[foozzie] Support multi-architecture builds

tools/foozzie/v8_foozzie.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.
 
 """
 V8 correctness fuzzer launcher script.
 """
 
 import argparse
@@ skipping 74 matching lines @@
 FUZZ_TEST_RE = re.compile(r'.*fuzz(-\d+\.js)')
 SOURCE_RE = re.compile(r'print\("v8-foozzie source: (.*)"\);')
 
 # The number of hex digits used from the hash of the original source file path.
 # Keep the number small to avoid duplicate explosion.
 ORIGINAL_SOURCE_HASH_LENGTH = 3
 
 # Placeholder string if no original source file could be determined.
 ORIGINAL_SOURCE_DEFAULT = 'none'
 
+
+def infer_arch(d8):
+  """Infer the V8 architecture from the build configuration next to the
+  executable.
+  """
+  with open(os.path.join(os.path.dirname(d8), 'v8_build_config.json')) as f:
+    arch = json.load(f)['v8_current_cpu']
+  return 'ia32' if arch == 'x86' else arch
+
+
 def parse_args():
   parser = argparse.ArgumentParser()
   parser.add_argument(
     '--random-seed', type=int, required=True,
     help='random seed passed to both runs')
   parser.add_argument(
-      '--first-arch', help='first architecture', default='x64')
-  parser.add_argument(
-      '--second-arch', help='second architecture', default='x64')
-  parser.add_argument(
       '--first-config', help='first configuration', default='fullcode')
   parser.add_argument(
       '--second-config', help='second configuration', default='fullcode')
   parser.add_argument(
       '--first-d8', default='d8',
       help='optional path to first d8 executable, '
            'default: bundled in the same directory as this script')
   parser.add_argument(
       '--second-d8',
       help='optional path to second d8 executable, default: same as first')
   parser.add_argument('testcase', help='path to test case')
   options = parser.parse_args()
 
-  # Ensure we make a sane comparison.
-  assert (options.first_arch != options.second_arch or
-          options.first_config != options.second_config) , (
-      'Need either arch or config difference.')
-  assert options.first_arch in SUPPORTED_ARCHS
-  assert options.second_arch in SUPPORTED_ARCHS
-  assert options.first_config in CONFIGS
-  assert options.second_config in CONFIGS
-
   # Ensure we have a test case.
   assert (os.path.exists(options.testcase) and
           os.path.isfile(options.testcase)), (
       'Test case %s doesn\'t exist' % options.testcase)
 
   # Use first d8 as default for second d8.
   options.second_d8 = options.second_d8 or options.first_d8
 
   # Ensure absolute paths.
   if not os.path.isabs(options.first_d8):
     options.first_d8 = os.path.join(BASE_PATH, options.first_d8)
   if not os.path.isabs(options.second_d8):
     options.second_d8 = os.path.join(BASE_PATH, options.second_d8)
 
   # Ensure executables exist.
   assert os.path.exists(options.first_d8)
   assert os.path.exists(options.second_d8)
 
-  # Ensure we use different executables when we claim we compare
-  # different architectures.
-  # TODO(machenbach): Infer arch from gn's build output.
-  if options.first_arch != options.second_arch:
-    assert options.first_d8 != options.second_d8
+  # Infer architecture from build artifacts.
+  options.first_arch = infer_arch(options.first_d8)
+  options.second_arch = infer_arch(options.second_d8)
+
+  # Ensure we make a sane comparison.
+  assert (options.first_arch != options.second_arch or
+          options.first_config != options.second_config), (
+      'Need either arch or config difference.')
+  assert options.first_arch in SUPPORTED_ARCHS
+  assert options.second_arch in SUPPORTED_ARCHS
+  assert options.first_config in CONFIGS
+  assert options.second_config in CONFIGS
 
   return options
 
 
 def get_meta_data(content):
   """Extracts original-source-file paths from test case content."""
   sources = []
   for line in content.splitlines():
     match = SOURCE_RE.match(line)
     if match:
@@ skipping 131 matching lines @@
         configs='', source_key='', suppression='wrong_usage')
     result = RETURN_FAIL
   except Exception as e:
     print FAILURE_HEADER_TEMPLATE % dict(
         configs='', source_key='', suppression='internal_error')
     print '# Internal error: %s' % e
     traceback.print_exc(file=sys.stdout)
     result = RETURN_FAIL
 
   sys.exit(result)