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use multiply instead of divides for DC prediction on X86

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Originally committed as revision 286 to svn://svn.ffmpeg.org/ffmpeg/trunk
This commit is contained in:
Michael Niedermayer 2002-02-05 22:51:23 +00:00
parent b81cf27484
commit 6fe84b4327
1 changed files with 10 additions and 12 deletions
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22
libavcodec/msmpeg4.c
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@ -50,6 +50,8 @@ static int msmpeg4_decode_dc(MpegEncContext * s, int n, int *dir_ptr);
static int msmpeg4_decode_motion(MpegEncContext * s, static int msmpeg4_decode_motion(MpegEncContext * s,
int *mx_ptr, int *my_ptr); int *mx_ptr, int *my_ptr);
extern UINT32 inverse[256];
#ifdef DEBUG #ifdef DEBUG
int intra_count = 0; int intra_count = 0;
int frame_count = 0; int frame_count = 0;
@ -438,26 +440,22 @@ static int msmpeg4_pred_dc(MpegEncContext * s, int n,
fact they decided to store the quantized DC (which would lead fact they decided to store the quantized DC (which would lead
to problems if Q could vary !) */ to problems if Q could vary !) */
#if defined ARCH_X86 && !defined PIC #if defined ARCH_X86 && !defined PIC
/* using 16bit divisions as they are large enough and 2x as fast */
asm volatile( asm volatile(
"movl %3, %%eax \n\t" "movl %3, %%eax \n\t"
"shrl $1, %%eax \n\t" "shrl $1, %%eax \n\t"
"addl %%eax, %2 \n\t" "addl %%eax, %2 \n\t"
"addl %%eax, %1 \n\t" "addl %%eax, %1 \n\t"
"addl %0, %%eax \n\t" "addl %0, %%eax \n\t"
"xorl %%edx, %%edx \n\t" "mull %4 \n\t"
"divw %w3 \n\t" "movl %%edx, %0 \n\t"
"movzwl %%ax, %0 \n\t"
"movl %1, %%eax \n\t" "movl %1, %%eax \n\t"
"xorl %%edx, %%edx \n\t" "mull %4 \n\t"
"divw %w3 \n\t" "movl %%edx, %1 \n\t"
"movzwl %%ax, %1 \n\t"
"movl %2, %%eax \n\t" "movl %2, %%eax \n\t"
"xorl %%edx, %%edx \n\t" "mull %4 \n\t"
"divw %w3 \n\t" "movl %%edx, %2 \n\t"
"movzwl %%ax, %2 \n\t" : "+r" (a), "+r" (b), "+r" (c)
: "+r" (a), "+r" (b), "+r" (c) : "g" (scale), "r" (inverse[scale])
: "r" (scale)
: "%eax", "%edx" : "%eax", "%edx"
); );
#else #else