gfx/2d/ConvolutionFilterAVX2.cpp

   1 /* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
   2 /* vim: set ts=8 sts=2 et sw=2 tw=80: */
   3 // Copyright (c) 2011-2016 Google Inc.
   4 // Use of this source code is governed by a BSD-style license that can be
   5 // found in the gfx/skia/LICENSE file.
   6
   7 #include "SkConvolver.h"
   8 #include <immintrin.h>
   9
  10 namespace skia {
  11
  12 void convolve_vertically_avx2(
  13     const SkConvolutionFilter1D::ConvolutionFixed* filter, int filterLen,
  14     unsigned char* const* srcRows, int width, unsigned char* out,
  15     bool hasAlpha) {
  16   // It's simpler to work with the output array in terms of 4-byte pixels.
  17   auto* dst = (int*)out;
  18
  19   // Output up to eight pixels per iteration.
  20   for (int x = 0; x < width; x += 8) {
  21     // Accumulated result for 4 (non-adjacent) pairs of pixels,
  22     // with each channel in signed 17.14 fixed point.
  23     auto accum04 = _mm256_setzero_si256(), accum15 = _mm256_setzero_si256(),
  24          accum26 = _mm256_setzero_si256(), accum37 = _mm256_setzero_si256();
  25
  26     // Convolve with the filter.  (This inner loop is where we spend ~all our
  27     // time.) While we can, we consume 2 filter coefficients and 2 rows of 8
  28     // pixels each at a time.
  29     auto convolve_16_pixels = [&](__m256i interlaced_coeffs,
  30                                   __m256i pixels_01234567,
  31                                   __m256i pixels_89ABCDEF) {
  32       // Interlaced R0R8 G0G8 B0B8 A0A8 R1R9 G1G9... 32 8-bit values each.
  33       auto _08194C5D = _mm256_unpacklo_epi8(pixels_01234567, pixels_89ABCDEF),
  34            _2A3B6E7F = _mm256_unpackhi_epi8(pixels_01234567, pixels_89ABCDEF);
  35
  36       // Still interlaced R0R8 G0G8... as above, each channel expanded to 16-bit
  37       // lanes.
  38       auto _084C = _mm256_unpacklo_epi8(_08194C5D, _mm256_setzero_si256()),
  39            _195D = _mm256_unpackhi_epi8(_08194C5D, _mm256_setzero_si256()),
  40            _2A6E = _mm256_unpacklo_epi8(_2A3B6E7F, _mm256_setzero_si256()),
  41            _3B7F = _mm256_unpackhi_epi8(_2A3B6E7F, _mm256_setzero_si256());
  42
  43       // accum0_R += R0*coeff0 + R8*coeff1, etc.
  44       accum04 = _mm256_add_epi32(accum04,
  45                                  _mm256_madd_epi16(_084C, interlaced_coeffs));
  46       accum15 = _mm256_add_epi32(accum15,
  47                                  _mm256_madd_epi16(_195D, interlaced_coeffs));
  48       accum26 = _mm256_add_epi32(accum26,
  49                                  _mm256_madd_epi16(_2A6E, interlaced_coeffs));
  50       accum37 = _mm256_add_epi32(accum37,
  51                                  _mm256_madd_epi16(_3B7F, interlaced_coeffs));
  52     };
  53
  54     int i = 0;
  55     for (; i < filterLen / 2 * 2; i += 2) {
  56       convolve_16_pixels(
  57           _mm256_set1_epi32(*(const int32_t*)(filter + i)),
  58           _mm256_loadu_si256((const __m256i*)(srcRows[i + 0] + x * 4)),
  59           _mm256_loadu_si256((const __m256i*)(srcRows[i + 1] + x * 4)));
  60     }
  61     if (i < filterLen) {
  62       convolve_16_pixels(
  63           _mm256_set1_epi32(*(const int16_t*)(filter + i)),
  64           _mm256_loadu_si256((const __m256i*)(srcRows[i] + x * 4)),
  65           _mm256_setzero_si256());
  66     }
  67
  68     // Trim the fractional parts off the accumulators.
  69     accum04 = _mm256_srai_epi32(accum04, 14);
  70     accum15 = _mm256_srai_epi32(accum15, 14);
  71     accum26 = _mm256_srai_epi32(accum26, 14);
  72     accum37 = _mm256_srai_epi32(accum37, 14);
  73
  74     // Pack back down to 8-bit channels.
  75     auto pixels = _mm256_packus_epi16(_mm256_packs_epi32(accum04, accum15),
  76                                       _mm256_packs_epi32(accum26, accum37));
  77
  78     if (hasAlpha) {
  79       // Clamp alpha to the max of r,g,b to make sure we stay premultiplied.
  80       __m256i max_rg = _mm256_max_epu8(pixels, _mm256_srli_epi32(pixels, 8)),
  81               max_rgb = _mm256_max_epu8(max_rg, _mm256_srli_epi32(pixels, 16));
  82       pixels = _mm256_max_epu8(pixels, _mm256_slli_epi32(max_rgb, 24));
  83     } else {
  84       // Force opaque.
  85       pixels = _mm256_or_si256(pixels, _mm256_set1_epi32(0xff000000));
  86     }
  87
  88     // Normal path to store 8 pixels.
  89     if (x + 8 <= width) {
  90       _mm256_storeu_si256((__m256i*)dst, pixels);
  91       dst += 8;
  92       continue;
  93     }
  94
  95     // Store one pixel at a time on the last iteration.
  96     for (int i = x; i < width; i++) {
  97       *dst++ = _mm_cvtsi128_si32(_mm256_castsi256_si128(pixels));
  98       pixels = _mm256_permutevar8x32_epi32(
  99           pixels, _mm256_setr_epi32(1, 2, 3, 4, 5, 6, 7, 0));
 100     }
 101   }
 102 }
 103
 104 }  // namespace skia