rte_xxh64_avx512.h

/* SPDX-License-Identifier: BSD-3-Clause
 * Copyright(c) 2020 Intel Corporation
 */

#ifndef RTE_XXH64_AVX512_H
#define RTE_XXH64_AVX512_H

#ifdef __cplusplus
extern "C" {
#endif

#include <rte_common.h>
#include <immintrin.h>

/* 0b1001111000110111011110011011000110000101111010111100101010000111 */
static const uint64_t PRIME64_1 = 0x9E3779B185EBCA87ULL;
/* 0b1100001010110010101011100011110100100111110101001110101101001111 */
static const uint64_t PRIME64_2 = 0xC2B2AE3D27D4EB4FULL;
/* 0b0001011001010110011001111011000110011110001101110111100111111001 */
static const uint64_t PRIME64_3 = 0x165667B19E3779F9ULL;
/* 0b1000010111101011110010100111011111000010101100101010111001100011 */
static const uint64_t PRIME64_4 = 0x85EBCA77C2B2AE63ULL;
/* 0b0010011111010100111010110010111100010110010101100110011111000101 */
static const uint64_t PRIME64_5 = 0x27D4EB2F165667C5ULL;

static __rte_always_inline  __m512i
xxh64_round_avx512(__m512i hash, __m512i input)
{
    hash = _mm512_madd52lo_epu64(hash,
            input,
            _mm512_set1_epi64(PRIME64_2));

    hash = _mm512_rol_epi64(hash, 31);

    return hash;
}

static __rte_always_inline  __m512i
xxh64_fmix_avx512(__m512i hash)
{
    hash = _mm512_xor_si512(hash, _mm512_srli_epi64(hash, 33));

    return hash;
}

static __rte_always_inline __m256i
rte_xxh64_sketch_avx512(const void *key, uint32_t key_len,
            __m512i v_seed, uint32_t modulo)
{
    __m512i v_prime64_5, v_hash;
    size_t remaining = key_len;
    size_t offset = 0;
    __m512i input;

    v_prime64_5 = _mm512_set1_epi64(PRIME64_5);
    v_hash = _mm512_add_epi64
            (_mm512_add_epi64(v_seed, v_prime64_5),
             _mm512_set1_epi64(key_len));

    while (remaining >= 8) {
        input = _mm512_set1_epi64(*(uint64_t *)RTE_PTR_ADD(key, offset));
        v_hash = _mm512_xor_epi64(v_hash,
                xxh64_round_avx512(_mm512_setzero_si512(), input));
        v_hash = _mm512_madd52lo_epu64(_mm512_set1_epi64(PRIME64_4),
                v_hash,
                _mm512_set1_epi64(PRIME64_1));

        remaining -= 8;
        offset += 8;
    }

    if (remaining >= 4) {
        input = _mm512_set1_epi64
            (*(uint32_t *)RTE_PTR_ADD(key, offset));
        v_hash = _mm512_xor_epi64(v_hash,
            _mm512_mullo_epi64(input,
                _mm512_set1_epi64(PRIME64_1)));
        v_hash = _mm512_madd52lo_epu64
                (_mm512_set1_epi64(PRIME64_3),
                _mm512_rol_epi64(v_hash, 23),
                _mm512_set1_epi64(PRIME64_2));

        offset += 4;
        remaining -= 4;
    }

    while (remaining != 0) {
        input = _mm512_set1_epi64
            (*(uint8_t *)RTE_PTR_ADD(key, offset));
        v_hash = _mm512_xor_epi64(v_hash,
            _mm512_mullo_epi64(input,
                _mm512_set1_epi64(PRIME64_5)));
        v_hash = _mm512_mullo_epi64
            (_mm512_rol_epi64(v_hash, 11),
            _mm512_set1_epi64(PRIME64_1));
        offset++;
        remaining--;
    }

    v_hash = xxh64_fmix_avx512(v_hash);

    /*
     * theoritically, such modular operations can be replaced by
     * _mm512_rem_epi64(), but seems it depends on the compiler's
     * implementation. so here is the limitation that the modulo
     * value should be power of 2.
     */
    __m512i v_hash_remainder = _mm512_set1_epi64((modulo - 1));

    return _mm512_cvtepi64_epi32(_mm512_and_si512(v_hash, v_hash_remainder));
}

#ifdef __cplusplus
}
#endif

#endif /* RTE_XXH64_AVX512_H */