1 // Copyright 2013 The Chromium Authors. All rights reserved. 2 // Use of this source code is governed by a BSD-style license that can be 3 // found in the LICENSE file. 4 5 #include "media/base/vector_math_testing.h" 6 7 #include <algorithm> 8 9 #include <xmmintrin.h> // NOLINT 10 11 namespace media { 12 namespace vector_math { 13 14 void FMUL_SSE(const float src[], float scale, int len, float dest[]) { 15 const int rem = len % 4; 16 const int last_index = len - rem; 17 __m128 m_scale = _mm_set_ps1(scale); 18 for (int i = 0; i < last_index; i += 4) 19 _mm_store_ps(dest + i, _mm_mul_ps(_mm_load_ps(src + i), m_scale)); 20 21 // Handle any remaining values that wouldn't fit in an SSE pass. 22 for (int i = last_index; i < len; ++i) 23 dest[i] = src[i] * scale; 24 } 25 26 void FMAC_SSE(const float src[], float scale, int len, float dest[]) { 27 const int rem = len % 4; 28 const int last_index = len - rem; 29 __m128 m_scale = _mm_set_ps1(scale); 30 for (int i = 0; i < last_index; i += 4) { 31 _mm_store_ps(dest + i, _mm_add_ps(_mm_load_ps(dest + i), 32 _mm_mul_ps(_mm_load_ps(src + i), m_scale))); 33 } 34 35 // Handle any remaining values that wouldn't fit in an SSE pass. 36 for (int i = last_index; i < len; ++i) 37 dest[i] += src[i] * scale; 38 } 39 40 // Convenience macro to extract float 0 through 3 from the vector |a|. This is 41 // needed because compilers other than clang don't support access via 42 // operator[](). 43 #define EXTRACT_FLOAT(a, i) \ 44 (i == 0 ? \ 45 _mm_cvtss_f32(a) : \ 46 _mm_cvtss_f32(_mm_shuffle_ps(a, a, i))) 47 48 std::pair<float, float> EWMAAndMaxPower_SSE( 49 float initial_value, const float src[], int len, float smoothing_factor) { 50 // When the recurrence is unrolled, we see that we can split it into 4 51 // separate lanes of evaluation: 52 // 53 // y[n] = a(S[n]^2) + (1-a)(y[n-1]) 54 // = a(S[n]^2) + (1-a)^1(aS[n-1]^2) + (1-a)^2(aS[n-2]^2) + ... 55 // = z[n] + (1-a)^1(z[n-1]) + (1-a)^2(z[n-2]) + (1-a)^3(z[n-3]) 56 // 57 // where z[n] = a(S[n]^2) + (1-a)^4(z[n-4]) + (1-a)^8(z[n-8]) + ... 58 // 59 // Thus, the strategy here is to compute z[n], z[n-1], z[n-2], and z[n-3] in 60 // each of the 4 lanes, and then combine them to give y[n]. 61 62 const int rem = len % 4; 63 const int last_index = len - rem; 64 65 const __m128 smoothing_factor_x4 = _mm_set_ps1(smoothing_factor); 66 const float weight_prev = 1.0f - smoothing_factor; 67 const __m128 weight_prev_x4 = _mm_set_ps1(weight_prev); 68 const __m128 weight_prev_squared_x4 = 69 _mm_mul_ps(weight_prev_x4, weight_prev_x4); 70 const __m128 weight_prev_4th_x4 = 71 _mm_mul_ps(weight_prev_squared_x4, weight_prev_squared_x4); 72 73 // Compute z[n], z[n-1], z[n-2], and z[n-3] in parallel in lanes 3, 2, 1 and 74 // 0, respectively. 75 __m128 max_x4 = _mm_setzero_ps(); 76 __m128 ewma_x4 = _mm_setr_ps(0.0f, 0.0f, 0.0f, initial_value); 77 int i; 78 for (i = 0; i < last_index; i += 4) { 79 ewma_x4 = _mm_mul_ps(ewma_x4, weight_prev_4th_x4); 80 const __m128 sample_x4 = _mm_load_ps(src + i); 81 const __m128 sample_squared_x4 = _mm_mul_ps(sample_x4, sample_x4); 82 max_x4 = _mm_max_ps(max_x4, sample_squared_x4); 83 // Note: The compiler optimizes this to a single multiply-and-accumulate 84 // instruction: 85 ewma_x4 = _mm_add_ps(ewma_x4, 86 _mm_mul_ps(sample_squared_x4, smoothing_factor_x4)); 87 } 88 89 // y[n] = z[n] + (1-a)^1(z[n-1]) + (1-a)^2(z[n-2]) + (1-a)^3(z[n-3]) 90 float ewma = EXTRACT_FLOAT(ewma_x4, 3); 91 ewma_x4 = _mm_mul_ps(ewma_x4, weight_prev_x4); 92 ewma += EXTRACT_FLOAT(ewma_x4, 2); 93 ewma_x4 = _mm_mul_ps(ewma_x4, weight_prev_x4); 94 ewma += EXTRACT_FLOAT(ewma_x4, 1); 95 ewma_x4 = _mm_mul_ss(ewma_x4, weight_prev_x4); 96 ewma += EXTRACT_FLOAT(ewma_x4, 0); 97 98 // Fold the maximums together to get the overall maximum. 99 max_x4 = _mm_max_ps(max_x4, 100 _mm_shuffle_ps(max_x4, max_x4, _MM_SHUFFLE(3, 3, 1, 1))); 101 max_x4 = _mm_max_ss(max_x4, _mm_shuffle_ps(max_x4, max_x4, 2)); 102 103 std::pair<float, float> result(ewma, EXTRACT_FLOAT(max_x4, 0)); 104 105 // Handle remaining values at the end of |src|. 106 for (; i < len; ++i) { 107 result.first *= weight_prev; 108 const float sample = src[i]; 109 const float sample_squared = sample * sample; 110 result.first += sample_squared * smoothing_factor; 111 result.second = std::max(result.second, sample_squared); 112 } 113 114 return result; 115 } 116 117 } // namespace vector_math 118 } // namespace media 119
