Aaru.Checksums.Native/fletcher16_avx2.c

/*
 * This file is part of the Aaru Data Preservation Suite.
 * Copyright (c) 2019-2025 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 "fletcher16.h"
#include "simd.h"

/**
 * @brief Calculate Fletcher-16 checksum for a given data using NEON instructions.
 *
 * This function calculates the Fletcher-16 checksum for a block of data using NEON vector instructions.
 *
 * @param sum1 Pointer to the variable where the first 8-bit checksum value is stored.
 * @param sum2 Pointer to the variable where the second 8-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 fletcher16_avx2(uint8_t *sum1, uint8_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;
    if(len >= BLOCK_SIZE)
    {
        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 %= FLETCHER16_MODULE;
            s2 %= FLETCHER16_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++); }
        s1 %= FLETCHER16_MODULE;
        s2 %= FLETCHER16_MODULE;
    }

    /*
     * Return the recombined sums.
     */
    *sum1 = s1 & 0xFF;
    *sum2 = s2 & 0xFF;
}

#endif