Re: [PATCH] Fix VRP update_value_range and caller (PR tree-optimization/65875)

[Richard Biener <rguenther@suse.de>]

On Mon, 27 Apr 2015, Jakub Jelinek wrote:

> 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.

Ah, I misread the || for a &&.  The patch is ok with just dropping
the == VR_VARYING check.

Thanks,
Richard.