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dsp/dec_sse2: DC16 / DC16NoLeft 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.

DC16: ~20% faster
DC16NoLeft: ~14% faster

Change-Id: I7ec3f8a6e5923f88a530f79fceb88d5001bef691
This commit is contained in:
James Zern 2015-04-08 18:39:21 -07:00
parent 8e515dfeda
commit 7df2049785
1 changed files with 17 additions and 8 deletions
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23
src/dsp/dec_sse2.c
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@ -1139,13 +1139,21 @@ static WEBP_INLINE void Put16(uint8_t v, uint8_t* dst) {
}
static void DC16(uint8_t* dst) { // DC
int DC = 16;
const __m128i zero = _mm_setzero_si128();
const __m128i top = _mm_loadu_si128((const __m128i*)(dst - BPS));
const __m128i sad8x2 = _mm_sad_epu8(top, zero);
// sum the two sads: sad8x2[0:1] + sad8x2[8:9]
const __m128i sum = _mm_add_epi16(sad8x2, _mm_shuffle_epi32(sad8x2, 2));
int left = 0;
int j;
for (j = 0; j < 16; ++j) {
DC += dst[-1 + j * BPS] + dst[j - BPS];
left += dst[-1 + j * BPS];
}
{
const int DC = _mm_cvtsi128_si32(sum) + left + 16;
Put16(DC >> 5, dst);
}
}
static void DC16NoTop(uint8_t* dst) { // DC with top samples not available
int DC = 8;
@ -1157,11 +1165,12 @@ static void DC16NoTop(uint8_t* dst) { // DC with top samples not available
}
static void DC16NoLeft(uint8_t* dst) { // DC with left samples not available
int DC = 8;
int i;
for (i = 0; i < 16; ++i) {
DC += dst[i - BPS];
}
const __m128i zero = _mm_setzero_si128();
const __m128i top = _mm_loadu_si128((const __m128i*)(dst - BPS));
const __m128i sad8x2 = _mm_sad_epu8(top, zero);
// sum the two sads: sad8x2[0:1] + sad8x2[8:9]
const __m128i sum = _mm_add_epi16(sad8x2, _mm_shuffle_epi32(sad8x2, 2));
const int DC = _mm_cvtsi128_si32(sum) + 8;
Put16(DC >> 4, dst);
}