mirror of https://github.com/PentHertz/srsLTE.git
Added comments to turbo decoder SSE
This commit is contained in:
ismagom
parent
f339bf6641
commit
6e76fd291e
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@ -54,12 +54,12 @@ typedef struct SRSLTE_API {
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int max_long_cb;
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int16_t *alpha;
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int16_t *branch;
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} srslte_map_gen_t;
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} map_gen_t;
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typedef struct SRSLTE_API {
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int max_long_cb;
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srslte_map_gen_t dec;
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map_gen_t dec;
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int16_t *app1;
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int16_t *app2;
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@ -52,14 +52,9 @@
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#define ZERO 0
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/************************************************
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*
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* MAP_GEN is the MAX-LOG-MAP generic implementation
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*
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************************************************/
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#ifdef LV_HAVE_SSE
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/* Computes the horizontal MAX from 8 16-bit integers using the minpos_epu16 SSE4.1 instruction */
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static inline int16_t hMax(__m128i buffer)
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{
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__m128i tmp1 = _mm_sub_epi8(_mm_set1_epi16(0x7FFF), buffer);
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@ -67,7 +62,8 @@ static inline int16_t hMax(__m128i buffer)
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return (int16_t)(_mm_cvtsi128_si32(tmp3));
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}
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void srslte_map_gen_beta(srslte_map_gen_t * s, int16_t * output, uint32_t long_cb)
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/* Computes beta values */
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void map_gen_beta(map_gen_t * s, int16_t * output, uint32_t long_cb)
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{
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int k;
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uint32_t end = long_cb + 3;
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@ -76,6 +72,7 @@ void srslte_map_gen_beta(srslte_map_gen_t * s, int16_t * output, uint32_t long_c
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__m128i beta_k = _mm_set_epi16(-INF, -INF, -INF, -INF, -INF, -INF, -INF, 0);
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__m128i g, bp, bn, alpha_k;
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/* Define the shuffle constant for the positive beta */
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__m128i shuf_bp = _mm_set_epi8(
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15, 14, // 7
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7, 6, // 3
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@ -87,6 +84,7 @@ void srslte_map_gen_beta(srslte_map_gen_t * s, int16_t * output, uint32_t long_c
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9, 8 // 4
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);
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/* Define the shuffle constant for the negative beta */
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__m128i shuf_bn = _mm_set_epi8(
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7, 6, // 3
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15, 14, // 7
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@ -100,7 +98,8 @@ void srslte_map_gen_beta(srslte_map_gen_t * s, int16_t * output, uint32_t long_c
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alphaPtr += long_cb-1;
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__m128i shuf_g[4];
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/* Define shuffle for branch costs */
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__m128i shuf_g[4];
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shuf_g[3] = _mm_set_epi8(3,2,1,0,1,0,3,2,3,2,1,0,1,0,3,2);
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shuf_g[2] = _mm_set_epi8(7,6,5,4,5,4,7,6,7,6,5,4,5,4,7,6);
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shuf_g[1] = _mm_set_epi8(11,10,9,8,9,8,11,10,11,10,9,8,9,8,11,10);
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@ -108,21 +107,31 @@ void srslte_map_gen_beta(srslte_map_gen_t * s, int16_t * output, uint32_t long_c
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__m128i gv;
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int16_t *b = &s->branch[2*long_cb-8];
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__m128i *gPtr = (__m128i*) b;
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/* Define shuffle for beta normalization */
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__m128i shuf_norm = _mm_set_epi8(1,0,1,0,1,0,1,0,1,0,1,0,1,0,1,0);
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/* This defines a beta computation step:
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* Adds and substracts the branch metrics to the previous beta step,
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* shuffles the states according to the trellis path and selects maximum state
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*/
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#define BETA_STEP(g) bp = _mm_add_epi16(beta_k, g);\
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bn = _mm_sub_epi16(beta_k, g);\
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bp = _mm_shuffle_epi8(bp, shuf_bp);\
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bn = _mm_shuffle_epi8(bn, shuf_bn);\
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beta_k = _mm_max_epi16(bp, bn);
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/* Loads the alpha metrics from memory and adds them to the temporal bn and bp
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* metrics. Then computes horizontal maximum of both metrics and computes difference
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*/
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#define BETA_STEP_CNT(c,d) g = _mm_shuffle_epi8(gv, shuf_g[c]);\
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BETA_STEP(g)\
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alpha_k = _mm_load_si128(alphaPtr);\
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alphaPtr--;\
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bp = _mm_add_epi16(bp, alpha_k);\
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bn = _mm_add_epi16(bn, alpha_k); output[k-d] = hMax(bn) - hMax(bp);
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/* The tail does not require to load alpha or produce outputs. Only update
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* beta metrics accordingly */
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for (k=end-1; k>=long_cb; k--) {
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int16_t g0 = s->branch[2*k];
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int16_t g1 = s->branch[2*k+1];
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@ -130,6 +139,8 @@ void srslte_map_gen_beta(srslte_map_gen_t * s, int16_t * output, uint32_t long_c
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BETA_STEP(g);
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}
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/* We inline 2 trelis steps for each normalization */
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__m128i norm;
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for (; k >= 0; k-=8) {
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gv = _mm_load_si128(gPtr);
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@ -151,7 +162,8 @@ void srslte_map_gen_beta(srslte_map_gen_t * s, int16_t * output, uint32_t long_c
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}
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}
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void srslte_map_gen_alpha(srslte_map_gen_t * s, uint32_t long_cb)
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/* Computes alpha metrics */
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void map_gen_alpha(map_gen_t * s, uint32_t long_cb)
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{
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uint32_t k;
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int16_t *alpha = s->alpha;
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@ -162,6 +174,7 @@ void srslte_map_gen_alpha(srslte_map_gen_t * s, uint32_t long_cb)
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alpha[i] = -INF;
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}
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/* Define the shuffle constant for the positive alpha */
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__m128i shuf_ap = _mm_set_epi8(
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15, 14, // 7
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9, 8, // 4
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@ -173,6 +186,7 @@ void srslte_map_gen_alpha(srslte_map_gen_t * s, uint32_t long_cb)
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3, 2 // 1
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);
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/* Define the shuffle constant for the negative alpha */
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__m128i shuf_an = _mm_set_epi8(
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13, 12, // 6
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11, 10, // 5
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@ -184,6 +198,7 @@ void srslte_map_gen_alpha(srslte_map_gen_t * s, uint32_t long_cb)
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1, 0 // 0
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);
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/* Define shuffle for branch costs */
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__m128i shuf_g[4];
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shuf_g[0] = _mm_set_epi8(3,2,3,2,1,0,1,0,1,0,1,0,3,2,3,2);
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shuf_g[1] = _mm_set_epi8(7,6,7,6,5,4,5,4,5,4,5,4,7,6,7,6);
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@ -201,6 +216,10 @@ void srslte_map_gen_alpha(srslte_map_gen_t * s, uint32_t long_cb)
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__m128i alpha_k = _mm_set_epi16(-INF, -INF, -INF, -INF, -INF, -INF, -INF, 0);
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/* This defines a alpha computation step:
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* Adds and substracts the branch metrics to the previous alpha step,
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* shuffles the states according to the trellis path and selects maximum state
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*/
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#define ALPHA_STEP(c) g = _mm_shuffle_epi8(gv, shuf_g[c]); \
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ap = _mm_add_epi16(alpha_k, g);\
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an = _mm_sub_epi16(alpha_k, g);\
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@ -209,7 +228,8 @@ void srslte_map_gen_alpha(srslte_map_gen_t * s, uint32_t long_cb)
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alpha_k = _mm_max_epi16(ap, an);\
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_mm_store_si128(alphaPtr, alpha_k);\
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alphaPtr++; \
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/* In this loop, we compute 8 steps and normalize twice for each branch metrics memory load */
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__m128i norm;
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for (k = 0; k < long_cb/8; k++) {
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gv = _mm_load_si128(gPtr);
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@ -231,7 +251,8 @@ void srslte_map_gen_alpha(srslte_map_gen_t * s, uint32_t long_cb)
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}
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}
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void srslte_map_gen_gamma(srslte_map_gen_t * h, int16_t *input, int16_t *app, int16_t *parity, uint32_t long_cb)
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/* Compute branch metrics (gamma) */
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void map_gen_gamma(map_gen_t * h, int16_t *input, int16_t *app, int16_t *parity, uint32_t long_cb)
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{
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__m128i res10, res20, res11, res21, res1, res2;
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__m128i in, ap, pa, g1, g0;
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@ -284,10 +305,10 @@ void srslte_map_gen_gamma(srslte_map_gen_t * h, int16_t *input, int16_t *app, in
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}
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}
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int srslte_map_gen_init(srslte_map_gen_t * h, int max_long_cb)
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/* Inititalizes constituent decoder object */
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int map_gen_init(map_gen_t * h, int max_long_cb)
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{
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bzero(h, sizeof(srslte_map_gen_t));
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bzero(h, sizeof(map_gen_t));
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h->alpha = srslte_vec_malloc(sizeof(int16_t) * (max_long_cb + SRSLTE_TCOD_TOTALTAIL + 1) * NUMSTATES);
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if (!h->alpha) {
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perror("srslte_vec_malloc");
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@ -302,7 +323,7 @@ int srslte_map_gen_init(srslte_map_gen_t * h, int max_long_cb)
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return 0;
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}
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void srslte_map_gen_free(srslte_map_gen_t * h)
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void map_gen_free(map_gen_t * h)
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{
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if (h->alpha) {
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free(h->alpha);
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@ -310,29 +331,26 @@ void srslte_map_gen_free(srslte_map_gen_t * h)
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if (h->branch) {
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free(h->branch);
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}
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bzero(h, sizeof(srslte_map_gen_t));
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bzero(h, sizeof(map_gen_t));
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}
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void srslte_map_gen_dec(srslte_map_gen_t * h, int16_t * input, int16_t *app, int16_t * parity, int16_t * output,
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/* Runs one instance of a decoder */
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void map_gen_dec(map_gen_t * h, int16_t * input, int16_t *app, int16_t * parity, int16_t * output,
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uint32_t long_cb)
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{
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// Compute branch metrics
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srslte_map_gen_gamma(h, input, app, parity, long_cb);
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map_gen_gamma(h, input, app, parity, long_cb);
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// Forward recursion
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srslte_map_gen_alpha(h, long_cb);
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map_gen_alpha(h, long_cb);
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// Backwards recursion + LLR computation
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srslte_map_gen_beta(h, output, long_cb);
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map_gen_beta(h, output, long_cb);
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}
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/************************************************
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*
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* TURBO DECODER INTERFACE
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*
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************************************************/
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/* Initializes the turbo decoder object */
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int srslte_tdec_sse_init(srslte_tdec_sse_t * h, uint32_t max_long_cb)
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{
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int ret = -1;
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@ -377,7 +395,7 @@ int srslte_tdec_sse_init(srslte_tdec_sse_t * h, uint32_t max_long_cb)
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goto clean_and_exit;
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}
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if (srslte_map_gen_init(&h->dec, h->max_long_cb)) {
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if (map_gen_init(&h->dec, h->max_long_cb)) {
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goto clean_and_exit;
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}
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@ -419,7 +437,7 @@ void srslte_tdec_sse_free(srslte_tdec_sse_t * h)
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free(h->parity1);
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}
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srslte_map_gen_free(&h->dec);
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map_gen_free(&h->dec);
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for (int i=0;i<SRSLTE_NOF_TC_CB_SIZES;i++) {
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srslte_tc_interl_free(&h->interleaver[i]);
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@ -428,6 +446,9 @@ void srslte_tdec_sse_free(srslte_tdec_sse_t * h)
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bzero(h, sizeof(srslte_tdec_sse_t));
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}
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/* Deinterleaves the 3 streams from the input (systematic and 2 parity bits) into
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* 3 buffers ready to be used by compute_gamma()
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*/
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void deinterleave_input(srslte_tdec_sse_t *h, int16_t *input, uint32_t long_cb) {
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uint32_t i;
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@ -512,6 +533,7 @@ void deinterleave_input(srslte_tdec_sse_t *h, int16_t *input, uint32_t long_cb)
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}
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/* Runs 1 turbo decoder iteration */
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void srslte_tdec_sse_iteration(srslte_tdec_sse_t * h, int16_t * input, uint32_t long_cb)
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{
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@ -530,9 +552,9 @@ void srslte_tdec_sse_iteration(srslte_tdec_sse_t * h, int16_t * input, uint32_t
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// Run MAP DEC #1
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if (h->n_iter == 0) {
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srslte_map_gen_dec(&h->dec, h->syst, NULL, h->parity0, h->ext1, long_cb);
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map_gen_dec(&h->dec, h->syst, NULL, h->parity0, h->ext1, long_cb);
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} else {
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srslte_map_gen_dec(&h->dec, h->syst, h->app1, h->parity0, h->ext1, long_cb);
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map_gen_dec(&h->dec, h->syst, h->app1, h->parity0, h->ext1, long_cb);
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}
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// Convert aposteriori information into extrinsic information
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@ -544,7 +566,7 @@ void srslte_tdec_sse_iteration(srslte_tdec_sse_t * h, int16_t * input, uint32_t
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srslte_vec_lut_sss(h->ext1, deinter, h->app2, long_cb);
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// Run MAP DEC #2. 2nd decoder uses apriori information as systematic bits
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srslte_map_gen_dec(&h->dec, h->app2, NULL, h->parity1, h->ext2, long_cb);
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map_gen_dec(&h->dec, h->app2, NULL, h->parity1, h->ext2, long_cb);
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// Deinterleaved extrinsic bits become apriori info for decoder 1
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srslte_vec_lut_sss(h->ext2, inter, h->app1, long_cb);
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@ -555,6 +577,7 @@ void srslte_tdec_sse_iteration(srslte_tdec_sse_t * h, int16_t * input, uint32_t
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}
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}
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/* Resets the decoder and sets the codeblock length */
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int srslte_tdec_sse_reset(srslte_tdec_sse_t * h, uint32_t long_cb)
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{
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if (long_cb > h->max_long_cb) {
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@ -616,6 +639,7 @@ void srslte_tdec_sse_decision_byte(srslte_tdec_sse_t * h, uint8_t *output, uint3
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}
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}
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/* Runs nof_iterations iterations and decides the output bits */
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int srslte_tdec_sse_run_all(srslte_tdec_sse_t * h, int16_t * input, uint8_t *output,
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uint32_t nof_iterations, uint32_t long_cb)
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{
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