Support AVX to speed up the FIR filters.

diff --git a/decode.cpp b/decode.cpp
index f9e525eeea07b8ebaf351d87d9870be36d1c22cb..3662566737d4d4fc415a525d2071f9185ce0e8b0 100644 (file)
--- a/decode.cpp
+++ b/decode.cpp
@@ -7,6 +7,9 @@
 #include <assert.h>
 #include <limits.h>
 #include <getopt.h>
+#ifdef __AVX__
+#include <immintrin.h>
+#endif
 #include <vector>
 #include <algorithm>
 
@@ -328,17 +331,30 @@ std::vector<float> crop(const std::vector<float>& pcm, float crop_start, float c
        return std::vector<float>(pcm.begin() + start_sample, pcm.begin() + end_sample);
 }
 
-// TODO: Support AVX here.
 std::vector<float> do_fir_filter(const std::vector<float>& pcm, const float* filter)
 {
        std::vector<float> filtered_pcm;
-       filtered_pcm.reserve(pcm.size());
-       for (unsigned i = NUM_FILTER_COEFF; i < pcm.size(); ++i) {
+       filtered_pcm.resize(pcm.size());
+       unsigned i = NUM_FILTER_COEFF;
+#ifdef __AVX__
+       unsigned avx_end = i + ((pcm.size() - i) & ~7);
+       for ( ; i < avx_end; i += 8) {
+               __m256 s = _mm256_setzero_ps();
+               for (int j = 0; j < NUM_FILTER_COEFF; ++j) {
+                       __m256 f = _mm256_set1_ps(filter[j]);
+                       s = _mm256_fmadd_ps(f, _mm256_load_ps(&pcm[i - j]), s);
+               }
+               _mm256_storeu_ps(&filtered_pcm[i], s);
+       }
+#endif
+       // Do what we couldn't do with AVX (which is everything for non-AVX machines)
+       // as scalar code.
+       for (; i < pcm.size(); ++i) {
                float s = 0.0f;
                for (int j = 0; j < NUM_FILTER_COEFF; ++j) {
                        s += filter[j] * pcm[i - j];
                }
-               filtered_pcm.push_back(s);
+               filtered_pcm[i] = s;
        }
 
        if (output_filtered) {