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Fix for issue #8442

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AVX optimized routine applying gain for Linux was causing SIGSEGV.
It was root caused to premature optimization on frames < 8, and
this commit fixes this issue.
This commit is contained in:
Ayan Shafqat 2020-10-17 10:03:26 -04:00
parent fe71fb1273
commit 1a7dc947a2
No known key found for this signature in database
GPG Key ID: DC1F419F580C03E3
1 changed files with 18 additions and 51 deletions
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69
libs/ardour/sse_functions_avx_linux.cc
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@ -243,55 +243,22 @@ x86_sse_avx_find_peaks(const float *src, uint32_t nframes, float *minf, float *m
C_FUNC void
x86_sse_avx_apply_gain_to_buffer(float *dst, uint32_t nframes, float gain)
{
// Convert to signed integer to prevent any arithmetic overflow errors
int32_t frames = (int32_t)nframes;
// Load gain vector to all elements of YMM register
__m256 vgain = _mm256_set1_ps(gain);
if (nframes) {
do {
__m128 g0 = _mm256_castps256_ps128(vgain);
// Here comes the horror, poor-man's loop unrolling
switch (((intptr_t)dst) % 32) {
case 0:
default:
// Buffer is aligned, skip to the next section of aligned
break;
case 4:
_mm_store_ss(dst, _mm_mul_ss(g0, _mm_load_ss(dst)));
while (!IS_ALIGNED_TO(dst, sizeof(__m256)) && (frames > 0)) {
_mm_store_ss(dst, _mm_mul_ps(g0, _mm_load_ss(dst)));
++dst;
--nframes;
case 8:
_mm_store_ss(dst, _mm_mul_ss(g0, _mm_load_ss(dst)));
++dst;
--nframes;
case 12:
_mm_store_ss(dst, _mm_mul_ss(g0, _mm_load_ss(dst)));
++dst;
--nframes;
case 16:
// This is a special case where pointer is 16 byte aligned
// for a XMM load/store operation.
_mm_store_ps(dst, _mm_mul_ps(g0, _mm_load_ps(dst)));
dst += 4;
nframes -= 4;
break;
case 20:
_mm_store_ss(dst, _mm_mul_ss(g0, _mm_load_ss(dst)));
++dst;
--nframes;
case 24:
_mm_store_ss(dst, _mm_mul_ss(g0, _mm_load_ss(dst)));
++dst;
--nframes;
case 28:
_mm_store_ss(dst, _mm_mul_ss(g0, _mm_load_ss(dst)));
++dst;
--nframes;
--frames;
}
} else {
return;
}
} while (0);
// Process the remaining samples 16 at a time
while (nframes >= 16)
while (frames >= 16)
{
#if defined(COMPILER_MSVC) || defined(COMPILER_MINGW)
_mm_prefetch(((char *)dst + (16 * sizeof(float))), _mm_hint(0));
@ -299,24 +266,24 @@ x86_sse_avx_apply_gain_to_buffer(float *dst, uint32_t nframes, float gain)
__builtin_prefetch(dst + (16 * sizeof(float)), 0, 0);
#endif
__m256 d0, d1;
d0 = _mm256_load_ps(dst + 0 );
d1 = _mm256_load_ps(dst + 8 );
d0 = _mm256_load_ps(dst + 0);
d1 = _mm256_load_ps(dst + 8);
d0 = _mm256_mul_ps(vgain, d0);
d1 = _mm256_mul_ps(vgain, d1);
_mm256_store_ps(dst + 0 , d0);
_mm256_store_ps(dst + 8 , d1);
_mm256_store_ps(dst + 0, d0);
_mm256_store_ps(dst + 8, d1);
dst += 16;
nframes -= 16;
frames -= 16;
}
// Process the remaining samples 8 at a time
while (nframes >= 8) {
while (frames >= 8) {
_mm256_store_ps(dst, _mm256_mul_ps(vgain, _mm256_load_ps(dst)));
dst += 8;
nframes -= 8;
frames -= 8;
}
@ -329,10 +296,10 @@ x86_sse_avx_apply_gain_to_buffer(float *dst, uint32_t nframes, float gain)
// Process the remaining samples
do {
__m128 g0 = _mm256_castps256_ps128(vgain);
while (nframes > 0) {
_mm_store_ss(dst, _mm_mul_ss(g0, _mm_load_ss(dst)));
while (frames > 0) {
_mm_store_ss(dst, _mm_mul_ps(g0, _mm_load_ss(dst)));
++dst;
--nframes;
--frames;
}
} while (0);
}