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Expand all overlapping 4-bit subsequences of a circular 16-bit sequence
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| static uint64_t | |
| b24_expand (uint16_t seq) | |
| { | |
| #define seq_prep(x) 0, (uint32_t)((x) << 12U | \ | |
| (x) >> 4U) << 16U | (x) | |
| __m128i k = _mm_shuffle_epi8( | |
| _mm_set_epi64x(seq_prep(seq)), | |
| _mm_set_epi64x(UINT64_C(0x0303030301010101), \ | |
| UINT64_C(0x0202020200000000))); | |
| #undef seq_prep | |
| #define pext_mask UINT64_C(0x783c1e0f783c1e0f) | |
| return _pext_u64((uint64_t)_mm_extract_epi64(k, 1), pext_mask) << 32U | |
| | _pext_u64((uint64_t)_mm_extract_epi64(k, 0), pext_mask); | |
| #undef pext_mask | |
| } |
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