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Re: [PATCH, i386]: Insert "cld" via optimize mode switching
On Mon, Dec 04, 2006 at 10:06:51PM +0100, Michael Matz wrote:
> Hi,
>
> On Mon, 4 Dec 2006, Uros Bizjak wrote:
>
> > >but will fail working with those changes. IMHO such routines would be
> > >extremely rare, if they exist at all, so that shouldn't hinder full
> > >progress by using mode switching for the direction flag.
> >
> > Going a bit further, and based on following assumptions:
> >
> > 1) function entry and exit modes are mandated by ABI, so we _know_ that
> > direction bit is cleared there
> > 2) asm should take care by itself to issue CLD before exit
> > 3) we never emit STD anywhere
> >
> > it is possible to argue, that gcc _does not need to emit any_ CLD
> > instructions.
>
> Yes, it is. I never quite understood why we emit them anyway, the only
FYI, icc dodsn't emit cld at all.
H.J.