From: Simon Hammett <khcm6sh AT dmu DOT ac DOT uk>
Newsgroups: comp.os.msdos.djgpp
Subject: Some Inline ASM questions
Date: Thu, 17 Oct 1996 16:33:41 +0100
Organization: De Montfort University MK
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To: djgpp AT delorie DOT com
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Hi all,
	After trawling throught the FAQ, the GNU C Preprocessor info, and the
GCC info I've decided to give up and ask for a hand...

in a simple GFX library I'm writting, I want to be able to change what
Resolution it works in by chaning a #define statement. This obviously
makes changing the code much easier. But I can't find anyway of using a
defined macro in a inline ASM("") statement ie:


#define	HREZ	640


some_routine()
{
asm	("

	movl	_Y_coord, %eax
	imul	$HREZ, %eax

	");
}

unfortunately this doesn't work as the PreProcessor ignores the HREZ
macro, so the linker tripes up.
I know I could just use a global varible and use imul _HREZ, %eax, but
I'd like to know how to use the #define's in the assembly code.

Also, is it possible to pass values to a inline asm, ie write a function
entirly in ASM with out having to use global varibles.

ie

int	some_function ( int x, int y );
{
asm	("

	movl	X(%sp), %eax
	imul	Y(%sp), %eax
	movl	%eax, RESULT( %sp )

	");
}

I'd like to be able to do this, without having to guess where the
varibles are on the stack, or having to enter absolute values for X, Y
and RESULT, which obviously would need changing if the passed parameters
are altered.

TIA, Sim