pqcrypto/crypto_kem/sntrup761/avx2/crypto_encode_761xfreeze3.c

#include "crypto_encode_761xfreeze3.h"
#include <immintrin.h>
#define int16 int16_t

#define p 761

void PQCLEAN_SNTRUP761_AVX2_crypto_encode_761xfreeze3(unsigned char *s, const void *v) {
    const int16 *r = v;

    int i = p - 16;
    for (;;) {
        do {
            __m256i x = _mm256_loadu_si256((__m256i *) r);
            __m256i y = _mm256_mulhrs_epi16(x, _mm256_set1_epi16(10923));
            x = _mm256_sub_epi16(x, y);
            y = _mm256_add_epi16(y, y);
            x = _mm256_sub_epi16(x, y);
            __m128i x0 = _mm256_extractf128_si256(x, 0);
            __m128i x1 = _mm256_extractf128_si256(x, 1);
            _mm_storeu_si128((__m128i *) s, _mm_packs_epi16(x0, x1));
            i -= 16;
            r += 16;
            s += 16;
        } while (i >= 0);
        if (i <= -16) {
            break;
        }
        r += i;
        s += i;
    }
}