gasm-sdk/asm/riscv_csr_test.go

// Copyright (c) 2026 Petr Balvín <opensource@petrbalvin.org> (https://petrbalvin.org)
// SPDX-License-Identifier: BSD-3-Clause

package asm

import (
	"fmt"
	"os"
	"path/filepath"
	"slices"
	"strings"
	"testing"

	"sourcedock.dev/petrbalvin/gasm-sdk/parser"
)

// TestRISCVCSRDifferential proves the whole CSR name table against the
// toolchain at once: one TEXT whose body reads every register the table
// carries (CSRRW X0, NAME, X5), assembled by gasm and by go tool asm, must
// agree byte for byte.  A single wrong address names its register through
// the first differing word: the CSR address occupies the instruction's top
// twelve bits, so 329 names spread over distinct words identify themselves.
func TestRISCVCSRDifferential(t *testing.T) {
	names := make([]string, 0, len(riscvCSRNames))
	for name := range riscvCSRNames {
		names = append(names, name)
	}
	slices.Sort(names)

	var body strings.Builder
	for _, name := range names {
		body.WriteString(fmt.Sprintf("\tCSRRW X0, %s, X5\n", name))
	}
	src := "#include \"textflag.h\"\n\nTEXT ·csrs(SB), NOSPLIT, $0\n" + body.String() + "\tRET\n"

	dir := t.TempDir()
	path := filepath.Join(dir, "csrs_riscv64.s")
	if err := os.WriteFile(path, []byte(src), 0o644); err != nil {
		t.Fatal(err)
	}
	assertRISCVDifferential(t, path, src, "csrs")
}

// TestRISCVCSRPseudosDifferential pins the CSR pseudo spellings against the
// oracle: the write-only forms (source first, CSR second), their immediate
// variants and the CSRR read pseudo, one word each.
func TestRISCVCSRPseudosDifferential(t *testing.T) {
	src := `#include "textflag.h"

TEXT ·csrps(SB), NOSPLIT, $0
	CSRS X5, TIME
	CSRC X5, CYCLE
	CSRW X5, INSTRET
	CSRSI $1, TIME
	CSRCI $2, CYCLE
	CSRWI $3, INSTRET
	CSRR VL, X10
	CSRRW X0, TIME, X11
	CSRRS X0, CYCLE, X12
	CSRRC X0, INSTRET, X13
	CSRRWI $4, TIME, X14
	CSRRSI $5, CYCLE, X15
	CSRRCI $6, INSTRET, X16
	RET
`
	dir := t.TempDir()
	path := filepath.Join(dir, "csrps_riscv64.s")
	if err := os.WriteFile(path, []byte(src), 0o644); err != nil {
		t.Fatal(err)
	}
	assertRISCVDifferential(t, path, src, "csrps")
}

// assertRISCVDifferential assembles the same source with gasm and with the
// toolchain for riscv64 and requires the named function's code bytes to
// agree.  The live oracle is a deliberate-run comparison, so -short skips it
// (the push pipeline's mode); the golden bytes of the individual encoders
// are pinned separately in every mode.
func assertRISCVDifferential(t *testing.T, path, src, fn string) {
	t.Helper()
	oracle := oracleFuncCode(t, toolAsmObject(t, path, "riscv64"))

	// The oracle keys its functions by the qualified object name
	// (pkg.name); match on the local part.
	want := map[string][]byte{}
	for name, code := range oracle {
		if _, after, ok := strings.Cut(name, "."); ok {
			want[after] = code
		} else {
			want[name] = code
		}
	}
	if want[fn] == nil {
		t.Fatalf("the oracle object carries no function %q (has %v)", fn, keysOf(want))
	}

	f, perrs := parser.Parse(path, src)
	if len(perrs) > 0 {
		t.Fatalf("parse: %v", perrs[0])
	}
	img, err := AssembleFileRISCV(f)
	if err != nil {
		t.Fatalf("AssembleFileRISCV: %v", err)
	}
	got := trimTrailingZeroWords(img.Code)
	wantB := trimTrailingZeroWords(want[fn])
	if !slices.Equal(got, wantB) {
		t.Errorf("%s: gasm and go tool asm disagree:\n gasm % x\n go   % x", fn, got, wantB)
	}
}