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Re: [tree-ssa] crash in coalesce_abnormal_edges, merge from mainline?
On Wed, 10 Sep 2003, Andrew MacLeod wrote:
> On Wed, 2003-09-10 at 12:58, Daniel Berlin wrote:
> >
>
> > > Ah, of course the drawback is that you wont be able to propagate it in
> > > all places, so you wont actually get rid of all copies, so you might end
> > > up worse off in some cases... Im not sure.
> > >
> > > Of course, that means it'll only affect variables that you couldn't
> > > copy propagate at all before this, so you'll be able to do some of the
> > > copy props... Is it generally a good or bad idea to do as many as
> > > possible knowing you can't do them all?
> >
> > This is actually bad for PRE, i was going to mention it. This blocks some
> > amount of expression movement because the names no longer match in the
> > expressions.
>
> What is bad for PRE? copy propagation in general, or just if you can't
> copy propoagate them all?
If you can't prop them all, propping some, is bad for PRE>
> Maybe PRE ought to know whats a copy of what
> too... :-)
Value number before PRE, and erase the problem completely. :)
>
>
> Andrew
>
>