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Date: Sat, 6 Nov 2010 22:25:16 +0300 (MSK)
From: malc <av1474@comtv.ru>
Subject: Re: [Qemu-devel] Bug report about x86 'bt' insn
In-Reply-To: <alpine.LNX.2.00.1011062220180.1907@linmac>
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References: <86eiay344b.fsf@shell.gmplib.org>
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To: Nathan Froyd <froydnj@codesourcery.com>
Cc: Torbjorn Granlund <tg@gmplib.org>, qemu-devel@nongnu.org

On Sat, 6 Nov 2010, malc wrote:

> On Sat, 6 Nov 2010, Nathan Froyd wrote:
> 
> > On Sat, Nov 06, 2010 at 07:24:39PM +0100, Torbjorn Granlund wrote:
> > > malc <av1474@comtv.ru> writes:
> > > 
> > >   ZF is undefined according to AMD's 24594.pdf page 69.
> > >   
> > > Ah, you're right.  It seems that all existing x86 implementations leave
> > > ZF alone, though.  (I am not arguing that qeum is broken, the bug is in
> > > my code.)
> > 
> > FWIW, the Intel manuals (253666, June 2010) state that the ZF flag is
> > unaffected, not just undefined.
> 
> (3-94 Vol. 2A BT it Test)
> 
> Flags Affected
> The CF flag contains the value of the selected bit. The OF, SF, ZF, AF, 
> and PF flags are undefined.
> 

And this one was March 2009 (conveniently having the same file name
253666), the September 2010 issue reads differently:

Flags Affected
The CF flag contains the value of the selected bit. The ZF flag is 
unaffected. The OF, SF, AF, and PF flags are undefined.

-- 
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