enable SSE2 in skia/convolver for linux32

skia/ext/convolver.cc

Index: skia/ext/convolver.cc
diff --git a/skia/ext/convolver.cc b/skia/ext/convolver.cc
index 47e3711fac4883c361e880b9cfce9241d52410c2..cbfa9315930edcc9664165a48dc667c2d7fba3b5 100644
--- a/skia/ext/convolver.cc
+++ b/skia/ext/convolver.cc
@@ -5,12 +5,9 @@
 #include <algorithm>
 
 #include "skia/ext/convolver.h"
+#include "skia/ext/convolver_SSE2.h"
 #include "third_party/skia/include/core/SkTypes.h"
 
-#if defined(SIMD_SSE2)
-#include <emmintrin.h>  // ARCH_CPU_X86_FAMILY was defined in build/config.h
-#endif
-
 namespace skia {
 
 namespace {
@@ -223,431 +220,23 @@ void ConvolveVertically(const ConvolutionFilter1D::Fixed* filter_values,
   }
 }
 
-
-// Convolves horizontally along a single row. The row data is given in
-// |src_data| and continues for the num_values() of the filter.
-void ConvolveHorizontally_SSE2(const unsigned char* src_data,
-                               const ConvolutionFilter1D& filter,
-                               unsigned char* out_row) {
-#if defined(SIMD_SSE2)
-  int num_values = filter.num_values();
-
-  int filter_offset, filter_length;
-  __m128i zero = _mm_setzero_si128();
-  __m128i mask[4];
-  // |mask| will be used to decimate all extra filter coefficients that are
-  // loaded by SIMD when |filter_length| is not divisible by 4.
-  // mask[0] is not used in following algorithm.
-  mask[1] = _mm_set_epi16(0, 0, 0, 0, 0, 0, 0, -1);
-  mask[2] = _mm_set_epi16(0, 0, 0, 0, 0, 0, -1, -1);
-  mask[3] = _mm_set_epi16(0, 0, 0, 0, 0, -1, -1, -1);
-
-  // Output one pixel each iteration, calculating all channels (RGBA) together.
-  for (int out_x = 0; out_x < num_values; out_x++) {
-    const ConvolutionFilter1D::Fixed* filter_values =
-        filter.FilterForValue(out_x, &filter_offset, &filter_length);
-
-    __m128i accum = _mm_setzero_si128();
-
-    // Compute the first pixel in this row that the filter affects. It will
-    // touch |filter_length| pixels (4 bytes each) after this.
-    const __m128i* row_to_filter =
-        reinterpret_cast<const __m128i*>(&src_data[filter_offset << 2]);
-
-    // We will load and accumulate with four coefficients per iteration.
-    for (int filter_x = 0; filter_x < filter_length >> 2; filter_x++) {
-
-      // Load 4 coefficients => duplicate 1st and 2nd of them for all channels.
-      __m128i coeff, coeff16;
-      // [16] xx xx xx xx c3 c2 c1 c0
-      coeff = _mm_loadl_epi64(reinterpret_cast<const __m128i*>(filter_values));
-      // [16] xx xx xx xx c1 c1 c0 c0
-      coeff16 = _mm_shufflelo_epi16(coeff, _MM_SHUFFLE(1, 1, 0, 0));
-      // [16] c1 c1 c1 c1 c0 c0 c0 c0
-      coeff16 = _mm_unpacklo_epi16(coeff16, coeff16);
-
-      // Load four pixels => unpack the first two pixels to 16 bits =>
-      // multiply with coefficients => accumulate the convolution result.
-      // [8] a3 b3 g3 r3 a2 b2 g2 r2 a1 b1 g1 r1 a0 b0 g0 r0
-      __m128i src8 = _mm_loadu_si128(row_to_filter);
-      // [16] a1 b1 g1 r1 a0 b0 g0 r0
-      __m128i src16 = _mm_unpacklo_epi8(src8, zero);
-      __m128i mul_hi = _mm_mulhi_epi16(src16, coeff16);
-      __m128i mul_lo = _mm_mullo_epi16(src16, coeff16);
-      // [32]  a0*c0 b0*c0 g0*c0 r0*c0
-      __m128i t = _mm_unpacklo_epi16(mul_lo, mul_hi);
-      accum = _mm_add_epi32(accum, t);
-      // [32]  a1*c1 b1*c1 g1*c1 r1*c1
-      t = _mm_unpackhi_epi16(mul_lo, mul_hi);
-      accum = _mm_add_epi32(accum, t);
-
-      // Duplicate 3rd and 4th coefficients for all channels =>
-      // unpack the 3rd and 4th pixels to 16 bits => multiply with coefficients
-      // => accumulate the convolution results.
-      // [16] xx xx xx xx c3 c3 c2 c2
-      coeff16 = _mm_shufflelo_epi16(coeff, _MM_SHUFFLE(3, 3, 2, 2));
-      // [16] c3 c3 c3 c3 c2 c2 c2 c2
-      coeff16 = _mm_unpacklo_epi16(coeff16, coeff16);
-      // [16] a3 g3 b3 r3 a2 g2 b2 r2
-      src16 = _mm_unpackhi_epi8(src8, zero);
-      mul_hi = _mm_mulhi_epi16(src16, coeff16);
-      mul_lo = _mm_mullo_epi16(src16, coeff16);
-      // [32]  a2*c2 b2*c2 g2*c2 r2*c2
-      t = _mm_unpacklo_epi16(mul_lo, mul_hi);
-      accum = _mm_add_epi32(accum, t);
-      // [32]  a3*c3 b3*c3 g3*c3 r3*c3
-      t = _mm_unpackhi_epi16(mul_lo, mul_hi);
-      accum = _mm_add_epi32(accum, t);
-
-      // Advance the pixel and coefficients pointers.
-      row_to_filter += 1;
-      filter_values += 4;
-    }
-
-    // When |filter_length| is not divisible by 4, we need to decimate some of
-    // the filter coefficient that was loaded incorrectly to zero; Other than
-    // that the algorithm is same with above, exceot that the 4th pixel will be
-    // always absent.
-    int r = filter_length&3;
-    if (r) {
-      // Note: filter_values must be padded to align_up(filter_offset, 8).
-      __m128i coeff, coeff16;
-      coeff = _mm_loadl_epi64(reinterpret_cast<const __m128i*>(filter_values));
-      // Mask out extra filter taps.
-      coeff = _mm_and_si128(coeff, mask[r]);
-      coeff16 = _mm_shufflelo_epi16(coeff, _MM_SHUFFLE(1, 1, 0, 0));
-      coeff16 = _mm_unpacklo_epi16(coeff16, coeff16);
-
-      // Note: line buffer must be padded to align_up(filter_offset, 16).
-      // We resolve this by use C-version for the last horizontal line.
-      __m128i src8 = _mm_loadu_si128(row_to_filter);
-      __m128i src16 = _mm_unpacklo_epi8(src8, zero);
-      __m128i mul_hi = _mm_mulhi_epi16(src16, coeff16);
-      __m128i mul_lo = _mm_mullo_epi16(src16, coeff16);
-      __m128i t = _mm_unpacklo_epi16(mul_lo, mul_hi);
-      accum = _mm_add_epi32(accum, t);
-      t = _mm_unpackhi_epi16(mul_lo, mul_hi);
-      accum = _mm_add_epi32(accum, t);
-
-      src16 = _mm_unpackhi_epi8(src8, zero);
-      coeff16 = _mm_shufflelo_epi16(coeff, _MM_SHUFFLE(3, 3, 2, 2));
-      coeff16 = _mm_unpacklo_epi16(coeff16, coeff16);
-      mul_hi = _mm_mulhi_epi16(src16, coeff16);
-      mul_lo = _mm_mullo_epi16(src16, coeff16);
-      t = _mm_unpacklo_epi16(mul_lo, mul_hi);
-      accum = _mm_add_epi32(accum, t);
-    }
-
-    // Shift right for fixed point implementation.
-    accum = _mm_srai_epi32(accum, ConvolutionFilter1D::kShiftBits);
-
-    // Packing 32 bits |accum| to 16 bits per channel (signed saturation).
-    accum = _mm_packs_epi32(accum, zero);
-    // Packing 16 bits |accum| to 8 bits per channel (unsigned saturation).
-    accum = _mm_packus_epi16(accum, zero);
-
-    // Store the pixel value of 32 bits.
-    *(reinterpret_cast<int*>(out_row)) = _mm_cvtsi128_si32(accum);
-    out_row += 4;
-  }
-#endif
-}
-
-// Convolves horizontally along four rows. The row data is given in
-// |src_data| and continues for the num_values() of the filter.
-// The algorithm is almost same as |ConvolveHorizontally_SSE2|. Please
-// refer to that function for detailed comments.
-void ConvolveHorizontally4_SSE2(const unsigned char* src_data[4],
-                                const ConvolutionFilter1D& filter,
-                                unsigned char* out_row[4]) {
-#if defined(SIMD_SSE2)
-  int num_values = filter.num_values();
-
-  int filter_offset, filter_length;
-  __m128i zero = _mm_setzero_si128();
-  __m128i mask[4];
-  // |mask| will be used to decimate all extra filter coefficients that are
-  // loaded by SIMD when |filter_length| is not divisible by 4.
-  // mask[0] is not used in following algorithm.
-  mask[1] = _mm_set_epi16(0, 0, 0, 0, 0, 0, 0, -1);
-  mask[2] = _mm_set_epi16(0, 0, 0, 0, 0, 0, -1, -1);
-  mask[3] = _mm_set_epi16(0, 0, 0, 0, 0, -1, -1, -1);
-
-  // Output one pixel each iteration, calculating all channels (RGBA) together.
-  for (int out_x = 0; out_x < num_values; out_x++) {
-    const ConvolutionFilter1D::Fixed* filter_values =
-        filter.FilterForValue(out_x, &filter_offset, &filter_length);
-
-    // four pixels in a column per iteration.
-    __m128i accum0 = _mm_setzero_si128();
-    __m128i accum1 = _mm_setzero_si128();
-    __m128i accum2 = _mm_setzero_si128();
-    __m128i accum3 = _mm_setzero_si128();
-    int start = (filter_offset<<2);
-    // We will load and accumulate with four coefficients per iteration.
-    for (int filter_x = 0; filter_x < (filter_length >> 2); filter_x++) {
-      __m128i coeff, coeff16lo, coeff16hi;
-      // [16] xx xx xx xx c3 c2 c1 c0
-      coeff = _mm_loadl_epi64(reinterpret_cast<const __m128i*>(filter_values));
-      // [16] xx xx xx xx c1 c1 c0 c0
-      coeff16lo = _mm_shufflelo_epi16(coeff, _MM_SHUFFLE(1, 1, 0, 0));
-      // [16] c1 c1 c1 c1 c0 c0 c0 c0
-      coeff16lo = _mm_unpacklo_epi16(coeff16lo, coeff16lo);
-      // [16] xx xx xx xx c3 c3 c2 c2
-      coeff16hi = _mm_shufflelo_epi16(coeff, _MM_SHUFFLE(3, 3, 2, 2));
-      // [16] c3 c3 c3 c3 c2 c2 c2 c2
-      coeff16hi = _mm_unpacklo_epi16(coeff16hi, coeff16hi);
-
-      __m128i src8, src16, mul_hi, mul_lo, t;
-
-#define ITERATION(src, accum)                                          \
-      src8 = _mm_loadu_si128(reinterpret_cast<const __m128i*>(src));   \
-      src16 = _mm_unpacklo_epi8(src8, zero);                           \
-      mul_hi = _mm_mulhi_epi16(src16, coeff16lo);                      \
-      mul_lo = _mm_mullo_epi16(src16, coeff16lo);                      \
-      t = _mm_unpacklo_epi16(mul_lo, mul_hi);                          \
-      accum = _mm_add_epi32(accum, t);                                 \
-      t = _mm_unpackhi_epi16(mul_lo, mul_hi);                          \
-      accum = _mm_add_epi32(accum, t);                                 \
-      src16 = _mm_unpackhi_epi8(src8, zero);                           \
-      mul_hi = _mm_mulhi_epi16(src16, coeff16hi);                      \
-      mul_lo = _mm_mullo_epi16(src16, coeff16hi);                      \
-      t = _mm_unpacklo_epi16(mul_lo, mul_hi);                          \
-      accum = _mm_add_epi32(accum, t);                                 \
-      t = _mm_unpackhi_epi16(mul_lo, mul_hi);                          \
-      accum = _mm_add_epi32(accum, t)
-
-      ITERATION(src_data[0] + start, accum0);
-      ITERATION(src_data[1] + start, accum1);
-      ITERATION(src_data[2] + start, accum2);
-      ITERATION(src_data[3] + start, accum3);
-
-      start += 16;
-      filter_values += 4;
-    }
-
-    int r = filter_length & 3;
-    if (r) {
-      // Note: filter_values must be padded to align_up(filter_offset, 8);
-      __m128i coeff;
-      coeff = _mm_loadl_epi64(reinterpret_cast<const __m128i*>(filter_values));
-      // Mask out extra filter taps.
-      coeff = _mm_and_si128(coeff, mask[r]);
-
-      __m128i coeff16lo = _mm_shufflelo_epi16(coeff, _MM_SHUFFLE(1, 1, 0, 0));
-      /* c1 c1 c1 c1 c0 c0 c0 c0 */
-      coeff16lo = _mm_unpacklo_epi16(coeff16lo, coeff16lo);
-      __m128i coeff16hi = _mm_shufflelo_epi16(coeff, _MM_SHUFFLE(3, 3, 2, 2));
-      coeff16hi = _mm_unpacklo_epi16(coeff16hi, coeff16hi);
-
-      __m128i src8, src16, mul_hi, mul_lo, t;
-
-      ITERATION(src_data[0] + start, accum0);
-      ITERATION(src_data[1] + start, accum1);
-      ITERATION(src_data[2] + start, accum2);
-      ITERATION(src_data[3] + start, accum3);
-    }
-
-    accum0 = _mm_srai_epi32(accum0, ConvolutionFilter1D::kShiftBits);
-    accum0 = _mm_packs_epi32(accum0, zero);
-    accum0 = _mm_packus_epi16(accum0, zero);
-    accum1 = _mm_srai_epi32(accum1, ConvolutionFilter1D::kShiftBits);
-    accum1 = _mm_packs_epi32(accum1, zero);
-    accum1 = _mm_packus_epi16(accum1, zero);
-    accum2 = _mm_srai_epi32(accum2, ConvolutionFilter1D::kShiftBits);
-    accum2 = _mm_packs_epi32(accum2, zero);
-    accum2 = _mm_packus_epi16(accum2, zero);
-    accum3 = _mm_srai_epi32(accum3, ConvolutionFilter1D::kShiftBits);
-    accum3 = _mm_packs_epi32(accum3, zero);
-    accum3 = _mm_packus_epi16(accum3, zero);
-
-    *(reinterpret_cast<int*>(out_row[0])) = _mm_cvtsi128_si32(accum0);
-    *(reinterpret_cast<int*>(out_row[1])) = _mm_cvtsi128_si32(accum1);
-    *(reinterpret_cast<int*>(out_row[2])) = _mm_cvtsi128_si32(accum2);
-    *(reinterpret_cast<int*>(out_row[3])) = _mm_cvtsi128_si32(accum3);
-
-    out_row[0] += 4;
-    out_row[1] += 4;
-    out_row[2] += 4;
-    out_row[3] += 4;
-  }
-#endif
-}
-
-// Does vertical convolution to produce one output row. The filter values and
-// length are given in the first two parameters. These are applied to each
-// of the rows pointed to in the |source_data_rows| array, with each row
-// being |pixel_width| wide.
-//
-// The output must have room for |pixel_width * 4| bytes.
-template<bool has_alpha>
-void ConvolveVertically_SSE2(const ConvolutionFilter1D::Fixed* filter_values,
-                             int filter_length,
-                             unsigned char* const* source_data_rows,
-                             int pixel_width,
-                             unsigned char* out_row) {
-#if defined(SIMD_SSE2)
-  int width = pixel_width & ~3;
-
-  __m128i zero = _mm_setzero_si128();
-  __m128i accum0, accum1, accum2, accum3, coeff16;
-  const __m128i* src;
-  // Output four pixels per iteration (16 bytes).
-  for (int out_x = 0; out_x < width; out_x += 4) {
-
-    // Accumulated result for each pixel. 32 bits per RGBA channel.
-    accum0 = _mm_setzero_si128();
-    accum1 = _mm_setzero_si128();
-    accum2 = _mm_setzero_si128();
-    accum3 = _mm_setzero_si128();
-
-    // Convolve with one filter coefficient per iteration.
-    for (int filter_y = 0; filter_y < filter_length; filter_y++) {
-
-      // Duplicate the filter coefficient 8 times.
-      // [16] cj cj cj cj cj cj cj cj
-      coeff16 = _mm_set1_epi16(filter_values[filter_y]);
-
-      // Load four pixels (16 bytes) together.
-      // [8] a3 b3 g3 r3 a2 b2 g2 r2 a1 b1 g1 r1 a0 b0 g0 r0
-      src = reinterpret_cast<const __m128i*>(
-          &source_data_rows[filter_y][out_x << 2]);
-      __m128i src8 = _mm_loadu_si128(src);
-
-      // Unpack 1st and 2nd pixels from 8 bits to 16 bits for each channels =>
-      // multiply with current coefficient => accumulate the result.
-      // [16] a1 b1 g1 r1 a0 b0 g0 r0
-      __m128i src16 = _mm_unpacklo_epi8(src8, zero);
-      __m128i mul_hi = _mm_mulhi_epi16(src16, coeff16);
-      __m128i mul_lo = _mm_mullo_epi16(src16, coeff16);
-      // [32] a0 b0 g0 r0
-      __m128i t = _mm_unpacklo_epi16(mul_lo, mul_hi);
-      accum0 = _mm_add_epi32(accum0, t);
-      // [32] a1 b1 g1 r1
-      t = _mm_unpackhi_epi16(mul_lo, mul_hi);
-      accum1 = _mm_add_epi32(accum1, t);
-
-      // Unpack 3rd and 4th pixels from 8 bits to 16 bits for each channels =>
-      // multiply with current coefficient => accumulate the result.
-      // [16] a3 b3 g3 r3 a2 b2 g2 r2
-      src16 = _mm_unpackhi_epi8(src8, zero);
-      mul_hi = _mm_mulhi_epi16(src16, coeff16);
-      mul_lo = _mm_mullo_epi16(src16, coeff16);
-      // [32] a2 b2 g2 r2
-      t = _mm_unpacklo_epi16(mul_lo, mul_hi);
-      accum2 = _mm_add_epi32(accum2, t);
-      // [32] a3 b3 g3 r3
-      t = _mm_unpackhi_epi16(mul_lo, mul_hi);
-      accum3 = _mm_add_epi32(accum3, t);
-    }
-
-    // Shift right for fixed point implementation.
-    accum0 = _mm_srai_epi32(accum0, ConvolutionFilter1D::kShiftBits);
-    accum1 = _mm_srai_epi32(accum1, ConvolutionFilter1D::kShiftBits);
-    accum2 = _mm_srai_epi32(accum2, ConvolutionFilter1D::kShiftBits);
-    accum3 = _mm_srai_epi32(accum3, ConvolutionFilter1D::kShiftBits);
-
-    // Packing 32 bits |accum| to 16 bits per channel (signed saturation).
-    // [16] a1 b1 g1 r1 a0 b0 g0 r0
-    accum0 = _mm_packs_epi32(accum0, accum1);
-    // [16] a3 b3 g3 r3 a2 b2 g2 r2
-    accum2 = _mm_packs_epi32(accum2, accum3);
-
-    // Packing 16 bits |accum| to 8 bits per channel (unsigned saturation).
-    // [8] a3 b3 g3 r3 a2 b2 g2 r2 a1 b1 g1 r1 a0 b0 g0 r0
-    accum0 = _mm_packus_epi16(accum0, accum2);
-
-    if (has_alpha) {
-      // Compute the max(ri, gi, bi) for each pixel.
-      // [8] xx a3 b3 g3 xx a2 b2 g2 xx a1 b1 g1 xx a0 b0 g0
-      __m128i a = _mm_srli_epi32(accum0, 8);
-      // [8] xx xx xx max3 xx xx xx max2 xx xx xx max1 xx xx xx max0
-      __m128i b = _mm_max_epu8(a, accum0);  // Max of r and g.
-      // [8] xx xx a3 b3 xx xx a2 b2 xx xx a1 b1 xx xx a0 b0
-      a = _mm_srli_epi32(accum0, 16);
-      // [8] xx xx xx max3 xx xx xx max2 xx xx xx max1 xx xx xx max0
-      b = _mm_max_epu8(a, b);  // Max of r and g and b.
-      // [8] max3 00 00 00 max2 00 00 00 max1 00 00 00 max0 00 00 00
-      b = _mm_slli_epi32(b, 24);
-
-      // Make sure the value of alpha channel is always larger than maximum
-      // value of color channels.
-      accum0 = _mm_max_epu8(b, accum0);
-    } else {
-      // Set value of alpha channels to 0xFF.
-      __m128i mask = _mm_set1_epi32(0xff000000);
-      accum0 = _mm_or_si128(accum0, mask);
-    }
-
-    // Store the convolution result (16 bytes) and advance the pixel pointers.
-    _mm_storeu_si128(reinterpret_cast<__m128i*>(out_row), accum0);
-    out_row += 16;
-  }
-
-  // When the width of the output is not divisible by 4, We need to save one
-  // pixel (4 bytes) each time. And also the fourth pixel is always absent.
-  if (pixel_width & 3) {
-    accum0 = _mm_setzero_si128();
-    accum1 = _mm_setzero_si128();
-    accum2 = _mm_setzero_si128();
-    for (int filter_y = 0; filter_y < filter_length; ++filter_y) {
-      coeff16 = _mm_set1_epi16(filter_values[filter_y]);
-      // [8] a3 b3 g3 r3 a2 b2 g2 r2 a1 b1 g1 r1 a0 b0 g0 r0
-      src = reinterpret_cast<const __m128i*>(
-          &source_data_rows[filter_y][width<<2]);
-      __m128i src8 = _mm_loadu_si128(src);
-      // [16] a1 b1 g1 r1 a0 b0 g0 r0
-      __m128i src16 = _mm_unpacklo_epi8(src8, zero);
-      __m128i mul_hi = _mm_mulhi_epi16(src16, coeff16);
-      __m128i mul_lo = _mm_mullo_epi16(src16, coeff16);
-      // [32] a0 b0 g0 r0
-      __m128i t = _mm_unpacklo_epi16(mul_lo, mul_hi);
-      accum0 = _mm_add_epi32(accum0, t);
-      // [32] a1 b1 g1 r1
-      t = _mm_unpackhi_epi16(mul_lo, mul_hi);
-      accum1 = _mm_add_epi32(accum1, t);
-      // [16] a3 b3 g3 r3 a2 b2 g2 r2
-      src16 = _mm_unpackhi_epi8(src8, zero);
-      mul_hi = _mm_mulhi_epi16(src16, coeff16);
-      mul_lo = _mm_mullo_epi16(src16, coeff16);
-      // [32] a2 b2 g2 r2
-      t = _mm_unpacklo_epi16(mul_lo, mul_hi);
-      accum2 = _mm_add_epi32(accum2, t);
-    }
-
-    accum0 = _mm_srai_epi32(accum0, ConvolutionFilter1D::kShiftBits);
-    accum1 = _mm_srai_epi32(accum1, ConvolutionFilter1D::kShiftBits);
-    accum2 = _mm_srai_epi32(accum2, ConvolutionFilter1D::kShiftBits);
-    // [16] a1 b1 g1 r1 a0 b0 g0 r0
-    accum0 = _mm_packs_epi32(accum0, accum1);
-    // [16] a3 b3 g3 r3 a2 b2 g2 r2
-    accum2 = _mm_packs_epi32(accum2, zero);
-    // [8] a3 b3 g3 r3 a2 b2 g2 r2 a1 b1 g1 r1 a0 b0 g0 r0
-    accum0 = _mm_packus_epi16(accum0, accum2);
-    if (has_alpha) {
-      // [8] xx a3 b3 g3 xx a2 b2 g2 xx a1 b1 g1 xx a0 b0 g0
-      __m128i a = _mm_srli_epi32(accum0, 8);
-      // [8] xx xx xx max3 xx xx xx max2 xx xx xx max1 xx xx xx max0
-      __m128i b = _mm_max_epu8(a, accum0);  // Max of r and g.
-      // [8] xx xx a3 b3 xx xx a2 b2 xx xx a1 b1 xx xx a0 b0
-      a = _mm_srli_epi32(accum0, 16);
-      // [8] xx xx xx max3 xx xx xx max2 xx xx xx max1 xx xx xx max0
-      b = _mm_max_epu8(a, b);  // Max of r and g and b.
-      // [8] max3 00 00 00 max2 00 00 00 max1 00 00 00 max0 00 00 00
-      b = _mm_slli_epi32(b, 24);
-      accum0 = _mm_max_epu8(b, accum0);
-    } else {
-      __m128i mask = _mm_set1_epi32(0xff000000);
-      accum0 = _mm_or_si128(accum0, mask);
-    }
-
-    for (int out_x = width; out_x < pixel_width; out_x++) {
-      *(reinterpret_cast<int*>(out_row)) = _mm_cvtsi128_si32(accum0);
-      accum0 = _mm_srli_si128(accum0, 4);
-      out_row += 4;
-    }
+void ConvolveVertically(const ConvolutionFilter1D::Fixed* filter_values,
+                        int filter_length,
+                        unsigned char* const* source_data_rows,
+                        int pixel_width,
+                        unsigned char* out_row,
+                        bool source_has_alpha) {
+  if (source_has_alpha) {
+    ConvolveVertically<true>(filter_values, filter_length,
+                             source_data_rows,
+                             pixel_width,
+                             out_row);
+  } else {
+    ConvolveVertically<false>(filter_values, filter_length,
+                              source_data_rows,
+                              pixel_width,
+                              out_row);
   }
-#endif
 }
 
 }  // namespace
@@ -715,6 +304,43 @@ void ConvolutionFilter1D::AddFilter(int filter_offset,
   max_filter_ = std::max(max_filter_, filter_length);
 }
 
+typedef void (*ConvolveVertically_pointer)(
+    const ConvolutionFilter1D::Fixed* filter_values,
+    int filter_length,
+    unsigned char* const* source_data_rows,
+    int pixel_width,
+    unsigned char* out_row,
+    bool has_alpha);
+typedef void (*Convolve4RowsHorizontally_pointer)(
+    const unsigned char* src_data[4],
+    const ConvolutionFilter1D& filter,
+    unsigned char* out_row[4]);
+typedef void (*ConvolveHorizontally_pointer)(
+    const unsigned char* src_data,
+    const ConvolutionFilter1D& filter,
+    unsigned char* out_row);
+
+struct ConvolveProcs {
+  // This is how many extra pixels may be read by the
+  // conolve*horizontally functions.
+  int extra_horizontal_reads;
+  ConvolveVertically_pointer convolve_vertically;
+  Convolve4RowsHorizontally_pointer convolve_4rows_horizontally;
+  ConvolveHorizontally_pointer convolve_horizontally;
+};
+
+void SetupSIMD(ConvolveProcs *procs) {
+#ifdef SIMD_SSE2
+  base::CPU cpu;
+  if (cpu.has_sse2()) {
+    procs->extra_horizontal_reads = 3;
+    procs->convolve_vertically = &ConvolveVertically_SSE2;
+    procs->convolve_4rows_horizontally = &Convolve4RowsHorizontally_SSE2;
+    procs->convolve_horizontally = &ConvolveHorizontally_SSE2;
+  }
+#endif
+}
+
 void BGRAConvolve2D(const unsigned char* source_data,
                     int source_byte_row_stride,
                     bool source_has_alpha,
@@ -722,12 +348,15 @@ void BGRAConvolve2D(const unsigned char* source_data,
                     const ConvolutionFilter1D& filter_y,
                     int output_byte_row_stride,
                     unsigned char* output,
-                    bool use_sse2) {
-#if !defined(SIMD_SSE2)
-  // Even we have runtime support for SSE2 instructions, since the binary
-  // was not built with SSE2 support, we had to fallback to C version.
-  use_sse2 = false;
-#endif
+                    bool use_simd_if_possible) {
+  ConvolveProcs simd;
+  simd.extra_horizontal_reads = 0;
+  simd.convolve_vertically = NULL;
+  simd.convolve_4rows_horizontally = NULL;
+  simd.convolve_horizontally = NULL;
+  if (use_simd_if_possible) {
+    SetupSIMD(&simd);
+  }
 
   int max_y_filter_size = filter_y.max_filter();
 
@@ -752,7 +381,8 @@ void BGRAConvolve2D(const unsigned char* source_data,
   // TODO(jiesun): We do not use aligned load from row buffer in vertical
   // convolution pass yet. Somehow Windows does not like it.
   int row_buffer_width = (filter_x.num_values() + 15) & ~0xF;
-  int row_buffer_height = max_y_filter_size + (use_sse2 ? 4 : 0);
+  int row_buffer_height = max_y_filter_size +
+      (simd.convolve_4rows_horizontally ? 4 : 0);
   CircularRowBuffer row_buffer(row_buffer_width,
                                row_buffer_height,
                                filter_offset);
@@ -775,7 +405,8 @@ void BGRAConvolve2D(const unsigned char* source_data,
   // rows we need to avoid the SSE implementation for here.
   filter_x.FilterForValue(filter_x.num_values() - 1, &last_filter_offset,
                           &last_filter_length);
-  int avoid_sse_rows = 1 + 3/(last_filter_offset + last_filter_length);
+  int avoid_simd_rows = 1 + simd.extra_horizontal_reads /
+      (last_filter_offset + last_filter_length);
 
   filter_y.FilterForValue(num_output_rows - 1, &last_filter_offset,
                           &last_filter_length);
@@ -785,49 +416,36 @@ void BGRAConvolve2D(const unsigned char* source_data,
                                             &filter_offset, &filter_length);
 
     // Generate output rows until we have enough to run the current filter.
-    if (use_sse2) {
-      while (next_x_row < filter_offset + filter_length) {
-        if (next_x_row + 3 < last_filter_offset + last_filter_length -
-            avoid_sse_rows) {
-          const unsigned char* src[4];
-          unsigned char* out_row[4];
-          for (int i = 0; i < 4; ++i) {
-            src[i] = &source_data[(next_x_row + i) * source_byte_row_stride];
-            out_row[i] = row_buffer.AdvanceRow();
-          }
-          ConvolveHorizontally4_SSE2(src, filter_x, out_row);
-          next_x_row += 4;
+    while (next_x_row < filter_offset + filter_length) {
+      if (simd.convolve_4rows_horizontally &&
+          next_x_row + 3 < last_filter_offset + last_filter_length -
+          avoid_simd_rows) {
+        const unsigned char* src[4];
+        unsigned char* out_row[4];
+        for (int i = 0; i < 4; ++i) {
+          src[i] = &source_data[(next_x_row + i) * source_byte_row_stride];
+          out_row[i] = row_buffer.AdvanceRow();
+        }
+        simd.convolve_4rows_horizontally(src, filter_x, out_row);
+        next_x_row += 4;
+      } else {
+        // Check if we need to avoid SSE2 for this row.
+        if (simd.convolve_horizontally &&
+            next_x_row < last_filter_offset + last_filter_length -
+            avoid_simd_rows) {
+          simd.convolve_horizontally(
+              &source_data[next_x_row * source_byte_row_stride],
+              filter_x, row_buffer.AdvanceRow());
         } else {
-          // Check if we need to avoid SSE2 for this row.
-          if (next_x_row >= last_filter_offset + last_filter_length -
-              avoid_sse_rows) {
-            if (source_has_alpha) {
-              ConvolveHorizontally<true>(
-                  &source_data[next_x_row * source_byte_row_stride],
-                  filter_x, row_buffer.AdvanceRow());
-            } else {
-              ConvolveHorizontally<false>(
-                  &source_data[next_x_row * source_byte_row_stride],
-                  filter_x, row_buffer.AdvanceRow());
-            }
+          if (source_has_alpha) {

[Stephen White, 2013/04/06 22:44:33]

Not new to this patch, but it seems a little strange that source_has_alpha is
relevant to the C++ path, but not the SSE2 path for the horizontal convolution. 
Maybe I'm missing something.

+            ConvolveHorizontally<true>(
+                &source_data[next_x_row * source_byte_row_stride],
+                filter_x, row_buffer.AdvanceRow());
           } else {
-            ConvolveHorizontally_SSE2(
+            ConvolveHorizontally<false>(
                 &source_data[next_x_row * source_byte_row_stride],
                 filter_x, row_buffer.AdvanceRow());
           }
-          next_x_row++;
-        }
-      }
-    } else {
-      while (next_x_row < filter_offset + filter_length) {
-        if (source_has_alpha) {
-          ConvolveHorizontally<true>(
-              &source_data[next_x_row * source_byte_row_stride],
-              filter_x, row_buffer.AdvanceRow());
-        } else {
-          ConvolveHorizontally<false>(
-              &source_data[next_x_row * source_byte_row_stride],
-              filter_x, row_buffer.AdvanceRow());
         }
         next_x_row++;
       }
@@ -846,26 +464,16 @@ void BGRAConvolve2D(const unsigned char* source_data,
     unsigned char* const* first_row_for_filter =
         &rows_to_convolve[filter_offset - first_row_in_circular_buffer];
 
-    if (source_has_alpha) {
-      if (use_sse2) {
-        ConvolveVertically_SSE2<true>(filter_values, filter_length,
-                                      first_row_for_filter,
-                                      filter_x.num_values(), cur_output_row);
-      } else {
-        ConvolveVertically<true>(filter_values, filter_length,
-                                 first_row_for_filter,
-                                 filter_x.num_values(), cur_output_row);
-      }
+    if (simd.convolve_vertically) {
+      simd.convolve_vertically(filter_values, filter_length,
+                               first_row_for_filter,
+                               filter_x.num_values(), cur_output_row,
+                               source_has_alpha);
     } else {
-      if (use_sse2) {
-        ConvolveVertically_SSE2<false>(filter_values, filter_length,
-                                       first_row_for_filter,
-                                       filter_x.num_values(), cur_output_row);
-      } else {
-        ConvolveVertically<false>(filter_values, filter_length,
-                                 first_row_for_filter,
-                                 filter_x.num_values(), cur_output_row);
-      }
+      ConvolveVertically(filter_values, filter_length,
+                         first_row_for_filter,
+                         filter_x.num_values(), cur_output_row,
+                         source_has_alpha);
     }
   }
 }