Message-Id: <199808010337.EAA08924@sable.ox.ac.uk>
Comments: Authenticated sender is <mert0407 AT sable DOT ox DOT ac DOT uk>
From: George Foot <george DOT foot AT merton DOT oxford DOT ac DOT uk>
To: drmcc AT ecr DOT mu DOT oz DOT au
Date: Sat, 1 Aug 1998 04:36:57 +0000
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Subject: Re: Inline asm
Reply-to: george DOT foot AT merton DOT oxford DOT ac DOT uk
CC: djgpp AT delorie DOT com
Precedence: bulk

On  1 Aug 98 at 12:20, Donald McComb wrote:

> Okay, I have a (very) limited knowledge of intel assembler, and I'd like
> to convert some inline asm in intel format which I've found in a book
> into AT&T format for use with djgpp.  Here's the intel asm:
> 
> 	_asm {
> 		push ds;
> 		les di, video_buffer;
> 		lds si, data;
> 		mov cx,320*200/2;
> 		cld;
> 		rep movsw;
> 		pop ds;
> 	}

How about this:  memcpy (video_buffer, data, 320*200);

That's assuming that `video_buffer' and `data' are just ordinary 
pointers.  Since 320*200 is a constant, gcc will inline this anyway 
to something like this:

    movl _video_buffer,%edi
    movl _data,%esi
    cld
    movl $16000,%ecx
    rep
    movsl

You can't ask for much more, can you? :)

Notes:

* ES and DS are automatically correctly set, because they're
normally both equal to our program's main segment, in which all our
heap resides.  

* gcc is copying longs here -- 16000 longs = 320*200 bytes.

* If you want to copy this code into extended inline assembler, 
you'll need to double up the % signs (as you did in your example).  
Or you could just arrange for all the values to be in the correct 
registers to begin with, and just put "cld ; rep ; movsl" as the 
instructions.

Ultimately, though, you might as well use memcpy since that's what 
it's for.

-- 
george DOT foot AT merton DOT oxford DOT ac DOT uk