tools: Add a script to generate arch-specific ctags

It would be better to generate ctags file for specified architecture so
this CL adds a script gen-tags.py to generate architecture specific
ctags.

  Usage:
      $ tools/dev/gen-tags.py [<arch>...]

  The example usage for 'x64' is as follows:
      $ tools/dev/gen-tags.py x64

  If no <arch> is given, it generates tags file for all arches:
      $ tools/dev/gen-tags.py

R=yangguo@chromium.org,jochen@chromium.org,jkummerow@chromium.org,clemensh@chromium.org

NOTRY=true

Review-Url: https://codereview.chromium.org/2762903002
Cr-Commit-Position: refs/heads/master@{#44032}

tools/dev/gen-tags.py

+#!/usr/bin/env python
+# Copyright 2017 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.
+"""\
+Convenience script for generating arch-specific ctags file.
+This script MUST be executed at the top directory.
+
+Usage:
+    $ tools/dev/gen-tags.py [<arch>...]
+
+The example usage is as follows:
+    $ tools/dev/gen-tags.py x64
+
+If no <arch> is given, it generates tags file for all arches:
+    $ tools/dev/gen-tags.py
+"""
+import os
+import subprocess
+import sys
+
+# All arches that this script understands.
+ARCHES = ["ia32", "x64", "arm", "arm64", "mips", "mips64", "ppc", "s390", "x87"]
+
+def PrintHelpAndExit():
+  print(__doc__)
+  sys.exit(0)
+
+
+def _Call(cmd, silent=False):
+  if not silent: print("# %s" % cmd)
+  return subprocess.call(cmd, shell=True)
+
+
+def ParseArguments(argv):
+  if not "tools/dev" in argv[0]:
+    PrintHelpAndExit()
+  argv = argv[1:]
+
+  # If no argument is given, then generate ctags for all arches.
+  if len(argv) == 0:
+    return ARCHES
+
+  user_arches = []
+  for argstring in argv:
+    if argstring in ("-h", "--help", "help"):
+      PrintHelpAndExit()
+    if argstring not in ARCHES:
+      print("Invalid argument: %s" % argstring)
+      sys.exit(1)
+    user_arches.append(argstring)
+
+  return user_arches
+
+
+def Exclude(fullpath, exclude_arches):
+  for arch in exclude_arches:
+    if ("/%s/" % arch) in fullpath: return True
+  return False
+
+
+def Main(argv):
+  user_arches = []
+
+  user_arches = ParseArguments(argv)
+
+  exclude_arches = list(ARCHES)
+  for user_arch in user_arches:
+    exclude_arches.remove(user_arch)
+
+  paths = ["include", "src", "test"]
+  exts = [".h", ".cc", ".c"]
+
+  gtags_filename = "gtags.files"
+
+  with open(gtags_filename, "w") as gtags:
+    for path in paths:
+      for root, dirs, files in os.walk(path):
+        for file in files:
+          if not file.endswith(tuple(exts)): continue
+          fullpath = os.path.join(root, file)
+          if Exclude(fullpath, exclude_arches): continue
+          gtags.write(fullpath + os.linesep)
+
+  _Call("ctags --fields=+l -L " + gtags_filename)
+
+
+if __name__ == "__main__":
+  sys.exit(Main(sys.argv))