riscv64: add tests for riscv64asm

Add validation tests for riscv64asm GNU/Plan9 decoder, including
objdump test and external test.

Change-Id: Id7442704ea7e10c22ca4a799cdfc9f7d043f85c3
Reviewed-on: https://go-review.googlesource.com/c/arch/+/602916
Reviewed-by: Meng Zhuo <[email protected]>
LUCI-TryBot-Result: Go LUCI <[email protected]>
Reviewed-by: David Chase <[email protected]>
Reviewed-by: Mark Ryan <[email protected]>
Reviewed-by: Cherry Mui <[email protected]>

riscv64/riscv64asm/decode_test.go

@@ -0,0 +1,80 @@
+// Copyright 2024 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package riscv64asm
+
+import (
+	"bufio"
+	"encoding/hex"
+	"os"
+	"path/filepath"
+	"strings"
+	"testing"
+)
+
+func testDecode(t *testing.T, syntax string) {
+	input := filepath.Join("testdata", syntax+"cases.txt")
+	f, err := os.Open(input)
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer f.Close()
+	scanner := bufio.NewScanner(f)
+	for scanner.Scan() {
+		line := strings.TrimSpace(scanner.Text())
+		if line == "" || strings.HasPrefix(line, "#") {
+			continue
+		}
+		f := strings.SplitN(line, "\t", 2)
+		i := strings.Index(f[0], "|")
+
+		if i < 0 {
+			t.Errorf("parsing %q: missing | separator", f[0])
+			continue
+		}
+		if i%2 != 0 {
+			t.Errorf("parsing %q: misaligned | separator", f[0])
+		}
+		code, err := hex.DecodeString(f[0][:i] + f[0][i+1:])
+		if err != nil {
+			t.Errorf("parsing %q: %v", f[0], err)
+			continue
+		}
+		asm0 := strings.Replace(f[1], "	", " ", -1)
+		asm := strings.TrimSpace(asm0)
+		inst, decodeErr := Decode(code)
+		if decodeErr != nil && decodeErr != errUnknown {
+			if asm == "illegalins" && decodeErr == errShort {
+				continue
+			}
+			// Some rarely used system instructions are not supported
+			// Following logicals will filter such unknown instructions
+			t.Errorf("parsing %x: %s", code, decodeErr)
+			continue
+		}
+
+		var out string
+		switch syntax {
+		case "gnu":
+			out = GNUSyntax(inst)
+		case "plan9":
+			out = GoSyntax(inst, 0, nil, nil)
+		default:
+			t.Errorf("unknown syntax %q", syntax)
+			continue
+		}
+
+		if asm != out {
+			t.Errorf("Decode(%s) [%s] = %s want %s", f[0], syntax, out, asm)
+		}
+	}
+}
+
+func TestDecodeGNUSyntax(t *testing.T) {
+	testDecode(t, "gnu")
+}
+
+func TestDecodeGoSyntax(t *testing.T) {
+	testDecode(t, "plan9")
+}