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

  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-sse2.h"

#include "shuffle-generic.h"

#include <stdlib.h>

/* Make sure SSE2 is available for the compilation target and compiler. */

#if defined(__SSE2__)

#include <emmintrin.h>

#include <stdint.h>

/* The next is useful for debugging purposes */

#if 0

#include <stdio.h>

#include <string.h>

static void printxmm(__m128i xmm0)

{

  uint8_t buf[16];

  ((__m128i *)buf)[0] = xmm0;

  printf("%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]);

}

#endif

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

static void

shuffle2_sse2(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;

  uint8_t* dest_for_jth_element;

  __m128i xmm0[2], xmm1[2];

  for (j = 0; j < vectorizable_elements; j += sizeof(__m128i)) {

    /* Fetch 16 elements (32 bytes) then transpose bytes, words and double words. */

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

      xmm0[k] = _mm_loadu_si128((__m128i*)(src + (j * bytesoftype) + (k * sizeof(__m128i))));

      xmm0[k] = _mm_shufflelo_epi16(xmm0[k], 0xd8);

      xmm0[k] = _mm_shufflehi_epi16(xmm0[k], 0xd8);

      xmm0[k] = _mm_shuffle_epi32(xmm0[k], 0xd8);

      xmm1[k] = _mm_shuffle_epi32(xmm0[k], 0x4e);

      xmm0[k] = _mm_unpacklo_epi8(xmm0[k], xmm1[k]);

      xmm0[k] = _mm_shuffle_epi32(xmm0[k], 0xd8);

      xmm1[k] = _mm_shuffle_epi32(xmm0[k], 0x4e);

      xmm0[k] = _mm_unpacklo_epi16(xmm0[k], xmm1[k]);

      xmm0[k] = _mm_shuffle_epi32(xmm0[k], 0xd8);

    }

    /* Transpose quad words */

    for (k = 0; k < 1; k++) {

      xmm1[k * 2] = _mm_unpacklo_epi64(xmm0[k], xmm0[k + 1]);

      xmm1[k * 2 + 1] = _mm_unpackhi_epi64(xmm0[k], xmm0[k + 1]);

    }

    /* Store the result vectors */

    dest_for_jth_element = dest + j;

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

      _mm_storeu_si128((__m128i*)(dest_for_jth_element + (k * total_elements)), xmm1[k]);

    }

  }

}

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

static void

shuffle4_sse2(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;

  uint8_t* dest_for_ith_element;

  __m128i xmm0[4], xmm1[4];

  for (i = 0; i < vectorizable_elements; i += sizeof(__m128i)) {

    /* Fetch 16 elements (64 bytes) then transpose bytes and words. */

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

      xmm0[j] = _mm_loadu_si128((__m128i*)(src + (i * bytesoftype) + (j * sizeof(__m128i))));

      xmm1[j] = _mm_shuffle_epi32(xmm0[j], 0xd8);

      xmm0[j] = _mm_shuffle_epi32(xmm0[j], 0x8d);

      xmm0[j] = _mm_unpacklo_epi8(xmm1[j], xmm0[j]);

      xmm1[j] = _mm_shuffle_epi32(xmm0[j], 0x04e);

      xmm0[j] = _mm_unpacklo_epi16(xmm0[j], xmm1[j]);

    }

    /* Transpose double words */

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

      xmm1[j * 2] = _mm_unpacklo_epi32(xmm0[j * 2], xmm0[j * 2 + 1]);

      xmm1[j * 2 + 1] = _mm_unpackhi_epi32(xmm0[j * 2], xmm0[j * 2 + 1]);

    }

    /* Transpose quad words */

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

      xmm0[j * 2] = _mm_unpacklo_epi64(xmm1[j], xmm1[j + 2]);

      xmm0[j * 2 + 1] = _mm_unpackhi_epi64(xmm1[j], xmm1[j + 2]);

    }

    /* Store the result vectors */

    dest_for_ith_element = dest + i;

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

      _mm_storeu_si128((__m128i*)(dest_for_ith_element + (j * total_elements)), xmm0[j]);

    }

  }

}

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

static void

shuffle8_sse2(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;

  uint8_t* dest_for_jth_element;

  __m128i xmm0[8], xmm1[8];

  for (j = 0; j < vectorizable_elements; j += sizeof(__m128i)) {

    /* Fetch 16 elements (128 bytes) then transpose bytes. */

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

      xmm0[k] = _mm_loadu_si128((__m128i*)(src + (j * bytesoftype) + (k * sizeof(__m128i))));

      xmm1[k] = _mm_shuffle_epi32(xmm0[k], 0x4e);

      xmm1[k] = _mm_unpacklo_epi8(xmm0[k], xmm1[k]);

    }

    /* Transpose words */

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

      xmm0[k * 2] = _mm_unpacklo_epi16(xmm1[l], xmm1[l + 1]);

      xmm0[k * 2 + 1] = _mm_unpackhi_epi16(xmm1[l], xmm1[l + 1]);

    }

    /* Transpose double words */

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

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

      xmm1[k * 2] = _mm_unpacklo_epi32(xmm0[l], xmm0[l + 2]);

      xmm1[k * 2 + 1] = _mm_unpackhi_epi32(xmm0[l], xmm0[l + 2]);

    }

    /* Transpose quad words */

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

      xmm0[k * 2] = _mm_unpacklo_epi64(xmm1[k], xmm1[k + 4]);

      xmm0[k * 2 + 1] = _mm_unpackhi_epi64(xmm1[k], xmm1[k + 4]);

    }

    /* Store the result vectors */

    dest_for_jth_element = dest + j;

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

      _mm_storeu_si128((__m128i*)(dest_for_jth_element + (k * total_elements)), xmm0[k]);

    }

  }

}

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

static void

shuffle16_sse2(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;

  uint8_t* dest_for_jth_element;

  __m128i xmm0[16], xmm1[16];

  for (j = 0; j < vectorizable_elements; j += sizeof(__m128i)) {

    /* Fetch 16 elements (256 bytes). */

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

      xmm0[k] = _mm_loadu_si128((__m128i*)(src + (j * bytesoftype) + (k * sizeof(__m128i))));

    }

    /* Transpose bytes */

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

      xmm1[k * 2] = _mm_unpacklo_epi8(xmm0[l], xmm0[l + 1]);

      xmm1[k * 2 + 1] = _mm_unpackhi_epi8(xmm0[l], xmm0[l + 1]);

    }

    /* Transpose words */

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

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

      xmm0[k * 2] = _mm_unpacklo_epi16(xmm1[l], xmm1[l + 2]);

      xmm0[k * 2 + 1] = _mm_unpackhi_epi16(xmm1[l], xmm1[l + 2]);

    }

    /* Transpose double words */

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

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

      xmm1[k * 2] = _mm_unpacklo_epi32(xmm0[l], xmm0[l + 4]);

      xmm1[k * 2 + 1] = _mm_unpackhi_epi32(xmm0[l], xmm0[l + 4]);

    }

    /* Transpose quad words */

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

      xmm0[k * 2] = _mm_unpacklo_epi64(xmm1[k], xmm1[k + 8]);

      xmm0[k * 2 + 1] = _mm_unpackhi_epi64(xmm1[k], xmm1[k + 8]);

    }

    /* Store the result vectors */

    dest_for_jth_element = dest + j;

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

      _mm_storeu_si128((__m128i*)(dest_for_jth_element + (k * total_elements)), xmm0[k]);

    }

  }

}

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

static void

shuffle16_tiled_sse2(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;

  const int32_t vecs_per_el_rem = bytesoftype % (int32_t)sizeof(__m128i);

  int k, l;

  uint8_t* dest_for_jth_element;

  __m128i xmm0[16], xmm1[16];

  for (j = 0; j < vectorizable_elements; j += sizeof(__m128i)) {

    /* 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_per_el_rem > 0 ? vecs_per_el_rem : (int32_t)sizeof(__m128i))) {

      /* Fetch elements in groups of 256 bytes */

      const uint8_t* const src_with_offset = src + offset_into_type;

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

        xmm0[k] = _mm_loadu_si128((__m128i*)(src_with_offset + (j + k) * bytesoftype));

      }

      /* Transpose bytes */

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

        xmm1[k * 2] = _mm_unpacklo_epi8(xmm0[l], xmm0[l + 1]);

        xmm1[k * 2 + 1] = _mm_unpackhi_epi8(xmm0[l], xmm0[l + 1]);

      }

      /* Transpose words */

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

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

        xmm0[k * 2] = _mm_unpacklo_epi16(xmm1[l], xmm1[l + 2]);

        xmm0[k * 2 + 1] = _mm_unpackhi_epi16(xmm1[l], xmm1[l + 2]);

      }

      /* Transpose double words */

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

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

        xmm1[k * 2] = _mm_unpacklo_epi32(xmm0[l], xmm0[l + 4]);

        xmm1[k * 2 + 1] = _mm_unpackhi_epi32(xmm0[l], xmm0[l + 4]);

      }

      /* Transpose quad words */

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

        xmm0[k * 2] = _mm_unpacklo_epi64(xmm1[k], xmm1[k + 8]);

        xmm0[k * 2 + 1] = _mm_unpackhi_epi64(xmm1[k], xmm1[k + 8]);

      }

      /* Store the result vectors */

      dest_for_jth_element = dest + j;

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

        _mm_storeu_si128((__m128i*)(dest_for_jth_element + (total_elements * (offset_into_type + k))), xmm0[k]);

      }

    }

  }

}

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

static void

unshuffle2_sse2(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;

  __m128i xmm0[2], xmm1[2];

  for (i = 0; i < vectorizable_elements; i += sizeof(__m128i)) {

    /* Load 16 elements (32 bytes) into 2 XMM registers. */

    const uint8_t* const src_for_ith_element = src + i;

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

      xmm0[j] = _mm_loadu_si128((__m128i*)(src_for_ith_element + (j * total_elements)));

    }

    /* Shuffle bytes */

    /* Compute the low 32 bytes */

    xmm1[0] = _mm_unpacklo_epi8(xmm0[0], xmm0[1]);

    /* Compute the hi 32 bytes */

    xmm1[1] = _mm_unpackhi_epi8(xmm0[0], xmm0[1]);

    /* Store the result vectors in proper order */

    _mm_storeu_si128((__m128i*)(dest + (i * bytesoftype) + (0 * sizeof(__m128i))), xmm1[0]);

    _mm_storeu_si128((__m128i*)(dest + (i * bytesoftype) + (1 * sizeof(__m128i))), xmm1[1]);

  }

}

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

static void

unshuffle4_sse2(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;

  __m128i xmm0[4], xmm1[4];

  for (i = 0; i < vectorizable_elements; i += sizeof(__m128i)) {

    /* Load 16 elements (64 bytes) into 4 XMM registers. */

    const uint8_t* const src_for_ith_element = src + i;

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

      xmm0[j] = _mm_loadu_si128((__m128i*)(src_for_ith_element + (j * total_elements)));

    }

    /* Shuffle bytes */

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

      /* Compute the low 32 bytes */

      xmm1[j] = _mm_unpacklo_epi8(xmm0[j * 2], xmm0[j * 2 + 1]);

      /* Compute the hi 32 bytes */

      xmm1[2 + j] = _mm_unpackhi_epi8(xmm0[j * 2], xmm0[j * 2 + 1]);

    }

    /* Shuffle 2-byte words */

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

      /* Compute the low 32 bytes */

      xmm0[j] = _mm_unpacklo_epi16(xmm1[j * 2], xmm1[j * 2 + 1]);

      /* Compute the hi 32 bytes */

      xmm0[2 + j] = _mm_unpackhi_epi16(xmm1[j * 2], xmm1[j * 2 + 1]);

    }

    /* Store the result vectors in proper order */

    _mm_storeu_si128((__m128i*)(dest + (i * bytesoftype) + (0 * sizeof(__m128i))), xmm0[0]);

    _mm_storeu_si128((__m128i*)(dest + (i * bytesoftype) + (1 * sizeof(__m128i))), xmm0[2]);

    _mm_storeu_si128((__m128i*)(dest + (i * bytesoftype) + (2 * sizeof(__m128i))), xmm0[1]);

    _mm_storeu_si128((__m128i*)(dest + (i * bytesoftype) + (3 * sizeof(__m128i))), xmm0[3]);

  }

}

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

static void

unshuffle8_sse2(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;

  __m128i xmm0[8], xmm1[8];

  for (i = 0; i < vectorizable_elements; i += sizeof(__m128i)) {

    /* Load 16 elements (128 bytes) into 8 XMM registers. */

    const uint8_t* const src_for_ith_element = src + i;

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

      xmm0[j] = _mm_loadu_si128((__m128i*)(src_for_ith_element + (j * total_elements)));

    }

    /* Shuffle bytes */

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

      /* Compute the low 32 bytes */

      xmm1[j] = _mm_unpacklo_epi8(xmm0[j * 2], xmm0[j * 2 + 1]);

      /* Compute the hi 32 bytes */

      xmm1[4 + j] = _mm_unpackhi_epi8(xmm0[j * 2], xmm0[j * 2 + 1]);

    }

    /* Shuffle 2-byte words */

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

      /* Compute the low 32 bytes */

      xmm0[j] = _mm_unpacklo_epi16(xmm1[j * 2], xmm1[j * 2 + 1]);

      /* Compute the hi 32 bytes */

      xmm0[4 + j] = _mm_unpackhi_epi16(xmm1[j * 2], xmm1[j * 2 + 1]);

    }

    /* Shuffle 4-byte dwords */

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

      /* Compute the low 32 bytes */

      xmm1[j] = _mm_unpacklo_epi32(xmm0[j * 2], xmm0[j * 2 + 1]);

      /* Compute the hi 32 bytes */

      xmm1[4 + j] = _mm_unpackhi_epi32(xmm0[j * 2], xmm0[j * 2 + 1]);

    }

    /* Store the result vectors in proper order */

    _mm_storeu_si128((__m128i*)(dest + (i * bytesoftype) + (0 * sizeof(__m128i))), xmm1[0]);

    _mm_storeu_si128((__m128i*)(dest + (i * bytesoftype) + (1 * sizeof(__m128i))), xmm1[4]);

    _mm_storeu_si128((__m128i*)(dest + (i * bytesoftype) + (2 * sizeof(__m128i))), xmm1[2]);

    _mm_storeu_si128((__m128i*)(dest + (i * bytesoftype) + (3 * sizeof(__m128i))), xmm1[6]);

    _mm_storeu_si128((__m128i*)(dest + (i * bytesoftype) + (4 * sizeof(__m128i))), xmm1[1]);

    _mm_storeu_si128((__m128i*)(dest + (i * bytesoftype) + (5 * sizeof(__m128i))), xmm1[5]);

    _mm_storeu_si128((__m128i*)(dest + (i * bytesoftype) + (6 * sizeof(__m128i))), xmm1[3]);

    _mm_storeu_si128((__m128i*)(dest + (i * bytesoftype) + (7 * sizeof(__m128i))), xmm1[7]);

  }

}

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

static void

unshuffle16_sse2(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;

  __m128i xmm1[16], xmm2[16];

  for (i = 0; i < vectorizable_elements; i += sizeof(__m128i)) {

    /* Load 16 elements (256 bytes) into 16 XMM registers. */

    const uint8_t* const src_for_ith_element = src + i;

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

      xmm1[j] = _mm_loadu_si128((__m128i*)(src_for_ith_element + (j * total_elements)));

    }

    /* Shuffle bytes */

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

      /* Compute the low 32 bytes */

      xmm2[j] = _mm_unpacklo_epi8(xmm1[j * 2], xmm1[j * 2 + 1]);

      /* Compute the hi 32 bytes */

      xmm2[8 + j] = _mm_unpackhi_epi8(xmm1[j * 2], xmm1[j * 2 + 1]);

    }

    /* Shuffle 2-byte words */

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

      /* Compute the low 32 bytes */

      xmm1[j] = _mm_unpacklo_epi16(xmm2[j * 2], xmm2[j * 2 + 1]);

      /* Compute the hi 32 bytes */

      xmm1[8 + j] = _mm_unpackhi_epi16(xmm2[j * 2], xmm2[j * 2 + 1]);

    }

    /* Shuffle 4-byte dwords */

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

      /* Compute the low 32 bytes */

      xmm2[j] = _mm_unpacklo_epi32(xmm1[j * 2], xmm1[j * 2 + 1]);

      /* Compute the hi 32 bytes */

      xmm2[8 + j] = _mm_unpackhi_epi32(xmm1[j * 2], xmm1[j * 2 + 1]);

    }

    /* Shuffle 8-byte qwords */

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

      /* Compute the low 32 bytes */

      xmm1[j] = _mm_unpacklo_epi64(xmm2[j * 2], xmm2[j * 2 + 1]);

      /* Compute the hi 32 bytes */

      xmm1[8 + j] = _mm_unpackhi_epi64(xmm2[j * 2], xmm2[j * 2 + 1]);

    }

    /* Store the result vectors in proper order */

    _mm_storeu_si128((__m128i*)(dest + (i * bytesoftype) + (0 * sizeof(__m128i))), xmm1[0]);

    _mm_storeu_si128((__m128i*)(dest + (i * bytesoftype) + (1 * sizeof(__m128i))), xmm1[8]);

    _mm_storeu_si128((__m128i*)(dest + (i * bytesoftype) + (2 * sizeof(__m128i))), xmm1[4]);

    _mm_storeu_si128((__m128i*)(dest + (i * bytesoftype) + (3 * sizeof(__m128i))), xmm1[12]);

    _mm_storeu_si128((__m128i*)(dest + (i * bytesoftype) + (4 * sizeof(__m128i))), xmm1[2]);

    _mm_storeu_si128((__m128i*)(dest + (i * bytesoftype) + (5 * sizeof(__m128i))), xmm1[10]);

    _mm_storeu_si128((__m128i*)(dest + (i * bytesoftype) + (6 * sizeof(__m128i))), xmm1[6]);

    _mm_storeu_si128((__m128i*)(dest + (i * bytesoftype) + (7 * sizeof(__m128i))), xmm1[14]);

    _mm_storeu_si128((__m128i*)(dest + (i * bytesoftype) + (8 * sizeof(__m128i))), xmm1[1]);

    _mm_storeu_si128((__m128i*)(dest + (i * bytesoftype) + (9 * sizeof(__m128i))), xmm1[9]);

    _mm_storeu_si128((__m128i*)(dest + (i * bytesoftype) + (10 * sizeof(__m128i))), xmm1[5]);

    _mm_storeu_si128((__m128i*)(dest + (i * bytesoftype) + (11 * sizeof(__m128i))), xmm1[13]);

    _mm_storeu_si128((__m128i*)(dest + (i * bytesoftype) + (12 * sizeof(__m128i))), xmm1[3]);

    _mm_storeu_si128((__m128i*)(dest + (i * bytesoftype) + (13 * sizeof(__m128i))), xmm1[11]);

    _mm_storeu_si128((__m128i*)(dest + (i * bytesoftype) + (14 * sizeof(__m128i))), xmm1[7]);

    _mm_storeu_si128((__m128i*)(dest + (i * bytesoftype) + (15 * sizeof(__m128i))), xmm1[15]);

  }

}

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

static void

unshuffle16_tiled_sse2(uint8_t* const dest, const uint8_t* const orig,

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

  int32_t i;

  const int32_t vecs_per_el_rem = bytesoftype % (int32_t)sizeof(__m128i);

  int j;

  uint8_t* dest_with_offset;

  __m128i xmm1[16], xmm2[16];

  /* The unshuffle loops are inverted (compared to shuffle_tiled16_sse2)

     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_per_el_rem > 0 ? vecs_per_el_rem : (int32_t)sizeof(__m128i))) {

    for (i = 0; i < vectorizable_elements; i += sizeof(__m128i)) {

      /* Load the first 128 bytes in 16 XMM registers */

      const uint8_t* const src_for_ith_element = orig + i;

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

        xmm1[j] = _mm_loadu_si128((__m128i*)(src_for_ith_element + (total_elements * (offset_into_type + j))));

      }

      /* Shuffle bytes */

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

        /* Compute the low 32 bytes */

        xmm2[j] = _mm_unpacklo_epi8(xmm1[j * 2], xmm1[j * 2 + 1]);

        /* Compute the hi 32 bytes */

        xmm2[8 + j] = _mm_unpackhi_epi8(xmm1[j * 2], xmm1[j * 2 + 1]);

      }

      /* Shuffle 2-byte words */

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

        /* Compute the low 32 bytes */

        xmm1[j] = _mm_unpacklo_epi16(xmm2[j * 2], xmm2[j * 2 + 1]);

        /* Compute the hi 32 bytes */

        xmm1[8 + j] = _mm_unpackhi_epi16(xmm2[j * 2], xmm2[j * 2 + 1]);

      }

      /* Shuffle 4-byte dwords */

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

        /* Compute the low 32 bytes */

        xmm2[j] = _mm_unpacklo_epi32(xmm1[j * 2], xmm1[j * 2 + 1]);

        /* Compute the hi 32 bytes */

        xmm2[8 + j] = _mm_unpackhi_epi32(xmm1[j * 2], xmm1[j * 2 + 1]);

      }

      /* Shuffle 8-byte qwords */

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

        /* Compute the low 32 bytes */

        xmm1[j] = _mm_unpacklo_epi64(xmm2[j * 2], xmm2[j * 2 + 1]);

        /* Compute the hi 32 bytes */

        xmm1[8 + j] = _mm_unpackhi_epi64(xmm2[j * 2], xmm2[j * 2 + 1]);

      }

      /* Store the result vectors in proper order */

      dest_with_offset = dest + offset_into_type;

      _mm_storeu_si128((__m128i*)(dest_with_offset + (i + 0) * bytesoftype), xmm1[0]);

      _mm_storeu_si128((__m128i*)(dest_with_offset + (i + 1) * bytesoftype), xmm1[8]);

      _mm_storeu_si128((__m128i*)(dest_with_offset + (i + 2) * bytesoftype), xmm1[4]);

      _mm_storeu_si128((__m128i*)(dest_with_offset + (i + 3) * bytesoftype), xmm1[12]);

      _mm_storeu_si128((__m128i*)(dest_with_offset + (i + 4) * bytesoftype), xmm1[2]);

      _mm_storeu_si128((__m128i*)(dest_with_offset + (i + 5) * bytesoftype), xmm1[10]);

      _mm_storeu_si128((__m128i*)(dest_with_offset + (i + 6) * bytesoftype), xmm1[6]);

      _mm_storeu_si128((__m128i*)(dest_with_offset + (i + 7) * bytesoftype), xmm1[14]);

      _mm_storeu_si128((__m128i*)(dest_with_offset + (i + 8) * bytesoftype), xmm1[1]);

      _mm_storeu_si128((__m128i*)(dest_with_offset + (i + 9) * bytesoftype), xmm1[9]);

      _mm_storeu_si128((__m128i*)(dest_with_offset + (i + 10) * bytesoftype), xmm1[5]);

      _mm_storeu_si128((__m128i*)(dest_with_offset + (i + 11) * bytesoftype), xmm1[13]);

      _mm_storeu_si128((__m128i*)(dest_with_offset + (i + 12) * bytesoftype), xmm1[3]);

      _mm_storeu_si128((__m128i*)(dest_with_offset + (i + 13) * bytesoftype), xmm1[11]);

      _mm_storeu_si128((__m128i*)(dest_with_offset + (i + 14) * bytesoftype), xmm1[7]);

      _mm_storeu_si128((__m128i*)(dest_with_offset + (i + 15) * bytesoftype), xmm1[15]);

    }

  }

}

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

void

shuffle_sse2(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(__m128i);

  /* 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;

  /* 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;

  }

  /* Optimized shuffle implementations */

  switch (bytesoftype) {

    case 2:

      shuffle2_sse2(_dest, _src, vectorizable_elements, total_elements);

      break;

    case 4:

      shuffle4_sse2(_dest, _src, vectorizable_elements, total_elements);

      break;

    case 8:

      shuffle8_sse2(_dest, _src, vectorizable_elements, total_elements);

      break;

    case 16:

      shuffle16_sse2(_dest, _src, vectorizable_elements, total_elements);

      break;

    default:

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

        shuffle16_tiled_sse2(_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_sse2(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(__m128i);

  /* 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;

  /* 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;

  }

  /* Optimized unshuffle implementations */

  switch (bytesoftype) {

    case 2:

      unshuffle2_sse2(_dest, _src, vectorizable_elements, total_elements);

      break;

    case 4:

      unshuffle4_sse2(_dest, _src, vectorizable_elements, total_elements);

      break;

    case 8:

      unshuffle8_sse2(_dest, _src, vectorizable_elements, total_elements);

      break;

    case 16:

      unshuffle16_sse2(_dest, _src, vectorizable_elements, total_elements);

      break;

    default:

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

        unshuffle16_tiled_sse2(_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_sse2 = true;

#else /* defined(__SSE2__) */

const bool is_shuffle_sse2 = false;

void shuffle_sse2(const int32_t bytesoftype, const int32_t blocksize,

                  const uint8_t *_src, uint8_t *_dest) {

  abort();

}

void unshuffle_sse2(const int32_t bytesoftype, const int32_t blocksize,

                    const uint8_t *_src, uint8_t *_dest) {

  abort();

}

#endif /* defined(__SSE2__) */