From b2c8d3e9e49ae69fde71542274aafb75902084ce Mon Sep 17 00:00:00 2001
From: Joel Linn <[EMAIL REDACTED]>
Date: Fri, 11 Jun 2021 22:14:54 +0200
Subject: [PATCH] audiocvt: 5.1 to Stereo conversion utilizing AVX
---
src/audio/SDL_audiocvt.c | 94 +++++++++++++++++++++++++++++++++++++++-
1 file changed, 93 insertions(+), 1 deletion(-)
diff --git a/src/audio/SDL_audiocvt.c b/src/audio/SDL_audiocvt.c
index 7c3e5bf37f..36c631a2fb 100644
--- a/src/audio/SDL_audiocvt.c
+++ b/src/audio/SDL_audiocvt.c
@@ -43,6 +43,10 @@
#define HAVE_SSE3_INTRINSICS 1
#endif
+#if defined(HAVE_IMMINTRIN_H) && !defined(SDL_DISABLE_IMMINTRIN_H)
+#define HAVE_AVX_INTRINSICS 1
+#endif
+
#if HAVE_SSE3_INTRINSICS
/* Convert from stereo to mono. Average left and right. */
static void SDLCALL
@@ -100,6 +104,88 @@ SDL_ConvertStereoToMono(SDL_AudioCVT * cvt, SDL_AudioFormat format)
}
}
+#if HAVE_AVX_INTRINSICS
+/* MSVC will always accept AVX intrinsics when compiling for x64 */
+#if defined(__clang__)
+#pragma clang attribute push (__attribute__((target("avx"))), apply_to=function)
+#elif defined(__GNUC__)
+#pragma GCC push_options
+#pragma GCC target("avx")
+#endif
+/* Convert from 5.1 to stereo. Average left and right, distribute center, discard LFE. */
+static void SDLCALL
+SDL_Convert51ToStereo_AVX(SDL_AudioCVT * cvt, SDL_AudioFormat format)
+{
+ float *dst = (float *) cvt->buf;
+ const float *src = dst;
+ int i = cvt->len_cvt / (sizeof (float) * 6);
+ const float two_fifths_f = 1.0f / 2.5f;
+ const __m256 two_fifths_v = _mm256_set1_ps(two_fifths_f);
+ const __m256 half = _mm256_set1_ps(0.5f);
+
+ LOG_DEBUG_CONVERT("5.1", "stereo (using AVX)");
+ SDL_assert(format == AUDIO_F32SYS);
+
+ /* SDL's 5.1 layout: FL+FR+FC+LFE+BL+BR */
+ /* This implementation is based on SDL_Convert51ToStereo_SSE */
+ /* Because AVX operates with two 128 bit lanes, the shuffling */
+ /* here is not very efficient. AVX512F lifts this limitation. */
+ while (i >= 4) {
+ __m128 in0 = _mm_loadu_ps(src); /* 0FL 0FR 0FC 0LF */
+ __m128 in1 = _mm_loadu_ps(src + 4); /* 0BL 0BR 1FL 1FR */
+ __m128 in2 = _mm_loadu_ps(src + 8); /* 1FC 1LF 1BL 1BR */
+ __m128 in3 = _mm_loadu_ps(src + 12); /* 2FL 2FR 2FC 2LF */
+ __m128 in4 = _mm_loadu_ps(src + 16); /* 2BL 2BR 3FL 3FR */
+ __m128 in5 = _mm_loadu_ps(src + 20); /* 3FC 3LF 3BL 3BR */
+
+ /* 0FC 0FC 1FC 1FC */
+ __m128 fc_distributed_lo = _mm_shuffle_ps(in0, in2, _MM_SHUFFLE(0, 0, 2, 2));
+ /* 2FC 2FC 3FC 3FC */
+ __m128 fc_distributed_hi = _mm_shuffle_ps(in3, in5, _MM_SHUFFLE(0, 0, 2, 2));
+ /* 0FC 0FC 1FC 1FC 2FC 2FC 3FC 3FC */
+ __m256 fc_distributed = _mm256_mul_ps(half, _mm256_insertf128_ps(_mm256_castps128_ps256(fc_distributed_lo), fc_distributed_hi, 1));
+
+ /* 0FL 0FR 1BL 1BR */
+ __m128 permuted0_lo = _mm_shuffle_ps(in0, in2, _MM_SHUFFLE(3, 2, 1, 0));
+ /* 2FL 2FR 3BL 3BR */
+ __m128 permuted0_hi = _mm_shuffle_ps(in3, in5, _MM_SHUFFLE(3, 2, 1, 0));
+ /* 0FL 0FR 1BL 1BR 2FL 2FR 3BL 3BR */
+ __m256 permuted0 = _mm256_insertf128_ps(_mm256_castps128_ps256(permuted0_lo), permuted0_hi, 1);
+ /* 0BL 0BR 1FL 1FR 2BL 2BR 3FL 3FR */
+ __m256 permuted1 = _mm256_insertf128_ps(_mm256_castps128_ps256(in1), in4, 1);
+
+ /* 0FL 0FR 1BL 1BR 2FL 2FR 3BL 3BR */
+ /* + 0BL 0BR 1FL 1FR 2BL 2BR 3FL 3FR */
+ /* = 0L 0R 1L 1R 2L 2R 3L 3R */
+ __m256 out = _mm256_add_ps(permuted0, permuted1);
+ out = _mm256_add_ps(out, fc_distributed);
+ out = _mm256_mul_ps(out, two_fifths_v);
+
+ _mm256_storeu_ps(dst, out);
+
+ i -= 4; src += 24; dst += 8;
+ }
+
+
+ /* Finish off any leftovers with scalar operations. */
+ while (i) {
+ const float front_center_distributed = src[2] * 0.5f;
+ dst[0] = (src[0] + front_center_distributed + src[4]) * two_fifths_f; /* left */
+ dst[1] = (src[1] + front_center_distributed + src[5]) * two_fifths_f; /* right */
+ i--; src += 6; dst+=2;
+ }
+
+ cvt->len_cvt /= 3;
+ if (cvt->filters[++cvt->filter_index]) {
+ cvt->filters[cvt->filter_index] (cvt, format);
+ }
+}
+#if defined(__clang__)
+#pragma clang attribute pop
+#elif defined(__GNUC__)
+#pragma GCC pop_options
+#endif
+#endif
#if HAVE_SSE_INTRINSICS
/* Convert from 5.1 to stereo. Average left and right, distribute center, discard LFE. */
@@ -1086,8 +1172,14 @@ SDL_BuildAudioCVT(SDL_AudioCVT * cvt,
if ((src_channels == 6) && (dst_channels <= 2)) {
SDL_AudioFilter filter = NULL;
+ #if HAVE_AVX_INTRINSICS
+ if (SDL_HasAVX()) {
+ filter = SDL_Convert51ToStereo_AVX;
+ }
+ #endif
+
#if HAVE_SSE_INTRINSICS
- if (SDL_HasSSE()) {
+ if (!filter && SDL_HasSSE()) {
filter = SDL_Convert51ToStereo_SSE;
}
#endif