235 lines
6.5 KiB
C
235 lines
6.5 KiB
C
/* K=15 r=1/6 Viterbi decoder for x86 SSE
|
|
* Copyright Mar 2004, Phil Karn, KA9Q
|
|
* May be used under the terms of the GNU Lesser General Public License (LGPL)
|
|
*/
|
|
#include <xmmintrin.h>
|
|
#include <stdio.h>
|
|
#include <stdlib.h>
|
|
#include <memory.h>
|
|
#include <limits.h>
|
|
#include "fec.h"
|
|
|
|
typedef union {
|
|
unsigned long w[512];
|
|
unsigned char c[2048];
|
|
} decision_t;
|
|
typedef union {
|
|
signed short s[16384];
|
|
__m64 v[4096];
|
|
} metric_t;
|
|
|
|
static union branchtab615 {
|
|
unsigned short s[8192];
|
|
__m64 v[2048];
|
|
} Branchtab615[6];
|
|
static int Init = 0;
|
|
|
|
/* State info for instance of Viterbi decoder */
|
|
struct v615 {
|
|
metric_t metrics1; /* path metric buffer 1 */
|
|
metric_t metrics2; /* path metric buffer 2 */
|
|
void *dp; /* Pointer to current decision */
|
|
metric_t *old_metrics,
|
|
*new_metrics; /* Pointers to path metrics, swapped on every bit */
|
|
void *decisions; /* Beginning of decisions for block */
|
|
};
|
|
|
|
/* Initialize Viterbi decoder for start of new frame */
|
|
int init_viterbi615_sse(void *p, int starting_state)
|
|
{
|
|
struct v615 *vp = p;
|
|
int i;
|
|
|
|
if (p == NULL) {
|
|
return -1;
|
|
}
|
|
for (i = 0; i < 16384; i++) {
|
|
vp->metrics1.s[i] = (SHRT_MIN + 5000);
|
|
}
|
|
|
|
vp->old_metrics = &vp->metrics1;
|
|
vp->new_metrics = &vp->metrics2;
|
|
vp->dp = vp->decisions;
|
|
vp->old_metrics->s[starting_state & 16383] =
|
|
SHRT_MIN; /* Bias known start state */
|
|
return 0;
|
|
}
|
|
|
|
/* Create a new instance of a Viterbi decoder */
|
|
void *create_viterbi615_sse(int len)
|
|
{
|
|
struct v615 *vp;
|
|
|
|
if (!Init) {
|
|
int polys[6] = { V615POLYA, V615POLYB, V615POLYC, V615POLYD, V615POLYE, V615POLYF };
|
|
set_viterbi615_polynomial_sse(polys);
|
|
}
|
|
|
|
if ((vp = (struct v615 *)malloc(sizeof(struct v615))) == NULL) {
|
|
return NULL;
|
|
}
|
|
if ((vp->decisions = malloc((len + 14) * sizeof(decision_t))) == NULL) {
|
|
free(vp);
|
|
return NULL;
|
|
}
|
|
init_viterbi615_sse(vp, 0);
|
|
return vp;
|
|
}
|
|
|
|
void set_viterbi615_polynomial_sse(int polys[6])
|
|
{
|
|
int state;
|
|
int i;
|
|
|
|
for (state = 0; state < 8192; state++) {
|
|
for (i = 0; i < 6; i++) {
|
|
Branchtab615[i].s[state] = (polys[i] < 0) ^ parity((2 * state) & abs(
|
|
polys[i])) ? 255 : 0;
|
|
}
|
|
}
|
|
Init++;
|
|
}
|
|
|
|
/* Viterbi chainback */
|
|
int chainback_viterbi615_sse(
|
|
void *p,
|
|
unsigned char *data, /* Decoded output data */
|
|
unsigned int nbits, /* Number of data bits */
|
|
unsigned int endstate) /* Terminal encoder state */
|
|
{
|
|
struct v615 *vp = p;
|
|
decision_t *d;
|
|
|
|
if (p == NULL) {
|
|
return -1;
|
|
}
|
|
d = (decision_t *)vp->decisions;
|
|
endstate %= 16384;
|
|
|
|
/* The store into data[] only needs to be done every 8 bits.
|
|
* But this avoids a conditional branch, and the writes will
|
|
* combine in the cache anyway
|
|
*/
|
|
d += 14; /* Look past tail */
|
|
while (nbits-- != 0) {
|
|
int k;
|
|
|
|
/* k = (d[nbits].w[endstate/32] >> (endstate%32)) & 1;*/
|
|
k = (d[nbits].c[endstate / 8] >> (endstate % 8)) & 1;
|
|
endstate = (k << 13) | (endstate >> 1);
|
|
data[nbits >> 3] = endstate >> 6;
|
|
}
|
|
return 0;
|
|
}
|
|
|
|
/* Delete instance of a Viterbi decoder */
|
|
void delete_viterbi615_sse(void *p)
|
|
{
|
|
struct v615 *vp = p;
|
|
|
|
if (vp != NULL) {
|
|
free(vp->decisions);
|
|
free(vp);
|
|
}
|
|
}
|
|
|
|
|
|
int update_viterbi615_blk_sse(void *p, unsigned char *syms, int nbits)
|
|
{
|
|
struct v615 *vp = p;
|
|
decision_t *d;
|
|
|
|
if (p == NULL) {
|
|
return -1;
|
|
}
|
|
d = (decision_t *)vp->dp;
|
|
while (nbits--) {
|
|
__m64 sym0v, sym1v, sym2v, sym3v, sym4v, sym5v;
|
|
void *tmp;
|
|
int i;
|
|
|
|
/* Splat the 0th symbol across sym0v, the 1st symbol across sym1v, etc */
|
|
sym0v = _mm_set1_pi16(syms[0]);
|
|
sym1v = _mm_set1_pi16(syms[1]);
|
|
sym2v = _mm_set1_pi16(syms[2]);
|
|
sym3v = _mm_set1_pi16(syms[3]);
|
|
sym4v = _mm_set1_pi16(syms[4]);
|
|
sym5v = _mm_set1_pi16(syms[5]);
|
|
syms += 6;
|
|
|
|
for (i = 0; i < 2048; i++) {
|
|
__m64 decision0, decision1, metric, m_metric, m0, m1, m2, m3, survivor0,
|
|
survivor1;
|
|
|
|
/* Form branch metrics
|
|
* Because Branchtab takes on values 0 and 255, and the values of sym?v are offset binary in the range 0-255,
|
|
* the XOR operations constitute conditional negation.
|
|
* metric and m_metric (-metric) are in the range 0-1530
|
|
*/
|
|
m0 = _mm_add_pi16(_mm_xor_si64(Branchtab615[0].v[i], sym0v),
|
|
_mm_xor_si64(Branchtab615[1].v[i], sym1v));
|
|
m1 = _mm_add_pi16(_mm_xor_si64(Branchtab615[2].v[i], sym2v),
|
|
_mm_xor_si64(Branchtab615[3].v[i], sym3v));
|
|
m2 = _mm_add_pi16(_mm_xor_si64(Branchtab615[4].v[i], sym4v),
|
|
_mm_xor_si64(Branchtab615[5].v[i], sym5v));
|
|
metric = _mm_add_pi16(m0, _mm_add_pi16(m1, m2));
|
|
m_metric = _mm_sub_pi16(_mm_set1_pi16(1530), metric);
|
|
|
|
/* Add branch metrics to path metrics */
|
|
m0 = _mm_adds_pi16(vp->old_metrics->v[i], metric);
|
|
m3 = _mm_adds_pi16(vp->old_metrics->v[2048 + i], metric);
|
|
m1 = _mm_adds_pi16(vp->old_metrics->v[2048 + i], m_metric);
|
|
m2 = _mm_adds_pi16(vp->old_metrics->v[i], m_metric);
|
|
|
|
/* Compare and select */
|
|
survivor0 = _mm_min_pi16(m0, m1);
|
|
survivor1 = _mm_min_pi16(m2, m3);
|
|
decision0 = _mm_cmpeq_pi16(survivor0, m1);
|
|
decision1 = _mm_cmpeq_pi16(survivor1, m3);
|
|
|
|
/* Pack decisions into 8 bits and store */
|
|
d->c[i] = _mm_movemask_pi8(_mm_unpacklo_pi8(_mm_packs_pi16(decision0,
|
|
_mm_setzero_si64()), _mm_packs_pi16(decision1, _mm_setzero_si64())));
|
|
|
|
/* Store surviving metrics */
|
|
vp->new_metrics->v[2 * i] = _mm_unpacklo_pi16(survivor0, survivor1);
|
|
vp->new_metrics->v[2 * i + 1] = _mm_unpackhi_pi16(survivor0, survivor1);
|
|
}
|
|
/* See if we need to renormalize
|
|
* Max metric spread for this code with 0-255 branch metrics is 12750
|
|
*/
|
|
if (vp->new_metrics->s[0] >= SHRT_MAX - 12750) {
|
|
int i, adjust;
|
|
__m64 adjustv;
|
|
union {
|
|
__m64 v;
|
|
signed short w[4];
|
|
} t;
|
|
|
|
/* Find smallest metric and set adjustv to bring it down to SHRT_MIN */
|
|
adjustv = vp->new_metrics->v[0];
|
|
for (i = 1; i < 4096; i++) {
|
|
adjustv = _mm_min_pi16(adjustv, vp->new_metrics->v[i]);
|
|
}
|
|
|
|
adjustv = _mm_min_pi16(adjustv, _mm_srli_si64(adjustv, 32));
|
|
adjustv = _mm_min_pi16(adjustv, _mm_srli_si64(adjustv, 16));
|
|
t.v = adjustv;
|
|
adjust = t.w[0] - SHRT_MIN;
|
|
adjustv = _mm_set1_pi16(adjust);
|
|
|
|
for (i = 0; i < 4096; i++) {
|
|
vp->new_metrics->v[i] = _mm_sub_pi16(vp->new_metrics->v[i], adjustv);
|
|
}
|
|
}
|
|
d++;
|
|
/* Swap pointers to old and new metrics */
|
|
tmp = vp->old_metrics;
|
|
vp->old_metrics = vp->new_metrics;
|
|
vp->new_metrics = tmp;
|
|
}
|
|
vp->dp = d;
|
|
_mm_empty();
|
|
return 0;
|
|
}
|