text: // Copyright 2014 Google Inc. All Rights Reserved.
  //
  // Use of this source code is governed by a BSD-style license
  // that can be found in the COPYING file in the root of the source
  // tree. An additional intellectual property rights grant can be found
  // in the file PATENTS. All contributing project authors may
  // be found in the AUTHORS file in the root of the source tree.
  // -----------------------------------------------------------------------------
  //
  // YUV->RGB conversion functions
  //
  // Author: Skal (pascal.massimino@gmail.com)
  
  #include "src/dsp/yuv.h"
  
  #if defined(WEBP_USE_SSE41)
  
  #include "src/dsp/common_sse41.h"
  #include <stdlib.h>
  #include <smmintrin.h>
  
  //-----------------------------------------------------------------------------
  // Convert spans of 32 pixels to various RGB formats for the fancy upsampler.
  
  // These constants are 14b fixed-point version of ITU-R BT.601 constants.
  // R = (19077 * y             + 26149 * v - 14234) >> 6
  // G = (19077 * y -  6419 * u - 13320 * v +  8708) >> 6
  // B = (19077 * y + 33050 * u             - 17685) >> 6
  static void ConvertYUV444ToRGB_SSE41(const __m128i* const Y0,
                                       const __m128i* const U0,
                                       const __m128i* const V0,
                                       __m128i* const R,
                                       __m128i* const G,
                                       __m128i* const B) {
    const __m128i k19077 = _mm_set1_epi16(19077);
    const __m128i k26149 = _mm_set1_epi16(26149);
    const __m128i k14234 = _mm_set1_epi16(14234);
    // 33050 doesn't fit in a signed short: only use this with unsigned arithmetic
    const __m128i k33050 = _mm_set1_epi16((short)33050);
    const __m128i k17685 = _mm_set1_epi16(17685);
    const __m128i k6419  = _mm_set1_epi16(6419);
    const __m128i k13320 = _mm_set1_epi16(13320);
    const __m128i k8708  = _mm_set1_epi16(8708);
  
    const __m128i Y1 = _mm_mulhi_epu16(*Y0, k19077);
  
    const __m128i R0 = _mm_mulhi_epu16(*V0, k26149);
    const __m128i R1 = _mm_sub_epi16(Y1, k14234);
    const __m128i R2 = _mm_add_epi16(R1, R0);
  
    const __m128i G0 = _mm_mulhi_epu16(*U0, k6419);
    const __m128i G1 = _mm_mulhi_epu16(*V0, k13320);
    const __m128i G2 = _mm_add_epi16(Y1, k8708);
    const __m128i G3 = _mm_add_epi16(G0, G1);
    const __m128i G4 = _mm_sub_epi16(G2, G3);
  
    // be careful with the saturated *unsigned* arithmetic here!
    const __m128i B0 = _mm_mulhi_epu16(*U0, k33050);
    const __m128i B1 = _mm_adds_epu16(B0, Y1);
    const __m128i B2 = _mm_subs_epu16(B1, k17685);
  
    // use logical shift for B2, which can be larger than 32767
    *R = _mm_srai_epi16(R2, 6);   // range: [-14234, 30815]
    *G = _mm_srai_epi16(G4, 6);   // range: [-10953, 27710]
    *B = _mm_srli_epi16(B2, 6);   // range: [0, 34238]
  }
  
  // Load the bytes into the *upper* part of 16b words. That's "<< 8", basically.
  static WEBP_INLINE __m128i Load_HI_16_SSE41(const uint8_t* src) {
    const __m128i zero = _mm_setzero_si128();
    return _mm_unpacklo_epi8(zero, _mm_loadl_epi64((const __m128i*)src));
  }
  
  // Load and replicate the U/V samples
  static WEBP_INLINE __m128i Load_UV_HI_8_SSE41(const uint8_t* src) {
    const __m128i zero = _mm_setzero_si128();
    const __m128i tmp0 = _mm_cvtsi32_si128(*(const uint32_t*)src);
    const __m128i tmp1 = _mm_unpacklo_epi8(zero, tmp0);
    return _mm_unpacklo_epi16(tmp1, tmp1);   // replicate samples
  }
  
  // Convert 32 samples of YUV444 to R/G/B
  static void YUV444ToRGB_SSE41(const uint8_t* const y,
                                const uint8_t* const u,
                                const uint8_t* const v,
                                __m128i* const R, __m128i* const G,
                                __m128i* const B) {
    const __m128i Y0 = Load_HI_16_SSE41(y), U0 = Load_HI_16_SSE41(u),
                  V0 = Load_HI_16_SSE41(v);
    ConvertYUV444ToRGB_SSE41(&Y0, &U0, &V0, R, G, B);
  }
  
  // Convert 32 samples of YUV420 to R/G/B
  static void YUV420ToRGB_SSE41(const uint8_t* const y,
                                const uint8_t* const u,
                                const uint8_t* const v,
                                __m128i* const R, __m128i* const G,
                                __m128i* const B) {
    const __m128i Y0 = Load_HI_16_SSE41(y), U0 = Load_UV_HI_8_SSE41(u),
                  V0 = Load_UV_HI_8_SSE41(v);
    ConvertYUV444ToRGB_SSE41(&Y0, &U0, &V0, R, G, B);
  }
  
  // Pack the planar buffers
  // rrrr... rrrr... gggg... gggg... bbbb... bbbb....
  // triplet by triplet in the output buffer rgb as rgbrgbrgbrgb ...
  static WEBP_INLINE void PlanarTo24b_SSE41(
      __m128i* const in0, __m128i* const in1, __m128i* const in2,
      __m128i* const in3, __m128i* const in4, __m128i* const in5,
      uint8_t* const rgb) {
    // The input is 6 registers of sixteen 8b but for the sake of explanation,
    // let's take 6 registers of four 8b values.
    // To pack, we will keep taking one every two 8b integer and move it
    // around as follows:
    // Input:
    //   r0r1r2r3 | r4r5r6r7 | g0g1g2g3 | g4g5g6g7 | b0b1b2b3 | b4b5b6b7
    // Split the 6 registers in two sets of 3 registers: the first set as the even
    // 8b bytes, the second the odd ones:
    //   r0r2r4r6 | g0g2g4g6 | b0b2b4b6 | r1r3r5r7 | g1g3g5g7 | b1b3b5b7
    // Repeat the same permutations twice more:
    //   r0r4g0g4 | b0b4r1r5 | g1g5b1b5 | r2r6g2g6 | b2b6r3r7 | g3g7b3b7
    //   r0g0b0r1 | g1b1r2g2 | b2r3g3b3 | r4g4b4r5 | g5b5r6g6 | b6r7g7b7
    VP8PlanarTo24b_SSE41(in0, in1, in2, in3, in4, in5);
  
    _mm_storeu_si128((__m128i*)(rgb +  0), *in0);
    _mm_storeu_si128((__m128i*)(rgb + 16), *in1);
    _mm_storeu_si128((__m128i*)(rgb + 32), *in2);
    _mm_storeu_si128((__m128i*)(rgb + 48), *in3);
    _mm_storeu_si128((__m128i*)(rgb + 64), *in4);
    _mm_storeu_si128((__m128i*)(rgb + 80), *in5);
  }
  
  void VP8YuvToRgb32_SSE41(const uint8_t* y, const uint8_t* u, const uint8_t* v,
                           uint8_t* dst) {
    __m128i R0, R1, R2, R3, G0, G1, G2, G3, B0, B1, B2, B3;
    __m128i rgb0, rgb1, rgb2, rgb3, rgb4, rgb5;
  
    YUV444ToRGB_SSE41(y + 0, u + 0, v + 0, &R0, &G0, &B0);
    YUV444ToRGB_SSE41(y + 8, u + 8, v + 8, &R1, &G1, &B1);
    YUV444ToRGB_SSE41(y + 16, u + 16, v + 16, &R2, &G2, &B2);
    YUV444ToRGB_SSE41(y + 24, u + 24, v + 24, &R3, &G3, &B3);
  
    // Cast to 8b and store as RRRRGGGGBBBB.
    rgb0 = _mm_packus_epi16(R0, R1);
    rgb1 = _mm_packus_epi16(R2, R3);
    rgb2 = _mm_packus_epi16(G0, G1);
    rgb3 = _mm_packus_epi16(G2, G3);
    rgb4 = _mm_packus_epi16(B0, B1);
    rgb5 = _mm_packus_epi16(B2, B3);
  
    // Pack as RGBRGBRGBRGB.
    PlanarTo24b_SSE41(&rgb0, &rgb1, &rgb2, &rgb3, &rgb4, &rgb5, dst);
  }
  
  void VP8YuvToBgr32_SSE41(const uint8_t* y, const uint8_t* u, const uint8_t* v,
                           uint8_t* dst) {
    __m128i R0, R1, R2, R3, G0, G1, G2, G3, B0, B1, B2, B3;
    __m128i bgr0, bgr1, bgr2, bgr3, bgr4, bgr5;
  
    YUV444ToRGB_SSE41(y +  0, u +  0, v +  0, &R0, &G0, &B0);
    YUV444ToRGB_SSE41(y +  8, u +  8, v +  8, &R1, &G1, &B1);
    YUV444ToRGB_SSE41(y + 16, u + 16, v + 16, &R2, &G2, &B2);
    YUV444ToRGB_SSE41(y + 24, u + 24, v + 24, &R3, &G3, &B3);
  
    // Cast to 8b and store as BBBBGGGGRRRR.
    bgr0 = _mm_packus_epi16(B0, B1);
    bgr1 = _mm_packus_epi16(B2, B3);
    bgr2 = _mm_packus_epi16(G0, G1);
    bgr3 = _mm_packus_epi16(G2, G3);
    bgr4 = _mm_packus_epi16(R0, R1);
    bgr5= _mm_packus_epi16(R2, R3);
  
    // Pack as BGRBGRBGRBGR.
    PlanarTo24b_SSE41(&bgr0, &bgr1, &bgr2, &bgr3, &bgr4, &bgr5, dst);
  }
  
  //-----------------------------------------------------------------------------
  // Arbitrary-length row conversion functions
  
  static void YuvToRgbRow_SSE41(const uint8_t* y,
                                const uint8_t* u, const uint8_t* v,
                                uint8_t* dst, int len) {
    int n;
    for (n = 0; n + 32 <= len; n += 32, dst += 32 * 3) {
      __m128i R0, R1, R2, R3, G0, G1, G2, G3, B0, B1, B2, B3;
      __m128i rgb0, rgb1, rgb2, rgb3, rgb4, rgb5;
  
      YUV420ToRGB_SSE41(y +  0, u +  0, v +  0, &R0, &G0, &B0);
      YUV420ToRGB_SSE41(y +  8, u +  4, v +  4, &R1, &G1, &B1);
      YUV420ToRGB_SSE41(y + 16, u +  8, v +  8, &R2, &G2, &B2);
      YUV420ToRGB_SSE41(y + 24, u + 12, v + 12, &R3, &G3, &B3);
  
      // Cast to 8b and store as RRRRGGGGBBBB.
      rgb0 = _mm_packus_epi16(R0, R1);
      rgb1 = _mm_packus_epi16(R2, R3);
      rgb2 = _mm_packus_epi16(G0, G1);
      rgb3 = _mm_packus_epi16(G2, G3);
      rgb4 = _mm_packus_epi16(B0, B1);
      rgb5 = _mm_packus_epi16(B2, B3);
  
      // Pack as RGBRGBRGBRGB.
      PlanarTo24b_SSE41(&rgb0, &rgb1, &rgb2, &rgb3, &rgb4, &rgb5, dst);
  
      y += 32;
      u += 16;
      v += 16;
    }
    for (; n < len; ++n) {   // Finish off
      VP8YuvToRgb(y[0], u[0], v[0], dst);
      dst += 3;
      y += 1;
      u += (n & 1);
      v += (n & 1);
    }
  }
  
  static void YuvToBgrRow_SSE41(const uint8_t* y,
                                const uint8_t* u, const uint8_t* v,
                                uint8_t* dst, int len) {
    int n;
    for (n = 0; n + 32 <= len; n += 32, dst += 32 * 3) {
      __m128i R0, R1, R2, R3, G0, G1, G2, G3, B0, B1, B2, B3;
      __m128i bgr0, bgr1, bgr2, bgr3, bgr4, bgr5;
  
      YUV420ToRGB_SSE41(y +  0, u +  0, v +  0, &R0, &G0, &B0);
      YUV420ToRGB_SSE41(y +  8, u +  4, v +  4, &R1, &G1, &B1);
      YUV420ToRGB_SSE41(y + 16, u +  8, v +  8, &R2, &G2, &B2);
      YUV420ToRGB_SSE41(y + 24, u + 12, v + 12, &R3, &G3, &B3);
  
      // Cast to 8b and store as BBBBGGGGRRRR.
      bgr0 = _mm_packus_epi16(B0, B1);
      bgr1 = _mm_packus_epi16(B2, B3);
      bgr2 = _mm_packus_epi16(G0, G1);
      bgr3 = _mm_packus_epi16(G2, G3);
      bgr4 = _mm_packus_epi16(R0, R1);
      bgr5 = _mm_packus_epi16(R2, R3);
  
      // Pack as BGRBGRBGRBGR.
      PlanarTo24b_SSE41(&bgr0, &bgr1, &bgr2, &bgr3, &bgr4, &bgr5, dst);
  
      y += 32;
      u += 16;
      v += 16;
    }
    for (; n < len; ++n) {   // Finish off
      VP8YuvToBgr(y[0], u[0], v[0], dst);
      dst += 3;
      y += 1;
      u += (n & 1);
      v += (n & 1);
    }
  }
  
  //------------------------------------------------------------------------------
  // Entry point
  
  extern void WebPInitSamplersSSE41(void);
  
  WEBP_TSAN_IGNORE_FUNCTION void WebPInitSamplersSSE41(void) {
    WebPSamplers[MODE_RGB]  = YuvToRgbRow_SSE41;
    WebPSamplers[MODE_BGR]  = YuvToBgrRow_SSE41;
  }
  
  //------------------------------------------------------------------------------
  // RGB24/32 -> YUV converters
  
  // Load eight 16b-words from *src.
  #define LOAD_16(src) _mm_loadu_si128((const __m128i*)(src))
  // Store either 16b-words into *dst
  #define STORE_16(V, dst) _mm_storeu_si128((__m128i*)(dst), (V))
  
  #define WEBP_SSE41_SHUFF(OUT)  do {                  \
    const __m128i tmp0 = _mm_shuffle_epi8(A0, shuff0); \
    const __m128i tmp1 = _mm_shuffle_epi8(A1, shuff1); \
    const __m128i tmp2 = _mm_shuffle_epi8(A2, shuff2); \
    const __m128i tmp3 = _mm_shuffle_epi8(A3, shuff0); \
    const __m128i tmp4 = _mm_shuffle_epi8(A4, shuff1); \
    const __m128i tmp5 = _mm_shuffle_epi8(A5, shuff2); \
                                                       \
    /* OR everything to get one channel */             \
    const __m128i tmp6 = _mm_or_si128(tmp0, tmp1);     \
    const __m128i tmp7 = _mm_or_si128(tmp3, tmp4);     \
    out[OUT + 0] = _mm_or_si128(tmp6, tmp2);           \
    out[OUT + 1] = _mm_or_si128(tmp7, tmp5);           \
  } while (0);
  
  // Unpack the 8b input rgbrgbrgbrgb ... as contiguous registers:
  // rrrr... rrrr... gggg... gggg... bbbb... bbbb....
  // Similar to PlanarTo24bHelper(), but in reverse order.
  static WEBP_INLINE void RGB24PackedToPlanar_SSE41(
      const uint8_t* const rgb, __m128i* const out /*out[6]*/) {
    const __m128i A0 = _mm_loadu_si128((const __m128i*)(rgb +  0));
    const __m128i A1 = _mm_loadu_si128((const __m128i*)(rgb + 16));
    const __m128i A2 = _mm_loadu_si128((const __m128i*)(rgb + 32));
    const __m128i A3 = _mm_loadu_si128((const __m128i*)(rgb + 48));
    const __m128i A4 = _mm_loadu_si128((const __m128i*)(rgb + 64));
    const __m128i A5 = _mm_loadu_si128((const __m128i*)(rgb + 80));
  
    // Compute RR.
    {
      const __m128i shuff0 = _mm_set_epi8(
          -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, 15, 12, 9, 6, 3, 0);
      const __m128i shuff1 = _mm_set_epi8(
          -1, -1, -1, -1, -1, 14, 11, 8, 5, 2, -1, -1, -1, -1, -1, -1);
      const __m128i shuff2 = _mm_set_epi8(
          13, 10, 7, 4, 1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1);
      WEBP_SSE41_SHUFF(0)
    }
    // Compute GG.
    {
      const __m128i shuff0 = _mm_set_epi8(
          -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, 13, 10, 7, 4, 1);
      const __m128i shuff1 = _mm_set_epi8(
          -1, -1, -1, -1, -1, 15, 12, 9, 6, 3, 0, -1, -1, -1, -1, -1);
      const __m128i shuff2 = _mm_set_epi8(
          14, 11, 8, 5, 2, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1);
      WEBP_SSE41_SHUFF(2)
    }
    // Compute BB.
    {
      const __m128i shuff0 = _mm_set_epi8(
          -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, 14, 11, 8, 5, 2);
      const __m128i shuff1 = _mm_set_epi8(
          -1, -1, -1, -1, -1, -1, 13, 10, 7, 4, 1, -1, -1, -1, -1, -1);
      const __m128i shuff2 = _mm_set_epi8(
          15, 12, 9, 6, 3, 0, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1);
      WEBP_SSE41_SHUFF(4)
    }
  }
  
  #undef WEBP_SSE41_SHUFF
  
  // Convert 8 packed ARGB to r[], g[], b[]
  static WEBP_INLINE void RGB32PackedToPlanar_SSE41(
      const uint32_t* const argb, __m128i* const rgb /*in[6]*/) {
    const __m128i zero = _mm_setzero_si128();
    __m128i a0 = LOAD_16(argb + 0);
    __m128i a1 = LOAD_16(argb + 4);
    __m128i a2 = LOAD_16(argb + 8);
    __m128i a3 = LOAD_16(argb + 12);
    VP8L32bToPlanar_SSE41(&a0, &a1, &a2, &a3);
    rgb[0] = _mm_unpacklo_epi8(a1, zero);
    rgb[1] = _mm_unpackhi_epi8(a1, zero);
    rgb[2] = _mm_unpacklo_epi8(a2, zero);
    rgb[3] = _mm_unpackhi_epi8(a2, zero);
    rgb[4] = _mm_unpacklo_epi8(a3, zero);
    rgb[5] = _mm_unpackhi_epi8(a3, zero);
  }
  
  // This macro computes (RG * MULT_RG + GB * MULT_GB + ROUNDER) >> DESCALE_FIX
  // It's a macro and not a function because we need to use immediate values with
  // srai_epi32, e.g.
  #define TRANSFORM(RG_LO, RG_HI, GB_LO, GB_HI, MULT_RG, MULT_GB, \
                    ROUNDER, DESCALE_FIX, OUT) do {               \
    const __m128i V0_lo = _mm_madd_epi16(RG_LO, MULT_RG);         \
    const __m128i V0_hi = _mm_madd_epi16(RG_HI, MULT_RG);         \
    const __m128i V1_lo = _mm_madd_epi16(GB_LO, MULT_GB);         \
    const __m128i V1_hi = _mm_madd_epi16(GB_HI, MULT_GB);         \
    const __m128i V2_lo = _mm_add_epi32(V0_lo, V1_lo);            \
    const __m128i V2_hi = _mm_add_epi32(V0_hi, V1_hi);            \
    const __m128i V3_lo = _mm_add_epi32(V2_lo, ROUNDER);          \
    const __m128i V3_hi = _mm_add_epi32(V2_hi, ROUNDER);          \
    const __m128i V5_lo = _mm_srai_epi32(V3_lo, DESCALE_FIX);     \
    const __m128i V5_hi = _mm_srai_epi32(V3_hi, DESCALE_FIX);     \
    (OUT) = _mm_packs_epi32(V5_lo, V5_hi);                        \
  } while (0)
  
  #define MK_CST_16(A, B) _mm_set_epi16((B), (A), (B), (A), (B), (A), (B), (A))
  static WEBP_INLINE void ConvertRGBToY_SSE41(const __m128i* const R,
                                              const __m128i* const G,
                                              const __m128i* const B,
                                              __m128i* const Y) {
    const __m128i kRG_y = MK_CST_16(16839, 33059 - 16384);
    const __m128i kGB_y = MK_CST_16(16384, 6420);
    const __m128i kHALF_Y = _mm_set1_epi32((16 << YUV_FIX) + YUV_HALF);
  
    const __m128i RG_lo = _mm_unpacklo_epi16(*R, *G);
    const __m128i RG_hi = _mm_unpackhi_epi16(*R, *G);
    const __m128i GB_lo = _mm_unpacklo_epi16(*G, *B);
    const __m128i GB_hi = _mm_unpackhi_epi16(*G, *B);
    TRANSFORM(RG_lo, RG_hi, GB_lo, GB_hi, kRG_y, kGB_y, kHALF_Y, YUV_FIX, *Y);
  }
  
  static WEBP_INLINE void ConvertRGBToUV_SSE41(const __m128i* const R,
                                               const __m128i* const G,
                                               const __m128i* const B,
                                               __m128i* const U,
                                               __m128i* const V) {
    const __m128i kRG_u = MK_CST_16(-9719, -19081);
    const __m128i kGB_u = MK_CST_16(0, 28800);
    const __m128i kRG_v = MK_CST_16(28800, 0);
    const __m128i kGB_v = MK_CST_16(-24116, -4684);
    const __m128i kHALF_UV = _mm_set1_epi32(((128 << YUV_FIX) + YUV_HALF) << 2);
  
    const __m128i RG_lo = _mm_unpacklo_epi16(*R, *G);
    const __m128i RG_hi = _mm_unpackhi_epi16(*R, *G);
    const __m128i GB_lo = _mm_unpacklo_epi16(*G, *B);
    const __m128i GB_hi = _mm_unpackhi_epi16(*G, *B);
    TRANSFORM(RG_lo, RG_hi, GB_lo, GB_hi, kRG_u, kGB_u,
              kHALF_UV, YUV_FIX + 2, *U);
    TRANSFORM(RG_lo, RG_hi, GB_lo, GB_hi, kRG_v, kGB_v,
              kHALF_UV, YUV_FIX + 2, *V);
  }
  
  #undef MK_CST_16
  #undef TRANSFORM
  
  static void ConvertRGB24ToY_SSE41(const uint8_t* rgb, uint8_t* y, int width) {
    const int max_width = width & ~31;
    int i;
    for (i = 0; i < max_width; rgb += 3 * 16 * 2) {
      __m128i rgb_plane[6];
      int j;
  
      RGB24PackedToPlanar_SSE41(rgb, rgb_plane);
  
      for (j = 0; j < 2; ++j, i += 16) {
        const __m128i zero = _mm_setzero_si128();
        __m128i r, g, b, Y0, Y1;
  
        // Convert to 16-bit Y.
        r = _mm_unpacklo_epi8(rgb_plane[0 + j], zero);
        g = _mm_unpacklo_epi8(rgb_plane[2 + j], zero);
        b = _mm_unpacklo_epi8(rgb_plane[4 + j], zero);
        ConvertRGBToY_SSE41(&r, &g, &b, &Y0);
  
        // Convert to 16-bit Y.
        r = _mm_unpackhi_epi8(rgb_plane[0 + j], zero);
        g = _mm_unpackhi_epi8(rgb_plane[2 + j], zero);
        b = _mm_unpackhi_epi8(rgb_plane[4 + j], zero);
        ConvertRGBToY_SSE41(&r, &g, &b, &Y1);
  
        // Cast to 8-bit and store.
        STORE_16(_mm_packus_epi16(Y0, Y1), y + i);
      }
    }
    for (; i < width; ++i, rgb += 3) {   // left-over
      y[i] = VP8RGBToY(rgb[0], rgb[1], rgb[2], YUV_HALF);
    }
  }
  
  static void ConvertBGR24ToY_SSE41(const uint8_t* bgr, uint8_t* y, int width) {
    const int max_width = width & ~31;
    int i;
    for (i = 0; i < max_width; bgr += 3 * 16 * 2) {
      __m128i bgr_plane[6];
      int j;
  
      RGB24PackedToPlanar_SSE41(bgr, bgr_plane);
  
      for (j = 0; j < 2; ++j, i += 16) {
        const __m128i zero = _mm_setzero_si128();
        __m128i r, g, b, Y0, Y1;
  
        // Convert to 16-bit Y.
        b = _mm_unpacklo_epi8(bgr_plane[0 + j], zero);
        g = _mm_unpacklo_epi8(bgr_plane[2 + j], zero);
        r = _mm_unpacklo_epi8(bgr_plane[4 + j], zero);
        ConvertRGBToY_SSE41(&r, &g, &b, &Y0);
  
        // Convert to 16-bit Y.
        b = _mm_unpackhi_epi8(bgr_plane[0 + j], zero);
        g = _mm_unpackhi_epi8(bgr_plane[2 + j], zero);
        r = _mm_unpackhi_epi8(bgr_plane[4 + j], zero);
        ConvertRGBToY_SSE41(&r, &g, &b, &Y1);
  
        // Cast to 8-bit and store.
        STORE_16(_mm_packus_epi16(Y0, Y1), y + i);
      }
    }
    for (; i < width; ++i, bgr += 3) {  // left-over
      y[i] = VP8RGBToY(bgr[2], bgr[1], bgr[0], YUV_HALF);
    }
  }
  
  static void ConvertARGBToY_SSE41(const uint32_t* argb, uint8_t* y, int width) {
    const int max_width = width & ~15;
    int i;
    for (i = 0; i < max_width; i += 16) {
      __m128i Y0, Y1, rgb[6];
      RGB32PackedToPlanar_SSE41(&argb[i], rgb);
      ConvertRGBToY_SSE41(&rgb[0], &rgb[2], &rgb[4], &Y0);
      ConvertRGBToY_SSE41(&rgb[1], &rgb[3], &rgb[5], &Y1);
      STORE_16(_mm_packus_epi16(Y0, Y1), y + i);
    }
    for (; i < width; ++i) {   // left-over
      const uint32_t p = argb[i];
      y[i] = VP8RGBToY((p >> 16) & 0xff, (p >> 8) & 0xff, (p >>  0) & 0xff,
                       YUV_HALF);
    }
  }
  
  // Horizontal add (doubled) of two 16b values, result is 16b.
  // in: A | B | C | D | ... -> out: 2*(A+B) | 2*(C+D) | ...
  static void HorizontalAddPack_SSE41(const __m128i* const A,
                                      const __m128i* const B,
                                      __m128i* const out) {
    const __m128i k2 = _mm_set1_epi16(2);
    const __m128i C = _mm_madd_epi16(*A, k2);
    const __m128i D = _mm_madd_epi16(*B, k2);
    *out = _mm_packs_epi32(C, D);
  }
  
  static void ConvertARGBToUV_SSE41(const uint32_t* argb,
                                    uint8_t* u, uint8_t* v,
                                    int src_width, int do_store) {
    const int max_width = src_width & ~31;
    int i;
    for (i = 0; i < max_width; i += 32, u += 16, v += 16) {
      __m128i rgb[6], U0, V0, U1, V1;
      RGB32PackedToPlanar_SSE41(&argb[i], rgb);
      HorizontalAddPack_SSE41(&rgb[0], &rgb[1], &rgb[0]);
      HorizontalAddPack_SSE41(&rgb[2], &rgb[3], &rgb[2]);
      HorizontalAddPack_SSE41(&rgb[4], &rgb[5], &rgb[4]);
      ConvertRGBToUV_SSE41(&rgb[0], &rgb[2], &rgb[4], &U0, &V0);
  
      RGB32PackedToPlanar_SSE41(&argb[i + 16], rgb);
      HorizontalAddPack_SSE41(&rgb[0], &rgb[1], &rgb[0]);
      HorizontalAddPack_SSE41(&rgb[2], &rgb[3], &rgb[2]);
      HorizontalAddPack_SSE41(&rgb[4], &rgb[5], &rgb[4]);
      ConvertRGBToUV_SSE41(&rgb[0], &rgb[2], &rgb[4], &U1, &V1);
  
      U0 = _mm_packus_epi16(U0, U1);
      V0 = _mm_packus_epi16(V0, V1);
      if (!do_store) {
        const __m128i prev_u = LOAD_16(u);
        const __m128i prev_v = LOAD_16(v);
        U0 = _mm_avg_epu8(U0, prev_u);
        V0 = _mm_avg_epu8(V0, prev_v);
      }
      STORE_16(U0, u);
      STORE_16(V0, v);
    }
    if (i < src_width) {  // left-over
      WebPConvertARGBToUV_C(argb + i, u, v, src_width - i, do_store);
    }
  }
  
  // Convert 16 packed ARGB 16b-values to r[], g[], b[]
  static WEBP_INLINE void RGBA32PackedToPlanar_16b_SSE41(
      const uint16_t* const rgbx,
      __m128i* const r, __m128i* const g, __m128i* const b) {
    const __m128i in0 = LOAD_16(rgbx +  0);  // r0 | g0 | b0 |x| r1 | g1 | b1 |x
    const __m128i in1 = LOAD_16(rgbx +  8);  // r2 | g2 | b2 |x| r3 | g3 | b3 |x
    const __m128i in2 = LOAD_16(rgbx + 16);  // r4 | ...
    const __m128i in3 = LOAD_16(rgbx + 24);  // r6 | ...
    // aarrggbb as 16-bit.
    const __m128i shuff0 =
        _mm_set_epi8(-1, -1, -1, -1, 13, 12, 5, 4, 11, 10, 3, 2, 9, 8, 1, 0);
    const __m128i shuff1 =
        _mm_set_epi8(13, 12, 5, 4, -1, -1, -1, -1, 11, 10, 3, 2, 9, 8, 1, 0);
    const __m128i A0 = _mm_shuffle_epi8(in0, shuff0);
    const __m128i A1 = _mm_shuffle_epi8(in1, shuff1);
    const __m128i A2 = _mm_shuffle_epi8(in2, shuff0);
    const __m128i A3 = _mm_shuffle_epi8(in3, shuff1);
    // R0R1G0G1
    // B0B1****
    // R2R3G2G3
    // B2B3****
    // (OR is used to free port 5 for the unpack)
    const __m128i B0 = _mm_unpacklo_epi32(A0, A1);
    const __m128i B1 = _mm_or_si128(A0, A1);
    const __m128i B2 = _mm_unpacklo_epi32(A2, A3);
    const __m128i B3 = _mm_or_si128(A2, A3);
    // Gather the channels.
    *r = _mm_unpacklo_epi64(B0, B2);
    *g = _mm_unpackhi_epi64(B0, B2);
    *b = _mm_unpackhi_epi64(B1, B3);
  }
  
  static void ConvertRGBA32ToUV_SSE41(const uint16_t* rgb,
                                      uint8_t* u, uint8_t* v, int width) {
    const int max_width = width & ~15;
    const uint16_t* const last_rgb = rgb + 4 * max_width;
    while (rgb < last_rgb) {
      __m128i r, g, b, U0, V0, U1, V1;
      RGBA32PackedToPlanar_16b_SSE41(rgb +  0, &r, &g, &b);
      ConvertRGBToUV_SSE41(&r, &g, &b, &U0, &V0);
      RGBA32PackedToPlanar_16b_SSE41(rgb + 32, &r, &g, &b);
      ConvertRGBToUV_SSE41(&r, &g, &b, &U1, &V1);
      STORE_16(_mm_packus_epi16(U0, U1), u);
      STORE_16(_mm_packus_epi16(V0, V1), v);
      u += 16;
      v += 16;
      rgb += 2 * 32;
    }
    if (max_width < width) {  // left-over
      WebPConvertRGBA32ToUV_C(rgb, u, v, width - max_width);
    }
  }
  
  //------------------------------------------------------------------------------
  
  extern void WebPInitConvertARGBToYUVSSE41(void);
  
  WEBP_TSAN_IGNORE_FUNCTION void WebPInitConvertARGBToYUVSSE41(void) {
    WebPConvertARGBToY = ConvertARGBToY_SSE41;
    WebPConvertARGBToUV = ConvertARGBToUV_SSE41;
  
    WebPConvertRGB24ToY = ConvertRGB24ToY_SSE41;
    WebPConvertBGR24ToY = ConvertBGR24ToY_SSE41;
  
    WebPConvertRGBA32ToUV = ConvertRGBA32ToUV_SSE41;
  }
  
  //------------------------------------------------------------------------------
  
  #else  // !WEBP_USE_SSE41
  
  WEBP_DSP_INIT_STUB(WebPInitSamplersSSE41)
  WEBP_DSP_INIT_STUB(WebPInitConvertARGBToYUVSSE41)
  
  #endif  // WEBP_USE_SSE41
  