[foozzie] Mock out WebAssembly when comparing with jitless

No-Try: true
Bug: chromium:1048620
Change-Id: I399144a9d8075efe40125dfcbe1dbbd0aabe0fe9
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2036080Reviewed-by: Mathias Bynens <mathias@chromium.org>
Reviewed-by: Tamer Tas <tmrts@chromium.org>
Commit-Queue: Michael Achenbach <machenbach@chromium.org>
Cr-Commit-Position: refs/heads/master@{#66112}

tools/clusterfuzz/BUILD.gn

@@ -13,6 +13,7 @@ if (v8_correctness_fuzzer) {
       "v8_fuzz_config.py",
       "v8_mock.js",
       "v8_mock_archs.js",
+      "v8_mock_webassembly.js",
       "v8_sanity_checks.js",
       "v8_suppressions.js",
       "v8_suppressions.py",

tools/clusterfuzz/v8_commands.py

@@ -33,18 +33,22 @@ DEFAULT_FILES = [
   os.path.join(BASE_PATH, 'v8_suppressions.js'),
 ]
 
-# Architecture-specific mock file
+# Config-specific mock files.
 ARCH_MOCKS = os.path.join(BASE_PATH, 'v8_mock_archs.js')
+WEBASSEMBLY_MOCKS = os.path.join(BASE_PATH, 'v8_mock_webassembly.js')
 
 # Timeout in seconds for one d8 run.
 TIMEOUT = 3
 
 
 def _startup_files(options):
-  """Default files and optional architecture-specific mock file."""
+  """Default files and optional config-specific mock files."""
   files = DEFAULT_FILES[:]
   if options.first.arch != options.second.arch:
     files.append(ARCH_MOCKS)
+  # Mock out WebAssembly when comparing with jitless mode.
+  if '--jitless' in options.first.flags + options.second.flags:
+    files.append(WEBASSEMBLY_MOCKS)
   return files
 
 

tools/clusterfuzz/v8_foozzie_test.py

@@ -156,14 +156,17 @@ def cut_verbose_output(stdout):
   return '\n'.join(stdout.split('\n')[4:])
 
 
-def run_foozzie(second_d8_dir, *extra_flags):
+def run_foozzie(second_d8_dir, *extra_flags, **kwargs):
+  second_config = 'ignition_turbo'
+  if 'second_config' in kwargs:
+    second_config = 'jitless'
   return subprocess.check_output([
     sys.executable, FOOZZIE,
     '--random-seed', '12345',
     '--first-d8', os.path.join(TEST_DATA, 'baseline', 'd8.py'),
     '--second-d8', os.path.join(TEST_DATA, second_d8_dir, 'd8.py'),
     '--first-config', 'ignition',
-    '--second-config', 'ignition_turbo',
+    '--second-config', second_config,
     os.path.join(TEST_DATA, 'fuzz-123.js'),
   ] + list(extra_flags))
 
@@ -183,6 +186,9 @@ class SystemTest(unittest.TestCase):
   def testSyntaxErrorDiffPass(self):
     stdout = run_foozzie('build1', '--skip-sanity-checks')
     self.assertEquals('# V8 correctness - pass\n', cut_verbose_output(stdout))
+    # Default comparison doesn't include any specific mock files.
+    self.assertNotIn('v8_mock_archs.js', stdout)
+    self.assertNotIn('v8_mock_webassembly.js', stdout)
 
   def testDifferentOutputFail(self):
     with open(os.path.join(TEST_DATA, 'failure_output.txt')) as f:
@@ -217,6 +223,16 @@ class SystemTest(unittest.TestCase):
     self.assertIn('v8_mock_archs.js', lines[1])
     self.assertIn('v8_mock_archs.js', lines[3])
 
+  def testJitless(self):
+    """Test that webassembly is mocked out when comparing with jitless."""
+    stdout = run_foozzie(
+        'build1', '--skip-sanity-checks', second_config='jitless')
+    lines = stdout.split('\n')
+    # TODO(machenbach): Don't depend on the command-lines being printed in
+    # particular lines.
+    self.assertIn('v8_mock_webassembly.js', lines[1])
+    self.assertIn('v8_mock_webassembly.js', lines[3])
+
 
 if __name__ == '__main__':
   unittest.main()

tools/clusterfuzz/v8_mock_webassembly.js

+// Copyright 2020 the V8 project authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+// This mocks out the WebAssembly object with a permissive dummy.
+
+(function () {
+  const handler = {
+    get: function(x, prop) {
+      if (prop == Symbol.toPrimitive) {
+        return function() { return undefined; };
+      }
+      return dummy;
+    },
+  };
+  const dummy = new Proxy(function () { return dummy; }, handler);
+  WebAssembly = dummy;
+})();