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/* Return the largest absolute value of a vector of signed shorts
* This is the Altivec SIMD version.
* Copyright 2004 Phil Karn, KA9Q
* May be used under the terms of the GNU Lesser General Public License (LGPL)
*/
#include "fec.h"
signed short peakval_av(signed short *in,int cnt){
vector signed short x;
int pad;
union { vector signed char cv; vector signed short hv; signed short s[8]; signed char c[16];} s;
vector signed short smallest,largest;
smallest = (vector signed short)(0);
largest = (vector signed short)(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);
}
smallest = vec_min(smallest,x);
largest = vec_max(largest,x);
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);
smallest = vec_min(smallest,x);
largest = vec_max(largest,x);
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);
smallest = vec_min(smallest,x);
largest = vec_max(largest,x);
}
/* Combine and extract result */
largest = vec_max(largest,vec_abs(smallest));
s.c[15] = 64; /* Shift right four 16-bit words */
largest = vec_max(largest,vec_sro(largest,s.cv));
s.c[15] = 32; /* Shift right two 16-bit words */
largest = vec_max(largest,vec_sro(largest,s.cv));
s.c[15] = 16; /* Shift right one 16-bit word */
largest = vec_max(largest,vec_sro(largest,s.cv));
s.hv = largest;
return s.s[7];
}
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