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Re: [PATCH] Fix VRP update_value_range and caller (PR tree-optimization/65875)
- From: Jakub Jelinek <jakub at redhat dot com>
- To: Richard Biener <rguenther at suse dot de>
- Cc: gcc-patches at gcc dot gnu dot org
- Date: Mon, 27 Apr 2015 10:12:10 +0200
- Subject: Re: [PATCH] Fix VRP update_value_range and caller (PR tree-optimization/65875)
- Authentication-results: sourceware.org; auth=none
- References: <20150424192256 dot GO1751 at tucnak dot redhat dot com> <alpine dot LSU dot 2 dot 11 dot 1504271003260 dot 20496 at zhemvz dot fhfr dot qr>
- Reply-to: Jakub Jelinek <jakub at redhat dot com>
On Mon, Apr 27, 2015 at 10:05:21AM +0200, Richard Biener wrote:
> > --- gcc/tree-vrp.c.jj 2015-04-20 14:35:39.000000000 +0200
> > +++ gcc/tree-vrp.c 2015-04-24 18:10:41.321367440 +0200
> > @@ -892,7 +892,12 @@ update_value_range (const_tree var, valu
> > UNDEFINED or from VARYING. */
> > if (new_vr->type == VR_UNDEFINED
> > || old_vr->type == VR_VARYING)
> > - set_value_range_to_varying (old_vr);
> > + {
> > + BITMAP_FREE (new_vr->equiv);
> > + set_value_range_to_varying (old_vr);
> > + set_value_range_to_varying (new_vr);
> > + return true;
>
> Actually we didn't change anything here (old_vr->type is VARYING already,
> so we shouldn't even have visited the stmt defining the SSA name again...
> eventually your fix below fixes that.
On the testcase, old_vr wasn't actually VARYING, but new_vr was UNDEFINED
(a result of intersecting disjoint ranges). While for old_vr->type ==
VR_VARYING I agree we shouldn't have been called on this.
And turning a VR_RANGE into VR_UNDEFINED is going in the wrong direction
in the lattice.
Jakub