From: Vic <tudor AT cam DOT org>
Newsgroups: comp.os.msdos.djgpp
Subject: Re: ok with negative values in inline asm?
Date: Sun, 24 May 1998 12:25:13 -0400
Organization: Communications Accessibles Montreal, Quebec Canada
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Viktor Lundstrom wrote:
> 
> I want to either subtract or add 1 to 32-bit register.
> Would this decrease whatever is in %%edi with 1? :
> asm ("movb $-1, %%ah
>           addl %%ah, %%edi"
>         :
>         :
>         :"%eax", "%edi");
> 
> Or do I have to use a 32bit register (ie. replacing ah with for
> example ebx)?

why not just use increment/decrement instructions? (Or do you want to
add a bigger negative number? )

anyways, the code y-=2; outputs addl $-2,%eax so I guess, yes, you can
use negative numbers.

BTW, group: is there an instruction in ASM for substraction, or just
addition?