Revert of Revert of SSE4 opaque blend using intrinsics instead of assembly.

src/opts/SkColor_opts_SSE2.h

 /*
  * Copyright 2014 The Android Open Source Project
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef SkColor_opts_SSE2_DEFINED
 #define SkColor_opts_SSE2_DEFINED
 
@@ skipping 188 matching lines @@
                                 SK_B32_SHIFT + (8 - SK_B16_BITS));
     b2 = _mm_and_si128(b2, _mm_set1_epi32(SK_B16_MASK));
     __m128i b = _mm_packs_epi32(b1, b2);
 
     // Store 8 16-bit colors in dst.
     __m128i d_pixel = SkPackRGB16_SSE2(r, g, b);
 
     return d_pixel;
 }
 
-// Portable version SkBlendARGB32 is in SkColorPriv.h.
+// Portable version is SkPMSrcOver in SkColorPriv.h.
+static inline __m128i SkPMSrcOver_SSE2(const __m128i& src, const __m128i& dst) {
+    return _mm_add_epi32(src,
+                         SkAlphaMulQ_SSE2(dst, _mm_sub_epi32(_mm_set1_epi32(256),
+                                                             SkGetPackedA32_SSE2(src))));
+}
+
+// Portable version is SkBlendARGB32 in SkColorPriv.h.
 static inline __m128i SkBlendARGB32_SSE2(const __m128i& src, const __m128i& dst,
                                          const __m128i& aa) {
     __m128i src_scale = SkAlpha255To256_SSE2(aa);
     // SkAlpha255To256(255 - SkAlphaMul(SkGetPackedA32(src), src_scale))
     __m128i dst_scale = SkGetPackedA32_SSE2(src);
     dst_scale = _mm_mullo_epi16(dst_scale, src_scale);
     dst_scale = _mm_srli_epi16(dst_scale, 8);
     dst_scale = _mm_sub_epi32(_mm_set1_epi32(256), dst_scale);
 
     __m128i result = SkAlphaMulQ_SSE2(src, src_scale);
@@ skipping 10 matching lines @@
     dst_scale = _mm_mullo_epi16(dst_scale, src_scale);
     dst_scale = _mm_srli_epi16(dst_scale, 8);
     dst_scale = _mm_sub_epi32(_mm_set1_epi32(256), dst_scale);
 
     __m128i result = SkAlphaMulQ_SSE2(src, alpha);
     return _mm_add_epi8(result, SkAlphaMulQ_SSE2(dst, dst_scale));
 }
 
 #undef ASSERT_EQ
 #endif // SkColor_opts_SSE2_DEFINED