gn: various gyp flag matching for 'base'

- Don't remove -fno-ident from gyp build (was added about 3y ago, seemingly unnecessary for current clang)
- Add -fno-slp-vectorize to GN to make builds match (both to be removed after next clang roll)
- Make usage of -Wno-reserved-user-defined-literal match (required for dbus pre-trusty)
- Add -march=x86-64 to gn cflags
- Default symbol_level based on is_debug, and turn it off by default in Release (same as gyp)

Also, fiddle with output of gyp_flag_compare.py.

R=brettw@chromium.org
BUG=335824

Review URL: https://codereview.chromium.org/562383002

Cr-Commit-Position: refs/heads/master@{#294489}

build/common.gypi

@@ -3654,9 +3654,6 @@
                 ],
               }],
               ['clang==1', {
-                'cflags!': [
-                  '-fno-ident',
-                ],
                 # TODO(thakis): Remove once http://llvm.org/PR20354 is fixed
                 # and the fix is in chromium.
                 'cflags': [ '-fno-slp-vectorize', ],

build/config/BUILDCONFIG.gn

@@ -22,7 +22,8 @@ declare_args() {
   #   2 means regular build with symbols.
   #   1 means minimal symbols, usually enough for backtraces only.
   #   0 means no symbols.
-  symbol_level = 2
+  #   -1 means auto-set (off in release, regular in debug).
+  symbol_level = -1
 
   # Component build.
   is_component_build = false
@@ -354,6 +355,17 @@ if (is_debug) {
 }
 _native_compiler_configs += [ _default_optimization_config ]
 
+# If it wasn't manually set, set to an appropriate default.
+if (symbol_level == -1) {
+  # Linux is slowed by having symbols as part of the target binary, whereas
+  # Mac and Windows have them separate, so in Release Linux, default them off.
+  if (is_debug || !is_linux) {
+    symbol_level = 2
+  } else {
+    symbol_level = 0
+  }
+}
+
 # Symbol setup.
 if (symbol_level == 2) {
   _default_symbols_config = "//build/config/compiler:symbols"

build/config/compiler/BUILD.gn

@@ -103,6 +103,14 @@ config("compiler") {
     }
   }
 
+  if (is_clang) {
+    cflags += [
+      # TODO(thakis): Remove once http://llvm.org/PR20354 is fixed
+      # and the fix is in chromium.
+      "-fno-slp-vectorize",
+    ]
+  }
+
   if (is_clang && !is_win) {
     # This is here so that all files get recompiled after a clang roll and
     # when turning clang on or off. (defines are passed via the command line,
@@ -150,7 +158,7 @@ config("compiler") {
     # CPU architecture. We may or may not be doing a cross compile now, so for
     # simplicity we always explicitly set the architecture.
     if (cpu_arch == "x64") {
-      cflags += [ "-m64" ]
+      cflags += [ "-m64", "-march=x86-64", ]
       ldflags += [ "-m64" ]
     } else if (cpu_arch == "x86") {
       cflags += [ "-m32" ]
@@ -704,14 +712,11 @@ config("default_warnings") {
         # which we no longer use. Check if it makes sense to remove
         # this as well. http://crbug.com/316352
         "-Wno-unneeded-internal-declaration",
-      ]
 
-      if (!is_mac && !is_ios) {
-        cflags_cc += [
+        # TODO(thakis): Remove, http://crbug.com/263960
         "-Wno-reserved-user-defined-literal",
       ]
     }
-    }
     if (gcc_version >= 48) {
       cflags_cc += [
         # See comment for -Wno-c++11-narrowing.

tools/gn/bin/gyp_flag_compare.py

@@ -13,6 +13,13 @@ import subprocess
 import sys
 
 
+# Must be in src/.
+os.chdir(os.path.join(os.path.dirname(__file__), '..', '..', '..'))
+
+
+g_total_differences = 0
+
+
 def FindAndRemoveArgWithValue(command_line, argname):
   """Given a command line as a list, remove and return the value of an option
   that takes a value as a separate entry.
@@ -42,6 +49,25 @@ def MergeSpacedArgs(command_line, argname):
   return result
 
 
+def NormalizeSymbolArguments(command_line):
+  """Normalize -g arguments.
+
+  If there's no -g args, it's equivalent to -g0. -g2 is equivalent to -g.
+  Modifies |command_line| in place.
+  """
+  # Strip -g0 if there's no symbols.
+  have_some_symbols = False
+  for x in command_line:
+    if x.startswith('-g') and x != '-g0':
+      have_some_symbols = True
+  if not have_some_symbols and '-g0' in command_line:
+    command_line.remove('-g0')
+
+  # Rename -g2 to -g.
+  if '-g2' in command_line:
+    command_line[index('-g2')] = '-g'
+
+
 def GetFlags(lines):
   """Turn a list of command lines into a semi-structured dict."""
   flags_by_output = {}
@@ -56,6 +82,8 @@ def GetFlags(lines):
     output_name = FindAndRemoveArgWithValue(command_line, '-o')
     dep_name = FindAndRemoveArgWithValue(command_line, '-MF')
 
+    NormalizeSymbolArguments(command_line)
+
     command_line = MergeSpacedArgs(command_line, '-Xclang')
 
     defines = [x for x in command_line if x.startswith('-D')]
@@ -74,6 +102,21 @@ def GetFlags(lines):
                                          x not in dash_f and \
                                          x not in warnings and \
                                          x not in cc_file]
+
+    # Filter for libFindBadConstructs.so having a relative path in one and
+    # absolute path in the other.
+    others_filtered = []
+    for x in others:
+      if x.startswith('-Xclang ') and x.endswith('libFindBadConstructs.so'):
+        others_filtered.append(
+            '-Xclang ' +
+            os.path.join(os.getcwd(),
+                         os.path.normpath(
+                             os.path.join('out/gn_flags', x.split(' ', 1)[1]))))
+      else:
+        others_filtered.append(x)
+    others = others_filtered
+
     flags_by_output[cc_file[0]] = {
       'output': output_name,
       'depname': dep_name,
@@ -89,25 +132,29 @@ def GetFlags(lines):
 def CompareLists(gyp, gn, name, dont_care_gyp=None, dont_care_gn=None):
   """Return a report of any differences between gyp and gn lists, ignoring
   anything in |dont_care_{gyp|gn}| respectively."""
+  global g_total_differences
   if not dont_care_gyp:
     dont_care_gyp = []
   if not dont_care_gn:
     dont_care_gn = []
   output = ''
   if gyp[name] != gn[name]:
-    output += '  %s differ:\n' % name
     gyp_set = set(gyp[name])
     gn_set = set(gn[name])
     missing_in_gyp = gyp_set - gn_set
     missing_in_gn = gn_set - gyp_set
     missing_in_gyp -= set(dont_care_gyp)
     missing_in_gn -= set(dont_care_gn)
+    if missing_in_gyp or missing_in_gn:
+      output += '  %s differ:\n' % name
     if missing_in_gyp:
       output += '    In gyp, but not in GN:\n      %s' % '\n      '.join(
           sorted(missing_in_gyp)) + '\n'
+      g_total_differences += len(missing_in_gyp)
     if missing_in_gn:
       output += '    In GN, but not in gyp:\n      %s' % '\n      '.join(
           sorted(missing_in_gn)) + '\n\n'
+      g_total_differences += len(missing_in_gn)
   return output
 
 
@@ -166,6 +213,7 @@ def main():
     print '\n'.join(sorted(files))
     print diff
 
+  print 'Total differences:', g_total_differences
   return 1 if files_with_given_differences or different_source_list else 0