Extract fec-3.0.1

1 files changed, 204 insertions, 0 deletions

diff --git a/viterbi615_sse2.c b/viterbi615_sse2.c
new file mode 100644
index 0000000..7f711e5
--- /dev/null
+++ b/viterbi615_sse2.c
@@ -0,0 +1,204 @@
+/* K=15 r=1/6 Viterbi decoder for x86 SSE2
+ * Copyright Mar 2004, Phil Karn, KA9Q
+ * May be used under the terms of the GNU Lesser General Public License (LGPL)
+ */
+#include <emmintrin.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <memory.h>
+#include <limits.h>
+#include "fec.h"
+
+typedef union { unsigned long w[512]; unsigned short s[1024];} decision_t;
+typedef union { signed short s[16384]; __m128i v[2048];} metric_t;
+
+static union branchtab615 { unsigned short s[8192]; __m128i v[1024];} 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_sse2(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_sse2(int len){
+  void *p;
+  struct v615 *vp;
+
+  if(!Init){
+    int polys[6] = { V615POLYA,V615POLYB,V615POLYC,V615POLYD,V615POLYE,V615POLYF };
+    set_viterbi615_polynomial_sse2(polys);
+  }
+
+  /* Ordinary malloc() only returns 8-byte alignment, we need 16 */
+  if(posix_memalign(&p, sizeof(__m128i),sizeof(struct v615)))
+    return NULL;
+
+  vp = (struct v615 *)p;
+  if((p = malloc((len+14)*sizeof(decision_t))) == NULL){
+    free(vp);
+    return NULL;
+  }
+  vp->decisions = (decision_t *)p;
+  init_viterbi615_sse2(vp,0);
+  return vp;
+}
+
+void set_viterbi615_polynomial_sse2(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_sse2(
+      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 = (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;
+    endstate = (k << 13) | (endstate >> 1);
+    data[nbits>>3] = endstate >> 6;
+  }
+  return 0;
+}
+
+/* Delete instance of a Viterbi decoder */
+void delete_viterbi615_sse2(void *p){
+  struct v615 *vp = p;
+
+  if(vp != NULL){
+    free(vp->decisions);
+    free(vp);
+  }
+}
+
+
+int update_viterbi615_blk_sse2(void *p,unsigned char *syms,int nbits){
+  struct v615 *vp = p;
+  decision_t *d = (decision_t *)vp->dp;
+
+  while(nbits--){
+    __m128i 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_epi16(syms[0]);
+    sym1v = _mm_set1_epi16(syms[1]);
+    sym2v = _mm_set1_epi16(syms[2]);
+    sym3v = _mm_set1_epi16(syms[3]);
+    sym4v = _mm_set1_epi16(syms[4]);
+    sym5v = _mm_set1_epi16(syms[5]);
+    syms += 6;
+
+    /* SSE2 doesn't support saturated adds on unsigned shorts, so we have to use signed shorts */
+    for(i=0;i<1024;i++){
+      __m128i 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_epi16(_mm_xor_si128(Branchtab615[0].v[i],sym0v),_mm_xor_si128(Branchtab615[1].v[i],sym1v));
+      m1 = _mm_add_epi16(_mm_xor_si128(Branchtab615[2].v[i],sym2v),_mm_xor_si128(Branchtab615[3].v[i],sym3v));
+      m2 = _mm_add_epi16(_mm_xor_si128(Branchtab615[4].v[i],sym4v),_mm_xor_si128(Branchtab615[5].v[i],sym5v));
+      metric = _mm_add_epi16(m0,_mm_add_epi16(m1,m2));
+      m_metric = _mm_sub_epi16(_mm_set1_epi16(1530),metric);
+    
+      /* Add branch metrics to path metrics */
+      m0 = _mm_adds_epi16(vp->old_metrics->v[i],metric);
+      m3 = _mm_adds_epi16(vp->old_metrics->v[1024+i],metric);
+      m1 = _mm_adds_epi16(vp->old_metrics->v[1024+i],m_metric);
+      m2 = _mm_adds_epi16(vp->old_metrics->v[i],m_metric);
+    
+      /* Compare and select */
+      survivor0 = _mm_min_epi16(m0,m1);
+      survivor1 = _mm_min_epi16(m2,m3);
+      decision0 = _mm_cmpeq_epi16(survivor0,m1);
+      decision1 = _mm_cmpeq_epi16(survivor1,m3);
+ 
+      /* Pack each set of decisions into 8 8-bit bytes, then interleave them and compress into 16 bits */
+      d->s[i] = _mm_movemask_epi8(_mm_unpacklo_epi8(_mm_packs_epi16(decision0,_mm_setzero_si128()),_mm_packs_epi16(decision1,_mm_setzero_si128())));
+
+      /* Store surviving metrics */
+      vp->new_metrics->v[2*i] = _mm_unpacklo_epi16(survivor0,survivor1);
+      vp->new_metrics->v[2*i+1] = _mm_unpackhi_epi16(survivor0,survivor1);
+    }
+    /* See if we need to renormalize
+     * Max metric spread for this code with 0-90 branch metrics is 405
+     */
+    if(vp->new_metrics->s[0] >= SHRT_MAX-12750){
+      int i,adjust;
+      __m128i adjustv;
+      union { __m128i v; signed short w[8]; } t;
+      
+      /* Find smallest metric and set adjustv to bring it down to SHRT_MIN */
+      adjustv = vp->new_metrics->v[0];
+      for(i=1;i<2048;i++)
+	adjustv = _mm_min_epi16(adjustv,vp->new_metrics->v[i]);
+
+      adjustv = _mm_min_epi16(adjustv,_mm_srli_si128(adjustv,8));
+      adjustv = _mm_min_epi16(adjustv,_mm_srli_si128(adjustv,4));
+      adjustv = _mm_min_epi16(adjustv,_mm_srli_si128(adjustv,2));
+      t.v = adjustv;
+      adjust = t.w[0] - SHRT_MIN;
+      adjustv = _mm_set1_epi16(adjust);
+
+      /* We cannot use a saturated subtract, because we often have to adjust by more than SHRT_MAX
+       * This is okay since it can't overflow anyway
+       */
+      for(i=0;i<2048;i++)
+	vp->new_metrics->v[i] = _mm_sub_epi16(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;
+  return 0;
+}
+
+