[foozzie] Filter some contradictory flags

Add logic to drop cyclic contradictory flags from
correctness-fuzzing command lines. Add the currently known
biggest offenders.

Without this, the correctness fuzzing harness runs into a CHECK
failure during smoke testing, when attempting to pass cyclic flags
to d8. It fails fast, but uselessly burns fuzzing time.

This change drops one of the known cyclic flags instead to make the
test run still useful. The precedence is right to left like in the
V8 test framework.

Additionally on Clusterfuzz, all crashes during smoke testing are
deduped as one crash report. We don't know if there are other
problems before this one is fixed/hidden.

No-Try: true
Bug: chromium:1330303
Change-Id: I06cbb4655cd3cf467f5cce6f84dba653834ca72e
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3865562
Reviewed-by: Clemens Backes <clemensb@chromium.org>
Commit-Queue: Michael Achenbach <machenbach@chromium.org>
Reviewed-by: Alexander Schulze <alexschulze@chromium.org>
Cr-Commit-Position: refs/heads/main@{#82939}

tools/clusterfuzz/foozzie/PRESUBMIT.py

@@ -12,7 +12,8 @@ USE_PYTHON3 = True
 def _RunTests(input_api, output_api):
   return input_api.RunTests(
       input_api.canned_checks.GetUnitTestsInDirectory(
-          input_api, output_api, '.', files_to_check=[r'.+_test\.py$']))
+          input_api, output_api, '.', files_to_check=[r'.+_test\.py$'],
+          run_on_python2=False))
 
 
 def _CommonChecks(input_api, output_api):

tools/clusterfuzz/foozzie/v8_foozzie.py

@@ -179,9 +179,33 @@ DISALLOWED_FLAGS = [
   '--multi-mapped-mock-allocator',
 ]
 
+# List pairs of flags that lead to contradictory cycles, i.e.:
+# A -> no-C and B -> C makes (A, B) contradictory.
+# No need to list other contradictions, they are omitted by the
+# --fuzzing flag).
+CONTRADICTORY_FLAGS = [
+  ('--always-turbofan', '--jitless'),
+]
+
 
 def filter_flags(flags):
-  return [flag for flag in flags if flag not in DISALLOWED_FLAGS]
+  """Drop disallowed and contradictory flags.
+
+  The precedence for contradictions is right to left, similar to the V8 test
+  framework.
+  """
+  result = []
+  flags_to_drop = set(DISALLOWED_FLAGS)
+  for flag in reversed(flags):
+    if flag in flags_to_drop:
+      continue
+    result.append(flag)
+    for contradicting_pair in CONTRADICTORY_FLAGS:
+      if contradicting_pair[0] == flag:
+        flags_to_drop.add(contradicting_pair[1])
+      if contradicting_pair[1] == flag:
+        flags_to_drop.add(contradicting_pair[0])
+  return list(reversed(result))
 
 
 def infer_arch(d8):
@@ -233,7 +257,7 @@ class ExecutionArgumentsConfig(object):
       d8 = os.path.join(BASE_PATH, d8)
     assert os.path.exists(d8)
 
-    flags = CONFIGS[config] + filter_flags(get('config_extra_flags'))
+    flags = filter_flags(CONFIGS[config] + get('config_extra_flags'))
 
     RunOptions = namedtuple('RunOptions', ['arch', 'config', 'd8', 'flags'])
     return RunOptions(infer_arch(d8), config, d8, flags)

tools/clusterfuzz/foozzie/v8_foozzie_test.py

@@ -8,6 +8,7 @@ import random
 import subprocess
 import sys
 import unittest
+import unittest.mock
 
 import v8_commands
 import v8_foozzie
@@ -233,6 +234,24 @@ other weird stuff
     check('12', '345', True, True, '12', '34')
     check('123', '45', True, True, '12', '45')
 
+  @unittest.mock.patch('v8_foozzie.DISALLOWED_FLAGS', ['A'])
+  @unittest.mock.patch('v8_foozzie.CONTRADICTORY_FLAGS',
+                       [('B', 'C'), ('B', 'D')])
+  def testFilterFlags(self):
+    def check(input_flags, expected):
+      self.assertEqual(expected, v8_foozzie.filter_flags(input_flags))
+
+    check([], [])
+    check(['A'], [])
+    check(['D', 'A'], ['D'])
+    check(['A', 'D'], ['D'])
+    check(['C', 'D'], ['C', 'D'])
+    check(['E', 'C', 'D', 'F'], ['E', 'C', 'D', 'F'])
+    check(['B', 'D'], ['D'])
+    check(['D', 'B'], ['B'])
+    check(['C', 'B', 'D'], ['C', 'D'])
+    check(['E', 'C', 'A', 'F', 'B', 'G', 'D'], ['E', 'C', 'F', 'G', 'D'])
+
 
 def cut_verbose_output(stdout, n_comp):
   # This removes the first lines containing d8 commands of `n_comp` comparison