happyz
/
llama.cpp
mirror of https://github.com/ggerganov/llama.cpp.git
1
0
Fork 0
Code Issues Packages Projects Releases Wiki Activity

avx2: drop 2 instructions, finally approach lut speed

This commit is contained in:
David Friehs 2026-02-16 01:44:54 +01:00
parent 16132d3814
commit bd7b45e165
1 changed files with 9 additions and 7 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

16
ggml/src/ggml-cpu/arch/x86/quants.c
View File

@ -2377,16 +2377,18 @@ static inline __m256i unpack_ksigns(const uint32_t packed) {
const __m128i shifts = _mm_setr_epi32(0, 7, 14, 21);
x = _mm_srlv_epi32(x, shifts);
// plut has 0x80 at locations that have odd bitcount, 0x00 at even bitcount
const __m128i mask = _mm_set1_epi32(0x0F);
const __m128i plut = _mm_setr_epi32(0x00808000, 0x80000080, 0x80000080, 0x00808000);
// popc_odd has 0x80 at locations that have odd bitcount, 0x00 at even bitcount
const __m128i mask_nib = _mm_set1_epi32(0x0F);
const __m128i popc_odd = _mm_setr_epi32(0x00808000, 0x80000080, 0x80000080, 0x00808000);
const __m128i p_l = _mm_shuffle_epi8(plut, _mm_and_si128(x, mask));
const __m128i p_h = _mm_shuffle_epi8(plut, _mm_and_si128(_mm_srli_epi32(x, 4), mask));
// xor bit 4-7 into the lower bit 0-3. this does not change if the set bit count is odd
__m128i p = _mm_srli_epi32(x, 4);
p = _mm_xor_si128(p, x);
p = _mm_and_si128(p, mask_nib);
p = _mm_shuffle_epi8(popc_odd, p);
// correct bit 7 via xor. bits 0-7 now ok, 8-31 still garbage
x = _mm_xor_si128(x, p_l);
x = _mm_xor_si128(x, p_h);
x = _mm_xor_si128(x, p);
// expand to __m256i, broadcast bytes 0, 4, 8, 12
const __m256i shf = _mm256_setr_epi64x(0x0000000000000000LL, 0x0404040404040404LL,