Re: Redundant logical operations left after early splitting

[Jeff Law <law at redhat dot com>]

Dave Korn wrote:
> On 20 February 2008 16:34, Jeff Law wrote:
>
> > Paolo Bonzini wrote:
> > > > > Is there any particular function or pass that should be dealing with
> > > > > IOR rx,0 - that I could trace thru and figure out why it does not
> > > > > like it (or never gets there)?
> > > > I would be looking in combine and simplify-rtx (which is called by
> > > > combine).  If your splitter triggers after combine, then I'm not
> > > > immediately sure where to look -- I'm not offhand aware of a pass
> > > > after combine which would call into simplify-rtx to perform this
> > > > optimization.
> > > Me neither, but this
>
> > > could be a place where it is done.
> > I'm still looking at this, but I don't see much of a chance to attack
> > this specific problem in the combiner.
> >
> > I'm thinking this is going to need to be attacked along one of three
> > lines:
>
>   In the meantime, Andy's quickest and safest option is probably to use peepholes to eliminate the redundant insns altogether, rather than having to replace them with nops.
Probably true.

Jeff