From a31630e0d5b9880c716d9004ef4154396ba41ebc Mon Sep 17 00:00:00 2001 From: "Matthias P. Braendli" Date: Thu, 2 Jan 2014 21:55:13 +0100 Subject: Extract fec-3.0.1 --- viterbi27_sse2.c | 180 +++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 180 insertions(+) create mode 100644 viterbi27_sse2.c (limited to 'viterbi27_sse2.c') diff --git a/viterbi27_sse2.c b/viterbi27_sse2.c new file mode 100644 index 0000000..bc01710 --- /dev/null +++ b/viterbi27_sse2.c @@ -0,0 +1,180 @@ +/* K=7 r=1/2 Viterbi decoder for SSE2 + * Feb 2004, Phil Karn, KA9Q + */ +#include +#include +#include +#include +#include "fec.h" + +typedef union { unsigned char c[64]; __m128i v[4]; } metric_t; +typedef union { unsigned long w[2]; unsigned char c[8]; unsigned short s[4]; __m64 v[1];} decision_t; +union branchtab27 { unsigned char c[32]; __m128i v[2];} Branchtab27_sse2[2]; +static int Init = 0; + +/* State info for instance of Viterbi decoder + * Don't change this without also changing references in sse2bfly27.s! + */ +struct v27 { + metric_t metrics1; /* path metric buffer 1 */ + metric_t metrics2; /* path metric buffer 2 */ + decision_t *dp; /* Pointer to current decision */ + metric_t *old_metrics,*new_metrics; /* Pointers to path metrics, swapped on every bit */ + decision_t *decisions; /* Beginning of decisions for block */ +}; + +/* Initialize Viterbi decoder for start of new frame */ +int init_viterbi27_sse2(void *p,int starting_state){ + struct v27 *vp = p; + int i; + + if(p == NULL) + return -1; + for(i=0;i<64;i++) + vp->metrics1.c[i] = 63; + + vp->old_metrics = &vp->metrics1; + vp->new_metrics = &vp->metrics2; + vp->dp = vp->decisions; + vp->old_metrics->c[starting_state & 63] = 0; /* Bias known start state */ + return 0; +} + +void set_viterbi27_polynomial_sse2(int polys[2]){ + int state; + + for(state=0;state < 32;state++){ + Branchtab27_sse2[0].c[state] = (polys[0] < 0) ^ parity((2*state) & abs(polys[0])) ? 255 : 0; + Branchtab27_sse2[1].c[state] = (polys[1] < 0) ^ parity((2*state) & abs(polys[1])) ? 255 : 0; + } + Init++; +} + + +/* Create a new instance of a Viterbi decoder */ +void *create_viterbi27_sse2(int len){ + void *p; + struct v27 *vp; + + if(!Init){ + int polys[2] = { V27POLYA, V27POLYB }; + set_viterbi27_polynomial_sse2(polys); + } + /* Ordinary malloc() only returns 8-byte alignment, we need 16 */ + if(posix_memalign(&p, sizeof(__m128i),sizeof(struct v27))) + return NULL; + vp = (struct v27 *)p; + + if((p = malloc((len+6)*sizeof(decision_t))) == NULL){ + free(vp); + return NULL; + } + vp->decisions = (decision_t *)p; + init_viterbi27_sse2(vp,0); + + return vp; +} + +/* Viterbi chainback */ +int chainback_viterbi27_sse2( + void *p, + unsigned char *data, /* Decoded output data */ + unsigned int nbits, /* Number of data bits */ + unsigned int endstate){ /* Terminal encoder state */ + struct v27 *vp = p; + decision_t *d; + + if(p == NULL) + return -1; + d = vp->decisions; + /* Make room beyond the end of the encoder register so we can + * accumulate a full byte of decoded data + */ + endstate %= 64; + endstate <<= 2; + + /* 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 += 6; /* Look past tail */ + while(nbits-- != 0){ + int k; + + k = (d[nbits].c[(endstate>>2)/8] >> ((endstate>>2)%8)) & 1; + data[nbits>>3] = endstate = (endstate >> 1) | (k << 7); + } + return 0; +} + +/* Delete instance of a Viterbi decoder */ +void delete_viterbi27_sse2(void *p){ + struct v27 *vp = p; + + if(vp != NULL){ + free(vp->decisions); + free(vp); + } +} + + +#if 0 +/* This code is turned off because it's slower than my hand-crafted assembler in sse2bfly27.s. But it does work. */ +void update_viterbi27_blk_sse2(void *p,unsigned char *syms,int nbits){ + struct v27 *vp = p; + decision_t *d; + + if(p == NULL) + return; + d = (decision_t *)vp->dp; + while(nbits--){ + __m128i sym0v,sym1v; + void *tmp; + int i; + + /* Splat the 0th symbol across sym0v, the 1st symbol across sym1v, etc */ + sym0v = _mm_set1_epi8(syms[0]); + sym1v = _mm_set1_epi8(syms[1]); + syms += 2; + + for(i=0;i<2;i++){ + __m128i decision0,decision1,metric,m_metric,m0,m1,m2,m3,survivor0,survivor1; + + /* Form branch metrics */ + metric = _mm_avg_epu8(_mm_xor_si128(Branchtab27_sse2[0].v[i],sym0v),_mm_xor_si128(Branchtab27_sse2[1].v[i],sym1v)); + /* There's no packed bytes right shift in SSE2, so we use the word version and mask + * (I'm *really* starting to like Altivec...) + */ + metric = _mm_srli_epi16(metric,3); + metric = _mm_and_si128(metric,_mm_set1_epi8(31)); + m_metric = _mm_sub_epi8(_mm_set1_epi8(31),metric); + + /* Add branch metrics to path metrics */ + m0 = _mm_add_epi8(vp->old_metrics->v[i],metric); + m3 = _mm_add_epi8(vp->old_metrics->v[2+i],metric); + m1 = _mm_add_epi8(vp->old_metrics->v[2+i],m_metric); + m2 = _mm_add_epi8(vp->old_metrics->v[i],m_metric); + + /* Compare and select, using modulo arithmetic */ + decision0 = _mm_cmpgt_epi8(_mm_sub_epi8(m0,m1),_mm_setzero_si128()); + decision1 = _mm_cmpgt_epi8(_mm_sub_epi8(m2,m3),_mm_setzero_si128()); + survivor0 = _mm_or_si128(_mm_and_si128(decision0,m1),_mm_andnot_si128(decision0,m0)); + survivor1 = _mm_or_si128(_mm_and_si128(decision1,m3),_mm_andnot_si128(decision1,m2)); + + /* Pack each set of decisions into 16 bits */ + d->s[2*i] = _mm_movemask_epi8(_mm_unpacklo_epi8(decision0,decision1)); + d->s[2*i+1] = _mm_movemask_epi8(_mm_unpackhi_epi8(decision0,decision1)); + + /* Store surviving metrics */ + vp->new_metrics->v[2*i] = _mm_unpacklo_epi8(survivor0,survivor1); + vp->new_metrics->v[2*i+1] = _mm_unpackhi_epi8(survivor0,survivor1); + } + 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; +} +#endif -- cgit v1.2.3