case trace.EventTaskEnd:
		return "task end"
	case trace.EventLog:
		log := ev.Log()
		if log.Category != "" {
			return fmt.Sprintf("log %q", log.Message)
		}
		return fmt.Sprintf("log (category: %s): %q", log.Category, log.Message)
	}
	return ""
}

func primaryGoroutine(ev *trace.Event) trace.GoID {
	if ev.Kind() != trace.EventStateTransition {

	t.Helper()

	if debugtrace {
		if indir != "" {
			t.Logf("in dir %s: ", indir)
		}
		t.Logf("cmd: %s %+v\n", testenv.GoToolPath(t), bargs)
	}
	cmd := testenv.Command(t, testenv.GoToolPath(t), bargs...)
	cmd.Dir = indir
	b, err := cmd.CombinedOutput()
	if len(b) != 0 {
		t.Logf("## build output:\n%s", b)
	}
	if err != nil {
		t.Fatalf("build error: %v", err)
	}
}

	cmd.Env = append(cmd.Env, "GOCOMPILEDEBUG=fmahash=1/0", "GOOS=linux", "GOARCH=arm64", "HOME="+tmpdir)
	t.Logf("%v", cmd)
	t.Logf("%v", cmd.Env)
	b, e := cmd.CombinedOutput()
	if e != nil {
		t.Errorf("build failed: %v\n%s", e, b)
	}
	s := string(b) // Looking for "GOFMAHASH triggered main.main:24"

	args = append(args, flags...)
	args = append(args, srcfname)
	cmd := testenv.Command(t, testenv.GoToolPath(t), args...)
	// "Bad line" bug #36683 is sensitive to being run in the source directory.
	cmd.Dir = "testdata"
	t.Logf("Running %v", cmd.Args)
	out, err := cmd.CombinedOutput()
	if err != nil {
		t.Fatalf("go build %s: %v\n%s", srcfname, err, out)
	}
	need := []string{
		"TEXT main.main(SB)",
	}

	if printCode {

						// test failure.
						t.Logf("test %s: %q section not in readonly segment",
							wsro.Name, test.name)
						t.Logf("section %s location: st=0x%x en=0x%x\n",
							wsro.Name, wsro.Addr, wsro.Addr+wsro.FileSize)
						t.Logf("sec %s found in these segments: ", wsro.Name)
						for _, p := range foundSegs {
							t.Logf(" %q", p.Type)
						}
						t.Logf("\nall segments: \n")

		for k, p := range passes {
			if p.name == a {
				i = k
			}
			if p.name == b {
				j = k
			}
		}
		if i < 0 {
			log.Panicf("pass %s not found", a)
		}
		if j < 0 {
			log.Panicf("pass %s not found", b)
		}
		if i >= j {
			log.Panicf("passes %s and %s out of order", a, b)
		}
	}

	if !*flagCheck {
		t.Skip("-check not specified")
	}
	root := testenv.GOROOT(t)
	rootFS := os.DirFS(root)
	files, err := fs.Glob(rootFS, "api/next/*.txt")
	if err != nil {
		t.Fatal(err)
	}
	t.Logf("checking release notes for %d files in api/next", len(files))
	docFS := os.DirFS(filepath.Join(root, "doc", "next"))
	// Check that each api/next file has a corresponding release note fragment.
	for _, apiFile := range files {

		cmd = "go list -mod=mod all"
	default:
		t.Fatalf(`unknown value for -testsum %q; may be "tidy", "listm", or "listall"`, *testSum)
	}

	log := new(strings.Builder)
	err := e.Execute(s, "updateSum", bufio.NewReader(strings.NewReader(cmd)), log)
	if log.Len() > 0 {
		t.Logf("%s", log)
	}
	if err != nil {
		t.Fatal(err)
	}

	newGomodData, err := os.ReadFile(s.Path("go.mod"))
	if err != nil {

	}
	diff := diff.Diff(readmePath, old, "readmeTmpl", buf.Bytes())
	if diff == nil {
		t.Logf("%s is up to date.", readmePath)
		return
	}

	if *fixReadme {
		if err := os.WriteFile(readmePath, buf.Bytes(), 0666); err != nil {
			t.Fatal(err)
		}
		t.Logf("wrote %d bytes to %s", buf.Len(), readmePath)
	} else {
		t.Logf("\n%s", diff)
		t.Errorf("%s is stale. To update, run 'go generate cmd/go'.", readmePath)
	}
}

func startProfile() {
	if *cpuprofile != "" {
		f, err := os.Create(*cpuprofile)
		if err != nil {
			log.Fatalf("%v", err)
		}
		if err := pprof.StartCPUProfile(f); err != nil {
			log.Fatalf("%v", err)
		}
		AtExit(func() {
			pprof.StopCPUProfile()
			if err = f.Close(); err != nil {
				log.Fatalf("error closing cpu profile: %v", err)
			}
		})
	}
	if *memprofile != "" {