Newsgroups: comp.os.msdos.djgpp
From: Peter Berdeklis <peter AT atmosp DOT physics DOT utoronto DOT ca>
Subject: Re: 32 bit registers 
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Organization: University of Toronto - Dept. of Physics
In-Reply-To: <59vm0n$7gu$1@troll.powertech.no> 
Date: Fri, 27 Dec 1996 14:11:56 GMT
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On Thu, 26 Dec 1996, Ove Kaaven wrote:

> Peter Berdeklis <peter AT atmosp DOT physics DOT utoronto DOT ca> wrote:
> 
> >On Thu, 26 Dec 1996, Ove Kaaven wrote:
> >> To load the 16-bit value in bx into the high-order word of eax and
> >> preserving everything else, you could try:
> >> 
> >> roll $16,%eax
> >> movw %bx,%ax
> >> roll $16,%eax
> >       ^^^ should be $17
> 
> >roll moves the last bit into the carry flag, so you have to roll one more 
> >bit (the last time only) to get the bit out of the carry flag and into 
> >the MSB of the register.
> 
> Really? I thought that was the behaviour of rcl, not rol, hmm...

Forgive me, I misread my reference.  rol _copies_ the last bit rotated 
into the carry flag, it doesn't shift through it as does rcl.  It's all 
getting so blurry! :)

---------------
Peter Berdeklis
Dept. of Physics, Univ. of Toronto