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Re: [PATCH] Fix inconsistent pruning of aliases
On Tue, 20 Nov 2007, Daniel Berlin wrote:
> On 11/20/07, Richard Guenther <rguenther@suse.de> wrote:
> > On Tue, 20 Nov 2007, Daniel Berlin wrote:
> >
> > > On 11/20/07, Richard Guenther <rguenther@suse.de> wrote:
>
> > > At this point, you need to recompute aliasing (or move propagation to
> > > a different point).
> > > Trying to work around that is not going to work very well, it's not
> > > what the machinery is meant for.
> >
> > Uhm, so we need to re-run may_alias after every copy-propagation?
> >
> > p_2 = p_1
> > *p_2;
>
> You at least need to copy the NMT from p_2 to p_1, yes.
>
> You can't add new dereferences without doing *something* to inform the
> alias machinery that new dereferences have occurred.
Ok, so in this case phicprop is broken. It propagates p_1 in
# p_2 = PHI <p_1(2)>
*p_2
but does not merge alias info from p_2.
Richard.