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

["dberlin at dberlin dot org" <gcc-bugzilla at gcc dot gnu dot org>]

------- 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.


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