Port SkBlurImage opts to SkOpts.

src/opts/SkBlurImage_opts.h

Index: src/opts/SkBlurImage_opts.h
diff --git a/src/opts/SkBlurImage_opts.h b/src/opts/SkBlurImage_opts.h
index 68352c5518edc2bdc30aebcab7672e861399790a..ee71204c61292fd337feebaa9b8d6416a68a00b4 100644
--- a/src/opts/SkBlurImage_opts.h
+++ b/src/opts/SkBlurImage_opts.h
@@ -1,5 +1,5 @@
 /*
- * Copyright 2013 The Android Open Source Project
+ * Copyright 2015 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
@@ -9,11 +9,231 @@
 #define SkBlurImage_opts_DEFINED
 
 #include "SkColorPriv.h"
+#include "SkTypes.h"
 
-typedef void (*SkBoxBlurProc)(const SkPMColor* src, int srcStride, SkPMColor* dst, int kernelSize,
-                              int leftOffset, int rightOffset, int width, int height);
+namespace SK_OPTS_NS {
+
+enum Direction { kX, kY };
+
+#if SK_CPU_SSE_LEVEL >= SK_CPU_SSE_LEVEL_SSE2
+template<Direction srcDirection, Direction dstDirection>
+void box_blur(const SkPMColor* src, int srcStride, SkPMColor* dst, int kernelSize,
+              int leftOffset, int rightOffset, int width, int height) {
+#if SK_CPU_SSE_LEVEL >= SK_CPU_SSE_LEVEL_SSE41
+    // ARGB -> 000A 000R 000G 000B
+    auto expand = [](int p) {
+        return _mm_cvtepu8_epi32(_mm_cvtsi32_si128(p));
+    };
+    // Axxx Rxxx Gxxx Bxxx -> ARGB
+    auto repack = [](__m128i p) {
+        const char _ = ~0;  // Don't care what ends up in these bytes.  This zeros them.
+        p = _mm_shuffle_epi8(p, _mm_set_epi8(_,_,_,_, _,_,_,_, _,_,_,_, 15,11,7,3));
+        return _mm_cvtsi128_si32(p);
+    };
+
+#else
+    // ARGB -> 000A 000R 000G 000B
+    auto expand = [](int p) {
+        auto result = _mm_cvtsi32_si128(p);
+        result = _mm_unpacklo_epi8(result, _mm_setzero_si128());
+        result = _mm_unpacklo_epi16(result, _mm_setzero_si128());
+        return result;
+    };
+    // Axxx Rxxx Gxxx Bxxx -> ARGB
+    auto repack = [](__m128i p) {
+        p = _mm_srli_epi32(p, 24);  // 000A 000R 000G 000B
+        p = _mm_packs_epi32(p, p);  // xxxx xxxx 0A0R 0G0B
+        p = _mm_packus_epi16(p, p); // xxxx xxxx xxxx ARGB
+        return _mm_cvtsi128_si32(p);
+    };
+
+    // _mm_mullo_epi32 is not available, so use the standard trick to emulate it.
+    auto _mm_mullo_epi32 = [](__m128i a, __m128i b) {
+        __m128i p02 = _mm_mul_epu32(a, b),
+                p13 = _mm_mul_epu32(_mm_srli_si128(a, 4),
+                                    _mm_srli_si128(b, 4));
+        return _mm_unpacklo_epi32(_mm_shuffle_epi32(p02, _MM_SHUFFLE(0,0,2,0)),
+                                  _mm_shuffle_epi32(p13, _MM_SHUFFLE(0,0,2,0)));
+    };
+#endif
+    const int rightBorder = SkMin32(rightOffset + 1, width);
+    const int srcStrideX = srcDirection == kX ? 1 : srcStride;
+    const int dstStrideX = dstDirection == kX ? 1 : height;
+    const int srcStrideY = srcDirection == kX ? srcStride : 1;
+    const int dstStrideY = dstDirection == kX ? width : 1;
+    const __m128i scale = _mm_set1_epi32((1 << 24) / kernelSize);
+    const __m128i half = _mm_set1_epi32(1 << 23);
+    for (int y = 0; y < height; ++y) {
+        __m128i sum = _mm_setzero_si128();
+        const SkPMColor* p = src;
+        for (int i = 0; i < rightBorder; ++i) {
+            sum = _mm_add_epi32(sum, expand(*p));
+            p += srcStrideX;
+        }
+
+        const SkPMColor* sptr = src;
+        SkColor* dptr = dst;
+        for (int x = 0; x < width; ++x) {
+            // TODO(mtklein): We are working in 8.24 here. Drop to 8.8 when the kernel is narrow?
+            // Multiply each component by scale (divide by kernel size) and add half to round.
+            auto result = _mm_mullo_epi32(sum, scale);
+            result = _mm_add_epi32(result, half);
+
+            // Now pack the top byte of each 32-bit lane back down into one 32-bit color.
+            // Axxx Rxxx Gxxx Bxxx -> xxxx xxxx xxxx ARGB
+            *dptr = repack(result);
+
+            // TODO(mtklein): experiment with breaking this loop into 3 parts
+            if (x >= leftOffset) {
+                SkColor l = *(sptr - leftOffset * srcStrideX);
+                sum = _mm_sub_epi32(sum, expand(l));
+            }
+            if (x + rightOffset + 1 < width) {
+                SkColor r = *(sptr + (rightOffset + 1) * srcStrideX);
+                sum = _mm_add_epi32(sum, expand(r));
+            }
+            sptr += srcStrideX;
+            if (srcDirection == kY) {
+                // TODO(mtklein): experiment with moving this prefetch forward
+                _mm_prefetch(reinterpret_cast<const char*>(sptr + (rightOffset + 1) * srcStrideX),
+                             _MM_HINT_T0);
+            }
+            dptr += dstStrideX;
+        }
+        src += srcStrideY;
+        dst += dstStrideY;
+    }
+}
+
+#elif defined(SK_ARM_HAS_NEON)
+
+// Fast path for kernel sizes between 2 and 127, working on two rows at a time.
+template<Direction srcDirection, Direction dstDirection>
+void box_blur_double(const SkPMColor** src, int srcStride, SkPMColor** dst, int kernelSize,
+                     int leftOffset, int rightOffset, int width, int* height) {
+    // Load 2 pixels from adjacent rows.
+    auto load_2_pixels = [&](const SkPMColor* s) {
+        if (srcDirection == kX) {
+            // 10% faster by adding these 2 prefetches
+            SK_PREFETCH(s + 16);
+            SK_PREFETCH(s + 16 + srcStride);
+            auto one = vld1_lane_u32(s +         0, vdup_n_u32(0), 0),
+                 two = vld1_lane_u32(s + srcStride,           one, 1);
+            return vreinterpret_u8_u32(two);
+        } else {
+            return vld1_u8((uint8_t*)s);
+        }
+    };
+    const int rightBorder = SkMin32(rightOffset + 1, width);
+    const int srcStrideX = srcDirection == kX ? 1 : srcStride;
+    const int dstStrideX = dstDirection == kX ? 1 : *height;
+    const int srcStrideY = srcDirection == kX ? srcStride : 1;
+    const int dstStrideY = dstDirection == kX ? width : 1;
+    const uint16x8_t scale = vdupq_n_u16((1 << 15) / kernelSize);
+
+    for (; *height >= 2; *height -= 2) {
+        uint16x8_t sum = vdupq_n_u16(0);
+        const SkPMColor* p = *src;
+        for (int i = 0; i < rightBorder; i++) {
+            sum = vaddw_u8(sum, load_2_pixels(p));
+            p += srcStrideX;
+        }
+
+        const SkPMColor* sptr = *src;
+        SkPMColor* dptr = *dst;
+        for (int x = 0; x < width; x++) {
+            // val = (sum * scale * 2 + 0x8000) >> 16
+            uint16x8_t resultPixels = vreinterpretq_u16_s16(vqrdmulhq_s16(
+                vreinterpretq_s16_u16(sum), vreinterpretq_s16_u16(scale)));
+            if (dstDirection == kX) {
+                uint32x2_t px2 = vreinterpret_u32_u8(vmovn_u16(resultPixels));
+                vst1_lane_u32(dptr +     0, px2, 0);
+                vst1_lane_u32(dptr + width, px2, 1);
+            } else {
+                vst1_u8((uint8_t*)dptr, vmovn_u16(resultPixels));
+            }
+
+            if (x >= leftOffset) {
+                sum = vsubw_u8(sum, load_2_pixels(sptr - leftOffset * srcStrideX));
+            }
+            if (x + rightOffset + 1 < width) {
+                sum = vaddw_u8(sum, load_2_pixels(sptr + (rightOffset + 1) * srcStrideX));
+            }
+            sptr += srcStrideX;
+            dptr += dstStrideX;
+        }
+        *src += srcStrideY * 2;
+        *dst += dstStrideY * 2;
+    }
+}
+
+template<Direction srcDirection, Direction dstDirection>
+void box_blur(const SkPMColor* src, int srcStride, SkPMColor* dst, int kernelSize,
+              int leftOffset, int rightOffset, int width, int height) {
+    // ARGB -> 0A0R 0G0B
+    auto expand = [](uint32_t p) {
+        return vget_low_u16(vmovl_u8(vreinterpret_u8_u32(vdup_n_u32(p))));
+    };
+    const int rightBorder = SkMin32(rightOffset + 1, width);
+    const int srcStrideX = srcDirection == kX ? 1 : srcStride;
+    const int dstStrideX = dstDirection == kX ? 1 : height;
+    const int srcStrideY = srcDirection == kX ? srcStride : 1;
+    const int dstStrideY = dstDirection == kX ? width : 1;
+    const uint32x4_t scale = vdupq_n_u32((1 << 24) / kernelSize);
+    const uint32x4_t half = vdupq_n_u32(1 << 23);
+
+    if (1 < kernelSize && kernelSize < 128) {
+        box_blur_double<srcDirection, dstDirection>(&src, srcStride, &dst, kernelSize,
+                                                    leftOffset, rightOffset, width, &height);
+    }
+
+    for (; height > 0; height--) {
+        uint32x4_t sum = vdupq_n_u32(0);
+        const SkPMColor* p = src;
+        for (int i = 0; i < rightBorder; ++i) {
+            sum = vaddw_u16(sum, expand(*p));
+            p += srcStrideX;
+        }
+
+        const SkPMColor* sptr = src;
+        SkPMColor* dptr = dst;
+        for (int x = 0; x < width; ++x) {
+            // ( half+sumA*scale half+sumR*scale half+sumG*scale half+sumB*scale )
+            uint32x4_t result = vmlaq_u32(half, sum, scale);
+
+            // Saturated conversion to 16-bit.
+            // ( AAAA RRRR GGGG BBBB ) -> ( 0A 0R 0G 0B )
+            uint16x4_t result16 = vqshrn_n_u32(result, 16);
+
+            // Saturated conversion to 8-bit.
+            // ( 0A 0R 0G 0B ) -> ( 0A 0R 0G 0B 0A 0R 0G 0B ) -> ( A R G B A R G B )
+            uint8x8_t result8 = vqshrn_n_u16(vcombine_u16(result16, result16), 8);
+
+            // ( A R G B A R G B ) -> ( ARGB ARGB ) -> ( ARGB )
+            // Store low 32 bits to destination.
+            vst1_lane_u32(dptr, vreinterpret_u32_u8(result8), 0);
+
+            if (x >= leftOffset) {
+                const SkPMColor* l = sptr - leftOffset * srcStrideX;
+                sum = vsubw_u16(sum, expand(*l));
+            }
+            if (x + rightOffset + 1 < width) {
+                const SkPMColor* r = sptr + (rightOffset + 1) * srcStrideX;
+                sum = vaddw_u16(sum, expand(*r));
+            }
+            sptr += srcStrideX;
+            if (srcDirection == kX) {
+                SK_PREFETCH(sptr + (rightOffset + 16) * srcStrideX);
+            }
+            dptr += dstStrideX;
+        }
+        src += srcStrideY;
+        dst += dstStrideY;
+    }
+}
+
+#endif
+
+}  // namespace SK_OPTS_NS
 
-bool SkBoxBlurGetPlatformProcs(SkBoxBlurProc* boxBlurX,
-                               SkBoxBlurProc* boxBlurXY,
-                               SkBoxBlurProc* boxBlurYX);
 #endif