Rewriting MatrixConvolution image filter with SSE and AVX2

src/opts/SkMatrixConvolutionImageFilter_opts_AVX2.cpp

+/*
+ * Copyright 2016 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#include "SkColor.h"
+#include "SkBitmap.h"
+#include "SkPoint.h"
+#include "SkColorPriv.h"
+
+#include <immintrin.h>
+
+
+namespace sk_avx2 {
+
+void SkMatrixConvolutionImageFilter_filterPixels_AVX2(
+                 const SkBitmap& src,
+                 SkBitmap* result,
+                 const SkIRect& r,
+                 const SkIRect& bounds,
+                 bool convolveAlpha,
+                 SkScalar* kernel,
+                 const SkISize& kernelSize,
+                 const SkIPoint&  kernelOffset,
+                 SkScalar gain,
+                 SkScalar bias)
+{
+    SkIRect rect(r);
+    if (!rect.intersect(bounds)) {
+        return;
+    }
+
+    __m256i mask = _mm256_set_epi8(128,128,128,3, 128,128,128,2, 128,128,128,1, 128,128,128,0,
+                                   128,128,128,3, 128,128,128,2, 128,128,128,1, 128,128,128,0);
+    __m256i mask_odd = _mm256_set_epi8(128,128,128,128, 128,128,128,128, 128,128,128,128, 128,128,128,128,
+                                       128,128,128,3, 128,128,128,2, 128,128,128,1, 128,128,128,0);
+    int width_even = 2*(kernelSize.fWidth/2);
+
+    for (int y = rect.fTop; y < rect.fBottom; ++y) {
+        SkPMColor* dptr = result->getAddr32(rect.fLeft - bounds.fLeft, y - bounds.fTop);
+        for (int x = rect.fLeft; x < rect.fRight; ++x) {
+            __m256 psum = _mm256_setzero_ps();
+            for (int cy = 0; cy < kernelSize.fHeight; cy++) {
+                int cx;
+                for (cx = 0; cx < width_even ; cx+=2) {
+                    SkPMColor s1 = *src.getAddr32(
+                        x + cx - kernelOffset.fX,
+                        y + cy - kernelOffset.fY);
+                    SkPMColor s2 = *src.getAddr32(
+                        x + cx - kernelOffset.fX + 1,
+                        y + cy - kernelOffset.fY);
+                    __m256i ps = _mm256_set_epi32(0, 0, 0, s2, 0, 0, 0, s1);
+                    __m256i ps_sh = _mm256_shuffle_epi8(ps, mask);
+                    __m256 pss = _mm256_cvtepi32_ps(ps_sh);
+
+                    SkScalar k1 = kernel[cy * kernelSize.fWidth + cx];
+                    SkScalar k2 = kernel[cy * kernelSize.fWidth + cx + 1];
+                    __m256 pk = _mm256_set_ps(k2,k2,k2,k2, k1,k1,k1,k1);
+
+                    __m256 pmul = _mm256_mul_ps(pss, pk);
+
+                    psum = _mm256_add_ps(psum, pmul);
+                }
+                if (cx < kernelSize.fWidth) {
+                    SkPMColor s1 = *src.getAddr32(
+                        x + cx - kernelOffset.fX,
+                        y + cy - kernelOffset.fY);
+
+                    __m256i ps = _mm256_set_epi32(0, 0, 0, 0, 0, 0, 0, s1);
+                    __m256i ps_sh = _mm256_shuffle_epi8(ps, mask_odd);
+
+                    SkScalar k = kernel[cy * kernelSize.fWidth + cx];
+                    __m256 pk = _mm256_set1_ps(k);
+
+                    __m256 pss = _mm256_cvtepi32_ps(ps_sh);
+                    __m256 pmul = _mm256_mul_ps(pss, pk);
+
+                    psum = _mm256_add_ps(psum, pmul);
+                }
+            }
+
+            union {
+                __m256 m256;
+                float f[8];
+            } conv = {psum};
+
+            SkScalar sumA, sumR, sumG, sumB;
+
+            sumA = conv.f[3] + conv.f[7];
+            sumR = conv.f[2] + conv.f[6];
+            sumG = conv.f[1] + conv.f[5];
+            sumB = conv.f[0] + conv.f[4];
+
+            int a = convolveAlpha
+                ? SkClampMax(SkScalarFloorToInt(SkScalarMul(sumA, gain) + bias), 255)
+                : 255;
+            int r = SkClampMax(SkScalarFloorToInt(SkScalarMul(sumR, gain) + bias), a);
+            int g = SkClampMax(SkScalarFloorToInt(SkScalarMul(sumG, gain) + bias), a);
+            int b = SkClampMax(SkScalarFloorToInt(SkScalarMul(sumB, gain) + bias), a);
+            if (!convolveAlpha) {
+                a = SkGetPackedA32(*src.getAddr32(x, y));
+                *dptr++ = SkPreMultiplyARGB(a, r, g, b);
+            } else {
+                *dptr++ = SkPackARGB32(a, r, g, b);
+            }
+        }
+    }
+}
+
+}