text: /*
   * Copyright 2012 The Android Open Source Project
   *
   * Use of this source code is governed by a BSD-style license that can be
   * found in the LICENSE file.
   */
  
  #include "SkBitmapProcState_opts_SSSE3.h"
  #include "SkColorPriv.h"
  #include "SkPaint.h"
  #include "SkUtils.h"
  
  /* With the exception of the compilers that don't support it, we always build the
   * SSSE3 functions and enable the caller to determine SSSE3 support.  However for
   * compilers that do not support SSSE3 we provide a stub implementation.
   */
  #if SK_CPU_SSE_LEVEL >= SK_CPU_SSE_LEVEL_SSSE3
  
  #include <tmmintrin.h>  // SSSE3
  
  // adding anonymous namespace seemed to force gcc to inline directly the
  // instantiation, instead of creating the functions
  // S32_generic_D32_filter_DX_SSSE3<true> and
  // S32_generic_D32_filter_DX_SSSE3<false> which were then called by the
  // external functions.
  namespace {
  // In this file, variations for alpha and non alpha versions are implemented
  // with a template, as it makes the code more compact and a bit easier to
  // maintain, while making the compiler generate the same exact code as with
  // two functions that only differ by a few lines.
  
  
  // Prepare all necessary constants for a round of processing for two pixel
  // pairs.
  // @param xy is the location where the xy parameters for four pixels should be
  //           read from. It is identical in concept with argument two of
  //           S32_{opaque}_D32_filter_DX methods.
  // @param mask_3FFF vector of 32 bit constants containing 3FFF,
  //                  suitable to mask the bottom 14 bits of a XY value.
  // @param mask_000F vector of 32 bit constants containing 000F,
  //                  suitable to mask the bottom 4 bits of a XY value.
  // @param sixteen_8bit vector of 8 bit components containing the value 16.
  // @param mask_dist_select vector of 8 bit components containing the shuffling
  //                         parameters to reorder x[0-3] parameters.
  // @param all_x_result vector of 8 bit components that will contain the
  //              (4x(x3), 4x(x2), 4x(x1), 4x(x0)) upon return.
  // @param sixteen_minus_x vector of 8 bit components, containing
  //              (4x(16 - x3), 4x(16 - x2), 4x(16 - x1), 4x(16 - x0))
  inline void PrepareConstantsTwoPixelPairs(const uint32_t* xy,
                                            const __m128i& mask_3FFF,
                                            const __m128i& mask_000F,
                                            const __m128i& sixteen_8bit,
                                            const __m128i& mask_dist_select,
                                            __m128i* all_x_result,
                                            __m128i* sixteen_minus_x,
                                            int* x0,
                                            int* x1) {
      const __m128i xx = _mm_loadu_si128(reinterpret_cast<const __m128i *>(xy));
  
      // 4 delta X
      // (x03, x02, x01, x00)
      const __m128i x0_wide = _mm_srli_epi32(xx, 18);
      // (x13, x12, x11, x10)
      const __m128i x1_wide = _mm_and_si128(xx, mask_3FFF);
  
      _mm_storeu_si128(reinterpret_cast<__m128i *>(x0), x0_wide);
      _mm_storeu_si128(reinterpret_cast<__m128i *>(x1), x1_wide);
  
      __m128i all_x = _mm_and_si128(_mm_srli_epi32(xx, 14), mask_000F);
  
      // (4x(x3), 4x(x2), 4x(x1), 4x(x0))
      all_x = _mm_shuffle_epi8(all_x, mask_dist_select);
  
      *all_x_result = all_x;
      // (4x(16-x3), 4x(16-x2), 4x(16-x1), 4x(16-x0))
      *sixteen_minus_x = _mm_sub_epi8(sixteen_8bit, all_x);
  }
  
  // Prepare all necessary constants for a round of processing for two pixel
  // pairs.
  // @param xy is the location where the xy parameters for four pixels should be
  //           read from. It is identical in concept with argument two of
  //           S32_{opaque}_D32_filter_DXDY methods.
  // @param mask_3FFF vector of 32 bit constants containing 3FFF,
  //                  suitable to mask the bottom 14 bits of a XY value.
  // @param mask_000F vector of 32 bit constants containing 000F,
  //                  suitable to mask the bottom 4 bits of a XY value.
  // @param sixteen_8bit vector of 8 bit components containing the value 16.
  // @param mask_dist_select vector of 8 bit components containing the shuffling
  //                         parameters to reorder x[0-3] parameters.
  // @param all_xy_result vector of 8 bit components that will contain the
  //              (4x(y1), 4x(y0), 4x(x1), 4x(x0)) upon return.
  // @param sixteen_minus_x vector of 8 bit components, containing
  //              (4x(16-y1), 4x(16-y0), 4x(16-x1), 4x(16-x0)).
  inline void PrepareConstantsTwoPixelPairsDXDY(const uint32_t* xy,
                                                const __m128i& mask_3FFF,
                                                const __m128i& mask_000F,
                                                const __m128i& sixteen_8bit,
                                                const __m128i& mask_dist_select,
                                                __m128i* all_xy_result,
                                                __m128i* sixteen_minus_xy,
                                                int* xy0, int* xy1) {
      const __m128i xy_wide =
                          _mm_loadu_si128(reinterpret_cast<const __m128i *>(xy));
  
      // (x10, y10, x00, y00)
      __m128i xy0_wide = _mm_srli_epi32(xy_wide, 18);
      // (y10, y00, x10, x00)
      xy0_wide =  _mm_shuffle_epi32(xy0_wide, _MM_SHUFFLE(2, 0, 3, 1));
      // (x11, y11, x01, y01)
      __m128i xy1_wide = _mm_and_si128(xy_wide, mask_3FFF);
      // (y11, y01, x11, x01)
      xy1_wide = _mm_shuffle_epi32(xy1_wide, _MM_SHUFFLE(2, 0, 3, 1));
  
      _mm_storeu_si128(reinterpret_cast<__m128i *>(xy0), xy0_wide);
      _mm_storeu_si128(reinterpret_cast<__m128i *>(xy1), xy1_wide);
  
      // (x1, y1, x0, y0)
      __m128i all_xy = _mm_and_si128(_mm_srli_epi32(xy_wide, 14), mask_000F);
      // (y1, y0, x1, x0)
      all_xy = _mm_shuffle_epi32(all_xy, _MM_SHUFFLE(2, 0, 3, 1));
      // (4x(y1), 4x(y0), 4x(x1), 4x(x0))
      all_xy = _mm_shuffle_epi8(all_xy, mask_dist_select);
  
      *all_xy_result = all_xy;
      // (4x(16-y1), 4x(16-y0), 4x(16-x1), 4x(16-x0))
      *sixteen_minus_xy = _mm_sub_epi8(sixteen_8bit, all_xy);
  }
  
  // Helper function used when processing one pixel pair.
  // @param pixel0..3 are the four input pixels
  // @param scale_x vector of 8 bit components to multiply the pixel[0:3]. This
  //                will contain (4x(x1, 16-x1), 4x(x0, 16-x0))
  //                or (4x(x3, 16-x3), 4x(x2, 16-x2))
  // @return a vector of 16 bit components containing:
  // (Aa2 * (16 - x1) + Aa3 * x1, ... , Ra0 * (16 - x0) + Ra1 * x0)
  inline __m128i ProcessPixelPairHelper(uint32_t pixel0,
                                        uint32_t pixel1,
                                        uint32_t pixel2,
                                        uint32_t pixel3,
                                        const __m128i& scale_x) {
      __m128i a0, a1, a2, a3;
      // Load 2 pairs of pixels
      a0 = _mm_cvtsi32_si128(pixel0);
      a1 = _mm_cvtsi32_si128(pixel1);
  
      // Interleave pixels.
      // (0, 0, 0, 0, 0, 0, 0, 0, Aa1, Aa0, Ba1, Ba0, Ga1, Ga0, Ra1, Ra0)
      a0 = _mm_unpacklo_epi8(a0, a1);
  
      a2 = _mm_cvtsi32_si128(pixel2);
      a3 = _mm_cvtsi32_si128(pixel3);
      // (0, 0, 0, 0, 0, 0, 0, 0, Aa3, Aa2, Ba3, Ba2, Ga3, Ga2, Ra3, Ra2)
      a2 = _mm_unpacklo_epi8(a2, a3);
  
      // two pairs of pixel pairs, interleaved.
      // (Aa3, Aa2, Ba3, Ba2, Ga3, Ga2, Ra3, Ra2,
      //  Aa1, Aa0, Ba1, Ba0, Ga1, Ga0, Ra1, Ra0)
      a0 = _mm_unpacklo_epi64(a0, a2);
  
      // multiply and sum to 16 bit components.
      // (Aa2 * (16 - x1) + Aa3 * x1, ... , Ra0 * (16 - x0) + Ra1 * x0)
      // At that point, we use up a bit less than 12 bits for each 16 bit
      // component:
      // All components are less than 255. So,
      // C0 * (16 - x) + C1 * x <= 255 * (16 - x) + 255 * x = 255 * 16.
      return _mm_maddubs_epi16(a0, scale_x);
  }
  
  // Scale back the results after multiplications to the [0:255] range, and scale
  // by alpha when has_alpha is true.
  // Depending on whether one set or two sets of multiplications had been applied,
  // the results have to be shifted by four places (dividing by 16), or shifted
  // by eight places (dividing by 256), since each multiplication is by a quantity
  // in the range [0:16].
  template<bool has_alpha, int scale>
  inline __m128i ScaleFourPixels(__m128i* pixels,
                                 const __m128i& alpha) {
      // Divide each 16 bit component by 16 (or 256 depending on scale).
      *pixels = _mm_srli_epi16(*pixels, scale);
  
      if (has_alpha) {
          // Multiply by alpha.
          *pixels = _mm_mullo_epi16(*pixels, alpha);
  
          // Divide each 16 bit component by 256.
          *pixels = _mm_srli_epi16(*pixels, 8);
      }
      return *pixels;
  }
  
  // Wrapper to calculate two output pixels from four input pixels. The
  // arguments are the same as ProcessPixelPairHelper. Technically, there are
  // eight input pixels, but since sub_y == 0, the factors applied to half of the
  // pixels is zero (sub_y), and are therefore omitted here to save on some
  // processing.
  // @param alpha when has_alpha is true, scale all resulting components by this
  //              value.
  // @return a vector of 16 bit components containing:
  // ((Aa2 * (16 - x1) + Aa3 * x1) * alpha, ...,
  // (Ra0 * (16 - x0) + Ra1 * x0) * alpha) (when has_alpha is true)
  // otherwise
  // (Aa2 * (16 - x1) + Aa3 * x1, ... , Ra0 * (16 - x0) + Ra1 * x0)
  // In both cases, the results are renormalized (divided by 16) to match the
  // expected formats when storing back the results into memory.
  template<bool has_alpha>
  inline __m128i ProcessPixelPairZeroSubY(uint32_t pixel0,
                                          uint32_t pixel1,
                                          uint32_t pixel2,
                                          uint32_t pixel3,
                                          const __m128i& scale_x,
                                          const __m128i& alpha) {
      __m128i sum = ProcessPixelPairHelper(pixel0, pixel1, pixel2, pixel3,
                                           scale_x);
      return ScaleFourPixels<has_alpha, 4>(&sum, alpha);
  }
  
  // Same as ProcessPixelPairZeroSubY, expect processing one output pixel at a
  // time instead of two. As in the above function, only two pixels are needed
  // to generate a single pixel since sub_y == 0.
  // @return same as ProcessPixelPairZeroSubY, except that only the bottom 4
  // 16 bit components are set.
  template<bool has_alpha>
  inline __m128i ProcessOnePixelZeroSubY(uint32_t pixel0,
                                         uint32_t pixel1,
                                         __m128i scale_x,
                                         __m128i alpha) {
      __m128i a0 = _mm_cvtsi32_si128(pixel0);
      __m128i a1 = _mm_cvtsi32_si128(pixel1);
  
      // Interleave
      a0 = _mm_unpacklo_epi8(a0, a1);
  
      // (a0 * (16-x) + a1 * x)
      __m128i sum = _mm_maddubs_epi16(a0, scale_x);
  
      return ScaleFourPixels<has_alpha, 4>(&sum, alpha);
  }
  
  // Methods when sub_y != 0
  
  
  // Same as ProcessPixelPairHelper, except that the values are scaled by y.
  // @param y vector of 16 bit components containing 'y' values. There are two
  //        cases in practice, where y will contain the sub_y constant, or will
  //        contain the 16 - sub_y constant.
  // @return vector of 16 bit components containing:
  // (y * (Aa2 * (16 - x1) + Aa3 * x1), ... , y * (Ra0 * (16 - x0) + Ra1 * x0))
  inline __m128i ProcessPixelPair(uint32_t pixel0,
                                  uint32_t pixel1,
                                  uint32_t pixel2,
                                  uint32_t pixel3,
                                  const __m128i& scale_x,
                                  const __m128i& y) {
      __m128i sum = ProcessPixelPairHelper(pixel0, pixel1, pixel2, pixel3,
                                           scale_x);
  
      // first row times 16-y or y depending on whether 'y' represents one or
      // the other.
      // Values will be up to 255 * 16 * 16 = 65280.
      // (y * (Aa2 * (16 - x1) + Aa3 * x1), ... ,
      //  y * (Ra0 * (16 - x0) + Ra1 * x0))
      sum = _mm_mullo_epi16(sum, y);
  
      return sum;
  }
  
  // Process two pixel pairs out of eight input pixels.
  // In other methods, the distinct pixels are passed one by one, but in this
  // case, the rows, and index offsets to the pixels into the row are passed
  // to generate the 8 pixels.
  // @param row0..1 top and bottom row where to find input pixels.
  // @param x0..1 offsets into the row for all eight input pixels.
  // @param all_y vector of 16 bit components containing the constant sub_y
  // @param neg_y vector of 16 bit components containing the constant 16 - sub_y
  // @param alpha vector of 16 bit components containing the alpha value to scale
  //        the results by, when has_alpha is true.
  // @return
  // (alpha * ((16-y) * (Aa2  * (16-x1) + Aa3  * x1) +
  //             y    * (Aa2' * (16-x1) + Aa3' * x1)),
  // ...
  //  alpha * ((16-y) * (Ra0  * (16-x0) + Ra1 * x0) +
  //             y    * (Ra0' * (16-x0) + Ra1' * x0))
  // With the factor alpha removed when has_alpha is false.
  // The values are scaled back to 16 bit components, but with only the bottom
  // 8 bits being set.
  template<bool has_alpha>
  inline __m128i ProcessTwoPixelPairs(const uint32_t* row0,
                                      const uint32_t* row1,
                                      const int* x0,
                                      const int* x1,
                                      const __m128i& scale_x,
                                      const __m128i& all_y,
                                      const __m128i& neg_y,
                                      const __m128i& alpha) {
      __m128i sum0 = ProcessPixelPair(
          row0[x0[0]], row0[x1[0]], row0[x0[1]], row0[x1[1]],
          scale_x, neg_y);
      __m128i sum1 = ProcessPixelPair(
          row1[x0[0]], row1[x1[0]], row1[x0[1]], row1[x1[1]],
          scale_x, all_y);
  
      // 2 samples fully summed.
      // ((16-y) * (Aa2 * (16-x1) + Aa3 * x1) +
      //  y * (Aa2' * (16-x1) + Aa3' * x1),
      // ...
      //  (16-y) * (Ra0 * (16 - x0) + Ra1 * x0)) +
      //  y * (Ra0' * (16-x0) + Ra1' * x0))
      // Each component, again can be at most 256 * 255 = 65280, so no overflow.
      sum0 = _mm_add_epi16(sum0, sum1);
  
      return ScaleFourPixels<has_alpha, 8>(&sum0, alpha);
  }
  
  // Similar to ProcessTwoPixelPairs except the pixel indexes.
  template<bool has_alpha>
  inline __m128i ProcessTwoPixelPairsDXDY(const uint32_t* row00,
                                          const uint32_t* row01,
                                          const uint32_t* row10,
                                          const uint32_t* row11,
                                          const int* xy0,
                                          const int* xy1,
                                          const __m128i& scale_x,
                                          const __m128i& all_y,
                                          const __m128i& neg_y,
                                          const __m128i& alpha) {
      // first row
      __m128i sum0 = ProcessPixelPair(
          row00[xy0[0]], row00[xy1[0]], row10[xy0[1]], row10[xy1[1]],
          scale_x, neg_y);
      // second row
      __m128i sum1 = ProcessPixelPair(
          row01[xy0[0]], row01[xy1[0]], row11[xy0[1]], row11[xy1[1]],
          scale_x, all_y);
  
      // 2 samples fully summed.
      // ((16-y1) * (Aa2 * (16-x1) + Aa3 * x1) +
      //  y0 * (Aa2' * (16-x1) + Aa3' * x1),
      // ...
      //  (16-y0) * (Ra0 * (16 - x0) + Ra1 * x0)) +
      //  y0 * (Ra0' * (16-x0) + Ra1' * x0))
      // Each component, again can be at most 256 * 255 = 65280, so no overflow.
      sum0 = _mm_add_epi16(sum0, sum1);
  
      return ScaleFourPixels<has_alpha, 8>(&sum0, alpha);
  }
  
  
  // Same as ProcessPixelPair, except that performing the math one output pixel
  // at a time. This means that only the bottom four 16 bit components are set.
  inline __m128i ProcessOnePixel(uint32_t pixel0, uint32_t pixel1,
                                 const __m128i& scale_x, const __m128i& y) {
      __m128i a0 = _mm_cvtsi32_si128(pixel0);
      __m128i a1 = _mm_cvtsi32_si128(pixel1);
  
      // Interleave
      // (0, 0, 0, 0, 0, 0, 0, 0, Aa1, Aa0, Ba1, Ba0, Ga1, Ga0, Ra1, Ra0)
      a0 = _mm_unpacklo_epi8(a0, a1);
  
      // (a0 * (16-x) + a1 * x)
      a0 = _mm_maddubs_epi16(a0, scale_x);
  
      // scale row by y
      return _mm_mullo_epi16(a0, y);
  }
  
  // Notes about the various tricks that are used in this implementation:
  // - specialization for sub_y == 0.
  // Statistically, 1/16th of the samples will have sub_y == 0. When this
  // happens, the math goes from:
  // (16 - x)*(16 - y)*a00 + x*(16 - y)*a01 + (16 - x)*y*a10 + x*y*a11
  // to:
  // (16 - x)*a00 + 16*x*a01
  // much simpler. The simplification makes for an easy boost in performance.
  // - calculating 4 output pixels at a time.
  //  This allows loading the coefficients x0 and x1 and shuffling them to the
  // optimum location only once per loop, instead of twice per loop.
  // This also allows us to store the four pixels with a single store.
  // - Use of 2 special SSSE3 instructions (comparatively to the SSE2 instruction
  // version):
  // _mm_shuffle_epi8 : this allows us to spread the coefficients x[0-3] loaded
  // in 32 bit values to 8 bit values repeated four times.
  // _mm_maddubs_epi16 : this allows us to perform multiplications and additions
  // in one swoop of 8bit values storing the results in 16 bit values. This
  // instruction is actually crucial for the speed of the implementation since
  // as one can see in the SSE2 implementation, all inputs have to be used as
  // 16 bits because the results are 16 bits. This basically allows us to process
  // twice as many pixel components per iteration.
  //
  // As a result, this method behaves faster than the traditional SSE2. The actual
  // boost varies greatly on the underlying architecture.
  template<bool has_alpha>
  void S32_generic_D32_filter_DX_SSSE3(const SkBitmapProcState& s,
                                       const uint32_t* xy,
                                       int count, uint32_t* colors) {
      SkASSERT(count > 0 && colors != nullptr);
      SkASSERT(s.fFilterLevel != kNone_SkFilterQuality);
      SkASSERT(kN32_SkColorType == s.fPixmap.colorType());
      if (has_alpha) {
          SkASSERT(s.fAlphaScale < 256);
      } else {
          SkASSERT(s.fAlphaScale == 256);
      }
  
      const uint8_t* src_addr =
              static_cast<const uint8_t*>(s.fPixmap.addr());
      const size_t rb = s.fPixmap.rowBytes();
      const uint32_t XY = *xy++;
      const unsigned y0 = XY >> 14;
      const uint32_t* row0 =
              reinterpret_cast<const uint32_t*>(src_addr + (y0 >> 4) * rb);
      const uint32_t* row1 =
              reinterpret_cast<const uint32_t*>(src_addr + (XY & 0x3FFF) * rb);
      const unsigned sub_y = y0 & 0xF;
  
      // vector constants
      const __m128i mask_dist_select = _mm_set_epi8(12, 12, 12, 12,
                                                    8,  8,  8,  8,
                                                    4,  4,  4,  4,
                                                    0,  0,  0,  0);
      const __m128i mask_3FFF = _mm_set1_epi32(0x3FFF);
      const __m128i mask_000F = _mm_set1_epi32(0x000F);
      const __m128i sixteen_8bit = _mm_set1_epi8(16);
      // (0, 0, 0, 0, 0, 0, 0, 0)
      const __m128i zero = _mm_setzero_si128();
  
      __m128i alpha = _mm_setzero_si128();
      if (has_alpha) {
          // 8x(alpha)
          alpha = _mm_set1_epi16(s.fAlphaScale);
      }
  
      if (sub_y == 0) {
          // Unroll 4x, interleave bytes, use pmaddubsw (all_x is small)
          while (count > 3) {
              count -= 4;
  
              int x0[4];
              int x1[4];
              __m128i all_x, sixteen_minus_x;
              PrepareConstantsTwoPixelPairs(xy, mask_3FFF, mask_000F,
                                            sixteen_8bit, mask_dist_select,
                                            &all_x, &sixteen_minus_x, x0, x1);
              xy += 4;
  
              // First pair of pixel pairs.
              // (4x(x1, 16-x1), 4x(x0, 16-x0))
              __m128i scale_x;
              scale_x = _mm_unpacklo_epi8(sixteen_minus_x, all_x);
  
              __m128i sum0 = ProcessPixelPairZeroSubY<has_alpha>(
                  row0[x0[0]], row0[x1[0]], row0[x0[1]], row0[x1[1]],
                  scale_x, alpha);
  
              // second pair of pixel pairs
              // (4x (x3, 16-x3), 4x (16-x2, x2))
              scale_x = _mm_unpackhi_epi8(sixteen_minus_x, all_x);
  
              __m128i sum1 = ProcessPixelPairZeroSubY<has_alpha>(
                  row0[x0[2]], row0[x1[2]], row0[x0[3]], row0[x1[3]],
                  scale_x, alpha);
  
              // Pack lower 4 16 bit values of sum into lower 4 bytes.
              sum0 = _mm_packus_epi16(sum0, sum1);
  
              // Extract low int and store.
              _mm_storeu_si128(reinterpret_cast<__m128i *>(colors), sum0);
  
              colors += 4;
          }
  
          // handle remainder
          while (count-- > 0) {
              uint32_t xx = *xy++;  // x0:14 | 4 | x1:14
              unsigned x0 = xx >> 18;
              unsigned x1 = xx & 0x3FFF;
  
              // 16x(x)
              const __m128i all_x = _mm_set1_epi8((xx >> 14) & 0x0F);
  
              // (16x(16-x))
              __m128i scale_x = _mm_sub_epi8(sixteen_8bit, all_x);
  
              scale_x = _mm_unpacklo_epi8(scale_x, all_x);
  
              __m128i sum = ProcessOnePixelZeroSubY<has_alpha>(
                  row0[x0], row0[x1],
                  scale_x, alpha);
  
              // Pack lower 4 16 bit values of sum into lower 4 bytes.
              sum = _mm_packus_epi16(sum, zero);
  
              // Extract low int and store.
              *colors++ = _mm_cvtsi128_si32(sum);
          }
      } else {  // more general case, y != 0
          // 8x(16)
          const __m128i sixteen_16bit = _mm_set1_epi16(16);
  
          // 8x (y)
          const __m128i all_y = _mm_set1_epi16(sub_y);
  
          // 8x (16-y)
          const __m128i neg_y = _mm_sub_epi16(sixteen_16bit, all_y);
  
          // Unroll 4x, interleave bytes, use pmaddubsw (all_x is small)
          while (count > 3) {
              count -= 4;
  
              int x0[4];
              int x1[4];
              __m128i all_x, sixteen_minus_x;
              PrepareConstantsTwoPixelPairs(xy, mask_3FFF, mask_000F,
                                            sixteen_8bit, mask_dist_select,
                                            &all_x, &sixteen_minus_x, x0, x1);
              xy += 4;
  
              // First pair of pixel pairs
              // (4x(x1, 16-x1), 4x(x0, 16-x0))
              __m128i scale_x;
              scale_x = _mm_unpacklo_epi8(sixteen_minus_x, all_x);
  
              __m128i sum0 = ProcessTwoPixelPairs<has_alpha>(
                  row0, row1, x0, x1,
                  scale_x, all_y, neg_y, alpha);
  
              // second pair of pixel pairs
              // (4x (x3, 16-x3), 4x (16-x2, x2))
              scale_x = _mm_unpackhi_epi8(sixteen_minus_x, all_x);
  
              __m128i sum1 = ProcessTwoPixelPairs<has_alpha>(
                  row0, row1, x0 + 2, x1 + 2,
                  scale_x, all_y, neg_y, alpha);
  
              // Do the final packing of the two results
  
              // Pack lower 4 16 bit values of sum into lower 4 bytes.
              sum0 = _mm_packus_epi16(sum0, sum1);
  
              // Extract low int and store.
              _mm_storeu_si128(reinterpret_cast<__m128i *>(colors), sum0);
  
              colors += 4;
          }
  
          // Left over.
          while (count-- > 0) {
              const uint32_t xx = *xy++;  // x0:14 | 4 | x1:14
              const unsigned x0 = xx >> 18;
              const unsigned x1 = xx & 0x3FFF;
  
              // 16x(x)
              const __m128i all_x = _mm_set1_epi8((xx >> 14) & 0x0F);
  
              // 16x (16-x)
              __m128i scale_x = _mm_sub_epi8(sixteen_8bit, all_x);
  
              // (8x (x, 16-x))
              scale_x = _mm_unpacklo_epi8(scale_x, all_x);
  
              // first row.
              __m128i sum0 = ProcessOnePixel(row0[x0], row0[x1], scale_x, neg_y);
              // second row.
              __m128i sum1 = ProcessOnePixel(row1[x0], row1[x1], scale_x, all_y);
  
              // Add both rows for full sample
              sum0 = _mm_add_epi16(sum0, sum1);
  
              sum0 = ScaleFourPixels<has_alpha, 8>(&sum0, alpha);
  
              // Pack lower 4 16 bit values of sum into lower 4 bytes.
              sum0 = _mm_packus_epi16(sum0, zero);
  
              // Extract low int and store.
              *colors++ = _mm_cvtsi128_si32(sum0);
          }
      }
  }
  
  /*
   * Similar to S32_generic_D32_filter_DX_SSSE3, we do not need to handle the
   * special case suby == 0 as suby is changing in every loop.
   */
  template<bool has_alpha>
  void S32_generic_D32_filter_DXDY_SSSE3(const SkBitmapProcState& s,
                                         const uint32_t* xy,
                                         int count, uint32_t* colors) {
      SkASSERT(count > 0 && colors != nullptr);
      SkASSERT(s.fFilterLevel != kNone_SkFilterQuality);
      SkASSERT(kN32_SkColorType == s.fPixmap.colorType());
      if (has_alpha) {
          SkASSERT(s.fAlphaScale < 256);
      } else {
          SkASSERT(s.fAlphaScale == 256);
      }
  
      const uint8_t* src_addr =
                          static_cast<const uint8_t*>(s.fPixmap.addr());
      const size_t rb = s.fPixmap.rowBytes();
  
      // vector constants
      const __m128i mask_dist_select = _mm_set_epi8(12, 12, 12, 12,
                                                    8,  8,  8,  8,
                                                    4,  4,  4,  4,
                                                    0,  0,  0,  0);
      const __m128i mask_3FFF = _mm_set1_epi32(0x3FFF);
      const __m128i mask_000F = _mm_set1_epi32(0x000F);
      const __m128i sixteen_8bit = _mm_set1_epi8(16);
  
      __m128i alpha;
      if (has_alpha) {
          // 8x(alpha)
          alpha = _mm_set1_epi16(s.fAlphaScale);
      }
  
      // Unroll 2x, interleave bytes, use pmaddubsw (all_x is small)
      while (count >= 2) {
          int xy0[4];
          int xy1[4];
          __m128i all_xy, sixteen_minus_xy;
          PrepareConstantsTwoPixelPairsDXDY(xy, mask_3FFF, mask_000F,
                                            sixteen_8bit, mask_dist_select,
                                           &all_xy, &sixteen_minus_xy, xy0, xy1);
  
          // (4x(x1, 16-x1), 4x(x0, 16-x0))
          __m128i scale_x = _mm_unpacklo_epi8(sixteen_minus_xy, all_xy);
          // (4x(0, y1), 4x(0, y0))
          __m128i all_y = _mm_unpackhi_epi8(all_xy, _mm_setzero_si128());
          __m128i neg_y = _mm_sub_epi16(_mm_set1_epi16(16), all_y);
  
          const uint32_t* row00 =
                      reinterpret_cast<const uint32_t*>(src_addr + xy0[2] * rb);
          const uint32_t* row01 =
                      reinterpret_cast<const uint32_t*>(src_addr + xy1[2] * rb);
          const uint32_t* row10 =
                      reinterpret_cast<const uint32_t*>(src_addr + xy0[3] * rb);
          const uint32_t* row11 =
                      reinterpret_cast<const uint32_t*>(src_addr + xy1[3] * rb);
  
          __m128i sum0 = ProcessTwoPixelPairsDXDY<has_alpha>(
                                          row00, row01, row10, row11, xy0, xy1,
                                          scale_x, all_y, neg_y, alpha);
  
          // Pack lower 4 16 bit values of sum into lower 4 bytes.
          sum0 = _mm_packus_epi16(sum0, _mm_setzero_si128());
  
          // Extract low int and store.
          _mm_storel_epi64(reinterpret_cast<__m128i *>(colors), sum0);
  
          xy += 4;
          colors += 2;
          count -= 2;
      }
  
      // Handle the remainder
      while (count-- > 0) {
          uint32_t data = *xy++;
          unsigned y0 = data >> 14;
          unsigned y1 = data & 0x3FFF;
          unsigned subY = y0 & 0xF;
          y0 >>= 4;
  
          data = *xy++;
          unsigned x0 = data >> 14;
          unsigned x1 = data & 0x3FFF;
          unsigned subX = x0 & 0xF;
          x0 >>= 4;
  
          const uint32_t* row0 =
                          reinterpret_cast<const uint32_t*>(src_addr + y0 * rb);
          const uint32_t* row1 =
                          reinterpret_cast<const uint32_t*>(src_addr + y1 * rb);
  
          // 16x(x)
          const __m128i all_x = _mm_set1_epi8(subX);
  
          // 16x (16-x)
          __m128i scale_x = _mm_sub_epi8(sixteen_8bit, all_x);
  
          // (8x (x, 16-x))
          scale_x = _mm_unpacklo_epi8(scale_x, all_x);
  
          // 8x(16)
          const __m128i sixteen_16bit = _mm_set1_epi16(16);
  
          // 8x (y)
          const __m128i all_y = _mm_set1_epi16(subY);
  
          // 8x (16-y)
          const __m128i neg_y = _mm_sub_epi16(sixteen_16bit, all_y);
  
          // first row.
          __m128i sum0 = ProcessOnePixel(row0[x0], row0[x1], scale_x, neg_y);
          // second row.
          __m128i sum1 = ProcessOnePixel(row1[x0], row1[x1], scale_x, all_y);
  
          // Add both rows for full sample
          sum0 = _mm_add_epi16(sum0, sum1);
  
          sum0 = ScaleFourPixels<has_alpha, 8>(&sum0, alpha);
  
          // Pack lower 4 16 bit values of sum into lower 4 bytes.
          sum0 = _mm_packus_epi16(sum0, _mm_setzero_si128());
  
          // Extract low int and store.
          *colors++ = _mm_cvtsi128_si32(sum0);
      }
  }
  }  // namespace
  
  void S32_opaque_D32_filter_DX_SSSE3(const SkBitmapProcState& s,
                                      const uint32_t* xy,
                                      int count, uint32_t* colors) {
      S32_generic_D32_filter_DX_SSSE3<false>(s, xy, count, colors);
  }
  
  void S32_alpha_D32_filter_DX_SSSE3(const SkBitmapProcState& s,
                                     const uint32_t* xy,
                                     int count, uint32_t* colors) {
      S32_generic_D32_filter_DX_SSSE3<true>(s, xy, count, colors);
  }
  
  void S32_opaque_D32_filter_DXDY_SSSE3(const SkBitmapProcState& s,
                                        const uint32_t* xy,
                                        int count, uint32_t* colors) {
      S32_generic_D32_filter_DXDY_SSSE3<false>(s, xy, count, colors);
  }
  
  void S32_alpha_D32_filter_DXDY_SSSE3(const SkBitmapProcState& s,
                                       const uint32_t* xy,
                                       int count, uint32_t* colors) {
      S32_generic_D32_filter_DXDY_SSSE3<true>(s, xy, count, colors);
  }
  
  #else // SK_CPU_SSE_LEVEL >= SK_CPU_SSE_LEVEL_SSSE3
  
  void S32_opaque_D32_filter_DX_SSSE3(const SkBitmapProcState& s,
                                      const uint32_t* xy,
                                      int count, uint32_t* colors) {
      sk_throw();
  }
  
  void S32_alpha_D32_filter_DX_SSSE3(const SkBitmapProcState& s,
                                     const uint32_t* xy,
                                     int count, uint32_t* colors) {
      sk_throw();
  }
  
  void S32_opaque_D32_filter_DXDY_SSSE3(const SkBitmapProcState& s,
                                        const uint32_t* xy,
                                        int count, uint32_t* colors) {
      sk_throw();
  }
  
  void S32_alpha_D32_filter_DXDY_SSSE3(const SkBitmapProcState& s,
                                       const uint32_t* xy,
                                       int count, uint32_t* colors) {
      sk_throw();
  }
  
  #endif
  