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dsp/dec_sse2: DC8uv / DC8uvNoLeft speedup

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use psadbw to perform top row summation; left remains in C as repacking
it into a vector to apply the same operation is too costly.

DC8uv: ~19% faster
DC8uvNoLeft: ~12% faster

Change-Id: I707c4f6177a65b5d1f2d3deeca87d2bb740185e2
This commit is contained in:
James Zern 2015-04-08 18:43:46 -07:00 committed by Gerrit Code Review
parent 7df2049785
commit 9904e365a8
1 changed files with 16 additions and 11 deletions
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27
src/dsp/dec_sse2.c
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@ -1208,21 +1208,26 @@ static WEBP_INLINE void Put8x8uv(uint8_t v, uint8_t* dst) {
}
static void DC8uv(uint8_t* dst) { // DC
int dc0 = 8;
int i;
for (i = 0; i < 8; ++i) {
dc0 += dst[i - BPS] + dst[-1 + i * BPS];
const __m128i zero = _mm_setzero_si128();
const __m128i top = _mm_loadl_epi64((const __m128i*)(dst - BPS));
const __m128i sum = _mm_sad_epu8(top, zero);
int left = 0;
int j;
for (j = 0; j < 8; ++j) {
left += dst[-1 + j * BPS];
}
{
const int DC = _mm_cvtsi128_si32(sum) + left + 8;
Put8x8uv(DC >> 4, dst);
}
Put8x8uv(dc0 >> 4, dst);
}
static void DC8uvNoLeft(uint8_t* dst) { // DC with no left samples
int dc0 = 4;
int i;
for (i = 0; i < 8; ++i) {
dc0 += dst[i - BPS];
}
Put8x8uv(dc0 >> 3, dst);
const __m128i zero = _mm_setzero_si128();
const __m128i top = _mm_loadl_epi64((const __m128i*)(dst - BPS));
const __m128i sum = _mm_sad_epu8(top, zero);
const int DC = _mm_cvtsi128_si32(sum) + 4;
Put8x8uv(DC >> 3, dst);
}
static void DC8uvNoTop(uint8_t* dst) { // DC with no top samples