gasm-sdk/asm/rendered_text_test.go

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

package asm

import (
	"encoding/hex"
	"strings"
	"testing"

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

// TestRenderedTextEncodes pins the encoder against the disassembler's
// renderings: every line here is a text the toolchain's own decoder prints
// for bytes its assembler produced (the disasm package's parity fixtures),
// so assembling the printed text must reproduce those bytes.  Each row was
// read back through the toolchain's decoder; the hex is the fixture's.
func TestRenderedTextEncodes(t *testing.T) {
	for _, tt := range []struct {
		text string
		want string
	}{
		// The segment-absolute rendering lowers to the FS-prefixed disp32
		// absolute, exactly what the 0(FS) spelling encodes.
		{"MOVQ FS:0, DX", "64488b142500000000"},
		// The bank-crossing quadword move takes the prefix by direction: the
		// MMX source carries F3, the XMM source F2.
		{"MOVQ2DQ M2, X11", "f3440fd6da"},
	} {
		src := "TEXT \u00b7k(SB), NOSPLIT, $0\n\t" + tt.text + "\n\tRET\n"
		f, errs := parser.Parse("k.s", src)
		if len(errs) > 0 {
			t.Errorf("%s: parse: %v", tt.text, errs[0])
			continue
		}
		img, err := AssembleFile(f)
		if err != nil {
			t.Errorf("%s: assemble: %v", tt.text, err)
			continue
		}
		fn := img.Funcs[0]
		code := img.Code[fn.Offset : fn.Offset+fn.Size]
		// The no-fallthrough rule appends the RET; the pinned instruction is
		// the prefix.
		got := hex.EncodeToString(code)
		if !strings.HasPrefix(got, tt.want) {
			t.Errorf("%s: bytes %s, want prefix %s", tt.text, got, tt.want)
		}
	}
}