You can not select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
79 lines
2.4 KiB
79 lines
2.4 KiB
/* Compute the sum of the squares of a vector of signed shorts
|
|
|
|
* This is the Altivec SIMD version. It's a little hairy because Altivec
|
|
* does not do 64-bit operations directly, so we have to accumulate separate
|
|
* 32-bit sums and carries
|
|
|
|
* Copyright 2004 Phil Karn, KA9Q
|
|
* May be used under the terms of the GNU Lesser General Public License (LGPL)
|
|
*/
|
|
|
|
#include "fec.h"
|
|
|
|
unsigned long long sumsq_av(signed short *in,int cnt){
|
|
long long sum;
|
|
vector signed short x;
|
|
vector unsigned int sums,carries,s1,s2;
|
|
int pad;
|
|
union { vector unsigned char cv; vector unsigned int iv; unsigned int w[4]; unsigned char c[16];} s;
|
|
|
|
carries = sums = (vector unsigned int)(0);
|
|
if((pad = (int)in & 15)!=0){
|
|
/* Load unaligned leading word */
|
|
x = vec_perm(vec_ld(0,in),(vector signed short)(0),vec_lvsl(0,in));
|
|
if(cnt < 8){ /* Shift right to chop stuff beyond end of short block */
|
|
s.c[15] = (8-cnt)<<4;
|
|
x = vec_sro(x,s.cv);
|
|
}
|
|
sums = (vector unsigned int)vec_msum(x,x,(vector signed int)(0));
|
|
in += 8-pad/2;
|
|
cnt -= 8-pad/2;
|
|
}
|
|
/* Everything is now aligned, rip through most of the block */
|
|
while(cnt >= 8){
|
|
x = vec_ld(0,in);
|
|
/* A single vec_msum cannot overflow, but we have to sum it with
|
|
* the earlier terms separately to handle the carries
|
|
* The cast to unsigned is OK because squares are always positive
|
|
*/
|
|
s1 = (vector unsigned int)vec_msum(x,x,(vector signed int)(0));
|
|
carries = vec_add(carries,vec_addc(sums,s1));
|
|
sums = vec_add(sums,s1);
|
|
in += 8;
|
|
cnt -= 8;
|
|
}
|
|
/* Handle trailing fragment, if any */
|
|
if(cnt > 0){
|
|
x = vec_ld(0,in);
|
|
s.c[15] = (8-cnt)<<4;
|
|
x = vec_sro(x,s.cv);
|
|
s1 = (vector unsigned int)vec_msum(x,x,(vector signed int)(0));
|
|
carries = vec_add(carries,vec_addc(sums,s1));
|
|
sums = vec_add(sums,s1);
|
|
}
|
|
/* Combine 4 sub-sums and carries */
|
|
s.c[15] = 64; /* Shift right two 32-bit words */
|
|
s1 = vec_sro(sums,s.cv);
|
|
s2 = vec_sro(carries,s.cv);
|
|
carries = vec_add(carries,vec_addc(sums,s1));
|
|
sums = vec_add(sums,s1);
|
|
carries = vec_add(carries,s2);
|
|
|
|
s.c[15] = 32; /* Shift right one 32-bit word */
|
|
s1 = vec_sro(sums,s.cv);
|
|
s2 = vec_sro(carries,s.cv);
|
|
carries = vec_add(carries,vec_addc(sums,s1));
|
|
sums = vec_add(sums,s1);
|
|
carries = vec_add(carries,s2);
|
|
|
|
/* Extract sum and carries from right-hand words and combine into result */
|
|
s.iv = sums;
|
|
sum = s.w[3];
|
|
|
|
s.iv = carries;
|
|
sum += (long long)s.w[3] << 32;
|
|
|
|
return sum;
|
|
}
|
|
|