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From: "aldyh at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug tree-optimization/107608] [13 Regression] Failure on fold-overflow-1.c and pr95115.c
Date: Mon, 05 Dec 2022 16:30:34 +0000 [thread overview]
Message-ID: <bug-107608-4-APlKo7MZLr@http.gcc.gnu.org/bugzilla/> (raw)
In-Reply-To: <bug-107608-4@http.gcc.gnu.org/bugzilla/>
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107608
--- Comment #9 from Aldy Hernandez <aldyh at gcc dot gnu.org> ---
(In reply to Richard Biener from comment #8)
> (In reply to Aldy Hernandez from comment #7)
> > (In reply to Richard Biener from comment #6)
> > > (In reply to Jakub Jelinek from comment #0)
> > > > ... but then
> > > > comes dom2 and happily replaces
> > > > _1 = 3.4028234663852885981170418348451692544e+38 * 2.0e+0;
> > > > return _1;
> > > > with
> > > > _1 = 3.4028234663852885981170418348451692544e+38 * 2.0e+0;
> > > > return Inf;
> > > > (I think this is still correct)
> > >
> > > Note this is also a pessimization code-generation wise since if we
> > > preserve the multiplication the result is readily available in a
> > > register but as optimized we have another constant pool entry and load.
> > >
> > > So we might want to consider not propagating constants generated by
> > > operations
> > > we cannot eliminate. If the only consumer is a compare-and-branch we
> > > can of course still end up with a seemingly dead stmt, so this would be only
> > > for the missed optimization.
> >
> > Up to y'all if this is the way to go, but here are some thoughts...
> >
> > Off the top of my head, we have VRP and DOM propagating constants.
> > Technically also simplify_using_ranges, but it's only called from VRP/DOM,
> > and it currently only works with integers, so we should be ok here.
> >
> > I think we could limit propagation in may_propagate_copy() which both VRP
> > and DOM gate on. VRP uses it through its use of substitute_and_fold_engine
> > and DOM uses it directly. Would this work?
>
> I don't think may_propagate_copy is the correct vehicle. Instead the
> substitute_and_fold_engine could only substitute from defs with no
> side-effects - IIRC it already refrains from propagating _into_ defs
> that will be removed after the propagation.
So where do you suggest we clamp this? The uses I can think of are VRP
(various places in tree-ssa-propagate.cc) and DOM (cprop_operand).
next prev parent reply other threads:[~2022-12-05 16:30 UTC|newest]
Thread overview: 51+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-11-10 9:47 [Bug tree-optimization/107608] New: [13 Regression] Failure on fold-overflow-1.c jakub at gcc dot gnu.org
2022-11-10 9:49 ` [Bug tree-optimization/107608] " jakub at gcc dot gnu.org
2022-11-10 13:47 ` rguenth at gcc dot gnu.org
2022-11-10 18:13 ` pinskia at gcc dot gnu.org
2022-11-11 7:18 ` pinskia at gcc dot gnu.org
2022-11-13 6:30 ` [Bug tree-optimization/107608] [13 Regression] Failure on fold-overflow-1.c and pr95115.c xry111 at gcc dot gnu.org
2022-11-28 10:06 ` rguenth at gcc dot gnu.org
2022-12-05 13:22 ` aldyh at gcc dot gnu.org
2022-12-05 15:14 ` rguenth at gcc dot gnu.org
2022-12-05 16:30 ` aldyh at gcc dot gnu.org [this message]
2022-12-16 13:20 ` jakub at gcc dot gnu.org
2022-12-16 13:32 ` rguenth at gcc dot gnu.org
2023-01-09 15:18 ` aldyh at gcc dot gnu.org
2023-01-10 8:56 ` rguenth at gcc dot gnu.org
2023-01-10 8:58 ` rguenth at gcc dot gnu.org
2023-01-10 10:20 ` aldyh at gcc dot gnu.org
2023-01-10 10:25 ` aldyh at gcc dot gnu.org
2023-01-10 11:00 ` rguenth at gcc dot gnu.org
2023-01-10 11:09 ` jakub at gcc dot gnu.org
2023-01-10 12:08 ` rguenther at suse dot de
2023-01-10 14:14 ` jakub at gcc dot gnu.org
2023-01-10 14:25 ` amacleod at redhat dot com
2023-01-10 14:33 ` aldyh at gcc dot gnu.org
2023-01-10 14:39 ` jakub at gcc dot gnu.org
2023-01-10 14:40 ` aldyh at gcc dot gnu.org
2023-01-10 14:42 ` jakub at gcc dot gnu.org
2023-01-12 11:42 ` aldyh at gcc dot gnu.org
2023-01-12 12:03 ` jakub at gcc dot gnu.org
2023-01-12 12:26 ` xry111 at gcc dot gnu.org
2023-01-13 13:19 ` aldyh at gcc dot gnu.org
2023-01-13 13:25 ` aldyh at gcc dot gnu.org
2023-01-15 15:43 ` cvs-commit at gcc dot gnu.org
2023-01-16 21:38 ` romain.geissler at amadeus dot com
2023-01-16 21:46 ` jakub at gcc dot gnu.org
2023-01-16 21:55 ` romain.geissler at amadeus dot com
2023-01-16 21:58 ` fw at gcc dot gnu.org
2023-01-18 12:26 ` aldyh at gcc dot gnu.org
2023-01-18 12:54 ` jakub at gcc dot gnu.org
2023-01-18 12:56 ` aldyh at gcc dot gnu.org
2023-01-18 13:00 ` rguenth at gcc dot gnu.org
2023-01-18 13:03 ` rguenth at gcc dot gnu.org
2023-01-18 13:05 ` rguenth at gcc dot gnu.org
2023-01-19 1:15 ` xry111 at gcc dot gnu.org
2023-01-19 7:17 ` rguenther at suse dot de
2023-01-26 14:29 ` xry111 at gcc dot gnu.org
2023-01-27 7:35 ` rguenth at gcc dot gnu.org
2023-01-27 7:59 ` xry111 at gcc dot gnu.org
2023-01-27 9:53 ` rguenther at suse dot de
2023-01-27 10:02 ` xry111 at gcc dot gnu.org
2023-01-27 10:13 ` jakub at gcc dot gnu.org
2023-01-27 11:30 ` rguenther at suse dot de
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