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sse2 in-loop: simplify SignedShift8b() a bit

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Change-Id: Ida3e096bb41451194d03dc7a97753a222ff0135c
This commit is contained in:
Pascal Massimino 2015-06-10 23:06:45 -07:00 committed by James Zern
parent 422ec9fb62
commit a729cff987
1 changed files with 4 additions and 5 deletions
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9
src/dsp/dec_sse2.c
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@ -301,11 +301,10 @@ static void TransformAC3(const int16_t* in, uint8_t* dst) {
// Shift each byte of "x" by 3 bits while preserving by the sign bit.
static WEBP_INLINE void SignedShift8b(__m128i* const x) {
const __m128i zero = _mm_setzero_si128();
const __m128i signs = _mm_cmpgt_epi8(zero, *x);
const __m128i lo_0 = _mm_unpacklo_epi8(*x, signs); // s8 -> s16 sign extend
const __m128i hi_0 = _mm_unpackhi_epi8(*x, signs);
const __m128i lo_1 = _mm_srai_epi16(lo_0, 3);
const __m128i hi_1 = _mm_srai_epi16(hi_0, 3);
const __m128i lo_0 = _mm_unpacklo_epi8(zero, *x);
const __m128i hi_0 = _mm_unpackhi_epi8(zero, *x);
const __m128i lo_1 = _mm_srai_epi16(lo_0, 3 + 8);
const __m128i hi_1 = _mm_srai_epi16(hi_0, 3 + 8);
*x = _mm_packs_epi16(lo_1, hi_1);
}