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94 lines
2.5 KiB
94 lines
2.5 KiB
4 months ago
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/* 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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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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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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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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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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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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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 { vector signed int v; signed int w[4];} 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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