[Bug tree-optimization/39074] PTA constraint processing for *x = y is wrong

["rguenther at suse dot de" <gcc-bugzilla at gcc dot gnu dot org>]

------- Comment #8 from rguenther at suse dot de  2009-02-04 09:35 -------
Subject: Re:  PTA constraint processing for *x
 = y is wrong

On Wed, 4 Feb 2009, dberlin at dberlin dot org wrote:

> ------- Comment #7 from dberlin at gcc dot gnu dot org  2009-02-04 00:29 -------
> Subject: Re:  PTA constraint processing for *x = 
>         y is wrong
> 
> On Tue, Feb 3, 2009 at 9:24 AM, rguenther at suse dot de
> <gcc-bugzilla@gcc.gnu.org> wrote:
> >
> >
> > ------- Comment #6 from rguenther at suse dot de  2009-02-03 14:24 -------
> > Subject: Re:  PTA constraint processing for *x
> >  = y is wrong
> >
> > On Tue, 3 Feb 2009, dberlin at dberlin dot org wrote:
> >
> >> Subject: Re:  PTA constraint processing for *x =
> >>         y is wrong
> >>
> >> There used to be a *ANYTHING = ANYTHING constraint + ANYTHING
> >> containing all the variables pointing to ANYTHING that would have
> >> taken care of this.
> >> You certainly don't want to dynamically add all variables at solving
> >> time yourself, since that can't be optimized.
> >
> > This is the reason it "works" for ESCAPED, there we have an
> > *ESCAPED = ESCAPED constraint.  It doesn't work for CALLUSED though,
> > I have a simple fix (CALLUSED is not big usually, so just not using
> > it as a placeholder fixes the issue here).
> >
> > For the ANYTHING problem I have just dealt with it in do_ds_constraint
> > (I'll post an updated patch soon after testing finished).
> 
> My onl concern is practicality.
> The last time I did this solely at solving time it was ridiculously
> slow on large cases, since the solver is much better at difference
> propagation.

Do you remember what testcase(s) this was?  I can certainly time
removing the shortcutting against handling *ANYTHING (and I'll try
to come up with a testcase that is not fixed with just removing
the shortcutting).

Richard.


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=39074