anchor.diff:        } else if (r == 4) {
           prefix += '-DEPOPTEVERY';
           extraFlags += ['--deoptimize_every=100'];
  -      } else if (r == 5) {
  +      } else if (r == 5 && !ffi) {
  +        // TODO: https://github.com/dart-lang/sdk/issues/37606
           prefix += '-STACKTRACEEVERY';
           extraFlags += ['--stacktrace_every=100'];
         } else if (r == 6) {
  
positive.code:     rand = new Random();
      tmpDir = Directory.systemTemp.createTempSync('dart_fuzz');
      fileName = '${tmpDir.path}/fuzz.dart';
      runner1 =
          TestRunner.getTestRunner(mode1, top, tmpDir.path, env, fileName, rand);
      runner2 =
          TestRunner.getTestRunner(mode2, top, tmpDir.path, env, fileName, rand);
      fp = samePrecision(mode1, mode2);
      ffi = ffiCapable(mode1, mode2);
      isolate =
          'Isolate (${tmpDir.path}) ${ffi ? "" : "NO-"}FFI ${fp ? "" : "NO-"}FP : '
          '${runner1.description} - ${runner2.description}';
  
negative.code:   String description;
  
    // Factory.
    static TestRunner getTestRunner(String mode, bool ffi, String top, String tmp,
        Map<String, String> env, String fileName, Random rand) {
      String prefix = mode.substring(0, 3).toUpperCase();
      String tag = getTag(mode);
  