| /*! \file conv_acc_generic.c |
| * Accelerated Viterbi decoder implementation |
| * for generic architectures without SSE support. */ |
| /* |
| * 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 <stdint.h> |
| #include <string.h> |
| |
| /* Add-Compare-Select (ACS-Butterfly) |
| * Compute 4 accumulated path metrics and 4 path selections. Note that path |
| * selections are store as -1 and 0 rather than 0 and 1. This is to match |
| * the output format of the SSE packed compare instruction 'pmaxuw'. |
| */ |
| |
| static void acs_butterfly(int state, int num_states, |
| int16_t metric, int16_t *sum, |
| int16_t *new_sum, int16_t *path) |
| { |
| int state0, state1; |
| int sum0, sum1, sum2, sum3; |
| |
| state0 = *(sum + (2 * state + 0)); |
| state1 = *(sum + (2 * state + 1)); |
| |
| sum0 = state0 + metric; |
| sum1 = state1 - metric; |
| sum2 = state0 - metric; |
| sum3 = state1 + metric; |
| |
| if (sum0 >= sum1) { |
| *new_sum = sum0; |
| *path = -1; |
| } else { |
| *new_sum = sum1; |
| *path = 0; |
| } |
| |
| if (sum2 >= sum3) { |
| *(new_sum + num_states / 2) = sum2; |
| *(path + num_states / 2) = -1; |
| } else { |
| *(new_sum + num_states / 2) = sum3; |
| *(path + num_states / 2) = 0; |
| } |
| } |
| |
| /* Branch metrics unit N=2 */ |
| static void gen_branch_metrics_n2(int num_states, const int8_t *seq, |
| const int16_t *out, int16_t *metrics) |
| { |
| int i; |
| |
| for (i = 0; i < num_states / 2; i++) { |
| metrics[i] = seq[0] * out[2 * i + 0] + |
| seq[1] * out[2 * i + 1]; |
| } |
| } |
| |
| /* Branch metrics unit N=3 */ |
| static void gen_branch_metrics_n3(int num_states, const int8_t *seq, |
| const int16_t *out, int16_t *metrics) |
| { |
| int i; |
| |
| for (i = 0; i < num_states / 2; i++) { |
| metrics[i] = seq[0] * out[4 * i + 0] + |
| seq[1] * out[4 * i + 1] + |
| seq[2] * out[4 * i + 2]; |
| } |
| } |
| |
| /* Branch metrics unit N=4 */ |
| static void gen_branch_metrics_n4(int num_states, const int8_t *seq, |
| const int16_t *out, int16_t *metrics) |
| { |
| int i; |
| |
| for (i = 0; i < num_states / 2; i++) { |
| metrics[i] = seq[0] * out[4 * i + 0] + |
| seq[1] * out[4 * i + 1] + |
| seq[2] * out[4 * i + 2] + |
| seq[3] * out[4 * i + 3]; |
| } |
| } |
| |
| /* Path metric unit */ |
| static void gen_path_metrics(int num_states, int16_t *sums, |
| int16_t *metrics, int16_t *paths, int norm) |
| { |
| int i; |
| int16_t min; |
| int16_t new_sums[num_states]; |
| |
| for (i = 0; i < num_states / 2; i++) |
| acs_butterfly(i, num_states, metrics[i], |
| sums, &new_sums[i], &paths[i]); |
| |
| if (norm) { |
| min = new_sums[0]; |
| |
| for (i = 1; i < num_states; i++) |
| if (new_sums[i] < min) |
| min = new_sums[i]; |
| |
| for (i = 0; i < num_states; i++) |
| new_sums[i] -= min; |
| } |
| |
| memcpy(sums, new_sums, num_states * sizeof(int16_t)); |
| } |
| |
| /* Not-aligned Memory Allocator */ |
| __attribute__ ((visibility("hidden"))) |
| int16_t *osmo_conv_gen_vdec_malloc(size_t n) |
| { |
| return (int16_t *) malloc(sizeof(int16_t) * n); |
| } |
| |
| __attribute__ ((visibility("hidden"))) |
| void osmo_conv_gen_vdec_free(int16_t *ptr) |
| { |
| free(ptr); |
| } |
| |
| /* 16-state branch-path metrics units (K=5) */ |
| __attribute__ ((visibility("hidden"))) |
| void osmo_conv_gen_metrics_k5_n2(const int8_t *seq, const int16_t *out, |
| int16_t *sums, int16_t *paths, int norm) |
| { |
| int16_t metrics[8]; |
| |
| gen_branch_metrics_n2(16, seq, out, metrics); |
| gen_path_metrics(16, sums, metrics, paths, norm); |
| } |
| |
| __attribute__ ((visibility("hidden"))) |
| void osmo_conv_gen_metrics_k5_n3(const int8_t *seq, const int16_t *out, |
| int16_t *sums, int16_t *paths, int norm) |
| { |
| int16_t metrics[8]; |
| |
| gen_branch_metrics_n3(16, seq, out, metrics); |
| gen_path_metrics(16, sums, metrics, paths, norm); |
| |
| } |
| |
| __attribute__ ((visibility("hidden"))) |
| void osmo_conv_gen_metrics_k5_n4(const int8_t *seq, const int16_t *out, |
| int16_t *sums, int16_t *paths, int norm) |
| { |
| int16_t metrics[8]; |
| |
| gen_branch_metrics_n4(16, seq, out, metrics); |
| gen_path_metrics(16, sums, metrics, paths, norm); |
| |
| } |
| |
| /* 64-state branch-path metrics units (K=7) */ |
| __attribute__ ((visibility("hidden"))) |
| void osmo_conv_gen_metrics_k7_n2(const int8_t *seq, const int16_t *out, |
| int16_t *sums, int16_t *paths, int norm) |
| { |
| int16_t metrics[32]; |
| |
| gen_branch_metrics_n2(64, seq, out, metrics); |
| gen_path_metrics(64, sums, metrics, paths, norm); |
| |
| } |
| |
| __attribute__ ((visibility("hidden"))) |
| void osmo_conv_gen_metrics_k7_n3(const int8_t *seq, const int16_t *out, |
| int16_t *sums, int16_t *paths, int norm) |
| { |
| int16_t metrics[32]; |
| |
| gen_branch_metrics_n3(64, seq, out, metrics); |
| gen_path_metrics(64, sums, metrics, paths, norm); |
| |
| } |
| |
| __attribute__ ((visibility("hidden"))) |
| void osmo_conv_gen_metrics_k7_n4(const int8_t *seq, const int16_t *out, |
| int16_t *sums, int16_t *paths, int norm) |
| { |
| int16_t metrics[32]; |
| |
| gen_branch_metrics_n4(64, seq, out, metrics); |
| gen_path_metrics(64, sums, metrics, paths, norm); |
| } |