[Bug tree-optimization/109695] [14 Regression] crash in gimple_ranger::range_of_expr since r14-377-gc92b8be9b52b7e

["aldyh at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109695

--- Comment #38 from Aldy Hernandez <aldyh at gcc dot gnu.org> ---
(In reply to Andrew Macleod from comment #37)
> (In reply to CVS Commits from comment #36)
> 
> >     For the curious, a particular hot spot for IPA in this area was:
> >     
> >     ipcp_vr_lattice::meet_with_1 (const value_range *other_vr)
> >     {
> >     ...
> >     ...
> >       value_range save (m_vr);
> >       m_vr.union_ (*other_vr);
> >       return m_vr != save;
> >     }
> >     
> >     The problem isn't the resizing (since we do that at most once) but the
> >     fact that for some functions with lots of callers we end up a huge
> >     range that gets copied and compared for every meet operation.  Maybe
> >     the IPA algorithm could be adjusted somehow??.
> 
> isn't the the same thing as 
> 
>   return m_vr.union_ (*other_vr);
> 
> which should be much faster without all the copying... ?

Indeed.  That is in the committed version of the patch.  I just forgot to
update the message.

The reason I didn't originally do as you suggested was that there was a bug in
the union code that returned TRUE for a union that hadn't changed anything. 
That has also been fixed in trunk.