Add a gyp flag for disabling sse2. This makes it easier for

build/common.gypi

 # Copyright (c) 2010 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 # IMPORTANT:
 # Please don't directly include this file if you are building via gyp_chromium,
 # since gyp_chromium is automatically forcing its inclusion.
 {
   'variables': {
     # .gyp files or targets should set chromium_code to 1 if they build
@@ skipping 88 matching lines @@
       'python_ver%': '2.5',
 
       # Set ARM-v7 compilation flags
       'armv7%': 0,
 
       # Set Neon compilation flags (only meaningful if armv7==1).
       'arm_neon%': 1,
 
       # The system root for cross-compiles. Default: none.
       'sysroot%': '',
+
+      # On Linux, we build with sse2 for Chromium builds.
+      'disable_sse2%': 0,
     },
 
     # Define branding and buildtype on the basis of their settings within the
     # variables sub-dict above, unless overridden.
     'branding%': '<(branding)',
     'buildtype%': '<(buildtype)',
     'target_arch%': '<(target_arch)',
     'host_arch%': '<(host_arch)',
     'toolkit_views%': '<(toolkit_views)',
     'chromeos%': '<(chromeos)',
     'inside_chromium_build%': '<(inside_chromium_build)',
     'fastbuild%': '<(fastbuild)',
     'linux_fpic%': '<(linux_fpic)',
     'python_ver%': '<(python_ver)',
     'armv7%': '<(armv7)',
     'arm_neon%': '<(arm_neon)',
     'sysroot%': '<(sysroot)',
+    'disable_sse2%': '<(disable_sse2)',
 
     # The release channel that this build targets. This is used to restrict
     # channel-specific build options, like which installer packages to create.
     # The default is 'all', which does no channel-specific filtering.
     'channel%': 'all',
 
     # Override chromium_mac_pch and set it to 0 to suppress the use of
     # precompiled headers on the Mac.  Prefix header injection may still be
     # used, but prefix headers will not be precompiled.  This is useful when
     # using distcc to distribute a build to compile slaves that don't
@@ skipping 773 matching lines @@
             # performance penalty.
             #
             # -mfpmath=sse -msse2 makes the compiler use SSE instructions
             # which keep floating-point values in SSE registers in its
             # native precision (32-bit for single precision, and 64-bit for
             # double precision values). This means the floating-point value
             # used during computation does not change depending on how the
             # compiler optimized the code, since the value is always kept
             # in its specified precision.
             'conditions': [
-              ['branding=="Chromium"', {
+              ['branding=="Chromium" and disable_sse2==0', {
                 'cflags': [
                   '-march=pentium4',

[agl, 2010/04/27 14:07:08]

This knocks out rather more than just SSE2, but whatever.

                   '-msse2',
                   '-mfpmath=sse',
                 ],
               }],
               # ChromeOS targets Pinetrail, which is ssse3, but most of the
               # benefit comes from sse2 so this setting allows ChromeOS
               # to build on other CPUs.  In the future -march=atom would help
               # but requires a newer compiler.
-              ['chromeos==1', {
+              ['chromeos==1 and disable_sse2==0', {
                 'cflags': [
                   '-msse2',
                 ],
               }],
             ],
             # -mmmx allows mmintrin.h to be used for mmx intrinsics.
             # video playback is mmx and sse2 optimized.
             'cflags': [
               '-m32',
               '-mmmx',
@@ skipping 364 matching lines @@
     # and therefore SYMROOT, needs to be set at the project level.
     'SYMROOT': '<(DEPTH)/xcodebuild',
   },
 }
 
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