blob: 1f70471abe583253be7dfe04c7b6879c393a16ed [file] [log] [blame]
 /* 16-bit signed integer dot product * Altivec-assisted version * Copyright 2004 Phil Karn * May be used under the terms of the GNU Lesser General Public License (LGPL) */ #include #include "fec.h" struct dotprod { int len; /* Number of coefficients */ /* On an Altivec machine, these hold 8 copies of the coefficients, * preshifted by 0,1,..7 words to meet all possible input data */ signed short *coeffs; }; /* Create and return a descriptor for use with the dot product function */ void *initdp_av(signed short coeffs[],int len){ struct dotprod *dp; int i,j; 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++){ dp->coeffs[i] = calloc(1+(len+i-1)/8,sizeof(vector signed short)); for(j=0;jcoeffs[i][j+i] = coeffs[j]; } return (void *)dp; } /* Free a dot product descriptor created earlier */ void freedp_av(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_av(void *p,signed short a[]){ struct dotprod *dp = (struct dotprod *)p; int al; vector signed short *ar,*d; vector signed int sums0,sums1,sums2,sums3; union { vector signed int v; signed int w;} s; int nblocks; /* round ar down to beginning of 16-byte block containing 0th element of * input buffer. Then set d to one of 8 sets of shifted coefficients */ ar = (vector signed short *)((int)a & ~15); al = ((int)a & 15)/sizeof(signed short); d = (vector signed short *)dp->coeffs[al]; nblocks = (dp->len+al-1)/8+1; /* Sum into four vectors each holding four 32-bit partial sums */ sums3 = sums2 = sums1 = sums0 = (vector signed int)(0); while(nblocks >= 4){ sums0 = vec_msums(ar[nblocks-1],d[nblocks-1],sums0); sums1 = vec_msums(ar[nblocks-2],d[nblocks-2],sums1); sums2 = vec_msums(ar[nblocks-3],d[nblocks-3],sums2); sums3 = vec_msums(ar[nblocks-4],d[nblocks-4],sums3); nblocks -= 4; } sums0 = vec_adds(sums0,sums1); sums2 = vec_adds(sums2,sums3); sums0 = vec_adds(sums0,sums2); while(nblocks-- > 0){ sums0 = vec_msums(ar[nblocks],d[nblocks],sums0); } /* Sum 4 partial sums into final result */ s.v = vec_sums(sums0,(vector signed int)(0)); return s.w; }