68 lines
1.8 KiB
C
68 lines
1.8 KiB
C
/* Return the largest absolute value of a vector of signed shorts
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* This is the Altivec SIMD version.
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* Copyright 2004 Phil Karn, KA9Q
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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 "fec.h"
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signed short peakval_av(signed short *in, int cnt)
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{
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vector signed short x;
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int pad;
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union {
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vector signed char cv;
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vector signed short hv;
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signed short s[8];
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signed char c[16];
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} s;
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vector signed short smallest, largest;
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smallest = (vector signed short)(0);
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largest = (vector signed short)(0);
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if ((pad = (int)in & 15) != 0) {
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/* Load unaligned leading word */
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x = vec_perm(vec_ld(0, in), (vector signed short)(0), vec_lvsl(0, in));
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if (cnt < 8) { /* Shift right to chop stuff beyond end of short block */
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s.c[15] = (8 - cnt) << 4;
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x = vec_sro(x, s.cv);
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}
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smallest = vec_min(smallest, x);
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largest = vec_max(largest, x);
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in += 8 - pad / 2;
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cnt -= 8 - pad / 2;
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}
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/* Everything is now aligned, rip through most of the block */
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while (cnt >= 8) {
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x = vec_ld(0, in);
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smallest = vec_min(smallest, x);
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largest = vec_max(largest, x);
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in += 8;
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cnt -= 8;
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}
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/* Handle trailing fragment, if any */
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if (cnt > 0) {
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x = vec_ld(0, in);
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s.c[15] = (8 - cnt) << 4;
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x = vec_sro(x, s.cv);
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smallest = vec_min(smallest, x);
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largest = vec_max(largest, x);
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}
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/* Combine and extract result */
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largest = vec_max(largest, vec_abs(smallest));
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s.c[15] = 64; /* Shift right four 16-bit words */
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largest = vec_max(largest, vec_sro(largest, s.cv));
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s.c[15] = 32; /* Shift right two 16-bit words */
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largest = vec_max(largest, vec_sro(largest, s.cv));
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s.c[15] = 16; /* Shift right one 16-bit word */
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largest = vec_max(largest, vec_sro(largest, s.cv));
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s.hv = largest;
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return s.s[7];
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}
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