Aaru.Checksums.Native/adler32_avx2.c

/*
 * This file is part of the Aaru Data Preservation Suite.
 * Copyright (c) 2019-2023 Natalia Portillo.
 * Copyright (C) 1995-2011 Mark Adler
 * Copyright (C) Jean-loup Gailly
 *
 * This software is provided 'as-is', without any express or implied
 * warranty.  In no event will the authors be held liable for any damages
 * arising from the use of this software.
 *
 * Permission is granted to anyone to use this software for any purpose,
 * including commercial applications, and to alter it and redistribute it
 * freely, subject to the following restrictions:
 *
 *  1. The origin of this software must not be misrepresented; you must not
 *     claim that you wrote the original software. If you use this software
 *     in a product, an acknowledgment in the product documentation would be
 *     appreciated but is not required.
 *
 *  2. Altered source versions must be plainly marked as such, and must not be
 *     misrepresented as being the original software.
 *  3. This notice may not be removed or altered from any source distribution.
 */

#if defined(__x86_64__) || defined(__amd64) || defined(_M_AMD64) || defined(_M_X64) || defined(__I386__) || \
    defined(__i386__) || defined(__THW_INTEL) || defined(_M_IX86)

#include <immintrin.h>
#include <stdint.h>

#include "library.h"
#include "adler32.h"
#include "simd.h"

/**
 * @brief Calculate Adler-32 checksum for a given data using AVX2 instructions.
 *
 * This function calculates the Adler-32 checksum for a block of data using AVX2 vector instructions.
 *
 * @param sum1 Pointer to the variable where the first 16-bit checksum value is stored.
 * @param sum2 Pointer to the variable where the second 16-bit checksum value is stored.
 * @param data Pointer to the data buffer.
 * @param len Length of the data buffer in bytes.
 */
AARU_EXPORT TARGET_WITH_AVX2 void AARU_CALL adler32_avx2(uint16_t *sum1, uint16_t *sum2, const uint8_t *data, long len)
{
    uint32_t s1 = *sum1;
    uint32_t s2 = *sum2;

    /*
     * Process the data in blocks.
     */
    const unsigned BLOCK_SIZE = 1 << 5;
    long           blocks     = len / BLOCK_SIZE;
    len -= blocks * BLOCK_SIZE;

    while(blocks)
    {
        unsigned n = NMAX / BLOCK_SIZE; /* The NMAX constraint. */

        if(n > blocks) n = (unsigned)blocks;
        blocks -= n;

        const __m256i tap  = _mm256_set_epi8(1,
                                             2,
                                             3,
                                             4,
                                             5,
                                             6,
                                             7,
                                             8,
                                             9,
                                             10,
                                             11,
                                             12,
                                             13,
                                             14,
                                             15,
                                             16,
                                             17,
                                             18,
                                             19,
                                             20,
                                             21,
                                             22,
                                             23,
                                             24,
                                             25,
                                             26,
                                             27,
                                             28,
                                             29,
                                             30,
                                             31,
                                             32);
        const __m256i zero = _mm256_setzero_si256();
        const __m256i ones = _mm256_set1_epi16(1);

        /*
         * Process n blocks of data. At most NMAX data bytes can be
         * processed before s2 must be reduced modulo BASE.
         */
        __m256i v_ps = _mm256_set_epi32(0, 0, 0, 0, 0, 0, 0, (s1 * n));
        __m256i v_s2 = _mm256_set_epi32(0, 0, 0, 0, 0, 0, 0, s2);
        __m256i v_s1 = _mm256_setzero_si256();
        do
        {
            /*
             * Load 32 input bytes.
             */
            const __m256i bytes = _mm256_lddqu_si256((__m256i *)(data));

            /*
             * Add previous block byte sum to v_ps.
             */
            v_ps = _mm256_add_epi32(v_ps, v_s1);
            /*
             * Horizontally add the bytes for s1, multiply-adds the
             * bytes by [ 32, 31, 30, ... ] for s2.
             */
            v_s1 = _mm256_add_epi32(v_s1, _mm256_sad_epu8(bytes, zero));
            const __m256i mad = _mm256_maddubs_epi16(bytes, tap);
            v_s2 = _mm256_add_epi32(v_s2, _mm256_madd_epi16(mad, ones));

            data += BLOCK_SIZE;
        }
        while(--n);

        __m128i sum = _mm_add_epi32(_mm256_castsi256_si128(v_s1), _mm256_extracti128_si256(v_s1, 1));
        __m128i hi  = _mm_unpackhi_epi64(sum, sum);
        sum = _mm_add_epi32(hi, sum);
        hi  = _mm_shuffle_epi32(sum, 177);
        sum = _mm_add_epi32(sum, hi);
        s1 += _mm_cvtsi128_si32(sum);

        v_s2 = _mm256_add_epi32(v_s2, _mm256_slli_epi32(v_ps, 5));
        sum  = _mm_add_epi32(_mm256_castsi256_si128(v_s2), _mm256_extracti128_si256(v_s2, 1));
        hi   = _mm_unpackhi_epi64(sum, sum);
        sum  = _mm_add_epi32(hi, sum);
        hi   = _mm_shuffle_epi32(sum, 177);
        sum  = _mm_add_epi32(sum, hi);
        s2   = _mm_cvtsi128_si32(sum);

        /*
         * Reduce.
         */
        s1 %= ADLER_MODULE;
        s2 %= ADLER_MODULE;
    }

    /*
     * Handle leftover data.
     */
    if(len)
    {
        if(len >= 16)
        {
            s2 += (s1 += *data++);
            s2 += (s1 += *data++);
            s2 += (s1 += *data++);
            s2 += (s1 += *data++);
            s2 += (s1 += *data++);
            s2 += (s1 += *data++);
            s2 += (s1 += *data++);
            s2 += (s1 += *data++);
            s2 += (s1 += *data++);
            s2 += (s1 += *data++);
            s2 += (s1 += *data++);
            s2 += (s1 += *data++);
            s2 += (s1 += *data++);
            s2 += (s1 += *data++);
            s2 += (s1 += *data++);
            s2 += (s1 += *data++);
            len -= 16;
        }
        while(len--)
        { s2 += (s1 += *data++); }
        if(s1 >= ADLER_MODULE) s1 -= ADLER_MODULE;
        s2 %= ADLER_MODULE;
    }
    /*
     * Return the recombined sums.
     */
    *sum1 = s1 & 0xFFFF;
    *sum2 = s2 & 0xFFFF;
}

#endif