text: // Copyright 2011 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.
  // -----------------------------------------------------------------------------
  //
  // SSE2 version of YUV to RGB upsampling functions.
  //
  // Author: somnath@google.com (Somnath Banerjee)
  
  #include "./dsp.h"
  
  #if defined(WEBP_USE_SSE2)
  
  #include <assert.h>
  #include <emmintrin.h>
  #include <string.h>
  #include "./yuv.h"
  
  #ifdef FANCY_UPSAMPLING
  
  // We compute (9*a + 3*b + 3*c + d + 8) / 16 as follows
  // u = (9*a + 3*b + 3*c + d + 8) / 16
  //   = (a + (a + 3*b + 3*c + d) / 8 + 1) / 2
  //   = (a + m + 1) / 2
  // where m = (a + 3*b + 3*c + d) / 8
  //         = ((a + b + c + d) / 2 + b + c) / 4
  //
  // Let's say  k = (a + b + c + d) / 4.
  // We can compute k as
  // k = (s + t + 1) / 2 - ((a^d) | (b^c) | (s^t)) & 1
  // where s = (a + d + 1) / 2 and t = (b + c + 1) / 2
  //
  // Then m can be written as
  // m = (k + t + 1) / 2 - (((b^c) & (s^t)) | (k^t)) & 1
  
  // Computes out = (k + in + 1) / 2 - ((ij & (s^t)) | (k^in)) & 1
  #define GET_M(ij, in, out) do {                                                \
    const __m128i tmp0 = _mm_avg_epu8(k, (in));     /* (k + in + 1) / 2 */       \
    const __m128i tmp1 = _mm_and_si128((ij), st);   /* (ij) & (s^t) */           \
    const __m128i tmp2 = _mm_xor_si128(k, (in));    /* (k^in) */                 \
    const __m128i tmp3 = _mm_or_si128(tmp1, tmp2);  /* ((ij) & (s^t)) | (k^in) */\
    const __m128i tmp4 = _mm_and_si128(tmp3, one);  /* & 1 -> lsb_correction */  \
    (out) = _mm_sub_epi8(tmp0, tmp4);    /* (k + in + 1) / 2 - lsb_correction */ \
  } while (0)
  
  // pack and store two alternating pixel rows
  #define PACK_AND_STORE(a, b, da, db, out) do {                                 \
    const __m128i t_a = _mm_avg_epu8(a, da);  /* (9a + 3b + 3c +  d + 8) / 16 */ \
    const __m128i t_b = _mm_avg_epu8(b, db);  /* (3a + 9b +  c + 3d + 8) / 16 */ \
    const __m128i t_1 = _mm_unpacklo_epi8(t_a, t_b);                             \
    const __m128i t_2 = _mm_unpackhi_epi8(t_a, t_b);                             \
    _mm_store_si128(((__m128i*)(out)) + 0, t_1);                                 \
    _mm_store_si128(((__m128i*)(out)) + 1, t_2);                                 \
  } while (0)
  
  // Loads 17 pixels each from rows r1 and r2 and generates 32 pixels.
  #define UPSAMPLE_32PIXELS(r1, r2, out) {                                       \
    const __m128i one = _mm_set1_epi8(1);                                        \
    const __m128i a = _mm_loadu_si128((const __m128i*)&(r1)[0]);                 \
    const __m128i b = _mm_loadu_si128((const __m128i*)&(r1)[1]);                 \
    const __m128i c = _mm_loadu_si128((const __m128i*)&(r2)[0]);                 \
    const __m128i d = _mm_loadu_si128((const __m128i*)&(r2)[1]);                 \
                                                                                 \
    const __m128i s = _mm_avg_epu8(a, d);        /* s = (a + d + 1) / 2 */       \
    const __m128i t = _mm_avg_epu8(b, c);        /* t = (b + c + 1) / 2 */       \
    const __m128i st = _mm_xor_si128(s, t);      /* st = s^t */                  \
                                                                                 \
    const __m128i ad = _mm_xor_si128(a, d);      /* ad = a^d */                  \
    const __m128i bc = _mm_xor_si128(b, c);      /* bc = b^c */                  \
                                                                                 \
    const __m128i t1 = _mm_or_si128(ad, bc);     /* (a^d) | (b^c) */             \
    const __m128i t2 = _mm_or_si128(t1, st);     /* (a^d) | (b^c) | (s^t) */     \
    const __m128i t3 = _mm_and_si128(t2, one);   /* (a^d) | (b^c) | (s^t) & 1 */ \
    const __m128i t4 = _mm_avg_epu8(s, t);                                       \
    const __m128i k = _mm_sub_epi8(t4, t3);      /* k = (a + b + c + d) / 4 */   \
    __m128i diag1, diag2;                                                        \
                                                                                 \
    GET_M(bc, t, diag1);                  /* diag1 = (a + 3b + 3c + d) / 8 */    \
    GET_M(ad, s, diag2);                  /* diag2 = (3a + b + c + 3d) / 8 */    \
                                                                                 \
    /* pack the alternate pixels */                                              \
    PACK_AND_STORE(a, b, diag1, diag2, out +      0);  /* store top */           \
    PACK_AND_STORE(c, d, diag2, diag1, out + 2 * 32);  /* store bottom */        \
  }
  
  // Turn the macro into a function for reducing code-size when non-critical
  static void Upsample32Pixels(const uint8_t r1[], const uint8_t r2[],
                               uint8_t* const out) {
    UPSAMPLE_32PIXELS(r1, r2, out);
  }
  
  #define UPSAMPLE_LAST_BLOCK(tb, bb, num_pixels, out) {                         \
    uint8_t r1[17], r2[17];                                                      \
    memcpy(r1, (tb), (num_pixels));                                              \
    memcpy(r2, (bb), (num_pixels));                                              \
    /* replicate last byte */                                                    \
    memset(r1 + (num_pixels), r1[(num_pixels) - 1], 17 - (num_pixels));          \
    memset(r2 + (num_pixels), r2[(num_pixels) - 1], 17 - (num_pixels));          \
    /* using the shared function instead of the macro saves ~3k code size */     \
    Upsample32Pixels(r1, r2, out);                                               \
  }
  
  #define CONVERT2RGB(FUNC, XSTEP, top_y, bottom_y,                              \
                      top_dst, bottom_dst, cur_x, num_pixels) {                  \
    int n;                                                                       \
    for (n = 0; n < (num_pixels); ++n) {                                         \
      FUNC(top_y[(cur_x) + n], r_u[n], r_v[n],                                   \
           top_dst + ((cur_x) + n) * XSTEP);                                     \
    }                                                                            \
    if (bottom_y != NULL) {                                                      \
      for (n = 0; n < (num_pixels); ++n) {                                       \
        FUNC(bottom_y[(cur_x) + n], r_u[64 + n], r_v[64 + n],                    \
             bottom_dst + ((cur_x) + n) * XSTEP);                                \
      }                                                                          \
    }                                                                            \
  }
  
  #define CONVERT2RGB_32(FUNC, XSTEP, top_y, bottom_y,                           \
                         top_dst, bottom_dst, cur_x) do {                        \
    FUNC##32(top_y + (cur_x), r_u, r_v, top_dst + (cur_x) * XSTEP);              \
    if (bottom_y != NULL) {                                                      \
      FUNC##32(bottom_y + (cur_x), r_u + 64, r_v + 64,                           \
               bottom_dst + (cur_x) * XSTEP);                                    \
    }                                                                            \
  } while (0)
  
  #define SSE2_UPSAMPLE_FUNC(FUNC_NAME, FUNC, XSTEP)                             \
  static void FUNC_NAME(const uint8_t* top_y, const uint8_t* bottom_y,           \
                        const uint8_t* top_u, const uint8_t* top_v,              \
                        const uint8_t* cur_u, const uint8_t* cur_v,              \
                        uint8_t* top_dst, uint8_t* bottom_dst, int len) {        \
    int uv_pos, pos;                                                             \
    /* 16byte-aligned array to cache reconstructed u and v */                    \
    uint8_t uv_buf[4 * 32 + 15];                                                 \
    uint8_t* const r_u = (uint8_t*)((uintptr_t)(uv_buf + 15) & ~15);             \
    uint8_t* const r_v = r_u + 32;                                               \
                                                                                 \
    assert(top_y != NULL);                                                       \
    {   /* Treat the first pixel in regular way */                               \
      const int u_diag = ((top_u[0] + cur_u[0]) >> 1) + 1;                       \
      const int v_diag = ((top_v[0] + cur_v[0]) >> 1) + 1;                       \
      const int u0_t = (top_u[0] + u_diag) >> 1;                                 \
      const int v0_t = (top_v[0] + v_diag) >> 1;                                 \
      FUNC(top_y[0], u0_t, v0_t, top_dst);                                       \
      if (bottom_y != NULL) {                                                    \
        const int u0_b = (cur_u[0] + u_diag) >> 1;                               \
        const int v0_b = (cur_v[0] + v_diag) >> 1;                               \
        FUNC(bottom_y[0], u0_b, v0_b, bottom_dst);                               \
      }                                                                          \
    }                                                                            \
    /* For UPSAMPLE_32PIXELS, 17 u/v values must be read-able for each block */  \
    for (pos = 1, uv_pos = 0; pos + 32 + 1 <= len; pos += 32, uv_pos += 16) {    \
      UPSAMPLE_32PIXELS(top_u + uv_pos, cur_u + uv_pos, r_u);                    \
      UPSAMPLE_32PIXELS(top_v + uv_pos, cur_v + uv_pos, r_v);                    \
      CONVERT2RGB_32(FUNC, XSTEP, top_y, bottom_y, top_dst, bottom_dst, pos);    \
    }                                                                            \
    if (len > 1) {                                                               \
      const int left_over = ((len + 1) >> 1) - (pos >> 1);                       \
      assert(left_over > 0);                                                     \
      UPSAMPLE_LAST_BLOCK(top_u + uv_pos, cur_u + uv_pos, left_over, r_u);       \
      UPSAMPLE_LAST_BLOCK(top_v + uv_pos, cur_v + uv_pos, left_over, r_v);       \
      CONVERT2RGB(FUNC, XSTEP, top_y, bottom_y, top_dst, bottom_dst,             \
                  pos, len - pos);                                               \
    }                                                                            \
  }
  
  // SSE2 variants of the fancy upsampler.
  SSE2_UPSAMPLE_FUNC(UpsampleRgbLinePair,  VP8YuvToRgb,  3)
  SSE2_UPSAMPLE_FUNC(UpsampleBgrLinePair,  VP8YuvToBgr,  3)
  SSE2_UPSAMPLE_FUNC(UpsampleRgbaLinePair, VP8YuvToRgba, 4)
  SSE2_UPSAMPLE_FUNC(UpsampleBgraLinePair, VP8YuvToBgra, 4)
  
  #undef GET_M
  #undef PACK_AND_STORE
  #undef UPSAMPLE_32PIXELS
  #undef UPSAMPLE_LAST_BLOCK
  #undef CONVERT2RGB
  #undef CONVERT2RGB_32
  #undef SSE2_UPSAMPLE_FUNC
  
  #endif  // FANCY_UPSAMPLING
  
  #endif   // WEBP_USE_SSE2
  
  //------------------------------------------------------------------------------
  
  extern void WebPInitUpsamplersSSE2(void);
  
  #ifdef FANCY_UPSAMPLING
  
  extern WebPUpsampleLinePairFunc WebPUpsamplers[/* MODE_LAST */];
  
  WEBP_TSAN_IGNORE_FUNCTION void WebPInitUpsamplersSSE2(void) {
  #if defined(WEBP_USE_SSE2)
    VP8YUVInitSSE2();
    WebPUpsamplers[MODE_RGB]  = UpsampleRgbLinePair;
    WebPUpsamplers[MODE_RGBA] = UpsampleRgbaLinePair;
    WebPUpsamplers[MODE_BGR]  = UpsampleBgrLinePair;
    WebPUpsamplers[MODE_BGRA] = UpsampleBgraLinePair;
    WebPUpsamplers[MODE_rgbA] = UpsampleRgbaLinePair;
    WebPUpsamplers[MODE_bgrA] = UpsampleBgraLinePair;
  #endif   // WEBP_USE_SSE2
  }
  
  #else
  
  // this empty function is to avoid an empty .o
  WEBP_TSAN_IGNORE_FUNCTION void WebPInitUpsamplersSSE2(void) {}
  
  #endif  // FANCY_UPSAMPLING
  