Re: Rep:Re: Rep:Re: [f-cpu] signed cmpl

[Yann Guidon <whygee@f-cpu.org>]

hi !

Michael Riepe wrote:

> On Wed, Dec 18, 2002 at 07:21:52PM +0100, Christophe Avoinne wrote:
>  
> > I think Nico wanted to say if our "gcc expert" can tell us if gcc often
> > produces instructions where a 6-bit immediate is likely to be enough. If so,
> > it can be a gain, if not, don't bother too much with a 6-bit immediate.
> >    
> I don't think that it's a property of the compiler - it depends on the
> code you compile. 6 bits isn't enough to encode ASCII, for example -
> so if you deal with character values a lot, 8 bits would be much
> better.
>  
A lot of instructions have a 8-bit constant mode.
there are already "issues" about how it is sign-extended
and how it behaves in SIMD modes.
If it's like that in 8-bit, it's certainly the same issues with 6 bits...

YG

*************************************************************
To unsubscribe, send an e-mail to majordomo@seul.org with
unsubscribe f-cpu       in the body. http://f-cpu.seul.org/