Xref: news2.mv.net comp.os.msdos.djgpp:7221
From: John Luebs <jkluebs AT sprynet DOT com>
Newsgroups: comp.os.msdos.djgpp
Subject: Re: Accessing Variables in Inline ASM
Date: Tue, 13 Aug 1996 20:30:27 -0400
Organization: EpiCenter Software
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Message-ID: <32111E23.40CF@sprynet.com>
References: <199608071658 DOT JAA08681 AT bluesky>
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To: djgpp AT delorie DOT com
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Kevin Baca wrote:
> 
> > Ok, I'm starting to get the hang of inline ASM, but I just can't
> > find a good reference on how to access variables via inline ASM.
> > I've heard that you must declare everything globally, but this can't
> > be the best solution.  Does anyone know a better way, or a place
> > where I could read up on the subject?  If I declare a variable
> > within a function, how can I use that variable in my inline ASM
> > routine?  If the function is recursive, how will that affect things?
> >  Thanks!
> >
> > -David :)
> 
> The following function adds 3 ints and returns the result.  You can
> see how it accesses local variables.  The "rm" means the variable
> could either be in a register or in memory.  Check out the info
> section of gcc on inline assembly for more of this kind of stuff.
> 
> int add3(int i, int j, int k)
> {
>    int ret;
> 
>   __asm__("
>            movl %1,%%eax
>            addl %2,%%eax
>            addl %3,%%eax"
>            : "=a" ret
>            : "rm" (i),"rm" (j),"rm" (k)
>            : "eax");
> 
>    return ret;
> }
> 
> -Kevin
Go to http://remus.rutgers.edu/~avly/djasm.html
It has the official tutorial to inline assembler, it gives alot of
information about how to deal with inputs, outputs, and handling
modified registers.