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x86 branchless cabac decoder

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slightly faster on P3

Originally committed as revision 6608 to svn://svn.ffmpeg.org/ffmpeg/trunk
This commit is contained in:
Michael Niedermayer 2006-10-09 20:51:33 +00:00
parent 2e1aee80f4
commit ef0090a998
1 changed files with 68 additions and 1 deletions
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69
libavcodec/cabac.h
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@ -31,6 +31,7 @@
#define CABAC_BITS 16
#define CABAC_MASK ((1<<CABAC_BITS)-1)
#define BRANCHLESS_CABAD 1
typedef struct CABACContext{
int low;
@ -374,7 +375,7 @@ static int get_cabac(CABACContext *c, uint8_t * const state){
#define BYTESTART "12+2*66*4+4*65"
#define BYTE "16+2*66*4+4*65"
#define BYTEEND "20+2*66*4+4*65"
#ifndef BRANCHLESS_CABAD
asm volatile(
"movzbl (%1), %%eax \n\t"
"movl "RANGE "(%2), %%ebx \n\t"
@ -446,6 +447,72 @@ static int get_cabac(CABACContext *c, uint8_t * const state){
:"r"(state), "r"(c)
: "%ecx", "%ebx", "%edx", "%esi"
);
#else
asm volatile(
"movzbl (%1), %%eax \n\t"
"movl "RANGE "(%2), %%ebx \n\t"
"movl "RANGE "(%2), %%edx \n\t"
"shrl $23, %%ebx \n\t"
"leal "LPS_RANGE"(%2, %%eax, 4), %%esi \n\t"
"movzbl (%%ebx, %%esi), %%esi \n\t"
"shll $17, %%esi \n\t"
"movl "LOW "(%2), %%ebx \n\t"
//eax:state ebx:low, edx:range, esi:RangeLPS
"subl %%esi, %%edx \n\t"
"movl %%edx, %%ecx \n\t"
"subl %%ebx, %%edx \n\t"
"sarl $31, %%edx \n\t" //lps_mask
"subl %%ecx, %%esi \n\t" //RangeLPS - range
"andl %%edx, %%esi \n\t" //(RangeLPS - range)&lps_mask
"addl %%ecx, %%esi \n\t" //new range
"andl %%edx, %%ecx \n\t"
"subl %%ecx, %%ebx \n\t"
//eax:state ebx:low edx:mask esi:range
"movl $-130, %%ecx \n\t"
"andl %%edx, %%ecx \n\t"
"addl %%eax, %%ecx \n\t"
"xorl %%edx, %%eax \n\t"
"movb "MPS_STATE"(%2, %%eax), %%cl \n\t"
"movb %%cl, (%1) \n\t"
"movl %%esi, %%edx \n\t"
//eax:bit ebx:low edx:range esi:range
"shr $19, %%esi \n\t"
"movb " MANGLE(ff_h264_norm_shift) "(%%esi), %%cl \n\t"
"shll %%cl, %%ebx \n\t"
"shll %%cl, %%edx \n\t"
"test %%bx, %%bx \n\t"
" jnz 1f \n\t"
"movl "BYTE "(%2), %%ecx \n\t"
"movzwl (%%ecx), %%esi \n\t"
"bswap %%esi \n\t"
"shrl $15, %%esi \n\t"
"subl $0xFFFF, %%esi \n\t"
"addl $2, %%ecx \n\t"
"movl %%ecx, "BYTE "(%2) \n\t"
"leal -1(%%ebx), %%ecx \n\t"
"xorl %%ebx, %%ecx \n\t"
"shrl $17, %%ecx \n\t"
"movb " MANGLE(ff_h264_norm_shift) "(%%ecx), %%cl \n\t"
"neg %%cl \n\t"
"add $7, %%cl \n\t"
"shll %%cl , %%esi \n\t"
"addl %%esi, %%ebx \n\t"
"1: \n\t"
"movl %%edx, "RANGE "(%2) \n\t"
"movl %%ebx, "LOW "(%2) \n\t"
"andl $1, %%eax \n\t"
:"=&a"(bit)
:"r"(state), "r"(c)
: "%ecx", "%ebx", "%edx", "%esi"
);
#endif
#else
int s = *state;
int RangeLPS= c->lps_range[s][c->range>>(CABAC_BITS+7)]<<(CABAC_BITS+1);