[SCM] libav/experimental: reordering instructions a little in decode_significance_x86() -> 2 instructions less / 1% faster decode_residual on P3

siretart at users.alioth.debian.org siretart at users.alioth.debian.org
Sun Jun 30 15:52:26 UTC 2013


The following commit has been merged in the experimental branch:
commit a616db285a1765f81887ed874cfa6ee95429ce0a
Author: Michael Niedermayer <michaelni at gmx.at>
Date:   Fri Oct 20 00:51:04 2006 +0000

    reordering instructions a little in decode_significance_x86() -> 2 instructions less / 1% faster decode_residual on P3
    
    Originally committed as revision 6741 to svn://svn.ffmpeg.org/ffmpeg/trunk

diff --git a/libavcodec/cabac.h b/libavcodec/cabac.h
index 9bea58b..5cf1a9e 100644
--- a/libavcodec/cabac.h
+++ b/libavcodec/cabac.h
@@ -684,11 +684,13 @@ static int decode_significance_x86(CABACContext *c, int max_coeff, uint8_t *sign
 
         "2:                                     \n\t"
 
-        BRANCHLESS_GET_CABAC("%0", "%3", "(%1)", "%%ebx", "%%bx", "%%esi", "%%edx", "%%dl")
+        BRANCHLESS_GET_CABAC("%%edx", "%3", "(%1)", "%%ebx", "%%bx", "%%esi", "%%eax", "%%al")
 
-        "test $1, %0                            \n\t"
+        "test $1, %%edx                         \n\t"
         " jz 3f                                 \n\t"
 
+        BRANCHLESS_GET_CABAC("%%edx", "%3", "61(%1)", "%%ebx", "%%bx", "%%esi", "%%eax", "%%al")
+
         "movl %2, %%eax                         \n\t"
         "movl %4, %%ecx                         \n\t"
         "addl %1, %%ecx                         \n\t"
@@ -696,9 +698,7 @@ static int decode_significance_x86(CABACContext *c, int max_coeff, uint8_t *sign
         "addl $4, %%eax                         \n\t"
         "movl %%eax, %2                         \n\t"
 
-        BRANCHLESS_GET_CABAC("%0", "%3", "61(%1)", "%%ebx", "%%bx", "%%esi", "%%edx", "%%dl")
-
-        "test $1, %%eax                         \n\t"
+        "test $1, %%edx                         \n\t"
         " jnz 4f                                \n\t"
 
         "3:                                     \n\t"
@@ -710,9 +710,7 @@ static int decode_significance_x86(CABACContext *c, int max_coeff, uint8_t *sign
         "addl %1, %%ecx                         \n\t"
         "movl %%ecx, (%%eax)                    \n\t"
         "addl $4, %%eax                         \n\t"
-        "movl %%eax, %2                         \n\t"
         "4:                                     \n\t"
-        "movl %2, %%eax                         \n\t"
         "addl %6, %%eax                         \n\t"
         "shr $2, %%eax                          \n\t"
 

-- 
Libav/FFmpeg packaging



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