/* 16-bit signed integer dot product
 * SSE2 version
 * Copyright 2004 Phil Karn
 * May be used under the terms of the GNU Lesser General Public License (LGPL)
 */
#define _XOPEN_SOURCE 600
#include <stdlib.h>
#include <memory.h>
#include "fec.h"

struct dotprod {
  int len; /* Number of coefficients */

  /* On a SSE2 machine, these hold 8 copies of the coefficients,
   * preshifted by 0,1,..7 words to meet all possible input data
   * alignments (see Intel ap559 on MMX dot products).
   */
  signed short *coeffs[8];
};

long dotprod_sse2_assist(signed short *a, signed short *b, int cnt);

/* Create and return a descriptor for use with the dot product function */
void *initdp_sse2(signed short coeffs[], int len)
{
  struct dotprod *dp;
  int i, j, blksize;

  if (len == 0) {
    return NULL;
  }

  dp = (struct dotprod *)calloc(1, sizeof(struct dotprod));
  dp->len = len;

  /* Make 8 copies of coefficients, one for each data alignment,
   * each aligned to 16-byte boundary
   */
  for (i = 0; i < 8; i++) {
    blksize = (1 + (len + i - 1) / 8) * 8 * sizeof(signed short);
    posix_memalign((void **)&dp->coeffs[i], 16, blksize);
    memset(dp->coeffs[i], 0, blksize);
    for (j = 0; j < len; j++) {
      dp->coeffs[i][j + i] = coeffs[j];
    }
  }
  return (void *)dp;
}


/* Free a dot product descriptor created earlier */
void freedp_sse2(void *p)
{
  struct dotprod *dp = (struct dotprod *)p;
  int i;

  for (i = 0; i < 8; i++)
    if (dp->coeffs[i] != NULL) {
      free(dp->coeffs[i]);
    }
  free(dp);
}

/* Compute a dot product given a descriptor and an input array
 * The length is taken from the descriptor
 */
long dotprod_sse2(void *p, signed short a[])
{
  struct dotprod *dp = (struct dotprod *)p;
  int al;
  signed short *ar;

  ar = (signed short *)((int)a & ~15);
  al = a - ar;

  /* Call assembler routine to do the work, passing number of 8-word blocks */
  return dotprod_sse2_assist(ar, dp->coeffs[al], (dp->len + al - 1) / 8 + 1);
}