Re: [Nasm-users] Setting/Clearing OF

[Robert A. <e.a...@st...>]

> Date: Tue, 11 Aug 2009 00:54:37 -0700
> From: hp...@zy...
> To: fbk...@zy...
> CC: e.a...@st...; nas...@li...
> Subject: Re: [Nasm-users] Setting/Clearing OF
> 
> On 08/10/2009 10:54 PM, Frank Kotler wrote:
>> 
>> "lahf" is only going to get the low 8 bits of the flags register, and OF 
>> is bit 11, so you'll have to resort to pushf, manipulate the dword on 
>> stack, and popf, I think. Something like this... (intended to be 
>> "portable")...
>> 
> 
> Another option is to perform an operation on the arithmetic flags that
> affects OF, and then use LAHF/SAHF to preserve the *other* AFs:
> 
> 	; Trashes AX
> clear_of:
> 	lahf
> 	xor al,al	; OF <- 0
> 	sahf
> 	ret
> 
> set_of:
> 	lahf
> 	mov al,127
> 	inc al		; OF <- 1
> 	sahf
> 	ret
> 
> -- 
> H. Peter Anvin, Intel Open Source Technology Center
> I work for Intel.  I don't speak on their behalf.
> 
> 
> 

Hi,

Thanks for the responses. I'll try both ways out to see which one works out the best for me.



Thanks again for your time,

Robert Alegrid

------------------------------------------------------------------------------
Robert Alegrid
RMIT University
Student #3164658
BP-079 Physics
BP-083 Mathematics

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