blob: 53c6acfd3b6d1493ec01e7940fd5b0d88ff67ee8 [file] [log] [blame]
 /* 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; }