// i.e., all hashes.  This will print all the FMAs; this test is only interested in one of them (that should appear near the end).
	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)
	}

// needed to reproduce the failure.
//
// The go command also checks the GOCOMPILEDEBUG environment variable for flags
// to pass to the compiler, so the above command is equivalent to:
//
//	bisect GOCOMPILEDEBUG=loopvarhash=PATTERN go test
//
// Finally, as mentioned earlier, the -compile flag allows shortening this command further:
//

		// for debugging the compiler, they are not settable using 'go env -w',
		// and so here we use os.Getenv, not cfg.Getenv.
		magic := []string{
			"GOCLOBBERDEADHASH",
			"GOSSAFUNC",
			"GOSSADIR",
			"GOCOMPILEDEBUG",
		}
		for _, env := range magic {
			if x := os.Getenv(env); x != "" {
				fmt.Fprintf(h, "magic %s=%s\n", env, x)
			}
		}

	case "gccgo":