/*********************************************************************

  Blosc - Blocked Shuffling and Compression Library

  Copyright (c) 2021  Blosc Development Team <blosc@blosc.org>

  https://blosc.org

  License: BSD 3-Clause (see LICENSE.txt)

  See LICENSE.txt for details about copyright and rights to use.

**********************************************************************/

#include "shuffle-avx2.h"

#include "shuffle-generic.h"

#include <stdlib.h>

/* Make sure AVX2 is available for the compilation target and compiler. */

#if defined(__AVX2__)

#include <immintrin.h>

#include <stdint.h>

/* The next is useful for debugging purposes */

#if 0

#include <stdio.h>

#include <string.h>

static void printymm32(__m256i ymm0)

{

  uint32_t buf[8];

  ((__m256i *)buf)[0] = ymm0;

  fprintf(stderr, "%x,%x,%x,%x,%x,%x,%x,%x\n",

          buf[0], buf[1], buf[2], buf[3],

          buf[4], buf[5], buf[6], buf[7]);

}

static void printymm(__m256i ymm0)

{

  uint8_t buf[32];

  ((__m256i *)buf)[0] = ymm0;

  fprintf(stderr, "%x,%x,%x,%x,%x,%x,%x,%x,%x,%x,%x,%x,%x,%x,%x,%x,%x,%x,%x,%x,%x,%x,%x,%x,%x,%x,%x,%x,%x,%x,%x,%x\n",

          buf[0], buf[1], buf[2], buf[3],

          buf[4], buf[5], buf[6], buf[7],

          buf[8], buf[9], buf[10], buf[11],

          buf[12], buf[13], buf[14], buf[15],

          buf[16], buf[17], buf[18], buf[19],

          buf[20], buf[21], buf[22], buf[23],

          buf[24], buf[25], buf[26], buf[27],

          buf[28], buf[29], buf[30], buf[31]);

}

#endif

/* GCC doesn't include the split load/store intrinsics

   needed for the tiled shuffle, so define them here. */

#if defined(__GNUC__) && !defined(__clang__) && !defined(__ICC)

static inline __m256i

__attribute__((__always_inline__))

_mm256_loadu2_m128i(const __m128i* const hiaddr, const __m128i* const loaddr) {

  return _mm256_inserti128_si256(

      _mm256_castsi128_si256(_mm_loadu_si128(loaddr)), _mm_loadu_si128(hiaddr), 1);

}

static inline void

__attribute__((__always_inline__))

_mm256_storeu2_m128i(__m128i* const hiaddr, __m128i* const loaddr, const __m256i a) {

  _mm_storeu_si128(loaddr, _mm256_castsi256_si128(a));

  _mm_storeu_si128(hiaddr, _mm256_extracti128_si256(a, 1));

}

#endif  /* defined(__GNUC__) */

/* Routine optimized for shuffling a buffer for a type size of 2 bytes. */

static void

shuffle2_avx2(uint8_t* const dest, const uint8_t* const src,

              const int32_t vectorizable_elements, const int32_t total_elements) {

  static const int32_t bytesoftype = 2;

  int32_t j;

  int k;

  __m256i ymm0[2], ymm1[2];

  /* Create the shuffle mask.

     NOTE: The XMM/YMM 'set' intrinsics require the arguments to be ordered from

     most to least significant (i.e., their order is reversed when compared to

     loading the mask from an array). */

  const __m256i shmask = _mm256_set_epi8(

      0x0f, 0x0d, 0x0b, 0x09, 0x07, 0x05, 0x03, 0x01,

      0x0e, 0x0c, 0x0a, 0x08, 0x06, 0x04, 0x02, 0x00,

      0x0f, 0x0d, 0x0b, 0x09, 0x07, 0x05, 0x03, 0x01,

      0x0e, 0x0c, 0x0a, 0x08, 0x06, 0x04, 0x02, 0x00);

  for (j = 0; j < vectorizable_elements; j += sizeof(__m256i)) {

    /* Fetch 32 elements (64 bytes) then transpose bytes, words and double words. */

    for (k = 0; k < 2; k++) {

      ymm0[k] = _mm256_loadu_si256((__m256i*)(src + (j * bytesoftype) + (k * sizeof(__m256i))));

      ymm1[k] = _mm256_shuffle_epi8(ymm0[k], shmask);

    }

    ymm0[0] = _mm256_permute4x64_epi64(ymm1[0], 0xd8);

    ymm0[1] = _mm256_permute4x64_epi64(ymm1[1], 0x8d);

    ymm1[0] = _mm256_blend_epi32(ymm0[0], ymm0[1], 0xf0);

    ymm0[1] = _mm256_blend_epi32(ymm0[0], ymm0[1], 0x0f);

    ymm1[1] = _mm256_permute4x64_epi64(ymm0[1], 0x4e);

    /* Store the result vectors */

    uint8_t* const dest_for_jth_element = dest + j;

    for (k = 0; k < 2; k++) {

      _mm256_storeu_si256((__m256i*)(dest_for_jth_element + (k * total_elements)), ymm1[k]);

    }

  }

}

/* Routine optimized for shuffling a buffer for a type size of 4 bytes. */

static void

shuffle4_avx2(uint8_t* const dest, const uint8_t* const src,

              const int32_t vectorizable_elements, const int32_t total_elements) {

  static const int32_t bytesoftype = 4;

  int32_t i;

  int j;

  __m256i ymm0[4], ymm1[4];

  /* Create the shuffle mask.

     NOTE: The XMM/YMM 'set' intrinsics require the arguments to be ordered from

     most to least significant (i.e., their order is reversed when compared to

     loading the mask from an array). */

  const __m256i mask = _mm256_set_epi32(

      0x07, 0x03, 0x06, 0x02, 0x05, 0x01, 0x04, 0x00);

  for (i = 0; i < vectorizable_elements; i += sizeof(__m256i)) {

    /* Fetch 32 elements (128 bytes) then transpose bytes and words. */

    for (j = 0; j < 4; j++) {

      ymm0[j] = _mm256_loadu_si256((__m256i*)(src + (i * bytesoftype) + (j * sizeof(__m256i))));

      ymm1[j] = _mm256_shuffle_epi32(ymm0[j], 0xd8);

      ymm0[j] = _mm256_shuffle_epi32(ymm0[j], 0x8d);

      ymm0[j] = _mm256_unpacklo_epi8(ymm1[j], ymm0[j]);

      ymm1[j] = _mm256_shuffle_epi32(ymm0[j], 0x04e);

      ymm0[j] = _mm256_unpacklo_epi16(ymm0[j], ymm1[j]);

    }

    /* Transpose double words */

    for (j = 0; j < 2; j++) {

      ymm1[j * 2] = _mm256_unpacklo_epi32(ymm0[j * 2], ymm0[j * 2 + 1]);

      ymm1[j * 2 + 1] = _mm256_unpackhi_epi32(ymm0[j * 2], ymm0[j * 2 + 1]);

    }

    /* Transpose quad words */

    for (j = 0; j < 2; j++) {

      ymm0[j * 2] = _mm256_unpacklo_epi64(ymm1[j], ymm1[j + 2]);

      ymm0[j * 2 + 1] = _mm256_unpackhi_epi64(ymm1[j], ymm1[j + 2]);

    }

    for (j = 0; j < 4; j++) {

      ymm0[j] = _mm256_permutevar8x32_epi32(ymm0[j], mask);

    }

    /* Store the result vectors */

    uint8_t* const dest_for_ith_element = dest + i;

    for (j = 0; j < 4; j++) {

      _mm256_storeu_si256((__m256i*)(dest_for_ith_element + (j * total_elements)), ymm0[j]);

    }

  }

}

/* Routine optimized for shuffling a buffer for a type size of 8 bytes. */

static void

shuffle8_avx2(uint8_t* const dest, const uint8_t* const src,

              const int32_t vectorizable_elements, const int32_t total_elements) {

  static const int32_t bytesoftype = 8;

  int32_t j;

  int k, l;

  __m256i ymm0[8], ymm1[8];

  for (j = 0; j < vectorizable_elements; j += sizeof(__m256i)) {

    /* Fetch 32 elements (256 bytes) then transpose bytes. */

    for (k = 0; k < 8; k++) {

      ymm0[k] = _mm256_loadu_si256((__m256i*)(src + (j * bytesoftype) + (k * sizeof(__m256i))));

      ymm1[k] = _mm256_shuffle_epi32(ymm0[k], 0x4e);

      ymm1[k] = _mm256_unpacklo_epi8(ymm0[k], ymm1[k]);

    }

    /* Transpose words */

    for (k = 0, l = 0; k < 4; k++, l += 2) {

      ymm0[k * 2] = _mm256_unpacklo_epi16(ymm1[l], ymm1[l + 1]);

      ymm0[k * 2 + 1] = _mm256_unpackhi_epi16(ymm1[l], ymm1[l + 1]);

    }

    /* Transpose double words */

    for (k = 0, l = 0; k < 4; k++, l++) {

      if (k == 2) l += 2;

      ymm1[k * 2] = _mm256_unpacklo_epi32(ymm0[l], ymm0[l + 2]);

      ymm1[k * 2 + 1] = _mm256_unpackhi_epi32(ymm0[l], ymm0[l + 2]);

    }

    /* Transpose quad words */

    for (k = 0; k < 4; k++) {

      ymm0[k * 2] = _mm256_unpacklo_epi64(ymm1[k], ymm1[k + 4]);

      ymm0[k * 2 + 1] = _mm256_unpackhi_epi64(ymm1[k], ymm1[k + 4]);

    }

    for (k = 0; k < 8; k++) {

      ymm1[k] = _mm256_permute4x64_epi64(ymm0[k], 0x72);

      ymm0[k] = _mm256_permute4x64_epi64(ymm0[k], 0xD8);

      ymm0[k] = _mm256_unpacklo_epi16(ymm0[k], ymm1[k]);

    }

    /* Store the result vectors */

    uint8_t* const dest_for_jth_element = dest + j;

    for (k = 0; k < 8; k++) {

      _mm256_storeu_si256((__m256i*)(dest_for_jth_element + (k * total_elements)), ymm0[k]);

    }

  }

}

/* Routine optimized for shuffling a buffer for a type size of 16 bytes. */

static void

shuffle16_avx2(uint8_t* const dest, const uint8_t* const src,

               const int32_t vectorizable_elements, const int32_t total_elements) {

  static const int32_t bytesoftype = 16;

  int32_t j;

  int k, l;

  __m256i ymm0[16], ymm1[16];

  /* Create the shuffle mask.

     NOTE: The XMM/YMM 'set' intrinsics require the arguments to be ordered from

     most to least significant (i.e., their order is reversed when compared to

     loading the mask from an array). */

  const __m256i shmask = _mm256_set_epi8(

      0x0f, 0x07, 0x0e, 0x06, 0x0d, 0x05, 0x0c, 0x04,

      0x0b, 0x03, 0x0a, 0x02, 0x09, 0x01, 0x08, 0x00,

      0x0f, 0x07, 0x0e, 0x06, 0x0d, 0x05, 0x0c, 0x04,

      0x0b, 0x03, 0x0a, 0x02, 0x09, 0x01, 0x08, 0x00);

  for (j = 0; j < vectorizable_elements; j += sizeof(__m256i)) {

    /* Fetch 32 elements (512 bytes) into 16 YMM registers. */

    for (k = 0; k < 16; k++) {

      ymm0[k] = _mm256_loadu_si256((__m256i*)(src + (j * bytesoftype) + (k * sizeof(__m256i))));

    }

    /* Transpose bytes */

    for (k = 0, l = 0; k < 8; k++, l += 2) {

      ymm1[k * 2] = _mm256_unpacklo_epi8(ymm0[l], ymm0[l + 1]);

      ymm1[k * 2 + 1] = _mm256_unpackhi_epi8(ymm0[l], ymm0[l + 1]);

    }

    /* Transpose words */

    for (k = 0, l = -2; k < 8; k++, l++) {

      if ((k % 2) == 0) l += 2;

      ymm0[k * 2] = _mm256_unpacklo_epi16(ymm1[l], ymm1[l + 2]);

      ymm0[k * 2 + 1] = _mm256_unpackhi_epi16(ymm1[l], ymm1[l + 2]);

    }

    /* Transpose double words */

    for (k = 0, l = -4; k < 8; k++, l++) {

      if ((k % 4) == 0) l += 4;

      ymm1[k * 2] = _mm256_unpacklo_epi32(ymm0[l], ymm0[l + 4]);

      ymm1[k * 2 + 1] = _mm256_unpackhi_epi32(ymm0[l], ymm0[l + 4]);

    }

    /* Transpose quad words */

    for (k = 0; k < 8; k++) {

      ymm0[k * 2] = _mm256_unpacklo_epi64(ymm1[k], ymm1[k + 8]);

      ymm0[k * 2 + 1] = _mm256_unpackhi_epi64(ymm1[k], ymm1[k + 8]);

    }

    for (k = 0; k < 16; k++) {

      ymm0[k] = _mm256_permute4x64_epi64(ymm0[k], 0xd8);

      ymm0[k] = _mm256_shuffle_epi8(ymm0[k], shmask);

    }

    /* Store the result vectors */

    uint8_t* const dest_for_jth_element = dest + j;

    for (k = 0; k < 16; k++) {

      _mm256_storeu_si256((__m256i*)(dest_for_jth_element + (k * total_elements)), ymm0[k]);

    }

  }

}

/* Routine optimized for shuffling a buffer for a type size larger than 16 bytes. */

static void

shuffle16_tiled_avx2(uint8_t* const dest, const uint8_t* const src,

                     const int32_t vectorizable_elements, const int32_t total_elements, const int32_t bytesoftype) {

  int32_t j;

  int k, l;

  __m256i ymm0[16], ymm1[16];

  const lldiv_t vecs_per_el = lldiv(bytesoftype, sizeof(__m128i));

  const int32_t vecs_rem = (int32_t)vecs_per_el.rem;

  /* Create the shuffle mask.

     NOTE: The XMM/YMM 'set' intrinsics require the arguments to be ordered from

     most to least significant (i.e., their order is reversed when compared to

     loading the mask from an array). */

  const __m256i shmask = _mm256_set_epi8(

      0x0f, 0x07, 0x0e, 0x06, 0x0d, 0x05, 0x0c, 0x04,

      0x0b, 0x03, 0x0a, 0x02, 0x09, 0x01, 0x08, 0x00,

      0x0f, 0x07, 0x0e, 0x06, 0x0d, 0x05, 0x0c, 0x04,

      0x0b, 0x03, 0x0a, 0x02, 0x09, 0x01, 0x08, 0x00);

  for (j = 0; j < vectorizable_elements; j += sizeof(__m256i)) {

    /* Advance the offset into the type by the vector size (in bytes), unless this is

    the initial iteration and the type size is not a multiple of the vector size.

    In that case, only advance by the number of bytes necessary so that the number

    of remaining bytes in the type will be a multiple of the vector size. */

    int32_t offset_into_type;

    for (offset_into_type = 0; offset_into_type < bytesoftype;

         offset_into_type += (offset_into_type == 0 && vecs_rem > 0 ? vecs_rem : (int32_t)sizeof(__m128i))) {

      /* Fetch elements in groups of 512 bytes */

      const uint8_t* const src_with_offset = src + offset_into_type;

      for (k = 0; k < 16; k++) {

        ymm0[k] = _mm256_loadu2_m128i(

            (__m128i*)(src_with_offset + (j + (2 * k) + 1) * bytesoftype),

            (__m128i*)(src_with_offset + (j + (2 * k)) * bytesoftype));

      }

      /* Transpose bytes */

      for (k = 0, l = 0; k < 8; k++, l += 2) {

        ymm1[k * 2] = _mm256_unpacklo_epi8(ymm0[l], ymm0[l + 1]);

        ymm1[k * 2 + 1] = _mm256_unpackhi_epi8(ymm0[l], ymm0[l + 1]);

      }

      /* Transpose words */

      for (k = 0, l = -2; k < 8; k++, l++) {

        if ((k % 2) == 0) l += 2;

        ymm0[k * 2] = _mm256_unpacklo_epi16(ymm1[l], ymm1[l + 2]);

        ymm0[k * 2 + 1] = _mm256_unpackhi_epi16(ymm1[l], ymm1[l + 2]);

      }

      /* Transpose double words */

      for (k = 0, l = -4; k < 8; k++, l++) {

        if ((k % 4) == 0) l += 4;

        ymm1[k * 2] = _mm256_unpacklo_epi32(ymm0[l], ymm0[l + 4]);

        ymm1[k * 2 + 1] = _mm256_unpackhi_epi32(ymm0[l], ymm0[l + 4]);

      }

      /* Transpose quad words */

      for (k = 0; k < 8; k++) {

        ymm0[k * 2] = _mm256_unpacklo_epi64(ymm1[k], ymm1[k + 8]);

        ymm0[k * 2 + 1] = _mm256_unpackhi_epi64(ymm1[k], ymm1[k + 8]);

      }

      for (k = 0; k < 16; k++) {

        ymm0[k] = _mm256_permute4x64_epi64(ymm0[k], 0xd8);

        ymm0[k] = _mm256_shuffle_epi8(ymm0[k], shmask);

      }

      /* Store the result vectors */

      uint8_t* const dest_for_jth_element = dest + j;

      for (k = 0; k < 16; k++) {

        _mm256_storeu_si256((__m256i*)(dest_for_jth_element + (total_elements * (offset_into_type + k))), ymm0[k]);

      }

    }

  }

}

/* Routine optimized for unshuffling a buffer for a type size of 2 bytes. */

static void

unshuffle2_avx2(uint8_t* const dest, const uint8_t* const src,

                const int32_t vectorizable_elements, const int32_t total_elements) {

  static const int32_t bytesoftype = 2;

  int32_t i;

  int j;

  __m256i ymm0[2], ymm1[2];

  for (i = 0; i < vectorizable_elements; i += sizeof(__m256i)) {

    /* Load 32 elements (64 bytes) into 2 YMM registers. */

    const uint8_t* const src_for_ith_element = src + i;

    for (j = 0; j < 2; j++) {

      ymm0[j] = _mm256_loadu_si256((__m256i*)(src_for_ith_element + (j * total_elements)));

    }

    /* Shuffle bytes */

    for (j = 0; j < 2; j++) {

      ymm0[j] = _mm256_permute4x64_epi64(ymm0[j], 0xd8);

    }

    /* Compute the low 64 bytes */

    ymm1[0] = _mm256_unpacklo_epi8(ymm0[0], ymm0[1]);

    /* Compute the hi 64 bytes */

    ymm1[1] = _mm256_unpackhi_epi8(ymm0[0], ymm0[1]);

    /* Store the result vectors in proper order */

    _mm256_storeu_si256((__m256i*)(dest + (i * bytesoftype) + (0 * sizeof(__m256i))), ymm1[0]);

    _mm256_storeu_si256((__m256i*)(dest + (i * bytesoftype) + (1 * sizeof(__m256i))), ymm1[1]);

  }

}

/* Routine optimized for unshuffling a buffer for a type size of 4 bytes. */

static void

unshuffle4_avx2(uint8_t* const dest, const uint8_t* const src,

                const int32_t vectorizable_elements, const int32_t total_elements) {

  static const int32_t bytesoftype = 4;

  int32_t i;

  int j;

  __m256i ymm0[4], ymm1[4];

  for (i = 0; i < vectorizable_elements; i += sizeof(__m256i)) {

    /* Load 32 elements (128 bytes) into 4 YMM registers. */

    const uint8_t* const src_for_ith_element = src + i;

    for (j = 0; j < 4; j++) {

      ymm0[j] = _mm256_loadu_si256((__m256i*)(src_for_ith_element + (j * total_elements)));

    }

    /* Shuffle bytes */

    for (j = 0; j < 2; j++) {

      /* Compute the low 64 bytes */

      ymm1[j] = _mm256_unpacklo_epi8(ymm0[j * 2], ymm0[j * 2 + 1]);

      /* Compute the hi 64 bytes */

      ymm1[2 + j] = _mm256_unpackhi_epi8(ymm0[j * 2], ymm0[j * 2 + 1]);

    }

    /* Shuffle 2-byte words */

    for (j = 0; j < 2; j++) {

      /* Compute the low 64 bytes */

      ymm0[j] = _mm256_unpacklo_epi16(ymm1[j * 2], ymm1[j * 2 + 1]);

      /* Compute the hi 64 bytes */

      ymm0[2 + j] = _mm256_unpackhi_epi16(ymm1[j * 2], ymm1[j * 2 + 1]);

    }

    ymm1[0] = _mm256_permute2x128_si256(ymm0[0], ymm0[2], 0x20);

    ymm1[1] = _mm256_permute2x128_si256(ymm0[1], ymm0[3], 0x20);

    ymm1[2] = _mm256_permute2x128_si256(ymm0[0], ymm0[2], 0x31);

    ymm1[3] = _mm256_permute2x128_si256(ymm0[1], ymm0[3], 0x31);

    /* Store the result vectors in proper order */

    for (j = 0; j < 4; j++) {

      _mm256_storeu_si256((__m256i*)(dest + (i * bytesoftype) + (j * sizeof(__m256i))), ymm1[j]);

    }

  }

}

/* Routine optimized for unshuffling a buffer for a type size of 8 bytes. */

static void

unshuffle8_avx2(uint8_t* const dest, const uint8_t* const src,

                const int32_t vectorizable_elements, const int32_t total_elements) {

  static const int32_t bytesoftype = 8;

  int32_t i;

  int j;

  __m256i ymm0[8], ymm1[8];

  for (i = 0; i < vectorizable_elements; i += sizeof(__m256i)) {

    /* Fetch 32 elements (256 bytes) into 8 YMM registers. */

    const uint8_t* const src_for_ith_element = src + i;

    for (j = 0; j < 8; j++) {

      ymm0[j] = _mm256_loadu_si256((__m256i*)(src_for_ith_element + (j * total_elements)));

    }

    /* Shuffle bytes */

    for (j = 0; j < 4; j++) {

      /* Compute the low 32 bytes */

      ymm1[j] = _mm256_unpacklo_epi8(ymm0[j * 2], ymm0[j * 2 + 1]);

      /* Compute the hi 32 bytes */

      ymm1[4 + j] = _mm256_unpackhi_epi8(ymm0[j * 2], ymm0[j * 2 + 1]);

    }

    /* Shuffle words */

    for (j = 0; j < 4; j++) {

      /* Compute the low 32 bytes */

      ymm0[j] = _mm256_unpacklo_epi16(ymm1[j * 2], ymm1[j * 2 + 1]);

      /* Compute the hi 32 bytes */

      ymm0[4 + j] = _mm256_unpackhi_epi16(ymm1[j * 2], ymm1[j * 2 + 1]);

    }

    for (j = 0; j < 8; j++) {

      ymm0[j] = _mm256_permute4x64_epi64(ymm0[j], 0xd8);

    }

    /* Shuffle 4-byte dwords */

    for (j = 0; j < 4; j++) {

      /* Compute the low 32 bytes */

      ymm1[j] = _mm256_unpacklo_epi32(ymm0[j * 2], ymm0[j * 2 + 1]);

      /* Compute the hi 32 bytes */

      ymm1[4 + j] = _mm256_unpackhi_epi32(ymm0[j * 2], ymm0[j * 2 + 1]);

    }

    /* Store the result vectors in proper order */

    _mm256_storeu_si256((__m256i*)(dest + (i * bytesoftype) + (0 * sizeof(__m256i))), ymm1[0]);

    _mm256_storeu_si256((__m256i*)(dest + (i * bytesoftype) + (1 * sizeof(__m256i))), ymm1[2]);

    _mm256_storeu_si256((__m256i*)(dest + (i * bytesoftype) + (2 * sizeof(__m256i))), ymm1[1]);

    _mm256_storeu_si256((__m256i*)(dest + (i * bytesoftype) + (3 * sizeof(__m256i))), ymm1[3]);

    _mm256_storeu_si256((__m256i*)(dest + (i * bytesoftype) + (4 * sizeof(__m256i))), ymm1[4]);

    _mm256_storeu_si256((__m256i*)(dest + (i * bytesoftype) + (5 * sizeof(__m256i))), ymm1[6]);

    _mm256_storeu_si256((__m256i*)(dest + (i * bytesoftype) + (6 * sizeof(__m256i))), ymm1[5]);

    _mm256_storeu_si256((__m256i*)(dest + (i * bytesoftype) + (7 * sizeof(__m256i))), ymm1[7]);

  }

}

/* Routine optimized for unshuffling a buffer for a type size of 16 bytes. */

static void

unshuffle16_avx2(uint8_t* const dest, const uint8_t* const src,

                 const int32_t vectorizable_elements, const int32_t total_elements) {

  static const int32_t bytesoftype = 16;

  int32_t i;

  int j;

  __m256i ymm0[16], ymm1[16];

  for (i = 0; i < vectorizable_elements; i += sizeof(__m256i)) {

    /* Fetch 32 elements (512 bytes) into 16 YMM registers. */

    const uint8_t* const src_for_ith_element = src + i;

    for (j = 0; j < 16; j++) {

      ymm0[j] = _mm256_loadu_si256((__m256i*)(src_for_ith_element + (j * total_elements)));

    }

    /* Shuffle bytes */

    for (j = 0; j < 8; j++) {

      /* Compute the low 32 bytes */

      ymm1[j] = _mm256_unpacklo_epi8(ymm0[j * 2], ymm0[j * 2 + 1]);

      /* Compute the hi 32 bytes */

      ymm1[8 + j] = _mm256_unpackhi_epi8(ymm0[j * 2], ymm0[j * 2 + 1]);

    }

    /* Shuffle 2-byte words */

    for (j = 0; j < 8; j++) {

      /* Compute the low 32 bytes */

      ymm0[j] = _mm256_unpacklo_epi16(ymm1[j * 2], ymm1[j * 2 + 1]);

      /* Compute the hi 32 bytes */

      ymm0[8 + j] = _mm256_unpackhi_epi16(ymm1[j * 2], ymm1[j * 2 + 1]);

    }

    /* Shuffle 4-byte dwords */

    for (j = 0; j < 8; j++) {

      /* Compute the low 32 bytes */

      ymm1[j] = _mm256_unpacklo_epi32(ymm0[j * 2], ymm0[j * 2 + 1]);

      /* Compute the hi 32 bytes */

      ymm1[8 + j] = _mm256_unpackhi_epi32(ymm0[j * 2], ymm0[j * 2 + 1]);

    }

    /* Shuffle 8-byte qwords */

    for (j = 0; j < 8; j++) {

      /* Compute the low 32 bytes */

      ymm0[j] = _mm256_unpacklo_epi64(ymm1[j * 2], ymm1[j * 2 + 1]);

      /* Compute the hi 32 bytes */

      ymm0[8 + j] = _mm256_unpackhi_epi64(ymm1[j * 2], ymm1[j * 2 + 1]);

    }

    for (j = 0; j < 8; j++) {

      ymm1[j] = _mm256_permute2x128_si256(ymm0[j], ymm0[j + 8], 0x20);

      ymm1[j + 8] = _mm256_permute2x128_si256(ymm0[j], ymm0[j + 8], 0x31);

    }

    /* Store the result vectors in proper order */

    _mm256_storeu_si256((__m256i*)(dest + (i * bytesoftype) + (0 * sizeof(__m256i))), ymm1[0]);

    _mm256_storeu_si256((__m256i*)(dest + (i * bytesoftype) + (1 * sizeof(__m256i))), ymm1[4]);

    _mm256_storeu_si256((__m256i*)(dest + (i * bytesoftype) + (2 * sizeof(__m256i))), ymm1[2]);

    _mm256_storeu_si256((__m256i*)(dest + (i * bytesoftype) + (3 * sizeof(__m256i))), ymm1[6]);

    _mm256_storeu_si256((__m256i*)(dest + (i * bytesoftype) + (4 * sizeof(__m256i))), ymm1[1]);

    _mm256_storeu_si256((__m256i*)(dest + (i * bytesoftype) + (5 * sizeof(__m256i))), ymm1[5]);

    _mm256_storeu_si256((__m256i*)(dest + (i * bytesoftype) + (6 * sizeof(__m256i))), ymm1[3]);

    _mm256_storeu_si256((__m256i*)(dest + (i * bytesoftype) + (7 * sizeof(__m256i))), ymm1[7]);

    _mm256_storeu_si256((__m256i*)(dest + (i * bytesoftype) + (8 * sizeof(__m256i))), ymm1[8]);

    _mm256_storeu_si256((__m256i*)(dest + (i * bytesoftype) + (9 * sizeof(__m256i))), ymm1[12]);

    _mm256_storeu_si256((__m256i*)(dest + (i * bytesoftype) + (10 * sizeof(__m256i))), ymm1[10]);

    _mm256_storeu_si256((__m256i*)(dest + (i * bytesoftype) + (11 * sizeof(__m256i))), ymm1[14]);

    _mm256_storeu_si256((__m256i*)(dest + (i * bytesoftype) + (12 * sizeof(__m256i))), ymm1[9]);

    _mm256_storeu_si256((__m256i*)(dest + (i * bytesoftype) + (13 * sizeof(__m256i))), ymm1[13]);

    _mm256_storeu_si256((__m256i*)(dest + (i * bytesoftype) + (14 * sizeof(__m256i))), ymm1[11]);

    _mm256_storeu_si256((__m256i*)(dest + (i * bytesoftype) + (15 * sizeof(__m256i))), ymm1[15]);

  }

}

/* Routine optimized for unshuffling a buffer for a type size of 12 bytes.

 * Based off 16-byte implementation*/

static void

unshuffle12_avx2(uint8_t* const dest, const uint8_t* const src,

    const int32_t vectorizable_elements, const int32_t total_elements) {

  static const int32_t bytesoftype = 12;

  int32_t i;

  int j;

  __m256i ymm0[16], ymm1[16];

  __m256i permute = _mm256_set_epi32(0,0,6,5,4,2,1,0);

  __m256i store_mask = _mm256_set_epi32(0x0, 0x0, 0xFFFFFFFF, 0xFFFFFFFF, 0xFFFFFFFF, 0xFFFFFFFF, 0xFFFFFFFF, 0xFFFFFFFF);

  int32_t jump = 2*bytesoftype;

  for (i = 0; i < vectorizable_elements; i += sizeof(__m256i)) {

    /* Fetch 24 elements (384 bytes) into 12 YMM registers. */

    const uint8_t* const src_for_ith_element = src + i;

    for (j = 0; j < bytesoftype; j++) {

      ymm0[j] = _mm256_loadu_si256((__m256i*)(src_for_ith_element + (j * total_elements)));

    }

    /* Initialize the last 4 registers (128 bytes) to null */

    for (j = bytesoftype; j < 16; j++) {

      ymm0[j] = _mm256_setzero_si256();

    }

    /* Shuffle bytes */

    for (j = 0; j < 8; j++) {

      /* Compute the low 32 bytes */

      ymm1[j] = _mm256_unpacklo_epi8(ymm0[j * 2], ymm0[j * 2 + 1]);

      /* Compute the hi 32 bytes */

      ymm1[8 + j] = _mm256_unpackhi_epi8(ymm0[j * 2], ymm0[j * 2 + 1]);

    }

    /* Shuffle 2-byte words */

    for (j = 0; j < 8; j++) {

      /* Compute the low 32 bytes */

      ymm0[j] = _mm256_unpacklo_epi16(ymm1[j * 2], ymm1[j * 2 + 1]);

      /* Compute the hi 32 bytes */

      ymm0[8 + j] = _mm256_unpackhi_epi16(ymm1[j * 2], ymm1[j * 2 + 1]);

    }

    /* Shuffle 4-byte dwords */

    for (j = 0; j < 8; j++) {

      /* Compute the low 32 bytes */

      ymm1[j] = _mm256_unpacklo_epi32(ymm0[j * 2], ymm0[j * 2 + 1]);

      /* Compute the hi 32 bytes */

      ymm1[8 + j] = _mm256_unpackhi_epi32(ymm0[j * 2], ymm0[j * 2 + 1]);

    }

    /* Shuffle 8-byte qwords */

    for (j = 0; j < 8; j++) {

      /* Compute the low 32 bytes */

      ymm0[j] = _mm256_unpacklo_epi64(ymm1[j * 2], ymm1[j * 2 + 1]);

      /* Compute the hi 32 bytes */

      ymm0[8 + j] = _mm256_unpackhi_epi64(ymm1[j * 2], ymm1[j * 2 + 1]);

    }

    for (j = 0; j < 8; j++) {

      ymm1[j] = _mm256_permute2x128_si256(ymm0[j], ymm0[j + 8], 0x20);

      ymm1[j + 8] = _mm256_permute2x128_si256(ymm0[j], ymm0[j + 8], 0x31);

      ymm1[j] = _mm256_permutevar8x32_epi32(ymm1[j], permute);

      ymm1[j+8] = _mm256_permutevar8x32_epi32(ymm1[j+8], permute);

    }

    _mm256_storeu_si256((__m256i*)(dest + (i * bytesoftype) + (0 * jump)), ymm1[0]);

    _mm256_storeu_si256((__m256i*)(dest + (i * bytesoftype) + (1 * jump)), ymm1[4]);

    _mm256_storeu_si256((__m256i*)(dest + (i * bytesoftype) + (2 * jump)), ymm1[2]);

    _mm256_storeu_si256((__m256i*)(dest + (i * bytesoftype) + (3 * jump)), ymm1[6]);

    _mm256_storeu_si256((__m256i*)(dest + (i * bytesoftype) + (4 * jump)), ymm1[1]);

    _mm256_storeu_si256((__m256i*)(dest + (i * bytesoftype) + (5 * jump)), ymm1[5]);

    _mm256_storeu_si256((__m256i*)(dest + (i * bytesoftype) + (6 * jump)), ymm1[3]);

    _mm256_storeu_si256((__m256i*)(dest + (i * bytesoftype) + (7 * jump)), ymm1[7]);

    _mm256_storeu_si256((__m256i*)(dest + (i * bytesoftype) + (8 * jump)), ymm1[8]);

    _mm256_storeu_si256((__m256i*)(dest + (i * bytesoftype) + (9 * jump)), ymm1[12]);

    _mm256_storeu_si256((__m256i*)(dest + (i * bytesoftype) + (10 * jump)), ymm1[10]);

    _mm256_storeu_si256((__m256i*)(dest + (i * bytesoftype) + (11 * jump)), ymm1[14]);

    _mm256_storeu_si256((__m256i*)(dest + (i * bytesoftype) + (12 * jump)), ymm1[9]);

    _mm256_storeu_si256((__m256i*)(dest + (i * bytesoftype) + (13 * jump)), ymm1[13]);

    _mm256_storeu_si256((__m256i*)(dest + (i * bytesoftype) + (14 * jump)), ymm1[11]);

    _mm256_maskstore_epi32((int *)(dest + (i * bytesoftype) + (15 * jump)), store_mask, ymm1[15]);

  }

}

/* Routine optimized for unshuffling a buffer for a type size larger than 16 bytes. */

static void

unshuffle16_tiled_avx2(const uint8_t *dest, const uint8_t* const src,

                       const int32_t vectorizable_elements, const int32_t total_elements, const int32_t bytesoftype) {

  int32_t i;

  int j;

  __m256i ymm0[16], ymm1[16];

  const lldiv_t vecs_per_el = lldiv(bytesoftype, sizeof(__m128i));

  const int32_t vecs_rem = (int32_t)vecs_per_el.rem;

  /* The unshuffle loops are inverted (compared to shuffle_tiled16_avx2)

     to optimize cache utilization. */

  int32_t offset_into_type;

  for (offset_into_type = 0; offset_into_type < bytesoftype;

       offset_into_type += (offset_into_type == 0 && vecs_rem > 0 ? vecs_rem : (int32_t)sizeof(__m128i))) {

    for (i = 0; i < vectorizable_elements; i += sizeof(__m256i)) {

      /* Load the first 16 bytes of 32 adjacent elements (512 bytes) into 16 YMM registers */

      const uint8_t* const src_for_ith_element = src + i;

      for (j = 0; j < 16; j++) {

        ymm0[j] = _mm256_loadu_si256((__m256i*)(src_for_ith_element + (total_elements * (offset_into_type + j))));

      }

      /* Shuffle bytes */

      for (j = 0; j < 8; j++) {

        /* Compute the low 32 bytes */

        ymm1[j] = _mm256_unpacklo_epi8(ymm0[j * 2], ymm0[j * 2 + 1]);

        /* Compute the hi 32 bytes */

        ymm1[8 + j] = _mm256_unpackhi_epi8(ymm0[j * 2], ymm0[j * 2 + 1]);

      }

      /* Shuffle 2-byte words */

      for (j = 0; j < 8; j++) {

        /* Compute the low 32 bytes */

        ymm0[j] = _mm256_unpacklo_epi16(ymm1[j * 2], ymm1[j * 2 + 1]);

        /* Compute the hi 32 bytes */

        ymm0[8 + j] = _mm256_unpackhi_epi16(ymm1[j * 2], ymm1[j * 2 + 1]);

      }

      /* Shuffle 4-byte dwords */

      for (j = 0; j < 8; j++) {

        /* Compute the low 32 bytes */

        ymm1[j] = _mm256_unpacklo_epi32(ymm0[j * 2], ymm0[j * 2 + 1]);

        /* Compute the hi 32 bytes */

        ymm1[8 + j] = _mm256_unpackhi_epi32(ymm0[j * 2], ymm0[j * 2 + 1]);

      }

      /* Shuffle 8-byte qwords */

      for (j = 0; j < 8; j++) {

        /* Compute the low 32 bytes */

        ymm0[j] = _mm256_unpacklo_epi64(ymm1[j * 2], ymm1[j * 2 + 1]);

        /* Compute the hi 32 bytes */

        ymm0[8 + j] = _mm256_unpackhi_epi64(ymm1[j * 2], ymm1[j * 2 + 1]);

      }

      for (j = 0; j < 8; j++) {

        ymm1[j] = _mm256_permute2x128_si256(ymm0[j], ymm0[j + 8], 0x20);

        ymm1[j + 8] = _mm256_permute2x128_si256(ymm0[j], ymm0[j + 8], 0x31);

      }

      /* Store the result vectors in proper order */

      const uint8_t* const dest_with_offset = dest + offset_into_type;

      _mm256_storeu2_m128i(

          (__m128i*)(dest_with_offset + (i + 0x01) * bytesoftype),

          (__m128i*)(dest_with_offset + (i + 0x00) * bytesoftype), ymm1[0]);

      _mm256_storeu2_m128i(

          (__m128i*)(dest_with_offset + (i + 0x03) * bytesoftype),

          (__m128i*)(dest_with_offset + (i + 0x02) * bytesoftype), ymm1[4]);

      _mm256_storeu2_m128i(

          (__m128i*)(dest_with_offset + (i + 0x05) * bytesoftype),

          (__m128i*)(dest_with_offset + (i + 0x04) * bytesoftype), ymm1[2]);

      _mm256_storeu2_m128i(

          (__m128i*)(dest_with_offset + (i + 0x07) * bytesoftype),

          (__m128i*)(dest_with_offset + (i + 0x06) * bytesoftype), ymm1[6]);

      _mm256_storeu2_m128i(

          (__m128i*)(dest_with_offset + (i + 0x09) * bytesoftype),

          (__m128i*)(dest_with_offset + (i + 0x08) * bytesoftype), ymm1[1]);

      _mm256_storeu2_m128i(

          (__m128i*)(dest_with_offset + (i + 0x0b) * bytesoftype),

          (__m128i*)(dest_with_offset + (i + 0x0a) * bytesoftype), ymm1[5]);

      _mm256_storeu2_m128i(

          (__m128i*)(dest_with_offset + (i + 0x0d) * bytesoftype),

          (__m128i*)(dest_with_offset + (i + 0x0c) * bytesoftype), ymm1[3]);

      _mm256_storeu2_m128i(

          (__m128i*)(dest_with_offset + (i + 0x0f) * bytesoftype),

          (__m128i*)(dest_with_offset + (i + 0x0e) * bytesoftype), ymm1[7]);

      _mm256_storeu2_m128i(

          (__m128i*)(dest_with_offset + (i + 0x11) * bytesoftype),

          (__m128i*)(dest_with_offset + (i + 0x10) * bytesoftype), ymm1[8]);

      _mm256_storeu2_m128i(

          (__m128i*)(dest_with_offset + (i + 0x13) * bytesoftype),

          (__m128i*)(dest_with_offset + (i + 0x12) * bytesoftype), ymm1[12]);

      _mm256_storeu2_m128i(

          (__m128i*)(dest_with_offset + (i + 0x15) * bytesoftype),

          (__m128i*)(dest_with_offset + (i + 0x14) * bytesoftype), ymm1[10]);

      _mm256_storeu2_m128i(

          (__m128i*)(dest_with_offset + (i + 0x17) * bytesoftype),

          (__m128i*)(dest_with_offset + (i + 0x16) * bytesoftype), ymm1[14]);

      _mm256_storeu2_m128i(

          (__m128i*)(dest_with_offset + (i + 0x19) * bytesoftype),

          (__m128i*)(dest_with_offset + (i + 0x18) * bytesoftype), ymm1[9]);

      _mm256_storeu2_m128i(

          (__m128i*)(dest_with_offset + (i + 0x1b) * bytesoftype),

          (__m128i*)(dest_with_offset + (i + 0x1a) * bytesoftype), ymm1[13]);

      _mm256_storeu2_m128i(

          (__m128i*)(dest_with_offset + (i + 0x1d) * bytesoftype),

          (__m128i*)(dest_with_offset + (i + 0x1c) * bytesoftype), ymm1[11]);

      _mm256_storeu2_m128i(

          (__m128i*)(dest_with_offset + (i + 0x1f) * bytesoftype),

          (__m128i*)(dest_with_offset + (i + 0x1e) * bytesoftype), ymm1[15]);

    }

  }

}

/* Shuffle a block.  This can never fail. */

void

shuffle_avx2(const int32_t bytesoftype, const int32_t blocksize,

             const uint8_t *_src, uint8_t *_dest) {

  const int32_t vectorized_chunk_size = bytesoftype * (int32_t)sizeof(__m256i);

  /* If the block size is too small to be vectorized,

     use the generic implementation. */

  if (blocksize < vectorized_chunk_size) {

    shuffle_generic(bytesoftype, blocksize, _src, _dest);

    return;

  }

  /* If the blocksize is not a multiple of both the typesize and

     the vector size, round the blocksize down to the next value

     which is a multiple of both. The vectorized shuffle can be

     used for that portion of the data, and the naive implementation

     can be used for the remaining portion. */

  const int32_t vectorizable_bytes = blocksize - (blocksize % vectorized_chunk_size);

  const int32_t vectorizable_elements = vectorizable_bytes / bytesoftype;

  const int32_t total_elements = blocksize / bytesoftype;

  /* Optimized shuffle implementations */

  switch (bytesoftype) {

    case 2:

      shuffle2_avx2(_dest, _src, vectorizable_elements, total_elements);

      break;

    case 4:

      shuffle4_avx2(_dest, _src, vectorizable_elements, total_elements);

      break;

    case 8:

      shuffle8_avx2(_dest, _src, vectorizable_elements, total_elements);

      break;

    case 16:

      shuffle16_avx2(_dest, _src, vectorizable_elements, total_elements);

      break;

    default:

      /* For types larger than 16 bytes, use the AVX2 tiled shuffle. */

      if (bytesoftype > (int32_t)sizeof(__m128i)) {

        shuffle16_tiled_avx2(_dest, _src, vectorizable_elements, total_elements, bytesoftype);

      }

      else {

        /* Non-optimized shuffle */

        shuffle_generic(bytesoftype, blocksize, _src, _dest);

        /* The non-optimized function covers the whole buffer,

           so we're done processing here. */

        return;

      }

  }

  /* If the buffer had any bytes at the end which couldn't be handled

     by the vectorized implementations, use the non-optimized version

     to finish them up. */

  if (vectorizable_bytes < blocksize) {

    shuffle_generic_inline(bytesoftype, vectorizable_bytes, blocksize, _src, _dest);

  }

}

/* Unshuffle a block.  This can never fail. */

void

unshuffle_avx2(const int32_t bytesoftype, const int32_t blocksize,

               const uint8_t *_src, uint8_t *_dest) {

  const int32_t vectorized_chunk_size = bytesoftype * (int32_t)sizeof(__m256i);

  /* If the block size is too small to be vectorized,

     use the generic implementation. */

  if (blocksize < vectorized_chunk_size) {

    unshuffle_generic(bytesoftype, blocksize, _src, _dest);

    return;

  }

  /* If the blocksize is not a multiple of both the typesize and

     the vector size, round the blocksize down to the next value

     which is a multiple of both. The vectorized unshuffle can be

     used for that portion of the data, and the naive implementation

     can be used for the remaining portion. */

  const int32_t vectorizable_bytes = blocksize - (blocksize % vectorized_chunk_size);

  const int32_t vectorizable_elements = vectorizable_bytes / bytesoftype;

  const int32_t total_elements = blocksize / bytesoftype;

  /* Optimized unshuffle implementations */

  switch (bytesoftype) {

    case 2:

      unshuffle2_avx2(_dest, _src, vectorizable_elements, total_elements);

      break;

    case 4:

      unshuffle4_avx2(_dest, _src, vectorizable_elements, total_elements);

      break;

    case 8:

      unshuffle8_avx2(_dest, _src, vectorizable_elements, total_elements);

      break;

    case 12:

      unshuffle12_avx2(_dest, _src, vectorizable_elements, total_elements);

      break;

    case 16:

      unshuffle16_avx2(_dest, _src, vectorizable_elements, total_elements);

      break;

    default:

      /* For types larger than 16 bytes, use the AVX2 tiled unshuffle. */

      if (bytesoftype > (int32_t)sizeof(__m128i)) {

        unshuffle16_tiled_avx2(_dest, _src, vectorizable_elements, total_elements, bytesoftype);

      }

      else {

        /* Non-optimized unshuffle */

        unshuffle_generic(bytesoftype, blocksize, _src, _dest);

        /* The non-optimized function covers the whole buffer,

           so we're done processing here. */

        return;

      }

  }

  /* If the buffer had any bytes at the end which couldn't be handled

     by the vectorized implementations, use the non-optimized version

     to finish them up. */

  if (vectorizable_bytes < blocksize) {

    unshuffle_generic_inline(bytesoftype, vectorizable_bytes, blocksize, _src, _dest);

  }

}

const bool is_shuffle_avx2 = true;

#else

const bool is_shuffle_avx2 = false;

void shuffle_avx2(const int32_t bytesoftype, const int32_t blocksize,

                  const uint8_t *_src, uint8_t *_dest) {

  abort();

}

void unshuffle_avx2(const int32_t bytesoftype, const int32_t blocksize,

                    const uint8_t *_src, uint8_t *_dest) {

  abort();

}

#endif /* defined(__AVX2__) */