test: add support for code generation tests (asmcheck)

The top-level test harness is modified to support a new kind
of test: "asmcheck". This is meant to replace asm_test.go
as an easier and more readable way to test code generation.

I've added a couple of codegen tests to get initial feedback
on the syntax. I've created them under a common "codegen"
subdirectory, so that it's easier to run them all with
"go run run.go -v codegen".

The asmcheck syntax allows to insert line comments that
can specify a regular expression to match in the assembly code,
for multiple architectures (the testsuite will automatically
build each testfile multiple times, one per mentioned architecture).

Negative matches are unsupported for now, so this cannot fully
replace asm_test yet.

Change-Id: Ifdbba389f01d55e63e73c99e5f5449e642101d55
Reviewed-on: https://go-review.googlesource.com/97355
Run-TryBot: Giovanni Bajo <rasky@develer.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Keith Randall <khr@golang.org>
Reviewed-by: Alberto Donizetti <alb.donizetti@gmail.com>

test/codegen/bits.go

+// asmcheck
+
+package codegen
+
+func bitcheck(a, b uint64) int {
+	if a&(1<<(b&63)) != 0 { // amd64:"BTQ"
+		return 1
+	}
+	return -1
+}

test/codegen/rotate.go

+// asmcheck
+
+package codegen
+
+import "math"
+
+func rot32(x uint32) uint32 {
+	var a uint32
+	a += x<<7 | x>>25 // amd64:"ROLL.*[$]7"  arm:"MOVW.*@>25"
+	a += x<<8 + x>>24 // amd64:`ROLL.*\$8`   arm:"MOVW.*@>24"
+	a += x<<9 ^ x>>23 // amd64:"ROLL.*\\$9"  arm:"MOVW.*@>23"
+	return a
+}
+
+func rot64(x uint64) uint64 {
+	var a uint64
+	a += x<<7 | x>>57 // amd64:"ROL"
+	a += x<<8 + x>>56 // amd64:"ROL"
+	a += x<<9 ^ x>>55 // amd64:"ROL"
+	return a
+}
+
+func copysign(a, b float64) float64 {
+	return math.Copysign(a, b)
+}

test/run.go

@@ -488,7 +488,7 @@ func (t *test) run() {
 		action = "rundir"
 	case "cmpout":
 		action = "run" // the run case already looks for <dir>/<test>.out files
-	case "compile", "compiledir", "build", "builddir", "run", "buildrun", "runoutput", "rundir":
+	case "compile", "compiledir", "build", "builddir", "run", "buildrun", "runoutput", "rundir", "asmcheck":
 		// nothing to do
 	case "errorcheckandrundir":
 		wantError = false // should be no error if also will run
@@ -593,6 +593,27 @@ func (t *test) run() {
 	default:
 		t.err = fmt.Errorf("unimplemented action %q", action)
 
+	case "asmcheck":
+		ops, archs := t.wantedAsmOpcodes(long)
+		for _, arch := range archs {
+			os.Setenv("GOOS", "linux")
+			os.Setenv("GOARCH", arch)
+
+			cmdline := []string{"go", "build", "-gcflags", "-S"}
+			cmdline = append(cmdline, flags...)
+			cmdline = append(cmdline, long)
+			out, err := runcmd(cmdline...)
+			if err != nil {
+				t.err = err
+				return
+			}
+			t.err = t.asmCheck(string(out), long, arch, ops[arch])
+			if t.err != nil {
+				return
+			}
+		}
+		return
+
 	case "errorcheck":
 		// TODO(gri) remove need for -C (disable printing of columns in error messages)
 		cmdline := []string{"go", "tool", "compile", "-C", "-e", "-o", "a.o"}
@@ -1226,6 +1247,109 @@ func (t *test) wantedErrors(file, short string) (errs []wantedError) {
 	return
 }
 
+var (
+	rxAsmCheck = regexp.MustCompile(`//(?:\s+(\w+):((?:"(?:.+?)")|(?:` + "`" + `(?:.+?)` + "`" + `)))+`)
+)
+
+type wantedAsmOpcode struct {
+	line     int
+	opcode   *regexp.Regexp
+	negative bool
+	found    bool
+}
+
+func (t *test) wantedAsmOpcodes(fn string) (map[string]map[string][]wantedAsmOpcode, []string) {
+	ops := make(map[string]map[string][]wantedAsmOpcode)
+	archs := make(map[string]bool)
+
+	src, _ := ioutil.ReadFile(fn)
+	for i, line := range strings.Split(string(src), "\n") {
+		matches := rxAsmCheck.FindStringSubmatch(line)
+		if len(matches) == 0 {
+			continue
+		}
+
+		lnum := fn + ":" + strconv.Itoa(i+1)
+		for j := 1; j < len(matches); j += 2 {
+			rxsrc, err := strconv.Unquote(matches[j+1])
+			if err != nil {
+				log.Fatalf("%s:%d: error unquoting string: %v", t.goFileName(), i+1, err)
+			}
+			oprx, err := regexp.Compile(rxsrc)
+			if err != nil {
+				log.Fatalf("%s:%d: %v", t.goFileName(), i+1, err)
+			}
+			arch := matches[j]
+			if ops[arch] == nil {
+				ops[arch] = make(map[string][]wantedAsmOpcode)
+			}
+			archs[arch] = true
+			ops[arch][lnum] = append(ops[arch][lnum], wantedAsmOpcode{
+				line:   i + 1,
+				opcode: oprx,
+			})
+		}
+	}
+
+	var sarchs []string
+	for a := range archs {
+		sarchs = append(sarchs, a)
+	}
+	sort.Strings(sarchs)
+
+	return ops, sarchs
+}
+
+func (t *test) asmCheck(outStr string, fn string, arch string, fullops map[string][]wantedAsmOpcode) (err error) {
+	defer func() {
+		if *verbose && err != nil {
+			log.Printf("%s gc output:\n%s", t, outStr)
+		}
+	}()
+
+	rxLine := regexp.MustCompile(fmt.Sprintf(`\((%s:\d+)\)\s+(.*)`, regexp.QuoteMeta(fn)))
+
+	for _, line := range strings.Split(outStr, "\n") {
+		matches := rxLine.FindStringSubmatch(line)
+		if len(matches) == 0 {
+			continue
+		}
+
+		ops := fullops[matches[1]]
+		asm := matches[2]
+		for i := range ops {
+			if !ops[i].found && ops[i].opcode.FindString(asm) != "" {
+				ops[i].found = true
+			}
+		}
+	}
+
+	var notfound []wantedAsmOpcode
+	for _, ops := range fullops {
+		for _, o := range ops {
+			if !o.found {
+				notfound = append(notfound, o)
+			}
+		}
+	}
+	if len(notfound) == 0 {
+		return
+	}
+
+	// At least one asmcheck failed; report them
+	sort.Slice(notfound, func(i, j int) bool {
+		return notfound[i].line < notfound[j].line
+	})
+
+	var errbuf bytes.Buffer
+	fmt.Fprintln(&errbuf)
+	for _, o := range notfound {
+		fmt.Fprintf(&errbuf, "%s:%d: %s: no match for opcode: %q\n", t.goFileName(), o.line, arch, o.opcode.String())
+	}
+	err = errors.New(errbuf.String())
+	return
+}
+
 // defaultRunOutputLimit returns the number of runoutput tests that
 // can be executed in parallel.
 func defaultRunOutputLimit() int {