Sk4x4f: Simplify x86 down to SSE2.

src/core/Sk4x4f.h

 /*
  * Copyright 2016 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef Sk4x4f_DEFINED
 #define Sk4x4f_DEFINED
 
 #include "SkNx.h"
 
 struct Sk4x4f {
     Sk4f r,g,b,a;
 
     static Sk4x4f Transpose(const Sk4f&, const Sk4f&, const Sk4f&, const Sk4f&);
     static Sk4x4f Transpose(const   float[16]);
     static Sk4x4f Transpose(const uint8_t[16]);
 
     void transpose(Sk4f*, Sk4f*, Sk4f*, Sk4f*) const;
     void transpose(  float[16]) const;
     void transpose(uint8_t[16]) const;
 };
 
-// TODO: SSE2, NEON
+// TODO: NEON
 
-#if 1 && !defined(SKNX_NO_SIMD) && SK_CPU_SSE_LEVEL >= SK_CPU_SSE_LEVEL_SSSE3
+#if 1 && !defined(SKNX_NO_SIMD) && SK_CPU_SSE_LEVEL >= SK_CPU_SSE_LEVEL_SSE2
 
 inline Sk4x4f Sk4x4f::Transpose(const Sk4f& x, const Sk4f& y, const Sk4f& z, const Sk4f& w) {
     auto r = x.fVec,
          g = y.fVec,
          b = z.fVec,
          a = w.fVec;
     _MM_TRANSPOSE4_PS(r,g,b,a);
     return { r,g,b,a };
 }
 
 inline Sk4x4f Sk4x4f::Transpose(const float fs[16]) {
     return Transpose(Sk4f::Load(fs+0), Sk4f::Load(fs+4), Sk4f::Load(fs+8), Sk4f::Load(fs+12));
 }
 
 inline Sk4x4f Sk4x4f::Transpose(const uint8_t bs[16]) {
     auto b16 = _mm_loadu_si128((const __m128i*)bs);
-    auto _ = ~0;  // Shuffles in a zero byte.
-    auto r = _mm_cvtepi32_ps(
-            _mm_shuffle_epi8(b16, _mm_setr_epi8(0,_,_,_,4,_,_,_, 8,_,_,_,12,_,_,_)));
-    auto g = _mm_cvtepi32_ps(
-            _mm_shuffle_epi8(b16, _mm_setr_epi8(1,_,_,_,5,_,_,_, 9,_,_,_,13,_,_,_)));
-    auto b = _mm_cvtepi32_ps(
-            _mm_shuffle_epi8(b16, _mm_setr_epi8(2,_,_,_,6,_,_,_,10,_,_,_,14,_,_,_)));
-    auto a = _mm_cvtepi32_ps(
-            _mm_shuffle_epi8(b16, _mm_setr_epi8(3,_,_,_,7,_,_,_,11,_,_,_,15,_,_,_)));
+
+    auto mask = _mm_set1_epi32(0xFF);
+    auto r = _mm_cvtepi32_ps(_mm_and_si128(mask,               (b16    ))),
+         g = _mm_cvtepi32_ps(_mm_and_si128(mask, _mm_srli_epi32(b16,  8))),
+         b = _mm_cvtepi32_ps(_mm_and_si128(mask, _mm_srli_epi32(b16, 16))),
+         a = _mm_cvtepi32_ps(                    _mm_srli_epi32(b16, 24));
     return { r,g,b,a };
 }
 
 inline void Sk4x4f::transpose(Sk4f* x, Sk4f* y, Sk4f* z, Sk4f* w) const {
     auto R = r.fVec,
          G = g.fVec,
          B = b.fVec,
          A = a.fVec;
     _MM_TRANSPOSE4_PS(R,G,B,A);
     *x = R;
     *y = G;
     *z = B;
     *w = A;
 }
 
 inline void Sk4x4f::transpose(float fs[16]) const {
     Sk4f x,y,z,w;
     this->transpose(&x,&y,&z,&w);
     x.store(fs+ 0);
     y.store(fs+ 4);
     z.store(fs+ 8);
     w.store(fs+12);
 }
 
 inline void Sk4x4f::transpose(uint8_t bs[16]) const {
-    auto packed = _mm_packus_epi16(_mm_packus_epi16(_mm_cvttps_epi32(r.fVec),
-                                                    _mm_cvttps_epi32(g.fVec)),
-                                   _mm_packus_epi16(_mm_cvttps_epi32(b.fVec),
-                                                    _mm_cvttps_epi32(a.fVec)));
-    _mm_storeu_si128((__m128i*)bs, _mm_shuffle_epi8(packed, _mm_setr_epi8(0, 4,  8, 12,
-                                                                          1, 5,  9, 13,
-                                                                          2, 6, 10, 14,
-                                                                          3, 7, 11, 15)));
+    auto R =                _mm_cvttps_epi32(r.fVec),
+         G = _mm_slli_epi32(_mm_cvttps_epi32(g.fVec),  8),
+         B = _mm_slli_epi32(_mm_cvttps_epi32(b.fVec), 16),
+         A = _mm_slli_epi32(_mm_cvttps_epi32(a.fVec), 24);
+    _mm_storeu_si128((__m128i*)bs, _mm_or_si128(A, _mm_or_si128(B, _mm_or_si128(G, R))));
 }
 
 #else
 
 inline Sk4x4f Sk4x4f::Transpose(const Sk4f& x, const Sk4f& y, const Sk4f& z, const Sk4f& w) {
     return {
         { x[0], y[0], z[0], w[0] },
         { x[1], y[1], z[1], w[1] },
         { x[2], y[2], z[2], w[2] },
         { x[3], y[3], z[3], w[3] },
@@ skipping 32 matching lines @@
 inline void Sk4x4f::transpose(uint8_t bs[16]) const {
     bs[ 0] = (uint8_t)r[0]; bs[ 1] = (uint8_t)g[0]; bs[ 2] = (uint8_t)b[0]; bs[ 3] = (uint8_t)a[0];
     bs[ 4] = (uint8_t)r[1]; bs[ 5] = (uint8_t)g[1]; bs[ 6] = (uint8_t)b[1]; bs[ 7] = (uint8_t)a[1];
     bs[ 8] = (uint8_t)r[2]; bs[ 9] = (uint8_t)g[2]; bs[10] = (uint8_t)b[2]; bs[11] = (uint8_t)a[2];
     bs[12] = (uint8_t)r[3]; bs[13] = (uint8_t)g[3]; bs[14] = (uint8_t)b[3]; bs[15] = (uint8_t)a[3];
 }
 
 #endif
 
 #endif//Sk4x4f_DEFINED