Cleanup with SkAlphaMulQ_SSE2()

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 45 matching lines @@
     __m128i ag = _mm_srli_epi16(c, 8);
     ASSERT_EQ(ag, _mm_and_si128(mask, ag));  // ag = _mm_srli_epi16(c, 8) did this for us.
     ag = _mm_mullo_epi16(ag, s);
 
     // (rb & mask) | (ag & ~mask)
     ASSERT_EQ(rb, _mm_and_si128(mask, rb));  // rb = _mm_srli_epi16(rb, 8) did this for us.
     ag = _mm_andnot_si128(mask, ag);
     return _mm_or_si128(rb, ag);
 }
 
+// Fast path for colors scale the same factor.

[mtklein, 2014/11/24 16:48:23]

Maybe  // Fast path for SkAlphaMulQ_SSE2 with a constant scale factor.

[qiankun, 2014/11/25 05:33:52]

Done.

+static inline __m128i SkAlphaMulQ_SSE2(const __m128i& c, const unsigned scale) {
+    __m128i mask = _mm_set1_epi32(0xFF00FF);
+    __m128i s = _mm_set1_epi16(scale << 8); // Move scale factor to upper byte of word.
+
+    // With mulhi, red and blue values are already in the right place and
+    // don't need to be divided by 256.
+    __m128i rb = _mm_and_si128(mask, c);
+    rb = _mm_mulhi_epu16(rb, s);
+
+    __m128i ag = _mm_srli_epi16(c, 8);
+    ag = _mm_mulhi_epu16(ag, s); // Alpha and green values are in the lower byte of each word.
+    ag = _mm_slli_epi16(ag, 8);  // Shift alpha and green to higher byte of each word.
+
+    return _mm_or_si128(rb, ag);
+}
+
 static inline __m128i SkGetPackedA32_SSE2(const __m128i& src) {
     __m128i a = _mm_slli_epi32(src, (24 - SK_A32_SHIFT));
     return _mm_srli_epi32(a, 24);
 }
 
 static inline __m128i SkGetPackedR32_SSE2(const __m128i& src) {
     __m128i r = _mm_slli_epi32(src, (24 - SK_R32_SHIFT));
     return _mm_srli_epi32(r, 24);
 }
 
@@ skipping 104 matching lines @@
     __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;
 }
 
 #undef ASSERT_EQ
 #endif // SkColor_opts_SSE2_DEFINED