Fine-tune pack_16x16b_to_16x2b
Avoid mm_set1 operation when it's possible to create the constant with
one bit-shift operation from another instead. Thanks Intel for
3-operand instruction encoding!
@@ -71,7 +71,7 @@ static INLINE uint32_t pack_16x16b_to_16x2b(__m256i src)
* XXXX XXXX YYYY YYYY Comparison result, for movemask
*/
const __m256i threes = _mm256_set1_epi16 (3);
- const __m256i cmpmask = _mm256_set1_epi16 (0x0180);
+ const __m256i cmpmask = _mm256_slli_epi16 (threes, 7); // 0x0180 (avoid set1)
__m256i clipped = _mm256_min_epu16 (src, threes);
__m256i shifted = _mm256_slli_epi16 (clipped, 7);
