[foozzie] Migrate configuration choice to V8

Before, configurations were chosen on clusterfuzz side. This migrates
the choice to the V8 repo, to enable easier changing it and to allow
sharing it between different fuzzers.

NOTRY=true
TBR=sergiyb@chromium.org

Bug: chromium:813833
Change-Id: I9890a36fd6aab171d3e13172fc55b274f189e532
Reviewed-on: https://chromium-review.googlesource.com/927681Reviewed-by: Michael Achenbach <machenbach@chromium.org>
Commit-Queue: Michael Achenbach <machenbach@chromium.org>
Cr-Commit-Position: refs/heads/master@{#51410}

tools/foozzie/BUILD.gn

@@ -9,6 +9,7 @@ if (v8_correctness_fuzzer) {
     sources = [
       "v8_commands.py",
       "v8_foozzie.py",
+      "v8_fuzz_config.py",
       "v8_mock.js",
       "v8_mock_archs.js",
       "v8_suppressions.js",

tools/foozzie/PRESUBMIT.py

+# Copyright 2018 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.
+
+def CheckChangeOnCommit(input_api, output_api):
+  tests = input_api.canned_checks.GetUnitTestsInDirectory(
+      input_api, output_api, '.', whitelist=['v8_foozzie_test.py$'])
+  return input_api.RunTests(tests)

tools/foozzie/v8_foozzie_test.py

+#!/usr/bin/env python
 # Copyright 2016 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.
@@ -8,12 +9,43 @@ import sys
 import unittest
 
 import v8_foozzie
+import v8_fuzz_config
 import v8_suppressions
 
 BASE_DIR = os.path.dirname(os.path.abspath(__file__))
 FOOZZIE = os.path.join(BASE_DIR, 'v8_foozzie.py')
 TEST_DATA = os.path.join(BASE_DIR, 'testdata')
 
+
+class ConfigTest(unittest.TestCase):
+  def testExperiments(self):
+    """Test that probabilities add up to 100 and that all config names exist.
+    """
+    EXPERIMENTS = v8_fuzz_config.FOOZZIE_EXPERIMENTS
+    CONFIGS = v8_foozzie.CONFIGS
+    assert sum(x[0] for x in EXPERIMENTS) == 100
+    assert all(map(lambda x: x[1] in CONFIGS, EXPERIMENTS))
+    assert all(map(lambda x: x[2] in CONFIGS, EXPERIMENTS))
+    assert all(map(lambda x: x[3].endswith('d8'), EXPERIMENTS))
+
+  def testConfig(self):
+    """Smoke test how to choose experiments.
+
+    When experiment distribution changes this test might change, too.
+    """
+    class Rng(object):
+      def random(self):
+        return 0.5
+    self.assertEqual(
+        [
+          '--first-config=ignition',
+          '--second-config=ignition_turbo',
+          '--second-d8=d8',
+        ],
+        v8_fuzz_config.Config('foo', Rng()).choose_foozzie_flags(),
+    )
+
+
 class UnitTest(unittest.TestCase):
   def testDiff(self):
     # TODO(machenbach): Mock out suppression configuration.
@@ -109,3 +141,7 @@ class SystemTest(unittest.TestCase):
     e = ctx.exception
     self.assertEquals(v8_foozzie.RETURN_FAIL, e.returncode)
     self.assertEquals(expected_output, cut_verbose_output(e.output))
+
+
+if __name__ == '__main__':
+  unittest.main()

tools/foozzie/v8_fuzz_config.py

+# Copyright 2018 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.
+
+import random
+
+# List of configuration experiments for correctness fuzzing.
+# List of <probability>, <1st config name>, <2nd config name>, <2nd d8>.
+# Probabilities must add up to 100.
+FOOZZIE_EXPERIMENTS = [
+  [5, 'ignition', 'ignition_asm', 'd8'],
+  [5, 'ignition', 'trusted', 'd8'],
+  [5, 'ignition', 'trusted_opt', 'd8'],
+  [10, 'ignition', 'slow_path', 'd8'],
+  [5, 'ignition', 'slow_path_opt', 'd8'],
+  [25, 'ignition', 'ignition_turbo', 'd8'],
+  [20, 'ignition', 'ignition_turbo_opt', 'd8'],
+  [5, 'ignition_turbo_opt', 'ignition_turbo_opt', 'clang_x86/d8'],
+  [5, 'ignition_turbo', 'ignition_turbo', 'clang_x86/d8'],
+  [5, 'ignition', 'ignition', 'clang_x86/d8'],
+  [5, 'ignition', 'ignition', 'clang_x64_v8_arm64/d8'],
+  [5, 'ignition', 'ignition', 'clang_x86_v8_arm/d8'],
+]
+
+class Config(object):
+  def __init__(self, name, rng=None):
+    self.name = name
+    self.rng = rng or random.Random()
+
+  def choose_foozzie_flags(self):
+    """Randomly chooses a configuration from FOOZZIE_EXPERIMENTS.
+
+    Returns: List of flags to pass to v8_foozzie.py fuzz harness.
+    """
+    acc = 0
+    threshold = self.rng.random() * 100
+    for prob, first_config, second_config, second_d8 in FOOZZIE_EXPERIMENTS:
+      acc += prob
+      if acc > threshold:
+        return [
+          '--first-config=' + first_config,
+          '--second-config=' + second_config,
+          '--second-d8=' + second_d8,
+        ]
+    assert False