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      1 /*
      2  * Copyright 2013 Google Inc.
      3  *
      4  * Use of this source code is governed by a BSD-style license that can be
      5  * found in the LICENSE file.
      6  */
      7 
      8 #include <emmintrin.h>
      9 #include "SkBitmap.h"
     10 #include "SkBitmapFilter_opts_SSE2.h"
     11 #include "SkBitmapProcState.h"
     12 #include "SkColor.h"
     13 #include "SkColorPriv.h"
     14 #include "SkConvolver.h"
     15 #include "SkShader.h"
     16 #include "SkUnPreMultiply.h"
     17 
     18 #if 0
     19 static inline void print128i(__m128i value) {
     20     int *v = (int*) &value;
     21     printf("% .11d % .11d % .11d % .11d\n", v[0], v[1], v[2], v[3]);
     22 }
     23 
     24 static inline void print128i_16(__m128i value) {
     25     short *v = (short*) &value;
     26     printf("% .5d % .5d % .5d % .5d % .5d % .5d % .5d % .5d\n", v[0], v[1], v[2], v[3], v[4], v[5], v[6], v[7]);
     27 }
     28 
     29 static inline void print128i_8(__m128i value) {
     30     unsigned char *v = (unsigned char*) &value;
     31     printf("%.3u %.3u %.3u %.3u %.3u %.3u %.3u %.3u %.3u %.3u %.3u %.3u %.3u %.3u %.3u %.3u\n",
     32            v[0], v[1], v[2], v[3], v[4], v[5], v[6], v[7],
     33            v[8], v[9], v[10], v[11], v[12], v[13], v[14], v[15]
     34            );
     35 }
     36 
     37 static inline void print128f(__m128 value) {
     38     float *f = (float*) &value;
     39     printf("%3.4f %3.4f %3.4f %3.4f\n", f[0], f[1], f[2], f[3]);
     40 }
     41 #endif
     42 
     43 // because the border is handled specially, this is guaranteed to have all 16 pixels
     44 // available to it without running off the bitmap's edge.
     45 
     46 void highQualityFilter_SSE2(const SkBitmapProcState& s, int x, int y,
     47                             SkPMColor* SK_RESTRICT colors, int count) {
     48 
     49     const int maxX = s.fBitmap->width();
     50     const int maxY = s.fBitmap->height();
     51     SkAutoTMalloc<SkScalar> xWeights(maxX);
     52 
     53     while (count-- > 0) {
     54         SkPoint srcPt;
     55         s.fInvProc(s.fInvMatrix, x + 0.5f, y + 0.5f, &srcPt);
     56         srcPt.fX -= SK_ScalarHalf;
     57         srcPt.fY -= SK_ScalarHalf;
     58 
     59         __m128 weight = _mm_setzero_ps();
     60         __m128 accum = _mm_setzero_ps();
     61 
     62         int y0 = SkClampMax(SkScalarCeilToInt(srcPt.fY-s.getBitmapFilter()->width()), maxY);
     63         int y1 = SkClampMax(SkScalarFloorToInt(srcPt.fY+s.getBitmapFilter()->width()+1), maxY);
     64         int x0 = SkClampMax(SkScalarCeilToInt(srcPt.fX-s.getBitmapFilter()->width()), maxX);
     65         int x1 = SkClampMax(SkScalarFloorToInt(srcPt.fX+s.getBitmapFilter()->width())+1, maxX);
     66 
     67         for (int srcX = x0; srcX < x1 ; srcX++) {
     68             // Looking these up once instead of each loop is a ~15% speedup.
     69             xWeights[srcX - x0] = s.getBitmapFilter()->lookupScalar((srcPt.fX - srcX));
     70         }
     71 
     72         for (int srcY = y0; srcY < y1; srcY++) {
     73             SkScalar yWeight = s.getBitmapFilter()->lookupScalar((srcPt.fY - srcY));
     74 
     75             for (int srcX = x0; srcX < x1 ; srcX++) {
     76                 SkScalar xWeight = xWeights[srcX - x0];
     77 
     78                 SkScalar combined_weight = SkScalarMul(xWeight, yWeight);
     79 
     80                 SkPMColor color = *s.fBitmap->getAddr32(srcX, srcY);
     81 
     82                 __m128i c = _mm_cvtsi32_si128(color);
     83                 c = _mm_unpacklo_epi8(c, _mm_setzero_si128());
     84                 c = _mm_unpacklo_epi16(c, _mm_setzero_si128());
     85                 __m128 cfloat = _mm_cvtepi32_ps(c);
     86 
     87                 __m128 weightVector = _mm_set1_ps(combined_weight);
     88                 accum = _mm_add_ps(accum, _mm_mul_ps(cfloat, weightVector));
     89                 weight = _mm_add_ps( weight, weightVector );
     90             }
     91         }
     92 
     93         accum = _mm_div_ps(accum, weight);
     94         accum = _mm_add_ps(accum, _mm_set1_ps(0.5f));
     95         __m128i accumInt = _mm_cvttps_epi32(accum);
     96         accumInt = _mm_packs_epi32(accumInt, _mm_setzero_si128());
     97         accumInt = _mm_packus_epi16(accumInt, _mm_setzero_si128());
     98         SkPMColor c = _mm_cvtsi128_si32(accumInt);
     99 
    100         int a = SkClampMax(SkGetPackedA32(c), 255);
    101         int r = SkClampMax(SkGetPackedR32(c), a);
    102         int g = SkClampMax(SkGetPackedG32(c), a);
    103         int b = SkClampMax(SkGetPackedB32(c), a);
    104 
    105         *colors++ = SkPackARGB32(a, r, g, b);
    106 
    107         x++;
    108     }
    109 }
    110 
    111 // Convolves horizontally along a single row. The row data is given in
    112 // |src_data| and continues for the num_values() of the filter.
    113 void convolveHorizontally_SSE2(const unsigned char* src_data,
    114                                const SkConvolutionFilter1D& filter,
    115                                unsigned char* out_row,
    116                                bool /*has_alpha*/) {
    117     int num_values = filter.numValues();
    118 
    119     int filter_offset, filter_length;
    120     __m128i zero = _mm_setzero_si128();
    121     __m128i mask[4];
    122     // |mask| will be used to decimate all extra filter coefficients that are
    123     // loaded by SIMD when |filter_length| is not divisible by 4.
    124     // mask[0] is not used in following algorithm.
    125     mask[1] = _mm_set_epi16(0, 0, 0, 0, 0, 0, 0, -1);
    126     mask[2] = _mm_set_epi16(0, 0, 0, 0, 0, 0, -1, -1);
    127     mask[3] = _mm_set_epi16(0, 0, 0, 0, 0, -1, -1, -1);
    128 
    129     // Output one pixel each iteration, calculating all channels (RGBA) together.
    130     for (int out_x = 0; out_x < num_values; out_x++) {
    131         const SkConvolutionFilter1D::ConvolutionFixed* filter_values =
    132             filter.FilterForValue(out_x, &filter_offset, &filter_length);
    133 
    134         __m128i accum = _mm_setzero_si128();
    135 
    136         // Compute the first pixel in this row that the filter affects. It will
    137         // touch |filter_length| pixels (4 bytes each) after this.
    138         const __m128i* row_to_filter =
    139             reinterpret_cast<const __m128i*>(&src_data[filter_offset << 2]);
    140 
    141         // We will load and accumulate with four coefficients per iteration.
    142         for (int filter_x = 0; filter_x < filter_length >> 2; filter_x++) {
    143 
    144             // Load 4 coefficients => duplicate 1st and 2nd of them for all channels.
    145             __m128i coeff, coeff16;
    146             // [16] xx xx xx xx c3 c2 c1 c0
    147             coeff = _mm_loadl_epi64(reinterpret_cast<const __m128i*>(filter_values));
    148             // [16] xx xx xx xx c1 c1 c0 c0
    149             coeff16 = _mm_shufflelo_epi16(coeff, _MM_SHUFFLE(1, 1, 0, 0));
    150             // [16] c1 c1 c1 c1 c0 c0 c0 c0
    151             coeff16 = _mm_unpacklo_epi16(coeff16, coeff16);
    152 
    153             // Load four pixels => unpack the first two pixels to 16 bits =>
    154             // multiply with coefficients => accumulate the convolution result.
    155             // [8] a3 b3 g3 r3 a2 b2 g2 r2 a1 b1 g1 r1 a0 b0 g0 r0
    156             __m128i src8 = _mm_loadu_si128(row_to_filter);
    157             // [16] a1 b1 g1 r1 a0 b0 g0 r0
    158             __m128i src16 = _mm_unpacklo_epi8(src8, zero);
    159             __m128i mul_hi = _mm_mulhi_epi16(src16, coeff16);
    160             __m128i mul_lo = _mm_mullo_epi16(src16, coeff16);
    161             // [32]  a0*c0 b0*c0 g0*c0 r0*c0
    162             __m128i t = _mm_unpacklo_epi16(mul_lo, mul_hi);
    163             accum = _mm_add_epi32(accum, t);
    164             // [32]  a1*c1 b1*c1 g1*c1 r1*c1
    165             t = _mm_unpackhi_epi16(mul_lo, mul_hi);
    166             accum = _mm_add_epi32(accum, t);
    167 
    168             // Duplicate 3rd and 4th coefficients for all channels =>
    169             // unpack the 3rd and 4th pixels to 16 bits => multiply with coefficients
    170             // => accumulate the convolution results.
    171             // [16] xx xx xx xx c3 c3 c2 c2
    172             coeff16 = _mm_shufflelo_epi16(coeff, _MM_SHUFFLE(3, 3, 2, 2));
    173             // [16] c3 c3 c3 c3 c2 c2 c2 c2
    174             coeff16 = _mm_unpacklo_epi16(coeff16, coeff16);
    175             // [16] a3 g3 b3 r3 a2 g2 b2 r2
    176             src16 = _mm_unpackhi_epi8(src8, zero);
    177             mul_hi = _mm_mulhi_epi16(src16, coeff16);
    178             mul_lo = _mm_mullo_epi16(src16, coeff16);
    179             // [32]  a2*c2 b2*c2 g2*c2 r2*c2
    180             t = _mm_unpacklo_epi16(mul_lo, mul_hi);
    181             accum = _mm_add_epi32(accum, t);
    182             // [32]  a3*c3 b3*c3 g3*c3 r3*c3
    183             t = _mm_unpackhi_epi16(mul_lo, mul_hi);
    184             accum = _mm_add_epi32(accum, t);
    185 
    186             // Advance the pixel and coefficients pointers.
    187             row_to_filter += 1;
    188             filter_values += 4;
    189         }
    190 
    191         // When |filter_length| is not divisible by 4, we need to decimate some of
    192         // the filter coefficient that was loaded incorrectly to zero; Other than
    193         // that the algorithm is same with above, exceot that the 4th pixel will be
    194         // always absent.
    195         int r = filter_length&3;
    196         if (r) {
    197             // Note: filter_values must be padded to align_up(filter_offset, 8).
    198             __m128i coeff, coeff16;
    199             coeff = _mm_loadl_epi64(reinterpret_cast<const __m128i*>(filter_values));
    200             // Mask out extra filter taps.
    201             coeff = _mm_and_si128(coeff, mask[r]);
    202             coeff16 = _mm_shufflelo_epi16(coeff, _MM_SHUFFLE(1, 1, 0, 0));
    203             coeff16 = _mm_unpacklo_epi16(coeff16, coeff16);
    204 
    205             // Note: line buffer must be padded to align_up(filter_offset, 16).
    206             // We resolve this by use C-version for the last horizontal line.
    207             __m128i src8 = _mm_loadu_si128(row_to_filter);
    208             __m128i src16 = _mm_unpacklo_epi8(src8, zero);
    209             __m128i mul_hi = _mm_mulhi_epi16(src16, coeff16);
    210             __m128i mul_lo = _mm_mullo_epi16(src16, coeff16);
    211             __m128i t = _mm_unpacklo_epi16(mul_lo, mul_hi);
    212             accum = _mm_add_epi32(accum, t);
    213             t = _mm_unpackhi_epi16(mul_lo, mul_hi);
    214             accum = _mm_add_epi32(accum, t);
    215 
    216             src16 = _mm_unpackhi_epi8(src8, zero);
    217             coeff16 = _mm_shufflelo_epi16(coeff, _MM_SHUFFLE(3, 3, 2, 2));
    218             coeff16 = _mm_unpacklo_epi16(coeff16, coeff16);
    219             mul_hi = _mm_mulhi_epi16(src16, coeff16);
    220             mul_lo = _mm_mullo_epi16(src16, coeff16);
    221             t = _mm_unpacklo_epi16(mul_lo, mul_hi);
    222             accum = _mm_add_epi32(accum, t);
    223         }
    224 
    225         // Shift right for fixed point implementation.
    226         accum = _mm_srai_epi32(accum, SkConvolutionFilter1D::kShiftBits);
    227 
    228         // Packing 32 bits |accum| to 16 bits per channel (signed saturation).
    229         accum = _mm_packs_epi32(accum, zero);
    230         // Packing 16 bits |accum| to 8 bits per channel (unsigned saturation).
    231         accum = _mm_packus_epi16(accum, zero);
    232 
    233         // Store the pixel value of 32 bits.
    234         *(reinterpret_cast<int*>(out_row)) = _mm_cvtsi128_si32(accum);
    235         out_row += 4;
    236     }
    237 }
    238 
    239 // Convolves horizontally along four rows. The row data is given in
    240 // |src_data| and continues for the num_values() of the filter.
    241 // The algorithm is almost same as |ConvolveHorizontally_SSE2|. Please
    242 // refer to that function for detailed comments.
    243 void convolve4RowsHorizontally_SSE2(const unsigned char* src_data[4],
    244                                     const SkConvolutionFilter1D& filter,
    245                                     unsigned char* out_row[4]) {
    246     int num_values = filter.numValues();
    247 
    248     int filter_offset, filter_length;
    249     __m128i zero = _mm_setzero_si128();
    250     __m128i mask[4];
    251     // |mask| will be used to decimate all extra filter coefficients that are
    252     // loaded by SIMD when |filter_length| is not divisible by 4.
    253     // mask[0] is not used in following algorithm.
    254     mask[1] = _mm_set_epi16(0, 0, 0, 0, 0, 0, 0, -1);
    255     mask[2] = _mm_set_epi16(0, 0, 0, 0, 0, 0, -1, -1);
    256     mask[3] = _mm_set_epi16(0, 0, 0, 0, 0, -1, -1, -1);
    257 
    258     // Output one pixel each iteration, calculating all channels (RGBA) together.
    259     for (int out_x = 0; out_x < num_values; out_x++) {
    260         const SkConvolutionFilter1D::ConvolutionFixed* filter_values =
    261             filter.FilterForValue(out_x, &filter_offset, &filter_length);
    262 
    263         // four pixels in a column per iteration.
    264         __m128i accum0 = _mm_setzero_si128();
    265         __m128i accum1 = _mm_setzero_si128();
    266         __m128i accum2 = _mm_setzero_si128();
    267         __m128i accum3 = _mm_setzero_si128();
    268         int start = (filter_offset<<2);
    269         // We will load and accumulate with four coefficients per iteration.
    270         for (int filter_x = 0; filter_x < (filter_length >> 2); filter_x++) {
    271             __m128i coeff, coeff16lo, coeff16hi;
    272             // [16] xx xx xx xx c3 c2 c1 c0
    273             coeff = _mm_loadl_epi64(reinterpret_cast<const __m128i*>(filter_values));
    274             // [16] xx xx xx xx c1 c1 c0 c0
    275             coeff16lo = _mm_shufflelo_epi16(coeff, _MM_SHUFFLE(1, 1, 0, 0));
    276             // [16] c1 c1 c1 c1 c0 c0 c0 c0
    277             coeff16lo = _mm_unpacklo_epi16(coeff16lo, coeff16lo);
    278             // [16] xx xx xx xx c3 c3 c2 c2
    279             coeff16hi = _mm_shufflelo_epi16(coeff, _MM_SHUFFLE(3, 3, 2, 2));
    280             // [16] c3 c3 c3 c3 c2 c2 c2 c2
    281             coeff16hi = _mm_unpacklo_epi16(coeff16hi, coeff16hi);
    282 
    283             __m128i src8, src16, mul_hi, mul_lo, t;
    284 
    285 #define ITERATION(src, accum)                                                \
    286             src8 = _mm_loadu_si128(reinterpret_cast<const __m128i*>(src));   \
    287             src16 = _mm_unpacklo_epi8(src8, zero);                           \
    288             mul_hi = _mm_mulhi_epi16(src16, coeff16lo);                      \
    289             mul_lo = _mm_mullo_epi16(src16, coeff16lo);                      \
    290             t = _mm_unpacklo_epi16(mul_lo, mul_hi);                          \
    291             accum = _mm_add_epi32(accum, t);                                 \
    292             t = _mm_unpackhi_epi16(mul_lo, mul_hi);                          \
    293             accum = _mm_add_epi32(accum, t);                                 \
    294             src16 = _mm_unpackhi_epi8(src8, zero);                           \
    295             mul_hi = _mm_mulhi_epi16(src16, coeff16hi);                      \
    296             mul_lo = _mm_mullo_epi16(src16, coeff16hi);                      \
    297             t = _mm_unpacklo_epi16(mul_lo, mul_hi);                          \
    298             accum = _mm_add_epi32(accum, t);                                 \
    299             t = _mm_unpackhi_epi16(mul_lo, mul_hi);                          \
    300             accum = _mm_add_epi32(accum, t)
    301 
    302             ITERATION(src_data[0] + start, accum0);
    303             ITERATION(src_data[1] + start, accum1);
    304             ITERATION(src_data[2] + start, accum2);
    305             ITERATION(src_data[3] + start, accum3);
    306 
    307             start += 16;
    308             filter_values += 4;
    309         }
    310 
    311         int r = filter_length & 3;
    312         if (r) {
    313             // Note: filter_values must be padded to align_up(filter_offset, 8);
    314             __m128i coeff;
    315             coeff = _mm_loadl_epi64(reinterpret_cast<const __m128i*>(filter_values));
    316             // Mask out extra filter taps.
    317             coeff = _mm_and_si128(coeff, mask[r]);
    318 
    319             __m128i coeff16lo = _mm_shufflelo_epi16(coeff, _MM_SHUFFLE(1, 1, 0, 0));
    320             /* c1 c1 c1 c1 c0 c0 c0 c0 */
    321             coeff16lo = _mm_unpacklo_epi16(coeff16lo, coeff16lo);
    322             __m128i coeff16hi = _mm_shufflelo_epi16(coeff, _MM_SHUFFLE(3, 3, 2, 2));
    323             coeff16hi = _mm_unpacklo_epi16(coeff16hi, coeff16hi);
    324 
    325             __m128i src8, src16, mul_hi, mul_lo, t;
    326 
    327             ITERATION(src_data[0] + start, accum0);
    328             ITERATION(src_data[1] + start, accum1);
    329             ITERATION(src_data[2] + start, accum2);
    330             ITERATION(src_data[3] + start, accum3);
    331         }
    332 
    333         accum0 = _mm_srai_epi32(accum0, SkConvolutionFilter1D::kShiftBits);
    334         accum0 = _mm_packs_epi32(accum0, zero);
    335         accum0 = _mm_packus_epi16(accum0, zero);
    336         accum1 = _mm_srai_epi32(accum1, SkConvolutionFilter1D::kShiftBits);
    337         accum1 = _mm_packs_epi32(accum1, zero);
    338         accum1 = _mm_packus_epi16(accum1, zero);
    339         accum2 = _mm_srai_epi32(accum2, SkConvolutionFilter1D::kShiftBits);
    340         accum2 = _mm_packs_epi32(accum2, zero);
    341         accum2 = _mm_packus_epi16(accum2, zero);
    342         accum3 = _mm_srai_epi32(accum3, SkConvolutionFilter1D::kShiftBits);
    343         accum3 = _mm_packs_epi32(accum3, zero);
    344         accum3 = _mm_packus_epi16(accum3, zero);
    345 
    346         *(reinterpret_cast<int*>(out_row[0])) = _mm_cvtsi128_si32(accum0);
    347         *(reinterpret_cast<int*>(out_row[1])) = _mm_cvtsi128_si32(accum1);
    348         *(reinterpret_cast<int*>(out_row[2])) = _mm_cvtsi128_si32(accum2);
    349         *(reinterpret_cast<int*>(out_row[3])) = _mm_cvtsi128_si32(accum3);
    350 
    351         out_row[0] += 4;
    352         out_row[1] += 4;
    353         out_row[2] += 4;
    354         out_row[3] += 4;
    355     }
    356 }
    357 
    358 // Does vertical convolution to produce one output row. The filter values and
    359 // length are given in the first two parameters. These are applied to each
    360 // of the rows pointed to in the |source_data_rows| array, with each row
    361 // being |pixel_width| wide.
    362 //
    363 // The output must have room for |pixel_width * 4| bytes.
    364 template<bool has_alpha>
    365 void convolveVertically_SSE2(const SkConvolutionFilter1D::ConvolutionFixed* filter_values,
    366                              int filter_length,
    367                              unsigned char* const* source_data_rows,
    368                              int pixel_width,
    369                              unsigned char* out_row) {
    370     int width = pixel_width & ~3;
    371 
    372     __m128i zero = _mm_setzero_si128();
    373     __m128i accum0, accum1, accum2, accum3, coeff16;
    374     const __m128i* src;
    375     // Output four pixels per iteration (16 bytes).
    376     for (int out_x = 0; out_x < width; out_x += 4) {
    377 
    378         // Accumulated result for each pixel. 32 bits per RGBA channel.
    379         accum0 = _mm_setzero_si128();
    380         accum1 = _mm_setzero_si128();
    381         accum2 = _mm_setzero_si128();
    382         accum3 = _mm_setzero_si128();
    383 
    384         // Convolve with one filter coefficient per iteration.
    385         for (int filter_y = 0; filter_y < filter_length; filter_y++) {
    386 
    387             // Duplicate the filter coefficient 8 times.
    388             // [16] cj cj cj cj cj cj cj cj
    389             coeff16 = _mm_set1_epi16(filter_values[filter_y]);
    390 
    391             // Load four pixels (16 bytes) together.
    392             // [8] a3 b3 g3 r3 a2 b2 g2 r2 a1 b1 g1 r1 a0 b0 g0 r0
    393             src = reinterpret_cast<const __m128i*>(
    394                 &source_data_rows[filter_y][out_x << 2]);
    395             __m128i src8 = _mm_loadu_si128(src);
    396 
    397             // Unpack 1st and 2nd pixels from 8 bits to 16 bits for each channels =>
    398             // multiply with current coefficient => accumulate the result.
    399             // [16] a1 b1 g1 r1 a0 b0 g0 r0
    400             __m128i src16 = _mm_unpacklo_epi8(src8, zero);
    401             __m128i mul_hi = _mm_mulhi_epi16(src16, coeff16);
    402             __m128i mul_lo = _mm_mullo_epi16(src16, coeff16);
    403             // [32] a0 b0 g0 r0
    404             __m128i t = _mm_unpacklo_epi16(mul_lo, mul_hi);
    405             accum0 = _mm_add_epi32(accum0, t);
    406             // [32] a1 b1 g1 r1
    407             t = _mm_unpackhi_epi16(mul_lo, mul_hi);
    408             accum1 = _mm_add_epi32(accum1, t);
    409 
    410             // Unpack 3rd and 4th pixels from 8 bits to 16 bits for each channels =>
    411             // multiply with current coefficient => accumulate the result.
    412             // [16] a3 b3 g3 r3 a2 b2 g2 r2
    413             src16 = _mm_unpackhi_epi8(src8, zero);
    414             mul_hi = _mm_mulhi_epi16(src16, coeff16);
    415             mul_lo = _mm_mullo_epi16(src16, coeff16);
    416             // [32] a2 b2 g2 r2
    417             t = _mm_unpacklo_epi16(mul_lo, mul_hi);
    418             accum2 = _mm_add_epi32(accum2, t);
    419             // [32] a3 b3 g3 r3
    420             t = _mm_unpackhi_epi16(mul_lo, mul_hi);
    421             accum3 = _mm_add_epi32(accum3, t);
    422         }
    423 
    424         // Shift right for fixed point implementation.
    425         accum0 = _mm_srai_epi32(accum0, SkConvolutionFilter1D::kShiftBits);
    426         accum1 = _mm_srai_epi32(accum1, SkConvolutionFilter1D::kShiftBits);
    427         accum2 = _mm_srai_epi32(accum2, SkConvolutionFilter1D::kShiftBits);
    428         accum3 = _mm_srai_epi32(accum3, SkConvolutionFilter1D::kShiftBits);
    429 
    430         // Packing 32 bits |accum| to 16 bits per channel (signed saturation).
    431         // [16] a1 b1 g1 r1 a0 b0 g0 r0
    432         accum0 = _mm_packs_epi32(accum0, accum1);
    433         // [16] a3 b3 g3 r3 a2 b2 g2 r2
    434         accum2 = _mm_packs_epi32(accum2, accum3);
    435 
    436         // Packing 16 bits |accum| to 8 bits per channel (unsigned saturation).
    437         // [8] a3 b3 g3 r3 a2 b2 g2 r2 a1 b1 g1 r1 a0 b0 g0 r0
    438         accum0 = _mm_packus_epi16(accum0, accum2);
    439 
    440         if (has_alpha) {
    441             // Compute the max(ri, gi, bi) for each pixel.
    442             // [8] xx a3 b3 g3 xx a2 b2 g2 xx a1 b1 g1 xx a0 b0 g0
    443             __m128i a = _mm_srli_epi32(accum0, 8);
    444             // [8] xx xx xx max3 xx xx xx max2 xx xx xx max1 xx xx xx max0
    445             __m128i b = _mm_max_epu8(a, accum0);  // Max of r and g.
    446             // [8] xx xx a3 b3 xx xx a2 b2 xx xx a1 b1 xx xx a0 b0
    447             a = _mm_srli_epi32(accum0, 16);
    448             // [8] xx xx xx max3 xx xx xx max2 xx xx xx max1 xx xx xx max0
    449             b = _mm_max_epu8(a, b);  // Max of r and g and b.
    450             // [8] max3 00 00 00 max2 00 00 00 max1 00 00 00 max0 00 00 00
    451             b = _mm_slli_epi32(b, 24);
    452 
    453             // Make sure the value of alpha channel is always larger than maximum
    454             // value of color channels.
    455             accum0 = _mm_max_epu8(b, accum0);
    456         } else {
    457             // Set value of alpha channels to 0xFF.
    458             __m128i mask = _mm_set1_epi32(0xff000000);
    459             accum0 = _mm_or_si128(accum0, mask);
    460         }
    461 
    462         // Store the convolution result (16 bytes) and advance the pixel pointers.
    463         _mm_storeu_si128(reinterpret_cast<__m128i*>(out_row), accum0);
    464         out_row += 16;
    465     }
    466 
    467     // When the width of the output is not divisible by 4, We need to save one
    468     // pixel (4 bytes) each time. And also the fourth pixel is always absent.
    469     if (pixel_width & 3) {
    470         accum0 = _mm_setzero_si128();
    471         accum1 = _mm_setzero_si128();
    472         accum2 = _mm_setzero_si128();
    473         for (int filter_y = 0; filter_y < filter_length; ++filter_y) {
    474             coeff16 = _mm_set1_epi16(filter_values[filter_y]);
    475             // [8] a3 b3 g3 r3 a2 b2 g2 r2 a1 b1 g1 r1 a0 b0 g0 r0
    476             src = reinterpret_cast<const __m128i*>(
    477                 &source_data_rows[filter_y][width<<2]);
    478             __m128i src8 = _mm_loadu_si128(src);
    479             // [16] a1 b1 g1 r1 a0 b0 g0 r0
    480             __m128i src16 = _mm_unpacklo_epi8(src8, zero);
    481             __m128i mul_hi = _mm_mulhi_epi16(src16, coeff16);
    482             __m128i mul_lo = _mm_mullo_epi16(src16, coeff16);
    483             // [32] a0 b0 g0 r0
    484             __m128i t = _mm_unpacklo_epi16(mul_lo, mul_hi);
    485             accum0 = _mm_add_epi32(accum0, t);
    486             // [32] a1 b1 g1 r1
    487             t = _mm_unpackhi_epi16(mul_lo, mul_hi);
    488             accum1 = _mm_add_epi32(accum1, t);
    489             // [16] a3 b3 g3 r3 a2 b2 g2 r2
    490             src16 = _mm_unpackhi_epi8(src8, zero);
    491             mul_hi = _mm_mulhi_epi16(src16, coeff16);
    492             mul_lo = _mm_mullo_epi16(src16, coeff16);
    493             // [32] a2 b2 g2 r2
    494             t = _mm_unpacklo_epi16(mul_lo, mul_hi);
    495             accum2 = _mm_add_epi32(accum2, t);
    496         }
    497 
    498         accum0 = _mm_srai_epi32(accum0, SkConvolutionFilter1D::kShiftBits);
    499         accum1 = _mm_srai_epi32(accum1, SkConvolutionFilter1D::kShiftBits);
    500         accum2 = _mm_srai_epi32(accum2, SkConvolutionFilter1D::kShiftBits);
    501         // [16] a1 b1 g1 r1 a0 b0 g0 r0
    502         accum0 = _mm_packs_epi32(accum0, accum1);
    503         // [16] a3 b3 g3 r3 a2 b2 g2 r2
    504         accum2 = _mm_packs_epi32(accum2, zero);
    505         // [8] a3 b3 g3 r3 a2 b2 g2 r2 a1 b1 g1 r1 a0 b0 g0 r0
    506         accum0 = _mm_packus_epi16(accum0, accum2);
    507         if (has_alpha) {
    508             // [8] xx a3 b3 g3 xx a2 b2 g2 xx a1 b1 g1 xx a0 b0 g0
    509             __m128i a = _mm_srli_epi32(accum0, 8);
    510             // [8] xx xx xx max3 xx xx xx max2 xx xx xx max1 xx xx xx max0
    511             __m128i b = _mm_max_epu8(a, accum0);  // Max of r and g.
    512             // [8] xx xx a3 b3 xx xx a2 b2 xx xx a1 b1 xx xx a0 b0
    513             a = _mm_srli_epi32(accum0, 16);
    514             // [8] xx xx xx max3 xx xx xx max2 xx xx xx max1 xx xx xx max0
    515             b = _mm_max_epu8(a, b);  // Max of r and g and b.
    516             // [8] max3 00 00 00 max2 00 00 00 max1 00 00 00 max0 00 00 00
    517             b = _mm_slli_epi32(b, 24);
    518             accum0 = _mm_max_epu8(b, accum0);
    519         } else {
    520             __m128i mask = _mm_set1_epi32(0xff000000);
    521             accum0 = _mm_or_si128(accum0, mask);
    522         }
    523 
    524         for (int out_x = width; out_x < pixel_width; out_x++) {
    525             *(reinterpret_cast<int*>(out_row)) = _mm_cvtsi128_si32(accum0);
    526             accum0 = _mm_srli_si128(accum0, 4);
    527             out_row += 4;
    528         }
    529     }
    530 }
    531 
    532 void convolveVertically_SSE2(const SkConvolutionFilter1D::ConvolutionFixed* filter_values,
    533                              int filter_length,
    534                              unsigned char* const* source_data_rows,
    535                              int pixel_width,
    536                              unsigned char* out_row,
    537                              bool has_alpha) {
    538     if (has_alpha) {
    539         convolveVertically_SSE2<true>(filter_values,
    540                                       filter_length,
    541                                       source_data_rows,
    542                                       pixel_width,
    543                                       out_row);
    544     } else {
    545         convolveVertically_SSE2<false>(filter_values,
    546                                        filter_length,
    547                                        source_data_rows,
    548                                        pixel_width,
    549                                        out_row);
    550     }
    551 }
    552 
    553 void applySIMDPadding_SSE2(SkConvolutionFilter1D *filter) {
    554     // Padding |paddingCount| of more dummy coefficients after the coefficients
    555     // of last filter to prevent SIMD instructions which load 8 or 16 bytes
    556     // together to access invalid memory areas. We are not trying to align the
    557     // coefficients right now due to the opaqueness of <vector> implementation.
    558     // This has to be done after all |AddFilter| calls.
    559     for (int i = 0; i < 8; ++i) {
    560         filter->addFilterValue(static_cast<SkConvolutionFilter1D::ConvolutionFixed>(0));
    561     }
    562 }
    563