103 lines
2.6 KiB
C
103 lines
2.6 KiB
C
/* 16-bit signed integer dot product
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* Altivec-assisted version
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* Copyright 2004 Phil Karn
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* May be used under the terms of the GNU Lesser General Public License (LGPL)
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*/
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#include <stdlib.h>
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#include "fec.h"
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struct dotprod {
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int len; /* Number of coefficients */
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/* On an Altivec machine, these hold 8 copies of the coefficients,
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* preshifted by 0,1,..7 words to meet all possible input data
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*/
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signed short *coeffs[8];
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};
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/* Create and return a descriptor for use with the dot product function */
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void *initdp_av(signed short coeffs[], int len)
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{
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struct dotprod *dp;
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int i, j;
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if (len == 0) {
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return NULL;
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}
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dp = (struct dotprod *)calloc(1, sizeof(struct dotprod));
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dp->len = len;
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/* Make 8 copies of coefficients, one for each data alignment,
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* each aligned to 16-byte boundary
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*/
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for (i = 0; i < 8; i++) {
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dp->coeffs[i] = calloc(1 + (len + i - 1) / 8, sizeof(vector signed short));
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for (j = 0; j < len; j++) {
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dp->coeffs[i][j + i] = coeffs[j];
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}
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}
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return (void *)dp;
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}
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/* Free a dot product descriptor created earlier */
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void freedp_av(void *p)
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{
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struct dotprod *dp = (struct dotprod *)p;
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int i;
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for (i = 0; i < 8; i++)
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if (dp->coeffs[i] != NULL) {
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free(dp->coeffs[i]);
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}
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free(dp);
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}
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/* Compute a dot product given a descriptor and an input array
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* The length is taken from the descriptor
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*/
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long dotprod_av(void *p, signed short a[])
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{
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struct dotprod *dp = (struct dotprod *)p;
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int al;
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vector signed short *ar, *d;
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vector signed int sums0, sums1, sums2, sums3;
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union {
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vector signed int v;
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signed int w[4];
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} s;
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int nblocks;
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/* round ar down to beginning of 16-byte block containing 0th element of
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* input buffer. Then set d to one of 8 sets of shifted coefficients
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*/
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ar = (vector signed short *)((int)a & ~15);
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al = ((int)a & 15) / sizeof(signed short);
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d = (vector signed short *)dp->coeffs[al];
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nblocks = (dp->len + al - 1) / 8 + 1;
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/* Sum into four vectors each holding four 32-bit partial sums */
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sums3 = sums2 = sums1 = sums0 = (vector signed int)(0);
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while (nblocks >= 4) {
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sums0 = vec_msums(ar[nblocks - 1], d[nblocks - 1], sums0);
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sums1 = vec_msums(ar[nblocks - 2], d[nblocks - 2], sums1);
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sums2 = vec_msums(ar[nblocks - 3], d[nblocks - 3], sums2);
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sums3 = vec_msums(ar[nblocks - 4], d[nblocks - 4], sums3);
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nblocks -= 4;
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}
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sums0 = vec_adds(sums0, sums1);
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sums2 = vec_adds(sums2, sums3);
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sums0 = vec_adds(sums0, sums2);
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while (nblocks-- > 0) {
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sums0 = vec_msums(ar[nblocks], d[nblocks], sums0);
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}
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/* Sum 4 partial sums into final result */
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s.v = vec_sums(sums0, (vector signed int)(0));
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return s.w[3];
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}
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