1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
|
/*! \file conv_acc.c
* Accelerated Viterbi decoder implementation. */
/*
* Copyright (C) 2013, 2014 Thomas Tsou <tom@tsou.cc>
*
* All Rights Reserved
*
* SPDX-License-Identifier: GPL-2.0+
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License along
* with this program; if not, write to the Free Software Foundation, Inc.,
* 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
*/
#include <stdlib.h>
#include <string.h>
#include <errno.h>
#include "config.h"
#include <osmocom/core/conv.h>
#define BIT2NRZ(REG,N) (((REG >> N) & 0x01) * 2 - 1) * -1
#define NUM_STATES(K) (K == 7 ? 64 : 16)
#define INIT_POINTERS(simd) \
{ \
osmo_conv_metrics_k5_n2 = osmo_conv_##simd##_metrics_k5_n2; \
osmo_conv_metrics_k5_n3 = osmo_conv_##simd##_metrics_k5_n3; \
osmo_conv_metrics_k5_n4 = osmo_conv_##simd##_metrics_k5_n4; \
osmo_conv_metrics_k7_n2 = osmo_conv_##simd##_metrics_k7_n2; \
osmo_conv_metrics_k7_n3 = osmo_conv_##simd##_metrics_k7_n3; \
osmo_conv_metrics_k7_n4 = osmo_conv_##simd##_metrics_k7_n4; \
vdec_malloc = &osmo_conv_##simd##_vdec_malloc; \
vdec_free = &osmo_conv_##simd##_vdec_free; \
}
static int init_complete = 0;
__attribute__ ((visibility("hidden"))) int avx2_supported = 0;
__attribute__ ((visibility("hidden"))) int ssse3_supported = 0;
__attribute__ ((visibility("hidden"))) int sse41_supported = 0;
/**
* These pointers are being initialized at runtime by the
* osmo_conv_init() depending on supported SIMD extensions.
*/
static int16_t *(*vdec_malloc)(size_t n);
static void (*vdec_free)(int16_t *ptr);
void (*osmo_conv_metrics_k5_n2)(const int8_t *seq,
const int16_t *out, int16_t *sums, int16_t *paths, int norm);
void (*osmo_conv_metrics_k5_n3)(const int8_t *seq,
const int16_t *out, int16_t *sums, int16_t *paths, int norm);
void (*osmo_conv_metrics_k5_n4)(const int8_t *seq,
const int16_t *out, int16_t *sums, int16_t *paths, int norm);
void (*osmo_conv_metrics_k7_n2)(const int8_t *seq,
const int16_t *out, int16_t *sums, int16_t *paths, int norm);
void (*osmo_conv_metrics_k7_n3)(const int8_t *seq,
const int16_t *out, int16_t *sums, int16_t *paths, int norm);
void (*osmo_conv_metrics_k7_n4)(const int8_t *seq,
const int16_t *out, int16_t *sums, int16_t *paths, int norm);
/* Forward malloc wrappers */
int16_t *osmo_conv_gen_vdec_malloc(size_t n);
void osmo_conv_gen_vdec_free(int16_t *ptr);
#if defined(HAVE_SSSE3)
int16_t *osmo_conv_sse_vdec_malloc(size_t n);
void osmo_conv_sse_vdec_free(int16_t *ptr);
#endif
#if defined(HAVE_SSSE3) && defined(HAVE_AVX2)
int16_t *osmo_conv_sse_avx_vdec_malloc(size_t n);
void osmo_conv_sse_avx_vdec_free(int16_t *ptr);
#endif
/* Forward Metric Units */
void osmo_conv_gen_metrics_k5_n2(const int8_t *seq, const int16_t *out,
int16_t *sums, int16_t *paths, int norm);
void osmo_conv_gen_metrics_k5_n3(const int8_t *seq, const int16_t *out,
int16_t *sums, int16_t *paths, int norm);
void osmo_conv_gen_metrics_k5_n4(const int8_t *seq, const int16_t *out,
int16_t *sums, int16_t *paths, int norm);
void osmo_conv_gen_metrics_k7_n2(const int8_t *seq, const int16_t *out,
int16_t *sums, int16_t *paths, int norm);
void osmo_conv_gen_metrics_k7_n3(const int8_t *seq, const int16_t *out,
int16_t *sums, int16_t *paths, int norm);
void osmo_conv_gen_metrics_k7_n4(const int8_t *seq, const int16_t *out,
int16_t *sums, int16_t *paths, int norm);
#if defined(HAVE_SSSE3)
void osmo_conv_sse_metrics_k5_n2(const int8_t *seq, const int16_t *out,
int16_t *sums, int16_t *paths, int norm);
void osmo_conv_sse_metrics_k5_n3(const int8_t *seq, const int16_t *out,
int16_t *sums, int16_t *paths, int norm);
void osmo_conv_sse_metrics_k5_n4(const int8_t *seq, const int16_t *out,
int16_t *sums, int16_t *paths, int norm);
void osmo_conv_sse_metrics_k7_n2(const int8_t *seq, const int16_t *out,
int16_t *sums, int16_t *paths, int norm);
void osmo_conv_sse_metrics_k7_n3(const int8_t *seq, const int16_t *out,
int16_t *sums, int16_t *paths, int norm);
void osmo_conv_sse_metrics_k7_n4(const int8_t *seq, const int16_t *out,
int16_t *sums, int16_t *paths, int norm);
#endif
#if defined(HAVE_SSSE3) && defined(HAVE_AVX2)
void osmo_conv_sse_avx_metrics_k5_n2(const int8_t *seq, const int16_t *out,
int16_t *sums, int16_t *paths, int norm);
void osmo_conv_sse_avx_metrics_k5_n3(const int8_t *seq, const int16_t *out,
int16_t *sums, int16_t *paths, int norm);
void osmo_conv_sse_avx_metrics_k5_n4(const int8_t *seq, const int16_t *out,
int16_t *sums, int16_t *paths, int norm);
void osmo_conv_sse_avx_metrics_k7_n2(const int8_t *seq, const int16_t *out,
int16_t *sums, int16_t *paths, int norm);
void osmo_conv_sse_avx_metrics_k7_n3(const int8_t *seq, const int16_t *out,
int16_t *sums, int16_t *paths, int norm);
void osmo_conv_sse_avx_metrics_k7_n4(const int8_t *seq, const int16_t *out,
int16_t *sums, int16_t *paths, int norm);
#endif
/* Trellis State
* state - Internal lshift register value
* prev - Register values of previous 0 and 1 states
*/
struct vstate {
unsigned state;
unsigned prev[2];
};
/* Trellis Object
* num_states - Number of states in the trellis
* sums - Accumulated path metrics
* outputs - Trellis output values
* vals - Input value that led to each state
*/
struct vtrellis {
int num_states;
int16_t *sums;
int16_t *outputs;
uint8_t *vals;
};
/* Viterbi Decoder
* n - Code order
* k - Constraint length
* len - Horizontal length of trellis
* recursive - Set to '1' if the code is recursive
* intrvl - Normalization interval
* trellis - Trellis object
* paths - Trellis paths
*/
struct vdecoder {
int n;
int k;
int len;
int recursive;
int intrvl;
struct vtrellis trellis;
int16_t **paths;
void (*metric_func)(const int8_t *, const int16_t *,
int16_t *, int16_t *, int);
};
/* Accessor calls */
static inline int conv_code_recursive(const struct osmo_conv_code *code)
{
return code->next_term_output ? 1 : 0;
}
/* Left shift and mask for finding the previous state */
static unsigned vstate_lshift(unsigned reg, int k, int val)
{
unsigned mask;
if (k == 5)
mask = 0x0e;
else if (k == 7)
mask = 0x3e;
else
mask = 0;
return ((reg << 1) & mask) | val;
}
/* Bit endian manipulators */
static inline unsigned bitswap2(unsigned v)
{
return ((v & 0x02) >> 1) | ((v & 0x01) << 1);
}
static inline unsigned bitswap3(unsigned v)
{
return ((v & 0x04) >> 2) | ((v & 0x02) >> 0) |
((v & 0x01) << 2);
}
static inline unsigned bitswap4(unsigned v)
{
return ((v & 0x08) >> 3) | ((v & 0x04) >> 1) |
((v & 0x02) << 1) | ((v & 0x01) << 3);
}
static inline unsigned bitswap5(unsigned v)
{
return ((v & 0x10) >> 4) | ((v & 0x08) >> 2) | ((v & 0x04) >> 0) |
((v & 0x02) << 2) | ((v & 0x01) << 4);
}
static inline unsigned bitswap6(unsigned v)
{
return ((v & 0x20) >> 5) | ((v & 0x10) >> 3) | ((v & 0x08) >> 1) |
((v & 0x04) << 1) | ((v & 0x02) << 3) | ((v & 0x01) << 5);
}
static unsigned bitswap(unsigned v, unsigned n)
{
switch (n) {
case 1:
return v;
case 2:
return bitswap2(v);
case 3:
return bitswap3(v);
case 4:
return bitswap4(v);
case 5:
return bitswap5(v);
case 6:
return bitswap6(v);
default:
return 0;
}
}
/* Generate non-recursive state output from generator state table
* Note that the shift register moves right (i.e. the most recent bit is
* shifted into the register at k-1 bit of the register), which is typical
* textbook representation. The API transition table expects the most recent
* bit in the low order bit, or left shift. A bitswap operation is required
* to accommodate the difference.
*/
static unsigned gen_output(struct vstate *state, int val,
const struct osmo_conv_code *code)
{
unsigned out, prev;
prev = bitswap(state->prev[0], code->K - 1);
out = code->next_output[prev][val];
out = bitswap(out, code->N);
return out;
}
/* Populate non-recursive trellis state
* For a given state defined by the k-1 length shift register, find the
* value of the input bit that drove the trellis to that state. Also
* generate the N outputs of the generator polynomial at that state.
*/
static int gen_state_info(uint8_t *val, unsigned reg,
int16_t *output, const struct osmo_conv_code *code)
{
int i;
unsigned out;
struct vstate state;
/* Previous '0' state */
state.state = reg;
state.prev[0] = vstate_lshift(reg, code->K, 0);
state.prev[1] = vstate_lshift(reg, code->K, 1);
*val = (reg >> (code->K - 2)) & 0x01;
/* Transition output */
out = gen_output(&state, *val, code);
/* Unpack to NRZ */
for (i = 0; i < code->N; i++)
output[i] = BIT2NRZ(out, i);
return 0;
}
/* Generate recursive state output from generator state table */
static unsigned gen_recursive_output(struct vstate *state,
uint8_t *val, unsigned reg,
const struct osmo_conv_code *code, int pos)
{
int val0, val1;
unsigned out, prev;
/* Previous '0' state */
prev = vstate_lshift(reg, code->K, 0);
prev = bitswap(prev, code->K - 1);
/* Input value */
val0 = (reg >> (code->K - 2)) & 0x01;
val1 = (code->next_term_output[prev] >> pos) & 0x01;
*val = val0 == val1 ? 0 : 1;
/* Wrapper for osmocom state access */
prev = bitswap(state->prev[0], code->K - 1);
/* Compute the transition output */
out = code->next_output[prev][*val];
out = bitswap(out, code->N);
return out;
}
/* Populate recursive trellis state
* The bit position of the systematic bit is not explicitly marked by the
* API, so it must be extracted from the generator table. Otherwise,
* populate the trellis similar to the non-recursive version.
* Non-systematic recursive codes are not supported.
*/
static int gen_recursive_state_info(uint8_t *val,
unsigned reg, int16_t *output, const struct osmo_conv_code *code)
{
int i, j, pos = -1;
int ns = NUM_STATES(code->K);
unsigned out;
struct vstate state;
/* Previous '0' and '1' states */
state.state = reg;
state.prev[0] = vstate_lshift(reg, code->K, 0);
state.prev[1] = vstate_lshift(reg, code->K, 1);
/* Find recursive bit location */
for (i = 0; i < code->N; i++) {
for (j = 0; j < ns; j++) {
if ((code->next_output[j][0] >> i) & 0x01)
break;
}
if (j == ns) {
pos = i;
break;
}
}
/* Non-systematic recursive code not supported */
if (pos < 0)
return -EPROTO;
/* Transition output */
out = gen_recursive_output(&state, val, reg, code, pos);
/* Unpack to NRZ */
for (i = 0; i < code->N; i++)
output[i] = BIT2NRZ(out, i);
return 0;
}
/* Release the trellis */
static void free_trellis(struct vtrellis *trellis)
{
if (!trellis)
return;
vdec_free(trellis->outputs);
vdec_free(trellis->sums);
free(trellis->vals);
}
/* Initialize the trellis object
* Initialization consists of generating the outputs and output value of a
* given state. Due to trellis symmetry and anti-symmetry, only one of the
* transition paths is utilized by the butterfly operation in the forward
* recursion, so only one set of N outputs is required per state variable.
*/
static int generate_trellis(struct vdecoder *dec,
const struct osmo_conv_code *code)
{
struct vtrellis *trellis = &dec->trellis;
int16_t *outputs;
int i, rc;
int ns = NUM_STATES(code->K);
int olen = (code->N == 2) ? 2 : 4;
trellis->num_states = ns;
trellis->sums = vdec_malloc(ns);
trellis->outputs = vdec_malloc(ns * olen);
trellis->vals = (uint8_t *) malloc(ns * sizeof(uint8_t));
if (!trellis->sums || !trellis->outputs || !trellis->vals) {
rc = -ENOMEM;
goto fail;
}
/* Populate the trellis state objects */
for (i = 0; i < ns; i++) {
outputs = &trellis->outputs[olen * i];
if (dec->recursive) {
rc = gen_recursive_state_info(&trellis->vals[i],
i, outputs, code);
} else {
rc = gen_state_info(&trellis->vals[i],
i, outputs, code);
}
if (rc < 0)
goto fail;
/* Set accumulated path metrics to zero */
trellis->sums[i] = 0;
}
/**
* For termination other than tail-biting, initialize the zero state
* as the encoder starting state. Initialize with the maximum
* accumulated sum at length equal to the constraint length.
*/
if (code->term != CONV_TERM_TAIL_BITING)
trellis->sums[0] = INT8_MAX * code->N * code->K;
return 0;
fail:
free_trellis(trellis);
return rc;
}
static void _traceback(struct vdecoder *dec,
unsigned state, uint8_t *out, int len)
{
int i;
unsigned path;
for (i = len - 1; i >= 0; i--) {
path = dec->paths[i][state] + 1;
out[i] = dec->trellis.vals[state];
state = vstate_lshift(state, dec->k, path);
}
}
static void _traceback_rec(struct vdecoder *dec,
unsigned state, uint8_t *out, int len)
{
int i;
unsigned path;
for (i = len - 1; i >= 0; i--) {
path = dec->paths[i][state] + 1;
out[i] = path ^ dec->trellis.vals[state];
state = vstate_lshift(state, dec->k, path);
}
}
/* Traceback and generate decoded output
* Find the largest accumulated path metric at the final state except for
* the zero terminated case, where we assume the final state is always zero.
*/
static int traceback(struct vdecoder *dec, uint8_t *out, int term, int len)
{
int i, sum, max = -1;
unsigned path, state = 0;
if (term != CONV_TERM_FLUSH) {
for (i = 0; i < dec->trellis.num_states; i++) {
sum = dec->trellis.sums[i];
if (sum > max) {
max = sum;
state = i;
}
}
if (max < 0)
return -EPROTO;
}
for (i = dec->len - 1; i >= len; i--) {
path = dec->paths[i][state] + 1;
state = vstate_lshift(state, dec->k, path);
}
if (dec->recursive)
_traceback_rec(dec, state, out, len);
else
_traceback(dec, state, out, len);
return 0;
}
/* Release decoder object */
static void vdec_deinit(struct vdecoder *dec)
{
if (!dec)
return;
free_trellis(&dec->trellis);
if (dec->paths != NULL) {
vdec_free(dec->paths[0]);
free(dec->paths);
}
}
/* Initialize decoder object with code specific params
* Subtract the constraint length K on the normalization interval to
* accommodate the initialization path metric at state zero.
*/
static int vdec_init(struct vdecoder *dec, const struct osmo_conv_code *code)
{
int i, ns, rc;
ns = NUM_STATES(code->K);
dec->n = code->N;
dec->k = code->K;
dec->recursive = conv_code_recursive(code);
dec->intrvl = INT16_MAX / (dec->n * INT8_MAX) - dec->k;
if (dec->k == 5) {
switch (dec->n) {
case 2:
dec->metric_func = osmo_conv_metrics_k5_n2;
break;
case 3:
dec->metric_func = osmo_conv_metrics_k5_n3;
break;
case 4:
dec->metric_func = osmo_conv_metrics_k5_n4;
break;
default:
return -EINVAL;
}
} else if (dec->k == 7) {
switch (dec->n) {
case 2:
dec->metric_func = osmo_conv_metrics_k7_n2;
break;
case 3:
dec->metric_func = osmo_conv_metrics_k7_n3;
break;
case 4:
dec->metric_func = osmo_conv_metrics_k7_n4;
break;
default:
return -EINVAL;
}
} else {
return -EINVAL;
}
if (code->term == CONV_TERM_FLUSH)
dec->len = code->len + code->K - 1;
else
dec->len = code->len;
rc = generate_trellis(dec, code);
if (rc)
return rc;
dec->paths = (int16_t **) malloc(sizeof(int16_t *) * dec->len);
if (!dec->paths)
goto enomem;
dec->paths[0] = vdec_malloc(ns * dec->len);
if (!dec->paths[0])
goto enomem;
for (i = 1; i < dec->len; i++)
dec->paths[i] = &dec->paths[0][i * ns];
return 0;
enomem:
vdec_deinit(dec);
return -ENOMEM;
}
/* Depuncture sequence with nagative value terminated puncturing matrix */
static int depuncture(const int8_t *in, const int *punc, int8_t *out, int len)
{
int i, n = 0, m = 0;
for (i = 0; i < len; i++) {
if (i == punc[n]) {
out[i] = 0;
n++;
continue;
}
out[i] = in[m++];
}
return 0;
}
/* Forward trellis recursion
* Generate branch metrics and path metrics with a combined function. Only
* accumulated path metric sums and path selections are stored. Normalize on
* the interval specified by the decoder.
*/
static void forward_traverse(struct vdecoder *dec, const int8_t *seq)
{
int i;
for (i = 0; i < dec->len; i++) {
dec->metric_func(&seq[dec->n * i],
dec->trellis.outputs,
dec->trellis.sums,
dec->paths[i],
!(i % dec->intrvl));
}
}
/* Convolutional decode with a decoder object
* Initial puncturing run if necessary followed by the forward recursion.
* For tail-biting perform a second pass before running the backward
* traceback operation.
*/
static int conv_decode(struct vdecoder *dec, const int8_t *seq,
const int *punc, uint8_t *out, int len, int term)
{
int8_t depunc[dec->len * dec->n];
if (punc) {
depuncture(seq, punc, depunc, dec->len * dec->n);
seq = depunc;
}
/* Propagate through the trellis with interval normalization */
forward_traverse(dec, seq);
if (term == CONV_TERM_TAIL_BITING)
forward_traverse(dec, seq);
return traceback(dec, out, term, len);
}
static void osmo_conv_init(void)
{
init_complete = 1;
#ifdef HAVE___BUILTIN_CPU_SUPPORTS
/* Detect CPU capabilities */
#ifdef HAVE_AVX2
avx2_supported = __builtin_cpu_supports("avx2");
#endif
#ifdef HAVE_SSSE3
ssse3_supported = __builtin_cpu_supports("ssse3");
#endif
#ifdef HAVE_SSE4_1
sse41_supported = __builtin_cpu_supports("sse4.1");
#endif
#endif
/**
* Usage of curly braces is mandatory,
* because we use multi-line define.
*/
#if defined(HAVE_SSSE3) && defined(HAVE_AVX2)
if (ssse3_supported && avx2_supported) {
INIT_POINTERS(sse_avx);
} else if (ssse3_supported) {
INIT_POINTERS(sse);
} else {
INIT_POINTERS(gen);
}
#elif defined(HAVE_SSSE3)
if (ssse3_supported) {
INIT_POINTERS(sse);
} else {
INIT_POINTERS(gen);
}
#else
INIT_POINTERS(gen);
#endif
}
/* All-in-one Viterbi decoding */
int osmo_conv_decode_acc(const struct osmo_conv_code *code,
const sbit_t *input, ubit_t *output)
{
int rc;
struct vdecoder dec;
if (!init_complete)
osmo_conv_init();
if ((code->N < 2) || (code->N > 4) || (code->len < 1) ||
((code->K != 5) && (code->K != 7)))
return -EINVAL;
rc = vdec_init(&dec, code);
if (rc)
return rc;
rc = conv_decode(&dec, input, code->puncture,
output, code->len, code->term);
vdec_deinit(&dec);
return rc;
}
|