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llama.cpp
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avx2: calculate ksigns instead of using keven_signs_q2xs

This commit is contained in:
David Friehs 2026-02-16 00:10:12 +01:00
parent ff4affb4c1
commit 16132d3814
1 changed files with 34 additions and 8 deletions
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42
ggml/src/ggml-cpu/arch/x86/quants.c
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@ -2369,6 +2369,35 @@ static const int8_t keven_signs_q2xs[1024] = {
};
#endif
#if defined(__AVX2__)
static inline __m256i unpack_ksigns(const uint32_t packed) {
__m128i x = _mm_set1_epi32(packed);
// shift each 32 bit value to their offset. bits 0-6 are ok, 7-31 are garbage
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);
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));
// 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);
// expand to __m256i, broadcast bytes 0, 4, 8, 12
const __m256i shf = _mm256_setr_epi64x(0x0000000000000000LL, 0x0404040404040404LL,
0x0808080808080808LL, 0x0C0C0C0C0C0C0C0CLL);
const __m256i y = _mm256_shuffle_epi8(_mm256_broadcastsi128_si256(x), shf);
const __m256i sel = _mm256_set1_epi64x(0x8040201008040201LL);
return _mm256_cmpeq_epi8(_mm256_and_si256(y, sel), sel);
}
#endif
void ggml_vec_dot_iq2_xxs_q8_K(int n, float * GGML_RESTRICT s, size_t bs, const void * GGML_RESTRICT vx, size_t bx, const void * GGML_RESTRICT vy, size_t by, int nrc) {
assert(n % QK_K == 0);
assert(nrc == 1);
@ -2384,8 +2413,6 @@ void ggml_vec_dot_iq2_xxs_q8_K(int n, float * GGML_RESTRICT s, size_t bs, const
#if defined(__AVX2__)
const uint64_t * signs64 = (const uint64_t *)keven_signs_q2xs;
uint32_t aux32[4];
const uint8_t * aux8 = (const uint8_t *)aux32;
@ -2402,12 +2429,11 @@ void ggml_vec_dot_iq2_xxs_q8_K(int n, float * GGML_RESTRICT s, size_t bs, const
memcpy(aux32, q2, 4*sizeof(uint32_t)); q2 += 8;
const __m256i q2_1 = _mm256_set_epi64x(iq2xxs_grid[aux8[ 3]], iq2xxs_grid[aux8[ 2]], iq2xxs_grid[aux8[1]], iq2xxs_grid[aux8[0]]);
const __m256i q2_2 = _mm256_set_epi64x(iq2xxs_grid[aux8[11]], iq2xxs_grid[aux8[10]], iq2xxs_grid[aux8[9]], iq2xxs_grid[aux8[8]]);
const __m256i s2_1 = _mm256_set_epi64x(signs64[(aux32[1] >> 21) & 127], signs64[(aux32[1] >> 14) & 127],
signs64[(aux32[1] >> 7) & 127], signs64[(aux32[1] >> 0) & 127]);
const __m256i s2_2 = _mm256_set_epi64x(signs64[(aux32[3] >> 21) & 127], signs64[(aux32[3] >> 14) & 127],
signs64[(aux32[3] >> 7) & 127], signs64[(aux32[3] >> 0) & 127]);
const __m256i q8s_1 = _mm256_sign_epi8(q8_1, s2_1);
const __m256i q8s_2 = _mm256_sign_epi8(q8_2, s2_2);
const __m256i s2_1 = unpack_ksigns(aux32[1]);
const __m256i s2_2 = unpack_ksigns(aux32[3]);
const __m256i q8s_1 = _mm256_sub_epi8(_mm256_xor_si256(q8_1, s2_1), s2_1);
const __m256i q8s_2 = _mm256_sub_epi8(_mm256_xor_si256(q8_2, s2_2), s2_2);
const __m256i dot1 = _mm256_maddubs_epi16(q2_1, q8s_1);
const __m256i dot2 = _mm256_maddubs_epi16(q2_2, q8s_2);
const uint16_t ls1 = aux32[1] >> 28;