Make gcmole execute in parallel.

tools/gcmole/parallel.py

Index: tools/gcmole/parallel.py
diff --git a/tools/gcmole/parallel.py b/tools/gcmole/parallel.py
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index 0000000000000000000000000000000000000000..0c045f423cb702583fd9387f2dcc723ba25c690a
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+++ b/tools/gcmole/parallel.py
@@ -0,0 +1,44 @@
+#!/usr/bin/env python
+# Copyright 2015 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 script calls the first argument for each of the following arguments in
+parallel. E.g.
+parallel.py "clang --opt" file1 file2
+calls
+clang --opt file1
+clang --opt file2
+
+The output (stdout and stderr) is concatenated sequentially in the form:
+______________ file1
+<output of clang --opt file1>
+______________ finish <exit code of clang --opt file1> ______________
+______________ file2
+<output of clang --opt file2>
+______________ finish <exit code of clang --opt file2> ______________
+"""
+
+import itertools
+import multiprocessing
+import subprocess
+import sys
+
+def invoke(cmdline):
+  try:
+    return (subprocess.check_output(
+        cmdline, shell=True, stderr=subprocess.STDOUT), 0)
+  except subprocess.CalledProcessError as e:
+    return (e.output, e.returncode)
+
+if __name__ == '__main__':
+  assert len(sys.argv) > 2
+  processes = multiprocessing.cpu_count()
+  pool = multiprocessing.Pool(processes=processes)
+  cmdlines = ["%s %s" % (sys.argv[1], filename) for filename in sys.argv[2:]]
+  for filename, result in itertools.izip(
+      sys.argv[2:], pool.imap(invoke, cmdlines)):
+    print "______________ %s" % filename
+    print result[0]
+    print "______________ finish %d ______________" % result[1]