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Comments: Authenticated sender is <salvador AT natacha DOT inti DOT edu DOT ar>
From: "Salvador Eduardo Tropea (SET)" <salvador AT natacha DOT inti DOT edu DOT ar>
To: Elliott Oti <e DOT oti AT stud DOT warande DOT ruu DOT nl DOT inti DOT edu DOT ar>, djgpp AT delorie DOT com
Date: Mon, 23 Dec 1996 15:47:34 +0000
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Subject: Re: memcpy(); is there something faster?

Hi Elliott
> Daniel Everton wrote:
> > 
> > Hi all,
> > 
> > In a program I'm currently writing I need to copy some biggish (64k)
> > shunks of memory around. I'm using memcpy() at the moment but it's not
> > quite fast enough. Is there some other function that any one can
> > suggest? The memory has all been allocated with malloc() and I'm not
> > copying between conventional memory or something like that. Any help
> > appreciated.
> 
>  
> Here's some code I originally got from Mihai Moise's port of GL,  it
> copies lng bytes from buffer src to buffer dst using movsl, with a movsb/movsw
> attached at the beginning & the end to even things out. For variable
> buffer sizes it should be faster than memcpy().
> 
> void CopyBuffer(void * dst, const void * src, int lng)
> {
>     asm("cld                 \n\t"
>         "movl %%edi,%%ecx    \n\t"
> 	"andl $1,%%ecx       \n\t"
> 	"subl %%ecx,%%edx    \n\t"
> 	"rep ; movsb         \n\t" 
> 	"movl %%edx,%%ecx    \n\t"
> 	"shrl $2,%%ecx       \n\t"
> 	"rep ; movsl         \n\t"
> 	"testb $1,%%dl       \n\t"
> 	"je 1f               \n\t"
> 	"movsb               \n"
> 	"1:\ttestb $2,%%dl   \n\t"
> 	"je 2f               \n\t"
> 	"movsw               \n"
> 	"2:                  \n"
> 	::"d" (lng),"D" ((long) dst),"S" ((long) src)
> 	: "cx","dx","di","si");
> }
That's practically equal to memcpy (you will save some little test at 
the begining of memcpy => 6 o 10 cicles in 128000)

SET 
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Salvador Eduardo Tropea (SET).
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