src/opts/SkBlurImageFilter_opts.h - skia.git - Git at Google

 /*
  * Copyright 2015 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */

 #ifndef SkBlurImageFilter_opts_DEFINED
 #define SkBlurImageFilter_opts_DEFINED

 #include "SkColorPriv.h"
 #include "SkTypes.h"

 namespace SK_OPTS_NS {

 enum class BlurDirection { kX, kY };

 #if SK_CPU_SSE_LEVEL >= SK_CPU_SSE_LEVEL_SSE2
 template<BlurDirection srcDirection, BlurDirection 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 == BlurDirection::kX ? 1 : srcStride;
     const int dstStrideX = dstDirection == BlurDirection::kX ? 1 : height;
     const int srcStrideY = srcDirection == BlurDirection::kX ? srcStride : 1;
     const int dstStrideY = dstDirection == BlurDirection::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 == BlurDirection::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<BlurDirection srcDirection, BlurDirection 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 == BlurDirection::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 == BlurDirection::kX ? 1 : srcStride;
     const int dstStrideX = dstDirection == BlurDirection::kX ? 1 : *height;
     const int srcStrideY = srcDirection == BlurDirection::kX ? srcStride : 1;
     const int dstStrideY = dstDirection == BlurDirection::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 == BlurDirection::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<BlurDirection srcDirection, BlurDirection 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 == BlurDirection::kX ? 1 : srcStride;
     const int dstStrideX = dstDirection == BlurDirection::kX ? 1 : height;
     const int srcStrideY = srcDirection == BlurDirection::kX ? srcStride : 1;
     const int dstStrideY = dstDirection == BlurDirection::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 == BlurDirection::kX) {
                 SK_PREFETCH(sptr + (rightOffset + 16) * srcStrideX);
             }
             dptr += dstStrideX;
         }
         src += srcStrideY;
         dst += dstStrideY;
     }
 }

 #else  // Neither NEON nor >=SSE2.

 template<BlurDirection srcDirection, BlurDirection dstDirection>
 static void box_blur(const SkPMColor* src, int srcStride, SkPMColor* dst, int kernelSize,
                      int leftOffset, int rightOffset, int width, int height) {
     int rightBorder = SkMin32(rightOffset + 1, width);
     int srcStrideX = srcDirection == BlurDirection::kX ? 1 : srcStride;
     int dstStrideX = dstDirection == BlurDirection::kX ? 1 : height;
     int srcStrideY = srcDirection == BlurDirection::kX ? srcStride : 1;
     int dstStrideY = dstDirection == BlurDirection::kX ? width : 1;
     uint32_t scale = (1 << 24) / kernelSize;
     uint32_t half = 1 << 23;
     for (int y = 0; y < height; ++y) {
         int sumA = 0, sumR = 0, sumG = 0, sumB = 0;
         const SkPMColor* p = src;
         for (int i = 0; i < rightBorder; ++i) {
             sumA += SkGetPackedA32(*p);
             sumR += SkGetPackedR32(*p);
             sumG += SkGetPackedG32(*p);
             sumB += SkGetPackedB32(*p);
             p += srcStrideX;
         }

         const SkPMColor* sptr = src;
         SkColor* dptr = dst;
         for (int x = 0; x < width; ++x) {
             *dptr = SkPackARGB32((sumA * scale + half) >> 24,
                                  (sumR * scale + half) >> 24,
                                  (sumG * scale + half) >> 24,
                                  (sumB * scale + half) >> 24);
             if (x >= leftOffset) {
                 SkColor l = *(sptr - leftOffset * srcStrideX);
                 sumA -= SkGetPackedA32(l);
                 sumR -= SkGetPackedR32(l);
                 sumG -= SkGetPackedG32(l);
                 sumB -= SkGetPackedB32(l);
             }
             if (x + rightOffset + 1 < width) {
                 SkColor r = *(sptr + (rightOffset + 1) * srcStrideX);
                 sumA += SkGetPackedA32(r);
                 sumR += SkGetPackedR32(r);
                 sumG += SkGetPackedG32(r);
                 sumB += SkGetPackedB32(r);
             }
             sptr += srcStrideX;
             if (srcDirection == BlurDirection::kY) {
                 SK_PREFETCH(sptr + (rightOffset + 1) * srcStrideX);
             }
             dptr += dstStrideX;
         }
         src += srcStrideY;
         dst += dstStrideY;
     }
 }

 #endif

 static auto box_blur_xx = &box_blur<BlurDirection::kX, BlurDirection::kX>,
             box_blur_xy = &box_blur<BlurDirection::kX, BlurDirection::kY>,
             box_blur_yx = &box_blur<BlurDirection::kY, BlurDirection::kX>;

 }  // namespace SK_OPTS_NS

 #endif
	/*
	* Copyright 2015 Google Inc.
	*
	* Use of this source code is governed by a BSD-style license that can be
	* found in the LICENSE file.
	*/

	#ifndef SkBlurImageFilter_opts_DEFINED
	#define SkBlurImageFilter_opts_DEFINED

	#include "SkColorPriv.h"
	#include "SkTypes.h"

	namespace SK_OPTS_NS {

	enum class BlurDirection { kX, kY };

	#if SK_CPU_SSE_LEVEL >= SK_CPU_SSE_LEVEL_SSE2
	template<BlurDirection srcDirection, BlurDirection 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 == BlurDirection::kX ? 1 : srcStride;
	const int dstStrideX = dstDirection == BlurDirection::kX ? 1 : height;
	const int srcStrideY = srcDirection == BlurDirection::kX ? srcStride : 1;
	const int dstStrideY = dstDirection == BlurDirection::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 == BlurDirection::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<BlurDirection srcDirection, BlurDirection 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 == BlurDirection::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 == BlurDirection::kX ? 1 : srcStride;
	const int dstStrideX = dstDirection == BlurDirection::kX ? 1 : *height;
	const int srcStrideY = srcDirection == BlurDirection::kX ? srcStride : 1;
	const int dstStrideY = dstDirection == BlurDirection::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 == BlurDirection::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<BlurDirection srcDirection, BlurDirection 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 == BlurDirection::kX ? 1 : srcStride;
	const int dstStrideX = dstDirection == BlurDirection::kX ? 1 : height;
	const int srcStrideY = srcDirection == BlurDirection::kX ? srcStride : 1;
	const int dstStrideY = dstDirection == BlurDirection::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+sumAscale half+sumRscale half+sumGscale half+sumBscale )
	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 == BlurDirection::kX) {
	SK_PREFETCH(sptr + (rightOffset + 16) * srcStrideX);
	}
	dptr += dstStrideX;
	}
	src += srcStrideY;
	dst += dstStrideY;
	}
	}

	#else // Neither NEON nor >=SSE2.

	template<BlurDirection srcDirection, BlurDirection dstDirection>
	static void box_blur(const SkPMColor* src, int srcStride, SkPMColor* dst, int kernelSize,
	int leftOffset, int rightOffset, int width, int height) {
	int rightBorder = SkMin32(rightOffset + 1, width);
	int srcStrideX = srcDirection == BlurDirection::kX ? 1 : srcStride;
	int dstStrideX = dstDirection == BlurDirection::kX ? 1 : height;
	int srcStrideY = srcDirection == BlurDirection::kX ? srcStride : 1;
	int dstStrideY = dstDirection == BlurDirection::kX ? width : 1;
	uint32_t scale = (1 << 24) / kernelSize;
	uint32_t half = 1 << 23;
	for (int y = 0; y < height; ++y) {
	int sumA = 0, sumR = 0, sumG = 0, sumB = 0;
	const SkPMColor* p = src;
	for (int i = 0; i < rightBorder; ++i) {
	sumA += SkGetPackedA32(*p);
	sumR += SkGetPackedR32(*p);
	sumG += SkGetPackedG32(*p);
	sumB += SkGetPackedB32(*p);
	p += srcStrideX;
	}

	const SkPMColor* sptr = src;
	SkColor* dptr = dst;
	for (int x = 0; x < width; ++x) {
	dptr = SkPackARGB32((sumA scale + half) >> 24,
	(sumR * scale + half) >> 24,
	(sumG * scale + half) >> 24,
	(sumB * scale + half) >> 24);
	if (x >= leftOffset) {
	SkColor l = (sptr - leftOffset srcStrideX);
	sumA -= SkGetPackedA32(l);
	sumR -= SkGetPackedR32(l);
	sumG -= SkGetPackedG32(l);
	sumB -= SkGetPackedB32(l);
	}
	if (x + rightOffset + 1 < width) {
	SkColor r = (sptr + (rightOffset + 1) srcStrideX);
	sumA += SkGetPackedA32(r);
	sumR += SkGetPackedR32(r);
	sumG += SkGetPackedG32(r);
	sumB += SkGetPackedB32(r);
	}
	sptr += srcStrideX;
	if (srcDirection == BlurDirection::kY) {
	SK_PREFETCH(sptr + (rightOffset + 1) * srcStrideX);
	}
	dptr += dstStrideX;
	}
	src += srcStrideY;
	dst += dstStrideY;
	}
	}

	#endif

	static auto box_blur_xx = &box_blur<BlurDirection::kX, BlurDirection::kX>,
	box_blur_xy = &box_blur<BlurDirection::kX, BlurDirection::kY>,
	box_blur_yx = &box_blur<BlurDirection::kY, BlurDirection::kX>;

	} // namespace SK_OPTS_NS

	#endif