text: // Copyright 2011 Google Inc. All Rights Reserved.
  //
  // This code is licensed under the same terms as WebM:
  //  Software License Agreement:  http://www.webmproject.org/license/software/
  //  Additional IP Rights Grant:  http://www.webmproject.org/license/additional/
  // -----------------------------------------------------------------------------
  //
  // SSE2 version of speed-critical encoding functions.
  //
  // Author: Christian Duvivier (cduvivier@google.com)
  
  #include "./dsp.h"
  
  #if defined(__cplusplus) || defined(c_plusplus)
  extern "C" {
  #endif
  
  #if defined(WEBP_USE_SSE2)
  #include <stdlib.h>  // for abs()
  #include <emmintrin.h>
  
  #include "../enc/vp8enci.h"
  
  //------------------------------------------------------------------------------
  // Compute susceptibility based on DCT-coeff histograms:
  // the higher, the "easier" the macroblock is to compress.
  
  static int CollectHistogramSSE2(const uint8_t* ref, const uint8_t* pred,
                                  int start_block, int end_block) {
    int histo[MAX_COEFF_THRESH + 1] = { 0 };
    int16_t out[16];
    int j, k;
    const __m128i max_coeff_thresh = _mm_set1_epi16(MAX_COEFF_THRESH);
    for (j = start_block; j < end_block; ++j) {
      VP8FTransform(ref + VP8DspScan[j], pred + VP8DspScan[j], out);
  
      // Convert coefficients to bin (within out[]).
      {
        // Load.
        const __m128i out0 = _mm_loadu_si128((__m128i*)&out[0]);
        const __m128i out1 = _mm_loadu_si128((__m128i*)&out[8]);
        // sign(out) = out >> 15  (0x0000 if positive, 0xffff if negative)
        const __m128i sign0 = _mm_srai_epi16(out0, 15);
        const __m128i sign1 = _mm_srai_epi16(out1, 15);
        // abs(out) = (out ^ sign) - sign
        const __m128i xor0 = _mm_xor_si128(out0, sign0);
        const __m128i xor1 = _mm_xor_si128(out1, sign1);
        const __m128i abs0 = _mm_sub_epi16(xor0, sign0);
        const __m128i abs1 = _mm_sub_epi16(xor1, sign1);
        // v = abs(out) >> 2
        const __m128i v0 = _mm_srai_epi16(abs0, 2);
        const __m128i v1 = _mm_srai_epi16(abs1, 2);
        // bin = min(v, MAX_COEFF_THRESH)
        const __m128i bin0 = _mm_min_epi16(v0, max_coeff_thresh);
        const __m128i bin1 = _mm_min_epi16(v1, max_coeff_thresh);
        // Store.
        _mm_storeu_si128((__m128i*)&out[0], bin0);
        _mm_storeu_si128((__m128i*)&out[8], bin1);
      }
  
      // Use bin to update histogram.
      for (k = 0; k < 16; ++k) {
        histo[out[k]]++;
      }
    }
  
    return VP8GetAlpha(histo);
  }
  
  //------------------------------------------------------------------------------
  // Transforms (Paragraph 14.4)
  
  // Does one or two inverse transforms.
  static void ITransformSSE2(const uint8_t* ref, const int16_t* in, uint8_t* dst,
                             int do_two) {
    // This implementation makes use of 16-bit fixed point versions of two
    // multiply constants:
    //    K1 = sqrt(2) * cos (pi/8) ~= 85627 / 2^16
    //    K2 = sqrt(2) * sin (pi/8) ~= 35468 / 2^16
    //
    // To be able to use signed 16-bit integers, we use the following trick to
    // have constants within range:
    // - Associated constants are obtained by subtracting the 16-bit fixed point
    //   version of one:
    //      k = K - (1 << 16)  =>  K = k + (1 << 16)
    //      K1 = 85267  =>  k1 =  20091
    //      K2 = 35468  =>  k2 = -30068
    // - The multiplication of a variable by a constant become the sum of the
    //   variable and the multiplication of that variable by the associated
    //   constant:
    //      (x * K) >> 16 = (x * (k + (1 << 16))) >> 16 = ((x * k ) >> 16) + x
    const __m128i k1 = _mm_set1_epi16(20091);
    const __m128i k2 = _mm_set1_epi16(-30068);
    __m128i T0, T1, T2, T3;
  
    // Load and concatenate the transform coefficients (we'll do two inverse
    // transforms in parallel). In the case of only one inverse transform, the
    // second half of the vectors will just contain random value we'll never
    // use nor store.
    __m128i in0, in1, in2, in3;
    {
      in0 = _mm_loadl_epi64((__m128i*)&in[0]);
      in1 = _mm_loadl_epi64((__m128i*)&in[4]);
      in2 = _mm_loadl_epi64((__m128i*)&in[8]);
      in3 = _mm_loadl_epi64((__m128i*)&in[12]);
      // a00 a10 a20 a30   x x x x
      // a01 a11 a21 a31   x x x x
      // a02 a12 a22 a32   x x x x
      // a03 a13 a23 a33   x x x x
      if (do_two) {
        const __m128i inB0 = _mm_loadl_epi64((__m128i*)&in[16]);
        const __m128i inB1 = _mm_loadl_epi64((__m128i*)&in[20]);
        const __m128i inB2 = _mm_loadl_epi64((__m128i*)&in[24]);
        const __m128i inB3 = _mm_loadl_epi64((__m128i*)&in[28]);
        in0 = _mm_unpacklo_epi64(in0, inB0);
        in1 = _mm_unpacklo_epi64(in1, inB1);
        in2 = _mm_unpacklo_epi64(in2, inB2);
        in3 = _mm_unpacklo_epi64(in3, inB3);
        // a00 a10 a20 a30   b00 b10 b20 b30
        // a01 a11 a21 a31   b01 b11 b21 b31
        // a02 a12 a22 a32   b02 b12 b22 b32
        // a03 a13 a23 a33   b03 b13 b23 b33
      }
    }
  
    // Vertical pass and subsequent transpose.
    {
      // First pass, c and d calculations are longer because of the "trick"
      // multiplications.
      const __m128i a = _mm_add_epi16(in0, in2);
      const __m128i b = _mm_sub_epi16(in0, in2);
      // c = MUL(in1, K2) - MUL(in3, K1) = MUL(in1, k2) - MUL(in3, k1) + in1 - in3
      const __m128i c1 = _mm_mulhi_epi16(in1, k2);
      const __m128i c2 = _mm_mulhi_epi16(in3, k1);
      const __m128i c3 = _mm_sub_epi16(in1, in3);
      const __m128i c4 = _mm_sub_epi16(c1, c2);
      const __m128i c = _mm_add_epi16(c3, c4);
      // d = MUL(in1, K1) + MUL(in3, K2) = MUL(in1, k1) + MUL(in3, k2) + in1 + in3
      const __m128i d1 = _mm_mulhi_epi16(in1, k1);
      const __m128i d2 = _mm_mulhi_epi16(in3, k2);
      const __m128i d3 = _mm_add_epi16(in1, in3);
      const __m128i d4 = _mm_add_epi16(d1, d2);
      const __m128i d = _mm_add_epi16(d3, d4);
  
      // Second pass.
      const __m128i tmp0 = _mm_add_epi16(a, d);
      const __m128i tmp1 = _mm_add_epi16(b, c);
      const __m128i tmp2 = _mm_sub_epi16(b, c);
      const __m128i tmp3 = _mm_sub_epi16(a, d);
  
      // Transpose the two 4x4.
      // a00 a01 a02 a03   b00 b01 b02 b03
      // a10 a11 a12 a13   b10 b11 b12 b13
      // a20 a21 a22 a23   b20 b21 b22 b23
      // a30 a31 a32 a33   b30 b31 b32 b33
      const __m128i transpose0_0 = _mm_unpacklo_epi16(tmp0, tmp1);
      const __m128i transpose0_1 = _mm_unpacklo_epi16(tmp2, tmp3);
      const __m128i transpose0_2 = _mm_unpackhi_epi16(tmp0, tmp1);
      const __m128i transpose0_3 = _mm_unpackhi_epi16(tmp2, tmp3);
      // a00 a10 a01 a11   a02 a12 a03 a13
      // a20 a30 a21 a31   a22 a32 a23 a33
      // b00 b10 b01 b11   b02 b12 b03 b13
      // b20 b30 b21 b31   b22 b32 b23 b33
      const __m128i transpose1_0 = _mm_unpacklo_epi32(transpose0_0, transpose0_1);
      const __m128i transpose1_1 = _mm_unpacklo_epi32(transpose0_2, transpose0_3);
      const __m128i transpose1_2 = _mm_unpackhi_epi32(transpose0_0, transpose0_1);
      const __m128i transpose1_3 = _mm_unpackhi_epi32(transpose0_2, transpose0_3);
      // a00 a10 a20 a30 a01 a11 a21 a31
      // b00 b10 b20 b30 b01 b11 b21 b31
      // a02 a12 a22 a32 a03 a13 a23 a33
      // b02 b12 a22 b32 b03 b13 b23 b33
      T0 = _mm_unpacklo_epi64(transpose1_0, transpose1_1);
      T1 = _mm_unpackhi_epi64(transpose1_0, transpose1_1);
      T2 = _mm_unpacklo_epi64(transpose1_2, transpose1_3);
      T3 = _mm_unpackhi_epi64(transpose1_2, transpose1_3);
      // a00 a10 a20 a30   b00 b10 b20 b30
      // a01 a11 a21 a31   b01 b11 b21 b31
      // a02 a12 a22 a32   b02 b12 b22 b32
      // a03 a13 a23 a33   b03 b13 b23 b33
    }
  
    // Horizontal pass and subsequent transpose.
    {
      // First pass, c and d calculations are longer because of the "trick"
      // multiplications.
      const __m128i four = _mm_set1_epi16(4);
      const __m128i dc = _mm_add_epi16(T0, four);
      const __m128i a =  _mm_add_epi16(dc, T2);
      const __m128i b =  _mm_sub_epi16(dc, T2);
      // c = MUL(T1, K2) - MUL(T3, K1) = MUL(T1, k2) - MUL(T3, k1) + T1 - T3
      const __m128i c1 = _mm_mulhi_epi16(T1, k2);
      const __m128i c2 = _mm_mulhi_epi16(T3, k1);
      const __m128i c3 = _mm_sub_epi16(T1, T3);
      const __m128i c4 = _mm_sub_epi16(c1, c2);
      const __m128i c = _mm_add_epi16(c3, c4);
      // d = MUL(T1, K1) + MUL(T3, K2) = MUL(T1, k1) + MUL(T3, k2) + T1 + T3
      const __m128i d1 = _mm_mulhi_epi16(T1, k1);
      const __m128i d2 = _mm_mulhi_epi16(T3, k2);
      const __m128i d3 = _mm_add_epi16(T1, T3);
      const __m128i d4 = _mm_add_epi16(d1, d2);
      const __m128i d = _mm_add_epi16(d3, d4);
  
      // Second pass.
      const __m128i tmp0 = _mm_add_epi16(a, d);
      const __m128i tmp1 = _mm_add_epi16(b, c);
      const __m128i tmp2 = _mm_sub_epi16(b, c);
      const __m128i tmp3 = _mm_sub_epi16(a, d);
      const __m128i shifted0 = _mm_srai_epi16(tmp0, 3);
      const __m128i shifted1 = _mm_srai_epi16(tmp1, 3);
      const __m128i shifted2 = _mm_srai_epi16(tmp2, 3);
      const __m128i shifted3 = _mm_srai_epi16(tmp3, 3);
  
      // Transpose the two 4x4.
      // a00 a01 a02 a03   b00 b01 b02 b03
      // a10 a11 a12 a13   b10 b11 b12 b13
      // a20 a21 a22 a23   b20 b21 b22 b23
      // a30 a31 a32 a33   b30 b31 b32 b33
      const __m128i transpose0_0 = _mm_unpacklo_epi16(shifted0, shifted1);
      const __m128i transpose0_1 = _mm_unpacklo_epi16(shifted2, shifted3);
      const __m128i transpose0_2 = _mm_unpackhi_epi16(shifted0, shifted1);
      const __m128i transpose0_3 = _mm_unpackhi_epi16(shifted2, shifted3);
      // a00 a10 a01 a11   a02 a12 a03 a13
      // a20 a30 a21 a31   a22 a32 a23 a33
      // b00 b10 b01 b11   b02 b12 b03 b13
      // b20 b30 b21 b31   b22 b32 b23 b33
      const __m128i transpose1_0 = _mm_unpacklo_epi32(transpose0_0, transpose0_1);
      const __m128i transpose1_1 = _mm_unpacklo_epi32(transpose0_2, transpose0_3);
      const __m128i transpose1_2 = _mm_unpackhi_epi32(transpose0_0, transpose0_1);
      const __m128i transpose1_3 = _mm_unpackhi_epi32(transpose0_2, transpose0_3);
      // a00 a10 a20 a30 a01 a11 a21 a31
      // b00 b10 b20 b30 b01 b11 b21 b31
      // a02 a12 a22 a32 a03 a13 a23 a33
      // b02 b12 a22 b32 b03 b13 b23 b33
      T0 = _mm_unpacklo_epi64(transpose1_0, transpose1_1);
      T1 = _mm_unpackhi_epi64(transpose1_0, transpose1_1);
      T2 = _mm_unpacklo_epi64(transpose1_2, transpose1_3);
      T3 = _mm_unpackhi_epi64(transpose1_2, transpose1_3);
      // a00 a10 a20 a30   b00 b10 b20 b30
      // a01 a11 a21 a31   b01 b11 b21 b31
      // a02 a12 a22 a32   b02 b12 b22 b32
      // a03 a13 a23 a33   b03 b13 b23 b33
    }
  
    // Add inverse transform to 'ref' and store.
    {
      const __m128i zero = _mm_set1_epi16(0);
      // Load the reference(s).
      __m128i ref0, ref1, ref2, ref3;
      if (do_two) {
        // Load eight bytes/pixels per line.
        ref0 = _mm_loadl_epi64((__m128i*)&ref[0 * BPS]);
        ref1 = _mm_loadl_epi64((__m128i*)&ref[1 * BPS]);
        ref2 = _mm_loadl_epi64((__m128i*)&ref[2 * BPS]);
        ref3 = _mm_loadl_epi64((__m128i*)&ref[3 * BPS]);
      } else {
        // Load four bytes/pixels per line.
        ref0 = _mm_cvtsi32_si128(*(int*)&ref[0 * BPS]);
        ref1 = _mm_cvtsi32_si128(*(int*)&ref[1 * BPS]);
        ref2 = _mm_cvtsi32_si128(*(int*)&ref[2 * BPS]);
        ref3 = _mm_cvtsi32_si128(*(int*)&ref[3 * BPS]);
      }
      // Convert to 16b.
      ref0 = _mm_unpacklo_epi8(ref0, zero);
      ref1 = _mm_unpacklo_epi8(ref1, zero);
      ref2 = _mm_unpacklo_epi8(ref2, zero);
      ref3 = _mm_unpacklo_epi8(ref3, zero);
      // Add the inverse transform(s).
      ref0 = _mm_add_epi16(ref0, T0);
      ref1 = _mm_add_epi16(ref1, T1);
      ref2 = _mm_add_epi16(ref2, T2);
      ref3 = _mm_add_epi16(ref3, T3);
      // Unsigned saturate to 8b.
      ref0 = _mm_packus_epi16(ref0, ref0);
      ref1 = _mm_packus_epi16(ref1, ref1);
      ref2 = _mm_packus_epi16(ref2, ref2);
      ref3 = _mm_packus_epi16(ref3, ref3);
      // Store the results.
      if (do_two) {
        // Store eight bytes/pixels per line.
        _mm_storel_epi64((__m128i*)&dst[0 * BPS], ref0);
        _mm_storel_epi64((__m128i*)&dst[1 * BPS], ref1);
        _mm_storel_epi64((__m128i*)&dst[2 * BPS], ref2);
        _mm_storel_epi64((__m128i*)&dst[3 * BPS], ref3);
      } else {
        // Store four bytes/pixels per line.
        *((int32_t *)&dst[0 * BPS]) = _mm_cvtsi128_si32(ref0);
        *((int32_t *)&dst[1 * BPS]) = _mm_cvtsi128_si32(ref1);
        *((int32_t *)&dst[2 * BPS]) = _mm_cvtsi128_si32(ref2);
        *((int32_t *)&dst[3 * BPS]) = _mm_cvtsi128_si32(ref3);
      }
    }
  }
  
  static void FTransformSSE2(const uint8_t* src, const uint8_t* ref,
                             int16_t* out) {
    const __m128i zero = _mm_setzero_si128();
    const __m128i seven = _mm_set1_epi16(7);
    const __m128i k7500 = _mm_set1_epi32(7500);
    const __m128i k14500 = _mm_set1_epi32(14500);
    const __m128i k51000 = _mm_set1_epi32(51000);
    const __m128i k12000_plus_one = _mm_set1_epi32(12000 + (1 << 16));
    const __m128i k5352_2217 = _mm_set_epi16(5352,  2217, 5352,  2217,
                                             5352,  2217, 5352,  2217);
    const __m128i k2217_5352 = _mm_set_epi16(2217, -5352, 2217, -5352,
                                             2217, -5352, 2217, -5352);
  
    __m128i v01, v32;
  
    // Difference between src and ref and initial transpose.
    {
      // Load src and convert to 16b.
      const __m128i src0 = _mm_loadl_epi64((__m128i*)&src[0 * BPS]);
      const __m128i src1 = _mm_loadl_epi64((__m128i*)&src[1 * BPS]);
      const __m128i src2 = _mm_loadl_epi64((__m128i*)&src[2 * BPS]);
      const __m128i src3 = _mm_loadl_epi64((__m128i*)&src[3 * BPS]);
      const __m128i src_0 = _mm_unpacklo_epi8(src0, zero);
      const __m128i src_1 = _mm_unpacklo_epi8(src1, zero);
      const __m128i src_2 = _mm_unpacklo_epi8(src2, zero);
      const __m128i src_3 = _mm_unpacklo_epi8(src3, zero);
      // Load ref and convert to 16b.
      const __m128i ref0 = _mm_loadl_epi64((__m128i*)&ref[0 * BPS]);
      const __m128i ref1 = _mm_loadl_epi64((__m128i*)&ref[1 * BPS]);
      const __m128i ref2 = _mm_loadl_epi64((__m128i*)&ref[2 * BPS]);
      const __m128i ref3 = _mm_loadl_epi64((__m128i*)&ref[3 * BPS]);
      const __m128i ref_0 = _mm_unpacklo_epi8(ref0, zero);
      const __m128i ref_1 = _mm_unpacklo_epi8(ref1, zero);
      const __m128i ref_2 = _mm_unpacklo_epi8(ref2, zero);
      const __m128i ref_3 = _mm_unpacklo_epi8(ref3, zero);
      // Compute difference.
      const __m128i diff0 = _mm_sub_epi16(src_0, ref_0);
      const __m128i diff1 = _mm_sub_epi16(src_1, ref_1);
      const __m128i diff2 = _mm_sub_epi16(src_2, ref_2);
      const __m128i diff3 = _mm_sub_epi16(src_3, ref_3);
  
      // Transpose.
      // 00 01 02 03   0 0 0 0
      // 10 11 12 13   0 0 0 0
      // 20 21 22 23   0 0 0 0
      // 30 31 32 33   0 0 0 0
      const __m128i transpose0_0 = _mm_unpacklo_epi16(diff0, diff1);
      const __m128i transpose0_1 = _mm_unpacklo_epi16(diff2, diff3);
      // 00 10 01 11   02 12 03 13
      // 20 30 21 31   22 32 23 33
      const __m128i v23 = _mm_unpackhi_epi32(transpose0_0, transpose0_1);
      v01 = _mm_unpacklo_epi32(transpose0_0, transpose0_1);
      v32 = _mm_shuffle_epi32(v23, _MM_SHUFFLE(1, 0, 3, 2));
      // a02 a12 a22 a32   a03 a13 a23 a33
      // a00 a10 a20 a30   a01 a11 a21 a31
      // a03 a13 a23 a33   a02 a12 a22 a32
    }
  
    // First pass and subsequent transpose.
    {
      // Same operations are done on the (0,3) and (1,2) pairs.
      // b0 = (a0 + a3) << 3
      // b1 = (a1 + a2) << 3
      // b3 = (a0 - a3) << 3
      // b2 = (a1 - a2) << 3
      const __m128i a01 = _mm_add_epi16(v01, v32);
      const __m128i a32 = _mm_sub_epi16(v01, v32);
      const __m128i b01 = _mm_slli_epi16(a01, 3);
      const __m128i b32 = _mm_slli_epi16(a32, 3);
      const __m128i b11 = _mm_unpackhi_epi64(b01, b01);
      const __m128i b22 = _mm_unpackhi_epi64(b32, b32);
  
      // e0 = b0 + b1
      // e2 = b0 - b1
      const __m128i e0 = _mm_add_epi16(b01, b11);
      const __m128i e2 = _mm_sub_epi16(b01, b11);
      const __m128i e02 = _mm_unpacklo_epi64(e0, e2);
  
      // e1 = (b3 * 5352 + b2 * 2217 + 14500) >> 12
      // e3 = (b3 * 2217 - b2 * 5352 +  7500) >> 12
      const __m128i b23 = _mm_unpacklo_epi16(b22, b32);
      const __m128i c1 = _mm_madd_epi16(b23, k5352_2217);
      const __m128i c3 = _mm_madd_epi16(b23, k2217_5352);
      const __m128i d1 = _mm_add_epi32(c1, k14500);
      const __m128i d3 = _mm_add_epi32(c3, k7500);
      const __m128i e1 = _mm_srai_epi32(d1, 12);
      const __m128i e3 = _mm_srai_epi32(d3, 12);
      const __m128i e13 = _mm_packs_epi32(e1, e3);
  
      // Transpose.
      // 00 01 02 03  20 21 22 23
      // 10 11 12 13  30 31 32 33
      const __m128i transpose0_0 = _mm_unpacklo_epi16(e02, e13);
      const __m128i transpose0_1 = _mm_unpackhi_epi16(e02, e13);
      // 00 10 01 11   02 12 03 13
      // 20 30 21 31   22 32 23 33
      const __m128i v23 = _mm_unpackhi_epi32(transpose0_0, transpose0_1);
      v01 = _mm_unpacklo_epi32(transpose0_0, transpose0_1);
      v32 = _mm_shuffle_epi32(v23, _MM_SHUFFLE(1, 0, 3, 2));
      // 02 12 22 32   03 13 23 33
      // 00 10 20 30   01 11 21 31
      // 03 13 23 33   02 12 22 32
    }
  
    // Second pass
    {
      // Same operations are done on the (0,3) and (1,2) pairs.
      // a0 = v0 + v3
      // a1 = v1 + v2
      // a3 = v0 - v3
      // a2 = v1 - v2
      const __m128i a01 = _mm_add_epi16(v01, v32);
      const __m128i a32 = _mm_sub_epi16(v01, v32);
      const __m128i a11 = _mm_unpackhi_epi64(a01, a01);
      const __m128i a22 = _mm_unpackhi_epi64(a32, a32);
  
      // d0 = (a0 + a1 + 7) >> 4;
      // d2 = (a0 - a1 + 7) >> 4;
      const __m128i b0 = _mm_add_epi16(a01, a11);
      const __m128i b2 = _mm_sub_epi16(a01, a11);
      const __m128i c0 = _mm_add_epi16(b0, seven);
      const __m128i c2 = _mm_add_epi16(b2, seven);
      const __m128i d0 = _mm_srai_epi16(c0, 4);
      const __m128i d2 = _mm_srai_epi16(c2, 4);
  
      // f1 = ((b3 * 5352 + b2 * 2217 + 12000) >> 16)
      // f3 = ((b3 * 2217 - b2 * 5352 + 51000) >> 16)
      const __m128i b23 = _mm_unpacklo_epi16(a22, a32);
      const __m128i c1 = _mm_madd_epi16(b23, k5352_2217);
      const __m128i c3 = _mm_madd_epi16(b23, k2217_5352);
      const __m128i d1 = _mm_add_epi32(c1, k12000_plus_one);
      const __m128i d3 = _mm_add_epi32(c3, k51000);
      const __m128i e1 = _mm_srai_epi32(d1, 16);
      const __m128i e3 = _mm_srai_epi32(d3, 16);
      const __m128i f1 = _mm_packs_epi32(e1, e1);
      const __m128i f3 = _mm_packs_epi32(e3, e3);
      // f1 = f1 + (a3 != 0);
      // The compare will return (0xffff, 0) for (==0, !=0). To turn that into the
      // desired (0, 1), we add one earlier through k12000_plus_one.
      const __m128i g1 = _mm_add_epi16(f1, _mm_cmpeq_epi16(a32, zero));
  
      _mm_storel_epi64((__m128i*)&out[ 0], d0);
      _mm_storel_epi64((__m128i*)&out[ 4], g1);
      _mm_storel_epi64((__m128i*)&out[ 8], d2);
      _mm_storel_epi64((__m128i*)&out[12], f3);
    }
  }
  
  //------------------------------------------------------------------------------
  // Metric
  
  static int SSE4x4SSE2(const uint8_t* a, const uint8_t* b) {
    const __m128i zero = _mm_set1_epi16(0);
  
    // Load values.
    const __m128i a0 = _mm_loadl_epi64((__m128i*)&a[BPS * 0]);
    const __m128i a1 = _mm_loadl_epi64((__m128i*)&a[BPS * 1]);
    const __m128i a2 = _mm_loadl_epi64((__m128i*)&a[BPS * 2]);
    const __m128i a3 = _mm_loadl_epi64((__m128i*)&a[BPS * 3]);
    const __m128i b0 = _mm_loadl_epi64((__m128i*)&b[BPS * 0]);
    const __m128i b1 = _mm_loadl_epi64((__m128i*)&b[BPS * 1]);
    const __m128i b2 = _mm_loadl_epi64((__m128i*)&b[BPS * 2]);
    const __m128i b3 = _mm_loadl_epi64((__m128i*)&b[BPS * 3]);
  
    // Combine pair of lines and convert to 16b.
    const __m128i a01 = _mm_unpacklo_epi32(a0, a1);
    const __m128i a23 = _mm_unpacklo_epi32(a2, a3);
    const __m128i b01 = _mm_unpacklo_epi32(b0, b1);
    const __m128i b23 = _mm_unpacklo_epi32(b2, b3);
    const __m128i a01s = _mm_unpacklo_epi8(a01, zero);
    const __m128i a23s = _mm_unpacklo_epi8(a23, zero);
    const __m128i b01s = _mm_unpacklo_epi8(b01, zero);
    const __m128i b23s = _mm_unpacklo_epi8(b23, zero);
  
    // Compute differences; (a-b)^2 = (abs(a-b))^2 = (sat8(a-b) + sat8(b-a))^2
    // TODO(cduvivier): Dissassemble and figure out why this is fastest. We don't
    //                  need absolute values, there is no need to do calculation
    //                  in 8bit as we are already in 16bit, ... Yet this is what
    //                  benchmarks the fastest!
    const __m128i d0 = _mm_subs_epu8(a01s, b01s);
    const __m128i d1 = _mm_subs_epu8(b01s, a01s);
    const __m128i d2 = _mm_subs_epu8(a23s, b23s);
    const __m128i d3 = _mm_subs_epu8(b23s, a23s);
  
    // Square and add them all together.
    const __m128i madd0 = _mm_madd_epi16(d0, d0);
    const __m128i madd1 = _mm_madd_epi16(d1, d1);
    const __m128i madd2 = _mm_madd_epi16(d2, d2);
    const __m128i madd3 = _mm_madd_epi16(d3, d3);
    const __m128i sum0 = _mm_add_epi32(madd0, madd1);
    const __m128i sum1 = _mm_add_epi32(madd2, madd3);
    const __m128i sum2 = _mm_add_epi32(sum0, sum1);
    int32_t tmp[4];
    _mm_storeu_si128((__m128i*)tmp, sum2);
    return (tmp[3] + tmp[2] + tmp[1] + tmp[0]);
  }
  
  //------------------------------------------------------------------------------
  // Texture distortion
  //
  // We try to match the spectral content (weighted) between source and
  // reconstructed samples.
  
  // Hadamard transform
  // Returns the difference between the weighted sum of the absolute value of
  // transformed coefficients.
  static int TTransformSSE2(const uint8_t* inA, const uint8_t* inB,
                            const uint16_t* const w) {
    int32_t sum[4];
    __m128i tmp_0, tmp_1, tmp_2, tmp_3;
    const __m128i zero = _mm_setzero_si128();
    const __m128i one = _mm_set1_epi16(1);
    const __m128i three = _mm_set1_epi16(3);
  
    // Load, combine and tranpose inputs.
    {
      const __m128i inA_0 = _mm_loadl_epi64((__m128i*)&inA[BPS * 0]);
      const __m128i inA_1 = _mm_loadl_epi64((__m128i*)&inA[BPS * 1]);
      const __m128i inA_2 = _mm_loadl_epi64((__m128i*)&inA[BPS * 2]);
      const __m128i inA_3 = _mm_loadl_epi64((__m128i*)&inA[BPS * 3]);
      const __m128i inB_0 = _mm_loadl_epi64((__m128i*)&inB[BPS * 0]);
      const __m128i inB_1 = _mm_loadl_epi64((__m128i*)&inB[BPS * 1]);
      const __m128i inB_2 = _mm_loadl_epi64((__m128i*)&inB[BPS * 2]);
      const __m128i inB_3 = _mm_loadl_epi64((__m128i*)&inB[BPS * 3]);
  
      // Combine inA and inB (we'll do two transforms in parallel).
      const __m128i inAB_0 = _mm_unpacklo_epi8(inA_0, inB_0);
      const __m128i inAB_1 = _mm_unpacklo_epi8(inA_1, inB_1);
      const __m128i inAB_2 = _mm_unpacklo_epi8(inA_2, inB_2);
      const __m128i inAB_3 = _mm_unpacklo_epi8(inA_3, inB_3);
      // a00 b00 a01 b01 a02 b03 a03 b03   0 0 0 0 0 0 0 0
      // a10 b10 a11 b11 a12 b12 a13 b13   0 0 0 0 0 0 0 0
      // a20 b20 a21 b21 a22 b22 a23 b23   0 0 0 0 0 0 0 0
      // a30 b30 a31 b31 a32 b32 a33 b33   0 0 0 0 0 0 0 0
  
      // Transpose the two 4x4, discarding the filling zeroes.
      const __m128i transpose0_0 = _mm_unpacklo_epi8(inAB_0, inAB_2);
      const __m128i transpose0_1 = _mm_unpacklo_epi8(inAB_1, inAB_3);
      // a00 a20  b00 b20  a01 a21  b01 b21  a02 a22  b02 b22  a03 a23  b03 b23
      // a10 a30  b10 b30  a11 a31  b11 b31  a12 a32  b12 b32  a13 a33  b13 b33
      const __m128i transpose1_0 = _mm_unpacklo_epi8(transpose0_0, transpose0_1);
      const __m128i transpose1_1 = _mm_unpackhi_epi8(transpose0_0, transpose0_1);
      // a00 a10 a20 a30  b00 b10 b20 b30  a01 a11 a21 a31  b01 b11 b21 b31
      // a02 a12 a22 a32  b02 b12 b22 b32  a03 a13 a23 a33  b03 b13 b23 b33
  
      // Convert to 16b.
      tmp_0 = _mm_unpacklo_epi8(transpose1_0, zero);
      tmp_1 = _mm_unpackhi_epi8(transpose1_0, zero);
      tmp_2 = _mm_unpacklo_epi8(transpose1_1, zero);
      tmp_3 = _mm_unpackhi_epi8(transpose1_1, zero);
      // a00 a10 a20 a30   b00 b10 b20 b30
      // a01 a11 a21 a31   b01 b11 b21 b31
      // a02 a12 a22 a32   b02 b12 b22 b32
      // a03 a13 a23 a33   b03 b13 b23 b33
    }
  
    // Horizontal pass and subsequent transpose.
    {
      // Calculate a and b (two 4x4 at once).
      const __m128i a0 = _mm_slli_epi16(_mm_add_epi16(tmp_0, tmp_2), 2);
      const __m128i a1 = _mm_slli_epi16(_mm_add_epi16(tmp_1, tmp_3), 2);
      const __m128i a2 = _mm_slli_epi16(_mm_sub_epi16(tmp_1, tmp_3), 2);
      const __m128i a3 = _mm_slli_epi16(_mm_sub_epi16(tmp_0, tmp_2), 2);
      // b0_extra = (a0 != 0);
      const __m128i b0_extra = _mm_andnot_si128(_mm_cmpeq_epi16 (a0, zero), one);
      const __m128i b0_base = _mm_add_epi16(a0, a1);
      const __m128i b1 = _mm_add_epi16(a3, a2);
      const __m128i b2 = _mm_sub_epi16(a3, a2);
      const __m128i b3 = _mm_sub_epi16(a0, a1);
      const __m128i b0 = _mm_add_epi16(b0_base, b0_extra);
      // a00 a01 a02 a03   b00 b01 b02 b03
      // a10 a11 a12 a13   b10 b11 b12 b13
      // a20 a21 a22 a23   b20 b21 b22 b23
      // a30 a31 a32 a33   b30 b31 b32 b33
  
      // Transpose the two 4x4.
      const __m128i transpose0_0 = _mm_unpacklo_epi16(b0, b1);
      const __m128i transpose0_1 = _mm_unpacklo_epi16(b2, b3);
      const __m128i transpose0_2 = _mm_unpackhi_epi16(b0, b1);
      const __m128i transpose0_3 = _mm_unpackhi_epi16(b2, b3);
      // a00 a10 a01 a11   a02 a12 a03 a13
      // a20 a30 a21 a31   a22 a32 a23 a33
      // b00 b10 b01 b11   b02 b12 b03 b13
      // b20 b30 b21 b31   b22 b32 b23 b33
      const __m128i transpose1_0 = _mm_unpacklo_epi32(transpose0_0, transpose0_1);
      const __m128i transpose1_1 = _mm_unpacklo_epi32(transpose0_2, transpose0_3);
      const __m128i transpose1_2 = _mm_unpackhi_epi32(transpose0_0, transpose0_1);
      const __m128i transpose1_3 = _mm_unpackhi_epi32(transpose0_2, transpose0_3);
      // a00 a10 a20 a30 a01 a11 a21 a31
      // b00 b10 b20 b30 b01 b11 b21 b31
      // a02 a12 a22 a32 a03 a13 a23 a33
      // b02 b12 a22 b32 b03 b13 b23 b33
      tmp_0 = _mm_unpacklo_epi64(transpose1_0, transpose1_1);
      tmp_1 = _mm_unpackhi_epi64(transpose1_0, transpose1_1);
      tmp_2 = _mm_unpacklo_epi64(transpose1_2, transpose1_3);
      tmp_3 = _mm_unpackhi_epi64(transpose1_2, transpose1_3);
      // a00 a10 a20 a30   b00 b10 b20 b30
      // a01 a11 a21 a31   b01 b11 b21 b31
      // a02 a12 a22 a32   b02 b12 b22 b32
      // a03 a13 a23 a33   b03 b13 b23 b33
    }
  
    // Vertical pass and difference of weighted sums.
    {
      // Load all inputs.
      // TODO(cduvivier): Make variable declarations and allocations aligned so
      //                  we can use _mm_load_si128 instead of _mm_loadu_si128.
      const __m128i w_0 = _mm_loadu_si128((__m128i*)&w[0]);
      const __m128i w_8 = _mm_loadu_si128((__m128i*)&w[8]);
  
      // Calculate a and b (two 4x4 at once).
      const __m128i a0 = _mm_add_epi16(tmp_0, tmp_2);
      const __m128i a1 = _mm_add_epi16(tmp_1, tmp_3);
      const __m128i a2 = _mm_sub_epi16(tmp_1, tmp_3);
      const __m128i a3 = _mm_sub_epi16(tmp_0, tmp_2);
      const __m128i b0 = _mm_add_epi16(a0, a1);
      const __m128i b1 = _mm_add_epi16(a3, a2);
      const __m128i b2 = _mm_sub_epi16(a3, a2);
      const __m128i b3 = _mm_sub_epi16(a0, a1);
  
      // Separate the transforms of inA and inB.
      __m128i A_b0 = _mm_unpacklo_epi64(b0, b1);
      __m128i A_b2 = _mm_unpacklo_epi64(b2, b3);
      __m128i B_b0 = _mm_unpackhi_epi64(b0, b1);
      __m128i B_b2 = _mm_unpackhi_epi64(b2, b3);
  
      {
        // sign(b) = b >> 15  (0x0000 if positive, 0xffff if negative)
        const __m128i sign_A_b0 = _mm_srai_epi16(A_b0, 15);
        const __m128i sign_A_b2 = _mm_srai_epi16(A_b2, 15);
        const __m128i sign_B_b0 = _mm_srai_epi16(B_b0, 15);
        const __m128i sign_B_b2 = _mm_srai_epi16(B_b2, 15);
  
        // b = abs(b) = (b ^ sign) - sign
        A_b0 = _mm_xor_si128(A_b0, sign_A_b0);
        A_b2 = _mm_xor_si128(A_b2, sign_A_b2);
        B_b0 = _mm_xor_si128(B_b0, sign_B_b0);
        B_b2 = _mm_xor_si128(B_b2, sign_B_b2);
        A_b0 = _mm_sub_epi16(A_b0, sign_A_b0);
        A_b2 = _mm_sub_epi16(A_b2, sign_A_b2);
        B_b0 = _mm_sub_epi16(B_b0, sign_B_b0);
        B_b2 = _mm_sub_epi16(B_b2, sign_B_b2);
      }
  
      // b = abs(b) + 3
      A_b0 = _mm_add_epi16(A_b0, three);
      A_b2 = _mm_add_epi16(A_b2, three);
      B_b0 = _mm_add_epi16(B_b0, three);
      B_b2 = _mm_add_epi16(B_b2, three);
  
      // abs((b + (b<0) + 3) >> 3) = (abs(b) + 3) >> 3
      // b = (abs(b) + 3) >> 3
      A_b0 = _mm_srai_epi16(A_b0, 3);
      A_b2 = _mm_srai_epi16(A_b2, 3);
      B_b0 = _mm_srai_epi16(B_b0, 3);
      B_b2 = _mm_srai_epi16(B_b2, 3);
  
      // weighted sums
      A_b0 = _mm_madd_epi16(A_b0, w_0);
      A_b2 = _mm_madd_epi16(A_b2, w_8);
      B_b0 = _mm_madd_epi16(B_b0, w_0);
      B_b2 = _mm_madd_epi16(B_b2, w_8);
      A_b0 = _mm_add_epi32(A_b0, A_b2);
      B_b0 = _mm_add_epi32(B_b0, B_b2);
  
      // difference of weighted sums
      A_b0 = _mm_sub_epi32(A_b0, B_b0);
      _mm_storeu_si128((__m128i*)&sum[0], A_b0);
    }
    return sum[0] + sum[1] + sum[2] + sum[3];
  }
  
  static int Disto4x4SSE2(const uint8_t* const a, const uint8_t* const b,
                          const uint16_t* const w) {
    const int diff_sum = TTransformSSE2(a, b, w);
    return (abs(diff_sum) + 8) >> 4;
  }
  
  static int Disto16x16SSE2(const uint8_t* const a, const uint8_t* const b,
                            const uint16_t* const w) {
    int D = 0;
    int x, y;
    for (y = 0; y < 16 * BPS; y += 4 * BPS) {
      for (x = 0; x < 16; x += 4) {
        D += Disto4x4SSE2(a + x + y, b + x + y, w);
      }
    }
    return D;
  }
  
  
  //------------------------------------------------------------------------------
  // Quantization
  //
  
  // Simple quantization
  static int QuantizeBlockSSE2(int16_t in[16], int16_t out[16],
                               int n, const VP8Matrix* const mtx) {
    const __m128i max_coeff_2047 = _mm_set1_epi16(2047);
    const __m128i zero = _mm_set1_epi16(0);
    __m128i sign0, sign8;
    __m128i coeff0, coeff8;
    __m128i out0, out8;
    __m128i packed_out;
  
    // Load all inputs.
    // TODO(cduvivier): Make variable declarations and allocations aligned so that
    //                  we can use _mm_load_si128 instead of _mm_loadu_si128.
    __m128i in0 = _mm_loadu_si128((__m128i*)&in[0]);
    __m128i in8 = _mm_loadu_si128((__m128i*)&in[8]);
    const __m128i sharpen0 = _mm_loadu_si128((__m128i*)&mtx->sharpen_[0]);
    const __m128i sharpen8 = _mm_loadu_si128((__m128i*)&mtx->sharpen_[8]);
    const __m128i iq0 = _mm_loadu_si128((__m128i*)&mtx->iq_[0]);
    const __m128i iq8 = _mm_loadu_si128((__m128i*)&mtx->iq_[8]);
    const __m128i bias0 = _mm_loadu_si128((__m128i*)&mtx->bias_[0]);
    const __m128i bias8 = _mm_loadu_si128((__m128i*)&mtx->bias_[8]);
    const __m128i q0 = _mm_loadu_si128((__m128i*)&mtx->q_[0]);
    const __m128i q8 = _mm_loadu_si128((__m128i*)&mtx->q_[8]);
    const __m128i zthresh0 = _mm_loadu_si128((__m128i*)&mtx->zthresh_[0]);
    const __m128i zthresh8 = _mm_loadu_si128((__m128i*)&mtx->zthresh_[8]);
  
    // sign(in) = in >> 15  (0x0000 if positive, 0xffff if negative)
    sign0 = _mm_srai_epi16(in0, 15);
    sign8 = _mm_srai_epi16(in8, 15);
  
    // coeff = abs(in) = (in ^ sign) - sign
    coeff0 = _mm_xor_si128(in0, sign0);
    coeff8 = _mm_xor_si128(in8, sign8);
    coeff0 = _mm_sub_epi16(coeff0, sign0);
    coeff8 = _mm_sub_epi16(coeff8, sign8);
  
    // coeff = abs(in) + sharpen
    coeff0 = _mm_add_epi16(coeff0, sharpen0);
    coeff8 = _mm_add_epi16(coeff8, sharpen8);
  
    // if (coeff > 2047) coeff = 2047
    coeff0 = _mm_min_epi16(coeff0, max_coeff_2047);
    coeff8 = _mm_min_epi16(coeff8, max_coeff_2047);
  
    // out = (coeff * iQ + B) >> QFIX;
    {
      // doing calculations with 32b precision (QFIX=17)
      // out = (coeff * iQ)
      __m128i coeff_iQ0H = _mm_mulhi_epu16(coeff0, iq0);
      __m128i coeff_iQ0L = _mm_mullo_epi16(coeff0, iq0);
      __m128i coeff_iQ8H = _mm_mulhi_epu16(coeff8, iq8);
      __m128i coeff_iQ8L = _mm_mullo_epi16(coeff8, iq8);
      __m128i out_00 = _mm_unpacklo_epi16(coeff_iQ0L, coeff_iQ0H);
      __m128i out_04 = _mm_unpackhi_epi16(coeff_iQ0L, coeff_iQ0H);
      __m128i out_08 = _mm_unpacklo_epi16(coeff_iQ8L, coeff_iQ8H);
      __m128i out_12 = _mm_unpackhi_epi16(coeff_iQ8L, coeff_iQ8H);
      // expand bias from 16b to 32b
      __m128i bias_00 = _mm_unpacklo_epi16(bias0, zero);
      __m128i bias_04 = _mm_unpackhi_epi16(bias0, zero);
      __m128i bias_08 = _mm_unpacklo_epi16(bias8, zero);
      __m128i bias_12 = _mm_unpackhi_epi16(bias8, zero);
      // out = (coeff * iQ + B)
      out_00 = _mm_add_epi32(out_00, bias_00);
      out_04 = _mm_add_epi32(out_04, bias_04);
      out_08 = _mm_add_epi32(out_08, bias_08);
      out_12 = _mm_add_epi32(out_12, bias_12);
      // out = (coeff * iQ + B) >> QFIX;
      out_00 = _mm_srai_epi32(out_00, QFIX);
      out_04 = _mm_srai_epi32(out_04, QFIX);
      out_08 = _mm_srai_epi32(out_08, QFIX);
      out_12 = _mm_srai_epi32(out_12, QFIX);
      // pack result as 16b
      out0 = _mm_packs_epi32(out_00, out_04);
      out8 = _mm_packs_epi32(out_08, out_12);
    }
  
    // get sign back (if (sign[j]) out_n = -out_n)
    out0 = _mm_xor_si128(out0, sign0);
    out8 = _mm_xor_si128(out8, sign8);
    out0 = _mm_sub_epi16(out0, sign0);
    out8 = _mm_sub_epi16(out8, sign8);
  
    // in = out * Q
    in0 = _mm_mullo_epi16(out0, q0);
    in8 = _mm_mullo_epi16(out8, q8);
  
    // if (coeff <= mtx->zthresh_) {in=0; out=0;}
    {
      __m128i cmp0 = _mm_cmpgt_epi16(coeff0, zthresh0);
      __m128i cmp8 = _mm_cmpgt_epi16(coeff8, zthresh8);
      in0 = _mm_and_si128(in0, cmp0);
      in8 = _mm_and_si128(in8, cmp8);
      _mm_storeu_si128((__m128i*)&in[0], in0);
      _mm_storeu_si128((__m128i*)&in[8], in8);
      out0 = _mm_and_si128(out0, cmp0);
      out8 = _mm_and_si128(out8, cmp8);
    }
  
    // zigzag the output before storing it.
    //
    // The zigzag pattern can almost be reproduced with a small sequence of
    // shuffles. After it, we only need to swap the 7th (ending up in third
    // position instead of twelfth) and 8th values.
    {
      __m128i outZ0, outZ8;
      outZ0 = _mm_shufflehi_epi16(out0,  _MM_SHUFFLE(2, 1, 3, 0));
      outZ0 = _mm_shuffle_epi32  (outZ0, _MM_SHUFFLE(3, 1, 2, 0));
      outZ0 = _mm_shufflehi_epi16(outZ0, _MM_SHUFFLE(3, 1, 0, 2));
      outZ8 = _mm_shufflelo_epi16(out8,  _MM_SHUFFLE(3, 0, 2, 1));
      outZ8 = _mm_shuffle_epi32  (outZ8, _MM_SHUFFLE(3, 1, 2, 0));
      outZ8 = _mm_shufflelo_epi16(outZ8, _MM_SHUFFLE(1, 3, 2, 0));
      _mm_storeu_si128((__m128i*)&out[0], outZ0);
      _mm_storeu_si128((__m128i*)&out[8], outZ8);
      packed_out = _mm_packs_epi16(outZ0, outZ8);
    }
    {
      const int16_t outZ_12 = out[12];
      const int16_t outZ_3 = out[3];
      out[3] = outZ_12;
      out[12] = outZ_3;
    }
  
    // detect if all 'out' values are zeroes or not
    {
      int32_t tmp[4];
      _mm_storeu_si128((__m128i*)tmp, packed_out);
      if (n) {
        tmp[0] &= ~0xff;
      }
      return (tmp[3] || tmp[2] || tmp[1] || tmp[0]);
    }
  }
  
  #endif   // WEBP_USE_SSE2
  
  //------------------------------------------------------------------------------
  // Entry point
  
  extern void VP8EncDspInitSSE2(void);
  
  void VP8EncDspInitSSE2(void) {
  #if defined(WEBP_USE_SSE2)
    VP8CollectHistogram = CollectHistogramSSE2;
    VP8EncQuantizeBlock = QuantizeBlockSSE2;
    VP8ITransform = ITransformSSE2;
    VP8FTransform = FTransformSSE2;
    VP8SSE4x4 = SSE4x4SSE2;
    VP8TDisto4x4 = Disto4x4SSE2;
    VP8TDisto16x16 = Disto16x16SSE2;
  #endif   // WEBP_USE_SSE2
  }
  
  #if defined(__cplusplus) || defined(c_plusplus)
  }    // extern "C"
  #endif
  