SSE4 opaque blend using intrinsics instead of assembly.

gyp/opts.gyp

 # Gyp file for opts projects
 {
   'targets': [
     # Due to an unfortunate intersection of lameness between gcc and gyp,
     # we have to build the *_SSE2.cpp files in a separate target.  The
     # gcc lameness is that, in order to compile SSE2 intrinsics code, it
     # must be passed the -msse2 flag.  However, with this flag, it may
     # emit SSE2 instructions even for scalar code, such as the CPUID
     # test used to test for the presence of SSE2.  So that, and all other
     # code must be compiled *without* -msse2.  The gyp lameness is that it
@@ skipping 189 matching lines @@
             '-mssse3',
           ],
         }],
       ],
     },
     # For the same lame reasons as what is done for skia_opts, we also have to
     # create another target specifically for SSE4 code as we would not want
     # to compile the SSE2 code with -msse4 which would potentially allow
     # gcc to generate SSE4 code.
     {
       'target_name': 'opts_sse4',

[Nico, 2015/01/26 22:23:02]

You probably need something like https://codereview.chromium.org/475273002 for
this target, else clang-cl will likely be unhappy about this.

       'product_name': 'skia_opts_sse4',
       'type': 'static_library',
       'standalone_static_library': 1,
       'dependencies': [
         'core.gyp:*',
         'effects.gyp:*'
       ],
       'include_dirs': [
         '../src/core',
         '../src/utils',
       ],
       'sources': [
+        '../src/opts/SkBlitRow_opts_SSE4.cpp',
         '../src/opts/SkBlurImage_opts_SSE4.cpp',
       ],
       'conditions': [
-        [ 'skia_arch_width == 64', {
-          'sources': [
-            '../src/opts/SkBlitRow_opts_SSE4_x64_asm.S',
-          ],
-        }],
-        [ 'skia_arch_width == 32', {
-          'sources': [
-            '../src/opts/SkBlitRow_opts_SSE4_asm.S',
-          ],
-        }],
         [ 'skia_os == "win"', {
             'defines' : [ 'SK_CPU_SSE_LEVEL=41' ],
         }],
         [ 'skia_os in ["linux", "freebsd", "openbsd", "solaris", "nacl", "chromeos", "android"] \
            and not skia_android_framework', {
           'cflags': [
             '-msse4.1',
           ],
         }],
         [ 'skia_os == "mac"', {
@@ skipping 53 matching lines @@
         '../src/opts/SkBlitMask_opts_arm_neon.cpp',
         '../src/opts/SkBlitRow_opts_arm_neon.cpp',
         '../src/opts/SkBlurImage_opts_neon.cpp',
         '../src/opts/SkMorphology_opts_neon.cpp',
         '../src/opts/SkTextureCompression_opts_neon.cpp',
         '../src/opts/SkXfermode_opts_arm_neon.cpp',
       ],
     },
   ],
 }