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93 lines
2.5 KiB
93 lines
2.5 KiB
/* 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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