linux_amd64.go

@@ -7,6 +7,7 @@ package debug
 
 import (
 	"fmt"
+	"strings"
 
 	"golang.org/x/arch/x86/x86asm"
 )
@@ -34,19 +35,19 @@ func (s *Session) Disassemble(addr uint64) (string, int, error) {
 // 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
+	var result strings.Builder
 	pc := addr
 	for range n {
 		text, length, err := s.Disassemble(pc)
 		if err != nil {
-			result += fmt.Sprintf("  %#08x: <error: %v>\n", pc, err)
+			result.WriteString(fmt.Sprintf("  %#08x: <error: %v>\n", pc, err))
 			break
 		}
-		result += fmt.Sprintf("  %#08x: %s\n", pc, text)
+		result.WriteString(fmt.Sprintf("  %#08x: %s\n", pc, text))
 		if length == 0 {
 			length = 1
 		}
 		pc += uint64(length)
 	}
-	return result
+	return result.String()
 }

debug/ptrace_linux.go

@@ -72,7 +72,7 @@ func LaunchWithBuffers(gasmBin, asmPath, funcName string, args []byte, bufSpec s
 	s := &Session{pid: cmd.Process.Pid, cmd: cmd}
 
 	readyFile := filepath.Join(tmpDir, "ready")
-	for i := 0; i < 500; i++ {
+	for range 500 {
 		if _, err := os.Stat(readyFile); err == nil {
 			break
 		}
@@ -86,7 +86,7 @@ func LaunchWithBuffers(gasmBin, asmPath, funcName string, args []byte, bufSpec s
 	}
 
 	entryFile := filepath.Join(tmpDir, "entry")
-	for i := 0; i < 500; i++ {
+	for range 500 {
 		if _, err := os.Stat(entryFile); err == nil {
 			break
 		}
@@ -115,7 +115,7 @@ func LaunchWithBuffers(gasmBin, asmPath, funcName string, args []byte, bufSpec s
 	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") {
+			for line := range strings.SplitSeq(strings.TrimSpace(string(data)), "\n") {
 				var addr uint64
 				if _, err := fmt.Sscanf(line, "%d", &addr); err == nil {
 					bufAddrs = append(bufAddrs, addr)
@@ -190,10 +190,7 @@ func (s *Session) ReadMemory(addr uint64, length int) ([]byte, error) {
 // 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
+		end := min(i+8, len(data))
-		if end > len(data) {
-			end = len(data)
-		}
 		var word uint64
 		for j := 0; j < end-i; j++ {
 			word |= uint64(data[i+j]) << (8 * j)
@@ -275,7 +272,7 @@ func findRWXMapping(pid int) uint64 {
 	if err != nil {
 		return 0
 	}
-	for _, line := range strings.Split(string(data), "\n") {
+	for line := range strings.SplitSeq(string(data), "\n") {
 		fields := strings.Fields(line)
 		if len(fields) < 2 {
 			continue

debug/ptrace_linux_amd64.go

@@ -89,8 +89,8 @@ func (s *Session) GetVectorRegs() (VectorRegs, error) {
 	if err != nil {
 		return v, err
 	}
-	for i := 0; i < 16; i++ {
+	for i := range 16 {
-		for j := 0; j < 16; j++ {
+		for j := range 16 {
 			v.YMM[i][j] = fp.XMM[i][j]
 		}
 	}

debug/repl.go

@@ -297,7 +297,7 @@ func REPL(s *Session, bm *Breakpoints, codeBase uint64, funcOffset, funcSize, ar
 					continue
 				}
 				if v > 255 {
-					for j := 0; j < 8; j++ {
+					for j := range 8 {
 						bytes = append(bytes, byte(v>>(8*j)))
 					}
 				} else {
@@ -482,10 +482,7 @@ func REPL(s *Session, bm *Breakpoints, codeBase uint64, funcOffset, funcSize, ar
 
 func hexDump(addr uint64, data []byte) {
 	for i := 0; i < len(data); i += 16 {
-		end := i + 16
+		end := min(i+16, len(data))
-		if end > len(data) {
-			end = len(data)
-		}
 		fmt.Printf("  %#08x:", addr+uint64(i))
 		for j := i; j < i+16; j++ {
 			if j < end {

debug/stopinfo_linux.go

@@ -61,7 +61,7 @@ func (s *Session) StopInfo() (StopReason, uint64) {
 	case trapBRKPT:
 		return StopBreakpoint, 0
 	case trapHWBRKPT:
-		addr := *(*uint64)(unsafe.Pointer(uintptr(unsafe.Pointer(&info)) + 16))
+		addr := *(*uint64)(unsafe.Add(unsafe.Pointer(&info), 16))
 		return StopWatchpoint, addr
 	default:
 		return StopSingleStep, 0

debug/target_linux.go

@@ -37,7 +37,7 @@ func setupBuffers(spec string, args []byte, argSize int, tmpDir string) ([]byte,
 		pattern string
 	}
 	var specs []bufSpec
-	for _, part := range strings.Split(spec, ",") {
+	for part := range strings.SplitSeq(spec, ",") {
 		fields := strings.SplitN(part, ":", 3)
 		if len(fields) != 3 {
 			continue

debug/tracer.go

@@ -36,7 +36,7 @@ func newMockTracer() *mockTracer {
 func (m *mockTracer) Peek(addr uint64) (uint64, error) {
 	m.peeks = append(m.peeks, addr)
 	var val uint64
-	for i := uint64(0); i < 8; i++ {
+	for i := range uint64(8) {
 		val |= uint64(m.mem[addr+i]) << (i * 8)
 	}
 	return val, nil
@@ -47,7 +47,7 @@ func (m *mockTracer) Poke(addr uint64, val uint64) error {
 		addr uint64
 		val  uint64
 	}{addr, val})
-	for i := uint64(0); i < 8; i++ {
+	for i := range uint64(8) {
 		m.mem[addr+i] = byte(val >> (i * 8))
 	}
 	return nil

debug/watchpoint_linux_amd64.go

@@ -26,7 +26,7 @@ var wpSlots [4]bool
 // 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++ {
+	for i := range 4 {
 		if !wpSlots[i] {
 			return i
 		}
@@ -122,7 +122,7 @@ func (s *Session) ClearWatchpoint(slot int) error {
 
 // ClearAllWatchpoints removes all hardware watchpoints.
 func (s *Session) ClearAllWatchpoints() error {
-	for slot := 0; slot < 4; slot++ {
+	for slot := range 4 {
 		if wpSlots[slot] {
 			if err := s.ClearWatchpoint(slot); err != nil {
 				return err

go.mod

@@ -4,4 +4,4 @@ go 1.27
 
 toolchain go1.27.0
 
-require golang.org/x/arch v0.29.0
+require golang.org/x/arch v0.30.0

go.sum

@@ -1,2 +1,4 @@
 golang.org/x/arch v0.29.0 h1:8sSET5wB0+exBm0FGmOtdHMqjlRdV2DRD3/IV6OZgho=
 golang.org/x/arch v0.29.0/go.mod h1:0X+GdSIP+kL5wPmpK7sdkEVTt2XoYP0cSjQSbZBwOi8=
+golang.org/x/arch v0.30.0 h1:sB9h+1gRGa2+LauFSV0tm8bK1J2yo1bx6/Uyi/P6DTU=
+golang.org/x/arch v0.30.0/go.mod h1:0X+GdSIP+kL5wPmpK7sdkEVTt2XoYP0cSjQSbZBwOi8=

lint/abi.go

@@ -74,7 +74,7 @@ func parseSignature(sig string) (*ast.FuncDecl, bool) {
 
 // signatureLine returns the first `func …` line from a doc comment, trimmed.
 func signatureLine(doc string) string {
-	for _, line := range strings.Split(doc, "\n") {
+	for line := range strings.SplitSeq(doc, "\n") {
 		if t := strings.TrimSpace(line); strings.HasPrefix(t, "func ") {
 			return t
 		}

lsp/protocol.go

@@ -215,7 +215,7 @@ const (
 // Hover is the hover response.
 type Hover struct {
 	Contents markupContent `json:"contents"`
-	Range    Range         `json:"range,omitempty"`
+	Range    Range         `json:"range"`
 }
 
 type markupContent struct {

verify/arm64_groundtruth_test.go

@@ -54,10 +54,7 @@ func TestGroundTruthARM64(t *testing.T) {
 				// The Go toolchain may add zero padding at the end of
 				// functions.  Compare up to the shorter length, then
 				// verify any trailing bytes are zero.
-				cmpLen := len(gasmCode)
+				cmpLen := min(len(goCode), len(gasmCode))
-				if len(goCode) < cmpLen {
-					cmpLen = len(goCode)
-				}
 				if !bytes.Equal(gasmCode[:cmpLen], goCode[:cmpLen]) {
 					t.Errorf("%s: MISMATCH gasm=%d go=%d bytes\n%s", fn.Name, len(gasmCode), len(goCode), diffHex(gasmCode, goCode))
 					continue

verify/buffers.go

@@ -25,7 +25,7 @@ func ParseBufSpec(spec string) ([]BufSpec, error) {
 		return nil, nil
 	}
 	var out []BufSpec
-	for _, part := range strings.Split(spec, ",") {
+	for part := range strings.SplitSeq(spec, ",") {
 		fields := strings.SplitN(part, ":", 3)
 		if len(fields) != 3 {
 			return nil, fmt.Errorf("verify: invalid buffer spec %q (expected name:size:pattern)", part)
@@ -185,7 +185,7 @@ func ParseScalarArgs(spec string) (map[string]uint64, error) {
 	if strings.TrimSpace(spec) == "" {
 		return out, nil
 	}
-	for _, part := range strings.Split(spec, ",") {
+	for part := range strings.SplitSeq(spec, ",") {
 		part = strings.TrimSpace(part)
 		if part == "" {
 			continue

verify/fuzz.go

@@ -61,8 +61,8 @@ func parseFuncSig(comment string) (funcSig, bool) {
 	if m == nil {
 		return funcSig{}, false
 	}
-	sig := funcSig{name: m[1]}
+	sig := funcSig{name: m[1],
-	sig.params = parseParams(m[2])
+		params: parseParams(m[2])}
 	// Results may be "(a int, b int)" or "int" or "(int, error)".
 	res := strings.TrimSpace(m[3])
 	res = strings.TrimPrefix(res, "(")
@@ -271,10 +271,7 @@ func genDualArgs(rng *rand.Rand, sig funcSig, argSize int) (gasmArgs, goArgs []b
 		case strings.HasPrefix(p.typ, "*["):
 			nElem := arrayLen(p.typ)
 			elem := elemSizeFor("[]" + p.typ[strings.Index(p.typ, "]")+1:])
-			size := nElem * elem
+			size := max(nElem*elem, 8)
-			if size < 8 {
-				size = 8
-			}
 			buf1 := make([]byte, size)
 			buf2 := make([]byte, size)
 			rng.Read(buf1)

verify/groundtruth.go

@@ -169,7 +169,7 @@ func extractGOOBJCode(data []byte) (map[string][]byte, error) {
 
 	result := make(map[string][]byte)
 	const kindSTEXT = 1
-	for s := 0; s < nSyms; s++ {
+	for s := range nSyms {
 		x := nonpkg[s*symSize:]
 		nameLen := le.Uint32(x[0:])
 		nameOff := le.Uint32(x[4:])

verify/l64_groundtruth_test.go

@@ -76,10 +76,7 @@ func maskRelocs(code []byte, relocs []asm.Reloc) []byte {
 
 func diffHex(a, b []byte) string {
 	var out bytes.Buffer
-	n := len(a)
+	n := max(len(b), len(a))
-	if len(b) > n {
-		n = len(b)
-	}
 	for i := 0; i < n; i += 4 {
 		ab, bb := "??", "??"
 		if i+4 <= len(a) {

verify/sigparse.go

@@ -32,8 +32,8 @@ func ParseFuncSig(comment string) (FuncSig, bool) {
 	if m == nil {
 		return FuncSig{}, false
 	}
-	sig := FuncSig{Name: m[1]}
+	sig := FuncSig{Name: m[1],
-	sig.Params = parseParamsExported(m[2])
+		Params: parseParamsExported(m[2])}
 	// Results may be "(a int, b int)" or "int" or "(int, error)".
 	res := strings.TrimSpace(m[3])
 	res = strings.TrimPrefix(res, "(")