/* adler32_ssse3.c -- compute the Adler-32 checksum of a data stream

 * Copyright (C) 1995-2011 Mark Adler

 * Authors:

 *   Adam Stylinski <kungfujesus06@gmail.com>

 *   Brian Bockelman <bockelman@gmail.com>

 * For conditions of distribution and use, see copyright notice in zlib.h

 */

#include "zbuild.h"

#include "adler32_p.h"

#include "adler32_ssse3_p.h"

#ifdef X86_SSSE3

#include <immintrin.h>

Z_INTERNAL uint32_t adler32_ssse3(uint32_t adler, const uint8_t *buf, size_t len) {

    uint32_t sum2;

     /* split Adler-32 into component sums */

    sum2 = (adler >> 16) & 0xffff;

    adler &= 0xffff;

    /* in case user likes doing a byte at a time, keep it fast */

    if (UNLIKELY(len == 1))

        return adler32_len_1(adler, buf, sum2);

    /* initial Adler-32 value (deferred check for len == 1 speed) */

    if (UNLIKELY(buf == NULL))

        return 1L;

    /* in case short lengths are provided, keep it somewhat fast */

    if (UNLIKELY(len < 16))

        return adler32_len_16(adler, buf, len, sum2);

    const __m128i dot2v = _mm_setr_epi8(32, 31, 30, 29, 28, 27, 26, 25, 24, 23, 22, 21, 20, 19, 18, 17);

    const __m128i dot2v_0 = _mm_setr_epi8(16, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, 1);

    const __m128i dot3v = _mm_set1_epi16(1);

    const __m128i zero = _mm_setzero_si128();

    __m128i vbuf, vs1_0, vs3, vs1, vs2, vs2_0, v_sad_sum1, v_short_sum2, v_short_sum2_0,

            vbuf_0, v_sad_sum2, vsum2, vsum2_0;

    /* If our buffer is unaligned (likely), make the determination whether

     * or not there's enough of a buffer to consume to make the scalar, aligning

     * additions worthwhile or if it's worth it to just eat the cost of an unaligned

     * load. This is a pretty simple test, just test if 16 - the remainder + len is

     * < 16 */

    size_t max_iters = NMAX;

    size_t rem = (uintptr_t)buf & 15;

    size_t align_offset = 16 - rem;

    size_t k = 0;

    if (rem) {

        if (len < 16 + align_offset) {

            /* Let's eat the cost of this one unaligned load so that

             * we don't completely skip over the vectorization. Doing

             * 16 bytes at a time unaligned is better than 16 + <= 15

             * sums */

            vbuf = _mm_loadu_si128((__m128i*)buf);

            len -= 16;

            buf += 16;

            vs1 = _mm_cvtsi32_si128(adler);

            vs2 = _mm_cvtsi32_si128(sum2);

            vs3 = _mm_setzero_si128();

            vs1_0 = vs1;

            goto unaligned_jmp;

        }

        for (size_t i = 0; i < align_offset; ++i) {

            adler += *(buf++);

            sum2 += adler;

        }

        /* lop off the max number of sums based on the scalar sums done

         * above */

        len -= align_offset;

        max_iters -= align_offset;

    }

    while (len >= 16) {

        vs1 = _mm_cvtsi32_si128(adler);

        vs2 = _mm_cvtsi32_si128(sum2);

        vs3 = _mm_setzero_si128();

        vs2_0 = _mm_setzero_si128();

        vs1_0 = vs1;

        k = (len < max_iters ? len : max_iters);

        k -= k % 16;

        len -= k;

        while (k >= 32) {

            /*

               vs1 = adler + sum(c[i])

               vs2 = sum2 + 16 vs1 + sum( (16-i+1) c[i] )

            */

            vbuf = _mm_load_si128((__m128i*)buf);

            vbuf_0 = _mm_load_si128((__m128i*)(buf + 16));

            buf += 32;

            k -= 32;

            v_sad_sum1 = _mm_sad_epu8(vbuf, zero);

            v_sad_sum2 = _mm_sad_epu8(vbuf_0, zero);

            vs1 = _mm_add_epi32(v_sad_sum1, vs1);

            vs3 = _mm_add_epi32(vs1_0, vs3);

            vs1 = _mm_add_epi32(v_sad_sum2, vs1);

            v_short_sum2 = _mm_maddubs_epi16(vbuf, dot2v);

            vsum2 = _mm_madd_epi16(v_short_sum2, dot3v);

            v_short_sum2_0 = _mm_maddubs_epi16(vbuf_0, dot2v_0);

            vs2 = _mm_add_epi32(vsum2, vs2);

            vsum2_0 = _mm_madd_epi16(v_short_sum2_0, dot3v);

            vs2_0 = _mm_add_epi32(vsum2_0, vs2_0);

            vs1_0 = vs1;

        }

        vs2 = _mm_add_epi32(vs2_0, vs2);

        vs3 = _mm_slli_epi32(vs3, 5);

        vs2 = _mm_add_epi32(vs3, vs2);

        vs3 = _mm_setzero_si128();

        while (k >= 16) {

            /*

               vs1 = adler + sum(c[i])

               vs2 = sum2 + 16 vs1 + sum( (16-i+1) c[i] )

            */

            vbuf = _mm_load_si128((__m128i*)buf);

            buf += 16;

            k -= 16;

unaligned_jmp:

            v_sad_sum1 = _mm_sad_epu8(vbuf, zero);

            vs1 = _mm_add_epi32(v_sad_sum1, vs1);

            vs3 = _mm_add_epi32(vs1_0, vs3);

            v_short_sum2 = _mm_maddubs_epi16(vbuf, dot2v_0);

            vsum2 = _mm_madd_epi16(v_short_sum2, dot3v);

            vs2 = _mm_add_epi32(vsum2, vs2);

            vs1_0 = vs1;

        }

        vs3 = _mm_slli_epi32(vs3, 4);

        vs2 = _mm_add_epi32(vs2, vs3);

        /* We don't actually need to do a full horizontal sum, since psadbw is actually doing

         * a partial reduction sum implicitly and only summing to integers in vector positions

         * 0 and 2. This saves us some contention on the shuffle port(s) */

        adler = partial_hsum(vs1) % BASE;

        sum2 = hsum(vs2) % BASE;

        max_iters = NMAX;

    }

    /* Process tail (len < 16).  */

    return adler32_len_16(adler, buf, len, sum2);

}

#endif