[numfuzz] Add cpu-features extra flags to numfuzz

This combines flags switching off CPU-features randomly with all
other flags on the numfuzz fuzzers.

In a follow up we can add also other interesting flags for testing
more features.

Bug: chromium:1021463
No-Try: true
Change-Id: Ia27d1b8b82dff2bf497242b30ec0b6ef2dfd722d
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1905846
Commit-Queue: Michael Achenbach <machenbach@chromium.org>
Reviewed-by: Clemens Backes <clemensb@chromium.org>
Cr-Commit-Position: refs/heads/master@{#64858}

tools/testrunner/testproc/fuzzer.py

@@ -8,6 +8,29 @@ import time
 from . import base
 
 
+# Extra flags randomly added to all fuzz tests with numfuzz. List of tuples
+# (probability, flag).
+EXTRA_FLAGS = [
+  (0.1, '--no-enable-sse3'),
+  (0.1, '--no-enable-ssse3'),
+  (0.1, '--no-enable-sse4_1'),
+  (0.1, '--no-enable-sse4_2'),
+  (0.1, '--no-enable-sahf'),
+  (0.1, '--no-enable-avx'),
+  (0.1, '--no-enable-fma3'),
+  (0.1, '--no-enable-bmi1'),
+  (0.1, '--no-enable-bmi2'),
+  (0.1, '--no-enable-lzcnt'),
+  (0.1, '--no-enable-popcnt'),
+]
+
+def random_extra_flags(rng):
+  """Returns a random list of flags chosen from the configurations in
+  EXTRA_FLAGS.
+  """
+  return [flag for prob, flag in EXTRA_FLAGS if rng.random() < prob]
+
+
 class FuzzerConfig(object):
   def __init__(self, probability, analyzer, fuzzer):
     """
@@ -92,7 +115,6 @@ class FuzzerProc(base.TestProcProducer):
       return self._create_subtest(test, 'analysis', flags=analysis_flags,
                                   keep_output=True)
 
-
   def _result_for(self, test, subtest, result):
     if not self._disable_analysis:
       if result is not None:
@@ -110,7 +132,7 @@ class FuzzerProc(base.TestProcProducer):
     # analysis phase at all, so no fuzzer has it's own analyzer.
     gens = []
     indexes = []
-    for i, fuzzer_config in enumerate(self._fuzzer_configs):
+    for fuzzer_config in self._fuzzer_configs:
       analysis_value = None
       if analysis_result and fuzzer_config.analyzer:
         analysis_value = fuzzer_config.analyzer.do_analysis(analysis_result)
@@ -132,7 +154,7 @@ class FuzzerProc(base.TestProcProducer):
       main_index = self._rng.choice(indexes)
       _, main_gen = gens[main_index]
 
-      flags = next(main_gen)
+      flags = random_extra_flags(self._rng) + next(main_gen)
       for index, (p, gen) in enumerate(gens):
         if index == main_index:
           continue