[CST-2] Comparative Architectures

[John Wyllie]

This is what the Ian Pratt told me:

> 'predicated execution' and 'conditional moves' are both
> techniques for 'straightening if-then-else code'.
>
> Pred. Ex. enables instructions on the 'wrong' path to be
> annulled.
>
> With cond. move., they get executed (so you have to be careful
> about side effects), but you can use the cond move to 'commit'
> one of the paths by selecting a result.

It doesn't make it any clearer to me.
Can anyone else explain it a bit better?

John






> -----Original Message-----
> From: cst-2-admin@srcf.ucam.org [mailto:cst-2-admin@srcf.ucam.org]On
> Behalf Of Alvin
> Sent: 30 May 2002 20:59
> To: cst-2@srcf.ucam.org
> Subject: Re: [CST-2] Comparative Architectures
>
>
> Not quite sure that's correct...  Surely all instruction's
> execution depend
> on the bits stored with the instruction, and I don't think you can change
> the bits of an instruction depending on certain conditions.
>
> Anyway, predicated instructions and conditional instructions both refer to
> the same chapter in Computer Architecture: A quantitative approach.  I'm
> happy to take that as the final word.
>
> Alvin
>
> > Predicated execution depends on a set of bits stored with the
> > instruction, whereas conditional moves depend on flags or a nominated
> > register.
> >
> > =========================
> > Stephen McIntosh.
> >
> > www.stephenmcintosh.com
>
>
>
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