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enc_sse2/CollectHistogram: simplify abs calculation

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max(out, 0 - out) works as well as (out ^ sign) - out

Change-Id: Id820ab9b296512cb0d56c8026b986bf98e3d3909
This commit is contained in:
James Zern 2015-05-08 19:49:08 -07:00
parent a6c1593645
commit 17dbd05819
1 changed files with 5 additions and 8 deletions
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13
src/dsp/enc_sse2.c
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@ -446,6 +446,7 @@ static void FTransformWHT(const int16_t* in, int16_t* out) {
static void CollectHistogram(const uint8_t* ref, const uint8_t* pred,
int start_block, int end_block,
VP8Histogram* const histo) {
const __m128i zero = _mm_setzero_si128();
const __m128i max_coeff_thresh = _mm_set1_epi16(MAX_COEFF_THRESH);
int j;
int distribution[MAX_COEFF_THRESH + 1] = { 0 };
@ -460,14 +461,10 @@ static void CollectHistogram(const uint8_t* ref, const uint8_t* pred,
// Load.
const __m128i out0 = _mm_loadu_si128((__m128i*)&out[0]);
const __m128i out1 = _mm_loadu_si128((__m128i*)&out[8]);
// sign(out) = out >> 15 (0x0000 if positive, 0xffff if negative)
const __m128i sign0 = _mm_srai_epi16(out0, 15);
const __m128i sign1 = _mm_srai_epi16(out1, 15);
// abs(out) = (out ^ sign) - sign
const __m128i xor0 = _mm_xor_si128(out0, sign0);
const __m128i xor1 = _mm_xor_si128(out1, sign1);
const __m128i abs0 = _mm_sub_epi16(xor0, sign0);
const __m128i abs1 = _mm_sub_epi16(xor1, sign1);
const __m128i d0 = _mm_sub_epi16(zero, out0);
const __m128i d1 = _mm_sub_epi16(zero, out1);
const __m128i abs0 = _mm_max_epi16(out0, d0); // abs(v), 16b
const __m128i abs1 = _mm_max_epi16(out1, d1);
// v = abs(out) >> 3
const __m128i v0 = _mm_srai_epi16(abs0, 3);
const __m128i v1 = _mm_srai_epi16(abs1, 3);