text: /*
   * Copyright 2011 Google Inc.
   *
   * Use of this source code is governed by a BSD-style license that can be
   * found in the LICENSE file.
   */
  
  #include "include/private/SkColorData.h"
  #include "src/core/SkBlitRow.h"
  #include "src/core/SkOpts.h"
  #include "src/core/SkUtils.h"
  
  // Everyone agrees memcpy() is the best way to do this.
  static void blit_row_s32_opaque(SkPMColor* dst,
                                  const SkPMColor* src,
                                  int count,
                                  U8CPU alpha) {
      SkASSERT(255 == alpha);
      memcpy(dst, src, count * sizeof(SkPMColor));
  }
  
  // We have SSE2, NEON, and portable implementations of
  // blit_row_s32_blend() and blit_row_s32a_blend().
  
  // TODO(mtklein): can we do better in NEON than 2 pixels at a time?
  
  #if SK_CPU_SSE_LEVEL >= SK_CPU_SSE_LEVEL_SSE2
      #include <emmintrin.h>
  
      static inline __m128i SkPMLerp_SSE2(const __m128i& src,
                                          const __m128i& dst,
                                          const unsigned src_scale) {
          // Computes dst + (((src - dst)*src_scale)>>8)
          const __m128i mask = _mm_set1_epi32(0x00FF00FF);
  
          // Unpack the 16x8-bit source into 2 8x16-bit splayed halves.
          __m128i src_rb = _mm_and_si128(mask, src);
          __m128i src_ag = _mm_srli_epi16(src, 8);
          __m128i dst_rb = _mm_and_si128(mask, dst);
          __m128i dst_ag = _mm_srli_epi16(dst, 8);
  
          // Compute scaled differences.
          __m128i diff_rb = _mm_sub_epi16(src_rb, dst_rb);
          __m128i diff_ag = _mm_sub_epi16(src_ag, dst_ag);
          __m128i s = _mm_set1_epi16(src_scale);
          diff_rb = _mm_mullo_epi16(diff_rb, s);
          diff_ag = _mm_mullo_epi16(diff_ag, s);
  
          // Pack the differences back together.
          diff_rb = _mm_srli_epi16(diff_rb, 8);
          diff_ag = _mm_andnot_si128(mask, diff_ag);
          __m128i diff = _mm_or_si128(diff_rb, diff_ag);
  
          // Add difference to destination.
          return _mm_add_epi8(dst, diff);
      }
  
  
      static void blit_row_s32_blend(SkPMColor* dst, const SkPMColor* src, int count, U8CPU alpha) {
          SkASSERT(alpha <= 255);
  
          auto src4 = (const __m128i*)src;
          auto dst4 = (      __m128i*)dst;
  
          while (count >= 4) {
              _mm_storeu_si128(dst4, SkPMLerp_SSE2(_mm_loadu_si128(src4),
                                                   _mm_loadu_si128(dst4),
                                                   SkAlpha255To256(alpha)));
              src4++;
              dst4++;
              count -= 4;
          }
  
          src = (const SkPMColor*)src4;
          dst = (      SkPMColor*)dst4;
  
          while (count --> 0) {
              *dst = SkPMLerp(*src, *dst, SkAlpha255To256(alpha));
              src++;
              dst++;
          }
      }
  
      static inline __m128i SkBlendARGB32_SSE2(const __m128i& src,
                                               const __m128i& dst,
                                               const unsigned aa) {
          unsigned alpha = SkAlpha255To256(aa);
          __m128i src_scale = _mm_set1_epi16(alpha);
          // SkAlphaMulInv256(SkGetPackedA32(src), src_scale)
          __m128i dst_scale = _mm_srli_epi32(src, 24);
          // High words in dst_scale are 0, so it's safe to multiply with 16-bit src_scale.
          dst_scale = _mm_mullo_epi16(dst_scale, src_scale);
          dst_scale = _mm_sub_epi32(_mm_set1_epi32(0xFFFF), dst_scale);
          dst_scale = _mm_add_epi32(dst_scale, _mm_srli_epi32(dst_scale, 8));
          dst_scale = _mm_srli_epi32(dst_scale, 8);
          // Duplicate scales into 2x16-bit pattern per pixel.
          dst_scale = _mm_shufflelo_epi16(dst_scale, _MM_SHUFFLE(2, 2, 0, 0));
          dst_scale = _mm_shufflehi_epi16(dst_scale, _MM_SHUFFLE(2, 2, 0, 0));
  
          const __m128i mask = _mm_set1_epi32(0x00FF00FF);
  
          // Unpack the 16x8-bit source/destination into 2 8x16-bit splayed halves.
          __m128i src_rb = _mm_and_si128(mask, src);
          __m128i src_ag = _mm_srli_epi16(src, 8);
          __m128i dst_rb = _mm_and_si128(mask, dst);
          __m128i dst_ag = _mm_srli_epi16(dst, 8);
  
          // Scale them.
          src_rb = _mm_mullo_epi16(src_rb, src_scale);
          src_ag = _mm_mullo_epi16(src_ag, src_scale);
          dst_rb = _mm_mullo_epi16(dst_rb, dst_scale);
          dst_ag = _mm_mullo_epi16(dst_ag, dst_scale);
  
          // Add the scaled source and destination.
          dst_rb = _mm_add_epi16(src_rb, dst_rb);
          dst_ag = _mm_add_epi16(src_ag, dst_ag);
  
          // Unsplay the halves back together.
          dst_rb = _mm_srli_epi16(dst_rb, 8);
          dst_ag = _mm_andnot_si128(mask, dst_ag);
          return _mm_or_si128(dst_rb, dst_ag);
      }
  
      static void blit_row_s32a_blend(SkPMColor* dst, const SkPMColor* src, int count, U8CPU alpha) {
          SkASSERT(alpha <= 255);
  
          auto src4 = (const __m128i*)src;
          auto dst4 = (      __m128i*)dst;
  
          while (count >= 4) {
              _mm_storeu_si128(dst4, SkBlendARGB32_SSE2(_mm_loadu_si128(src4),
                                                        _mm_loadu_si128(dst4),
                                                        alpha));
              src4++;
              dst4++;
              count -= 4;
          }
  
          src = (const SkPMColor*)src4;
          dst = (      SkPMColor*)dst4;
  
          while (count --> 0) {
              *dst = SkBlendARGB32(*src, *dst, alpha);
              src++;
              dst++;
          }
      }
  
  #elif defined(SK_ARM_HAS_NEON)
      #include <arm_neon.h>
  
      static void blit_row_s32_blend(SkPMColor* dst, const SkPMColor* src, int count, U8CPU alpha) {
          SkASSERT(alpha <= 255);
  
          uint16_t src_scale = SkAlpha255To256(alpha);
          uint16_t dst_scale = 256 - src_scale;
  
          while (count >= 2) {
              uint8x8_t vsrc, vdst, vres;
              uint16x8_t vsrc_wide, vdst_wide;
  
              vsrc = vreinterpret_u8_u32(vld1_u32(src));
              vdst = vreinterpret_u8_u32(vld1_u32(dst));
  
              vsrc_wide = vmovl_u8(vsrc);
              vsrc_wide = vmulq_u16(vsrc_wide, vdupq_n_u16(src_scale));
  
              vdst_wide = vmull_u8(vdst, vdup_n_u8(dst_scale));
  
              vdst_wide += vsrc_wide;
              vres = vshrn_n_u16(vdst_wide, 8);
  
              vst1_u32(dst, vreinterpret_u32_u8(vres));
  
              src += 2;
              dst += 2;
              count -= 2;
          }
  
          if (count == 1) {
              uint8x8_t vsrc = vdup_n_u8(0), vdst = vdup_n_u8(0), vres;
              uint16x8_t vsrc_wide, vdst_wide;
  
              vsrc = vreinterpret_u8_u32(vld1_lane_u32(src, vreinterpret_u32_u8(vsrc), 0));
              vdst = vreinterpret_u8_u32(vld1_lane_u32(dst, vreinterpret_u32_u8(vdst), 0));
  
              vsrc_wide = vmovl_u8(vsrc);
              vsrc_wide = vmulq_u16(vsrc_wide, vdupq_n_u16(src_scale));
              vdst_wide = vmull_u8(vdst, vdup_n_u8(dst_scale));
              vdst_wide += vsrc_wide;
              vres = vshrn_n_u16(vdst_wide, 8);
  
              vst1_lane_u32(dst, vreinterpret_u32_u8(vres), 0);
          }
      }
  
      static void blit_row_s32a_blend(SkPMColor* dst, const SkPMColor* src, int count, U8CPU alpha) {
          SkASSERT(alpha < 255);
  
          unsigned alpha256 = SkAlpha255To256(alpha);
  
          if (count & 1) {
              uint8x8_t vsrc = vdup_n_u8(0), vdst = vdup_n_u8(0), vres;
              uint16x8_t vdst_wide, vsrc_wide;
              unsigned dst_scale;
  
              vsrc = vreinterpret_u8_u32(vld1_lane_u32(src, vreinterpret_u32_u8(vsrc), 0));
              vdst = vreinterpret_u8_u32(vld1_lane_u32(dst, vreinterpret_u32_u8(vdst), 0));
  
              dst_scale = vget_lane_u8(vsrc, 3);
              dst_scale = SkAlphaMulInv256(dst_scale, alpha256);
  
              vsrc_wide = vmovl_u8(vsrc);
              vsrc_wide = vmulq_n_u16(vsrc_wide, alpha256);
  
              vdst_wide = vmovl_u8(vdst);
              vdst_wide = vmulq_n_u16(vdst_wide, dst_scale);
  
              vdst_wide += vsrc_wide;
              vres = vshrn_n_u16(vdst_wide, 8);
  
              vst1_lane_u32(dst, vreinterpret_u32_u8(vres), 0);
              dst++;
              src++;
              count--;
          }
  
          uint8x8_t alpha_mask;
          static const uint8_t alpha_mask_setup[] = {3,3,3,3,7,7,7,7};
          alpha_mask = vld1_u8(alpha_mask_setup);
  
          while (count) {
  
              uint8x8_t vsrc, vdst, vres, vsrc_alphas;
              uint16x8_t vdst_wide, vsrc_wide, vsrc_scale, vdst_scale;
  
              __builtin_prefetch(src+32);
              __builtin_prefetch(dst+32);
  
              vsrc = vreinterpret_u8_u32(vld1_u32(src));
              vdst = vreinterpret_u8_u32(vld1_u32(dst));
  
              vsrc_scale = vdupq_n_u16(alpha256);
  
              vsrc_alphas = vtbl1_u8(vsrc, alpha_mask);
              vdst_scale = vmovl_u8(vsrc_alphas);
              // Calculate SkAlphaMulInv256(vdst_scale, vsrc_scale).
              // A 16-bit lane would overflow if we used 0xFFFF here,
              // so use an approximation with 0xFF00 that is off by 1,
              // and add back 1 after to get the correct value.
              // This is valid if alpha256 <= 255.
              vdst_scale = vmlsq_u16(vdupq_n_u16(0xFF00), vdst_scale, vsrc_scale);
              vdst_scale = vsraq_n_u16(vdst_scale, vdst_scale, 8);
              vdst_scale = vsraq_n_u16(vdupq_n_u16(1), vdst_scale, 8);
  
              vsrc_wide = vmovl_u8(vsrc);
              vsrc_wide *= vsrc_scale;
  
              vdst_wide = vmovl_u8(vdst);
              vdst_wide *= vdst_scale;
  
              vdst_wide += vsrc_wide;
              vres = vshrn_n_u16(vdst_wide, 8);
  
              vst1_u32(dst, vreinterpret_u32_u8(vres));
  
              src += 2;
              dst += 2;
              count -= 2;
          }
      }
  
  #else
      static void blit_row_s32_blend(SkPMColor* dst, const SkPMColor* src, int count, U8CPU alpha) {
          SkASSERT(alpha <= 255);
          while (count --> 0) {
              *dst = SkPMLerp(*src, *dst, SkAlpha255To256(alpha));
              src++;
              dst++;
          }
      }
  
      static void blit_row_s32a_blend(SkPMColor* dst, const SkPMColor* src, int count, U8CPU alpha) {
          SkASSERT(alpha <= 255);
          while (count --> 0) {
              *dst = SkBlendARGB32(*src, *dst, alpha);
              src++;
              dst++;
          }
      }
  #endif
  
  SkBlitRow::Proc32 SkBlitRow::Factory32(unsigned flags) {
      static const SkBlitRow::Proc32 kProcs[] = {
          blit_row_s32_opaque,
          blit_row_s32_blend,
          nullptr,  // blit_row_s32a_opaque is in SkOpts
          blit_row_s32a_blend
      };
  
      SkASSERT(flags < SK_ARRAY_COUNT(kProcs));
      flags &= SK_ARRAY_COUNT(kProcs) - 1;  // just to be safe
  
      return flags == 2 ? SkOpts::blit_row_s32a_opaque
                        : kProcs[flags];
  }
  
  void SkBlitRow::Color32(SkPMColor dst[], const SkPMColor src[], int count, SkPMColor color) {
      switch (SkGetPackedA32(color)) {
          case   0: memmove(dst, src, count * sizeof(SkPMColor)); return;
          case 255: sk_memset32(dst, color, count);               return;
      }
      return SkOpts::blit_row_color32(dst, src, count, color);
  }
  