opencv

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/* adler32_ssse3.c -- compute the Adler-32 checksum of a data stream
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 * Copyright (C) 1995-2011 Mark Adler
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 * Authors:
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 *   Adam Stylinski <kungfujesus06@gmail.com>
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 *   Brian Bockelman <bockelman@gmail.com>
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 * For conditions of distribution and use, see copyright notice in zlib.h
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 */
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#include "../../zbuild.h"
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#include "../../adler32_p.h"
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#include "adler32_ssse3_p.h"
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#ifdef X86_SSSE3
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#include <immintrin.h>
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Z_INTERNAL uint32_t adler32_ssse3(uint32_t adler, const uint8_t *buf, size_t len) {
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    uint32_t sum2;
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     /* split Adler-32 into component sums */
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    sum2 = (adler >> 16) & 0xffff;
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    adler &= 0xffff;
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    /* in case user likes doing a byte at a time, keep it fast */
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    if (UNLIKELY(len == 1))
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        return adler32_len_1(adler, buf, sum2);
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    /* initial Adler-32 value (deferred check for len == 1 speed) */
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    if (UNLIKELY(buf == NULL))
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        return 1L;
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    /* in case short lengths are provided, keep it somewhat fast */
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    if (UNLIKELY(len < 16))
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        return adler32_len_16(adler, buf, len, sum2);
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    const __m128i dot2v = _mm_setr_epi8(32, 31, 30, 29, 28, 27, 26, 25, 24, 23, 22, 21, 20, 19, 18, 17);
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    const __m128i dot2v_0 = _mm_setr_epi8(16, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, 1);
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    const __m128i dot3v = _mm_set1_epi16(1);
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    const __m128i zero = _mm_setzero_si128();
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    __m128i vbuf, vs1_0, vs3, vs1, vs2, vs2_0, v_sad_sum1, v_short_sum2, v_short_sum2_0,
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            vbuf_0, v_sad_sum2, vsum2, vsum2_0;
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    /* If our buffer is unaligned (likely), make the determination whether
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     * or not there's enough of a buffer to consume to make the scalar, aligning
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     * additions worthwhile or if it's worth it to just eat the cost of an unaligned
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     * load. This is a pretty simple test, just test if 16 - the remainder + len is
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     * < 16 */
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    size_t max_iters = NMAX;
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    size_t rem = (uintptr_t)buf & 15;
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    size_t align_offset = 16 - rem;
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    size_t k = 0;
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    if (rem) {
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        if (len < 16 + align_offset) {
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            /* Let's eat the cost of this one unaligned load so that
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             * we don't completely skip over the vectorization. Doing
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             * 16 bytes at a time unaligned is better than 16 + <= 15
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             * sums */
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            vbuf = _mm_loadu_si128((__m128i*)buf);
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            len -= 16;
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            buf += 16;
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            vs1 = _mm_cvtsi32_si128(adler);
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            vs2 = _mm_cvtsi32_si128(sum2);
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            vs3 = _mm_setzero_si128();
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            vs1_0 = vs1;
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            goto unaligned_jmp;
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        }
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        for (size_t i = 0; i < align_offset; ++i) {
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            adler += *(buf++);
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            sum2 += adler;
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        }
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        /* lop off the max number of sums based on the scalar sums done
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         * above */
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        len -= align_offset;
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        max_iters -= align_offset;
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    }
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    while (len >= 16) {
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        vs1 = _mm_cvtsi32_si128(adler);
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        vs2 = _mm_cvtsi32_si128(sum2);
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        vs3 = _mm_setzero_si128();
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        vs2_0 = _mm_setzero_si128();
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        vs1_0 = vs1;
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        k = (len < max_iters ? len : max_iters);
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        k -= k % 16;
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        len -= k;
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        while (k >= 32) {
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            /*
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               vs1 = adler + sum(c[i])
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               vs2 = sum2 + 16 vs1 + sum( (16-i+1) c[i] )
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            */
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            vbuf = _mm_load_si128((__m128i*)buf);
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            vbuf_0 = _mm_load_si128((__m128i*)(buf + 16));
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            buf += 32;
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            k -= 32;
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            v_sad_sum1 = _mm_sad_epu8(vbuf, zero);
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            v_sad_sum2 = _mm_sad_epu8(vbuf_0, zero);
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            vs1 = _mm_add_epi32(v_sad_sum1, vs1);
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            vs3 = _mm_add_epi32(vs1_0, vs3);
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            vs1 = _mm_add_epi32(v_sad_sum2, vs1);
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            v_short_sum2 = _mm_maddubs_epi16(vbuf, dot2v);
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            vsum2 = _mm_madd_epi16(v_short_sum2, dot3v);
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            v_short_sum2_0 = _mm_maddubs_epi16(vbuf_0, dot2v_0);
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            vs2 = _mm_add_epi32(vsum2, vs2);
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            vsum2_0 = _mm_madd_epi16(v_short_sum2_0, dot3v);
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            vs2_0 = _mm_add_epi32(vsum2_0, vs2_0);
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            vs1_0 = vs1;
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        }
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        vs2 = _mm_add_epi32(vs2_0, vs2);
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        vs3 = _mm_slli_epi32(vs3, 5);
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        vs2 = _mm_add_epi32(vs3, vs2);
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        vs3 = _mm_setzero_si128();
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        while (k >= 16) {
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            /*
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               vs1 = adler + sum(c[i])
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               vs2 = sum2 + 16 vs1 + sum( (16-i+1) c[i] )
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            */
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            vbuf = _mm_load_si128((__m128i*)buf);
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            buf += 16;
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            k -= 16;
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unaligned_jmp:
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            v_sad_sum1 = _mm_sad_epu8(vbuf, zero);
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            vs1 = _mm_add_epi32(v_sad_sum1, vs1);
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            vs3 = _mm_add_epi32(vs1_0, vs3);
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            v_short_sum2 = _mm_maddubs_epi16(vbuf, dot2v_0);
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            vsum2 = _mm_madd_epi16(v_short_sum2, dot3v);
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            vs2 = _mm_add_epi32(vsum2, vs2);
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            vs1_0 = vs1;
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        }
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        vs3 = _mm_slli_epi32(vs3, 4);
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        vs2 = _mm_add_epi32(vs2, vs3);
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        /* We don't actually need to do a full horizontal sum, since psadbw is actually doing
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         * a partial reduction sum implicitly and only summing to integers in vector positions
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         * 0 and 2. This saves us some contention on the shuffle port(s) */
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        adler = partial_hsum(vs1) % BASE;
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        sum2 = hsum(vs2) % BASE;
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        max_iters = NMAX;
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    }
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    /* Process tail (len < 16).  */
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    return adler32_len_16(adler, buf, len, sum2);
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}
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#endif
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