Add '-d' flag to dump-static-initializers.py

tools/linux/dump-static-initializers.py

Index: tools/linux/dump-static-initializers.py
diff --git a/tools/linux/dump-static-initializers.py b/tools/linux/dump-static-initializers.py
index 14fe46994a89a4aa3d017e174ccbce290a1484b9..412c77f1320e31940fa62a0dda1d925a4bc22217 100755
--- a/tools/linux/dump-static-initializers.py
+++ b/tools/linux/dump-static-initializers.py
@@ -96,14 +96,18 @@ def QualifyFilename(filename, symbol):
 #   0000000001919920 0000000000000008 b _ZN12_GLOBAL__N_119g_nine_box_prelightE
 nm_re = re.compile(r'(\S+) (\S+) t _GLOBAL__I_(.*)')
 def ParseNm(binary):
-  """Given a binary, yield static initializers as (start, size, file) pairs."""
+  """Given a binary, yield static initializers as (file, start, size) tuples."""

[Tyler Breisacher (Chromium), 2012/01/26 22:36:33]

I switched the order so that it would always be sorted by filename. The start is
likely to change from one build to the next, but the filename is not.

 
   nm = subprocess.Popen(['nm', '-S', binary], stdout=subprocess.PIPE)
+  files = []

[Lei Zhang, 2012/01/27 19:18:38]

This defeats the purpose of having the yield().

[Tyler Breisacher (Chromium), 2012/01/30 23:28:16]

Done. Also at line 135 in patchset 4.

   for line in nm.stdout:
     match = nm_re.match(line)
     if match:
       addr, size, filename = match.groups()
-      yield int(addr, 16), int(size, 16), filename
+      files.append((filename, int(addr, 16), int(size, 16)))
+
+  for f in sorted(files):

[Evan Martin, 2012/01/27 19:52:09]

I'd weakly prefer for this function to remain unsorted and have the caller sort
if it needs it.  That would allow you to keep the yield as well.

[Tyler Breisacher (Chromium), 2012/01/30 23:28:16]

Done.

+    yield f
 
 
 # Regex matching objdump output for the symbols we're interested in.
@@ -132,54 +136,76 @@ def ExtractSymbolReferences(binary, start, end):
         # Probably a relative jump within this function.
         continue
       refs.add(ref)
-      continue
 
   for ref in sorted(refs):
     yield ref
 
-
 def main():
-  parser = optparse.OptionParser(usage='%prog filename')
-  parser.add_option('-i', '--instances', dest='calculate_instances',
+  parser = optparse.OptionParser(usage='%prog [option] filename')
+  parser.add_option('-f', '--files', dest='count_files',
+                    action='store_true', default=False,
+                    help='Print out the number of files containing static '
+                         'initializers')
+  parser.add_option('-i', '--instances', dest='count_initializers',
+                    action='store_true', default=False,
+                    help='Print out the number of static initializers')
+  parser.add_option('-d', '--diffable', dest='diffable',
                     action='store_true', default=False,
-                    help='Only print out the number of static initializers')
+                    help='Prints the filename on each line, for more easily '
+                         'diff-able output.')
   opts, args = parser.parse_args()
   if len(args) != 1:
     parser.error('missing filename argument')
     return 1
   binary = args[0]
 
-  demangler = Demangler()
-  static_initializers_count = 0
-  for addr, size, filename in ParseNm(binary):
-    if size == 2:

[Tyler Breisacher (Chromium), 2012/01/26 22:36:33]

I discussed this with fischman@ and he said that we *do* want to count these
little two-byte ctors, because they still get called at runtime, even though
they don't do anything. If I'm understanding
http://neugierig.org/software/chromium/notes/2011/08/static-initializers.html
correctly, what's important is reducing the *number* of SIs, not just getting
rid of the biggest ones.

[Lei Zhang, 2012/01/27 19:18:38]

From the comment, it sounds like many of these are accidentally generated in the
current version of gcc and there's nothing we can do to fix them. Counting them
won't do us any good.

[Tyler Breisacher (Chromium), 2012/01/27 19:44:19]

But we can make sure they're not called at load time. On the other hand, if
we're going to switch to GCC 4.6+ at some point, then maybe it doesn't matter.

[Evan Martin, 2012/01/27 19:52:09]

Yes, that is my belief.  Removing them will make the code needlessly cluttered
and it's really a compiler bug.

-      # gcc generates a two-byte 'repz retq' initializer when there is nothing
-      # to do.  jyasskin tells me this is fixed in gcc 4.6.
-      # Two bytes is too small to do anything, so just ignore it.
-      continue
+  if opts.count_files and opts.count_initializers:
+    parser.error('-f and -i are mutually exclusive')
+    return 1
+
+  if opts.diffable and (opts.count_initializers or opts.count_files):
+    parser.error('-d cannot be used with -f or -i')
+    return 1
 
-    if (opts.calculate_instances):
-      static_initializers_count += 1
+  demangler = Demangler()
+  file_count = 0
+  initializer_count = 0
+  for filename, addr, size in ParseNm(binary):
+    if opts.count_files:
+      file_count += 1

[Lei Zhang, 2012/01/27 19:18:38]

Isn't this going to count a given file multiple times?

[Tyler Breisacher (Chromium), 2012/01/27 19:44:19]

I don't think so, because of the |continue| after it.

       continue
 
-    ref_output = ''
+    ref_output = []
     qualified_filename = QualifyFilenameAsProto(filename)
     for ref in ExtractSymbolReferences(binary, addr, addr+size):
+      if opts.count_initializers:
+        initializer_count += 1
+        continue
+
       ref = demangler.Demangle(ref)
       if qualified_filename == filename:
         qualified_filename = QualifyFilename(filename, ref)
       if ref in NOTES:
-        ref_output = ref_output + '  %s [%s]\n' % (ref, NOTES[ref])
+        ref_output.append('  %s [%s]' % (ref, NOTES[ref]))
       else:
-        ref_output = ref_output + '  ' + ref + '\n'
-    print '%s (initializer offset 0x%x size 0x%x)' % (qualified_filename,
-                                                      addr, size)
-    print ref_output
+        ref_output.append('  ' + ref)
 
-  if opts.calculate_instances:
-    print static_initializers_count
-  return 0
+    if opts.count_initializers:
+      continue
+
+    if opts.diffable:
+      print '\n'.join(qualified_filename + r for r in ref_output)
+    else:
+      print '%s (initializer offset 0x%x size 0x%x)' % (qualified_filename,
+                                                        addr, size)
+      print '\n'.join(ref_output) + '\n'
 
+  if opts.count_files:
+    print file_count
+
+  if opts.count_initializers:
+    print initializer_count
+  return 0
 
 if '__main__' == __name__:
   sys.exit(main())