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pixelutils: Comment on (lack of) sad_8x8_sse2

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Signed-off-by: Peter Cordes <peter@cordes.ca>
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Peter Cordes 2015-01-29 17:20:27 -04:00 committed by Michael Niedermayer
parent 4da3a14f3c
commit 9e5687adf2
1 changed files with 6 additions and 0 deletions
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6
libavutil/x86/pixelutils_init.c
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@ -43,6 +43,12 @@ void ff_pixelutils_sad_init_x86(av_pixelutils_sad_fn *sad, int aligned)
sad[2] = ff_pixelutils_sad_8x8_mmx; sad[2] = ff_pixelutils_sad_8x8_mmx;
} }
// The best way to use SSE2 would be to do 2 SADs in parallel,
// but we'd have to modify the pixelutils API to return SIMD functions.
// It's probably not faster to shuffle data around
// to get two lines of 8 pixels into a single 16byte register,
// so just use the MMX 8x8 version even when SSE2 is available.
if (EXTERNAL_MMXEXT(cpu_flags)) { if (EXTERNAL_MMXEXT(cpu_flags)) {
sad[2] = ff_pixelutils_sad_8x8_mmxext; sad[2] = ff_pixelutils_sad_8x8_mmxext;
sad[3] = ff_pixelutils_sad_16x16_mmxext; sad[3] = ff_pixelutils_sad_16x16_mmxext;