68 lines
2.4 KiB
C
68 lines
2.4 KiB
C
#include "cbd.h"
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#include "params.h"
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#include <immintrin.h>
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#include <stdint.h>
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/*************************************************
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* Name: cbd2
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*
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* Description: Given an array of uniformly random bytes, compute
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* polynomial with coefficients distributed according to
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* a centered binomial distribution with parameter eta=2
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*
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* Arguments: - poly *r: pointer to output polynomial
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* - const __m256i *buf: pointer to aligned input byte array
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**************************************************/
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static void cbd2(poly *restrict r, const __m256i buf[2 * KYBER_N / 128]) {
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unsigned int i;
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__m256i f0, f1, f2, f3;
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const __m256i mask55 = _mm256_set1_epi32(0x55555555);
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const __m256i mask33 = _mm256_set1_epi32(0x33333333);
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const __m256i mask03 = _mm256_set1_epi32(0x03030303);
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const __m256i mask0F = _mm256_set1_epi32(0x0F0F0F0F);
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for (i = 0; i < KYBER_N / 64; i++) {
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f0 = _mm256_load_si256(&buf[i]);
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f1 = _mm256_srli_epi16(f0, 1);
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f0 = _mm256_and_si256(mask55, f0);
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f1 = _mm256_and_si256(mask55, f1);
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f0 = _mm256_add_epi8(f0, f1);
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f1 = _mm256_srli_epi16(f0, 2);
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f0 = _mm256_and_si256(mask33, f0);
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f1 = _mm256_and_si256(mask33, f1);
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f0 = _mm256_add_epi8(f0, mask33);
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f0 = _mm256_sub_epi8(f0, f1);
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f1 = _mm256_srli_epi16(f0, 4);
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f0 = _mm256_and_si256(mask0F, f0);
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f1 = _mm256_and_si256(mask0F, f1);
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f0 = _mm256_sub_epi8(f0, mask03);
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f1 = _mm256_sub_epi8(f1, mask03);
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f2 = _mm256_unpacklo_epi8(f0, f1);
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f3 = _mm256_unpackhi_epi8(f0, f1);
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f0 = _mm256_cvtepi8_epi16(_mm256_castsi256_si128(f2));
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f1 = _mm256_cvtepi8_epi16(_mm256_extracti128_si256(f2, 1));
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f2 = _mm256_cvtepi8_epi16(_mm256_castsi256_si128(f3));
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f3 = _mm256_cvtepi8_epi16(_mm256_extracti128_si256(f3, 1));
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_mm256_store_si256(&r->vec[4 * i + 0], f0);
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_mm256_store_si256(&r->vec[4 * i + 1], f2);
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_mm256_store_si256(&r->vec[4 * i + 2], f1);
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_mm256_store_si256(&r->vec[4 * i + 3], f3);
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}
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}
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/* buf 32 bytes longer for cbd3 */
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void PQCLEAN_KYBER76890S_AVX2_poly_cbd_eta1(poly *r, const __m256i buf[KYBER_ETA1 * KYBER_N / 128 + 1]) {
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cbd2(r, buf);
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}
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void PQCLEAN_KYBER76890S_AVX2_poly_cbd_eta2(poly *r, const __m256i buf[KYBER_ETA2 * KYBER_N / 128]) {
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cbd2(r, buf);
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}
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