Bill Yi | 4e213d5 | 2015-06-23 13:53:11 -0700 | [diff] [blame] | 1 | /* 16-bit signed integer dot product |
| 2 | * Altivec-assisted version |
| 3 | * Copyright 2004 Phil Karn |
| 4 | * May be used under the terms of the GNU Lesser General Public License (LGPL) |
| 5 | */ |
| 6 | #include <stdlib.h> |
| 7 | #include "fec.h" |
| 8 | |
| 9 | struct dotprod { |
| 10 | int len; /* Number of coefficients */ |
| 11 | |
| 12 | /* On an Altivec machine, these hold 8 copies of the coefficients, |
| 13 | * preshifted by 0,1,..7 words to meet all possible input data |
| 14 | */ |
| 15 | signed short *coeffs[8]; |
| 16 | }; |
| 17 | |
| 18 | /* Create and return a descriptor for use with the dot product function */ |
| 19 | void *initdp_av(signed short coeffs[],int len){ |
| 20 | struct dotprod *dp; |
| 21 | int i,j; |
| 22 | |
| 23 | if(len == 0) |
| 24 | return NULL; |
| 25 | |
| 26 | dp = (struct dotprod *)calloc(1,sizeof(struct dotprod)); |
| 27 | dp->len = len; |
| 28 | |
| 29 | /* Make 8 copies of coefficients, one for each data alignment, |
| 30 | * each aligned to 16-byte boundary |
| 31 | */ |
| 32 | for(i=0;i<8;i++){ |
| 33 | dp->coeffs[i] = calloc(1+(len+i-1)/8,sizeof(vector signed short)); |
| 34 | for(j=0;j<len;j++) |
| 35 | dp->coeffs[i][j+i] = coeffs[j]; |
| 36 | } |
| 37 | return (void *)dp; |
| 38 | } |
| 39 | |
| 40 | |
| 41 | /* Free a dot product descriptor created earlier */ |
| 42 | void freedp_av(void *p){ |
| 43 | struct dotprod *dp = (struct dotprod *)p; |
| 44 | int i; |
| 45 | |
| 46 | for(i=0;i<8;i++) |
| 47 | if(dp->coeffs[i] != NULL) |
| 48 | free(dp->coeffs[i]); |
| 49 | free(dp); |
| 50 | } |
| 51 | |
| 52 | /* Compute a dot product given a descriptor and an input array |
| 53 | * The length is taken from the descriptor |
| 54 | */ |
| 55 | long dotprod_av(void *p,signed short a[]){ |
| 56 | struct dotprod *dp = (struct dotprod *)p; |
| 57 | int al; |
| 58 | vector signed short *ar,*d; |
| 59 | vector signed int sums0,sums1,sums2,sums3; |
| 60 | union { vector signed int v; signed int w[4];} s; |
| 61 | int nblocks; |
| 62 | |
| 63 | /* round ar down to beginning of 16-byte block containing 0th element of |
| 64 | * input buffer. Then set d to one of 8 sets of shifted coefficients |
| 65 | */ |
| 66 | ar = (vector signed short *)((int)a & ~15); |
| 67 | al = ((int)a & 15)/sizeof(signed short); |
| 68 | d = (vector signed short *)dp->coeffs[al]; |
| 69 | |
| 70 | nblocks = (dp->len+al-1)/8+1; |
| 71 | |
| 72 | /* Sum into four vectors each holding four 32-bit partial sums */ |
| 73 | sums3 = sums2 = sums1 = sums0 = (vector signed int)(0); |
| 74 | while(nblocks >= 4){ |
| 75 | sums0 = vec_msums(ar[nblocks-1],d[nblocks-1],sums0); |
| 76 | sums1 = vec_msums(ar[nblocks-2],d[nblocks-2],sums1); |
| 77 | sums2 = vec_msums(ar[nblocks-3],d[nblocks-3],sums2); |
| 78 | sums3 = vec_msums(ar[nblocks-4],d[nblocks-4],sums3); |
| 79 | nblocks -= 4; |
| 80 | } |
| 81 | sums0 = vec_adds(sums0,sums1); |
| 82 | sums2 = vec_adds(sums2,sums3); |
| 83 | sums0 = vec_adds(sums0,sums2); |
| 84 | while(nblocks-- > 0){ |
| 85 | sums0 = vec_msums(ar[nblocks],d[nblocks],sums0); |
| 86 | } |
| 87 | /* Sum 4 partial sums into final result */ |
| 88 | s.v = vec_sums(sums0,(vector signed int)(0)); |
| 89 | |
| 90 | return s.w[3]; |
| 91 | } |
| 92 | |
| 93 | |