go-libwebp

cost_sse2.c (4571B)

---

 // Copyright 2015 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 cost functions
 //
 // Author: Skal (pascal.massimino@gmail.com)
 
 #include "src/dsp/dsp.h"
 
 #if defined(WEBP_USE_SSE2)
 #include <emmintrin.h>
 
 #include <assert.h>
 
 #include "src/webp/types.h"
 #include "src/dsp/cpu.h"
 #include "src/enc/cost_enc.h"
 #include "src/enc/vp8i_enc.h"
 #include "src/utils/utils.h"
 
 //------------------------------------------------------------------------------
 
 static void SetResidualCoeffs_SSE2(const int16_t* WEBP_RESTRICT const coeffs,
                                    VP8Residual* WEBP_RESTRICT const res) {
   const __m128i c0 = _mm_loadu_si128((const __m128i*)(coeffs + 0));
   const __m128i c1 = _mm_loadu_si128((const __m128i*)(coeffs + 8));
   // Use SSE2 to compare 16 values with a single instruction.
   const __m128i zero = _mm_setzero_si128();
   const __m128i m0 = _mm_packs_epi16(c0, c1);
   const __m128i m1 = _mm_cmpeq_epi8(m0, zero);
   // Get the comparison results as a bitmask into 16bits. Negate the mask to get
   // the position of entries that are not equal to zero. We don't need to mask
   // out least significant bits according to res->first, since coeffs[0] is 0
   // if res->first > 0.
   const uint32_t mask = 0x0000ffffu ^ (uint32_t)_mm_movemask_epi8(m1);
   // The position of the most significant non-zero bit indicates the position of
   // the last non-zero value.
   assert(res->first == 0 || coeffs[0] == 0);
   res->last = mask ? BitsLog2Floor(mask) : -1;
   res->coeffs = coeffs;
 }
 
 static int GetResidualCost_SSE2(int ctx0, const VP8Residual* const res) {
   uint8_t levels[16], ctxs[16];
   uint16_t abs_levels[16];
   int n = res->first;
   // should be prob[VP8EncBands[n]], but it's equivalent for n=0 or 1
   const int p0 = res->prob[n][ctx0][0];
   CostArrayPtr const costs = res->costs;
   const uint16_t* t = costs[n][ctx0];
   // bit_cost(1, p0) is already incorporated in t[] tables, but only if ctx != 0
   // (as required by the syntax). For ctx0 == 0, we need to add it here or it'll
   // be missing during the loop.
   int cost = (ctx0 == 0) ? VP8BitCost(1, p0) : 0;
 
   if (res->last < 0) {
     return VP8BitCost(0, p0);
   }
 
   {   // precompute clamped levels and contexts, packed to 8b.
     const __m128i zero = _mm_setzero_si128();
     const __m128i kCst2 = _mm_set1_epi8(2);
     const __m128i kCst67 = _mm_set1_epi8(MAX_VARIABLE_LEVEL);
     const __m128i c0 = _mm_loadu_si128((const __m128i*)&res->coeffs[0]);
     const __m128i c1 = _mm_loadu_si128((const __m128i*)&res->coeffs[8]);
     const __m128i D0 = _mm_sub_epi16(zero, c0);
     const __m128i D1 = _mm_sub_epi16(zero, c1);
     const __m128i E0 = _mm_max_epi16(c0, D0);   // abs(v), 16b
     const __m128i E1 = _mm_max_epi16(c1, D1);
     const __m128i F = _mm_packs_epi16(E0, E1);
     const __m128i G = _mm_min_epu8(F, kCst2);    // context = 0,1,2
     const __m128i H = _mm_min_epu8(F, kCst67);   // clamp_level in [0..67]
 
     _mm_storeu_si128((__m128i*)&ctxs[0], G);
     _mm_storeu_si128((__m128i*)&levels[0], H);
 
     _mm_storeu_si128((__m128i*)&abs_levels[0], E0);
     _mm_storeu_si128((__m128i*)&abs_levels[8], E1);
   }
   for (; n < res->last; ++n) {
     const int ctx = ctxs[n];
     const int level = levels[n];
     const int flevel = abs_levels[n];   // full level
     cost += VP8LevelFixedCosts[flevel] + t[level];  // simplified VP8LevelCost()
     t = costs[n + 1][ctx];
   }
   // Last coefficient is always non-zero
   {
     const int level = levels[n];
     const int flevel = abs_levels[n];
     assert(flevel != 0);
     cost += VP8LevelFixedCosts[flevel] + t[level];
     if (n < 15) {
       const int b = VP8EncBands[n + 1];
       const int ctx = ctxs[n];
       const int last_p0 = res->prob[b][ctx][0];
       cost += VP8BitCost(0, last_p0);
     }
   }
   return cost;
 }
 
 //------------------------------------------------------------------------------
 // Entry point
 
 extern void VP8EncDspCostInitSSE2(void);
 
 WEBP_TSAN_IGNORE_FUNCTION void VP8EncDspCostInitSSE2(void) {
   VP8SetResidualCoeffs = SetResidualCoeffs_SSE2;
   VP8GetResidualCost = GetResidualCost_SSE2;
 }
 
 #else  // !WEBP_USE_SSE2
 
 WEBP_DSP_INIT_STUB(VP8EncDspCostInitSSE2)
 
 #endif  // WEBP_USE_SSE2