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From: "pinskia at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug tree-optimization/68131] missed optimization and warning for
 broken overflow check
Date: Tue, 24 Oct 2023 20:45:50 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D68131

--- Comment #5 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
(In reply to Marc Glisse from comment #3)
> (In reply to Richard Biener from comment #2)
> > We indeed do not have this optimization, only A + CST CMP CST to A CMP =
CST'
> > and related.  Note that _9 might be negative so we also need range info
> > for this.  VRPs symbolic range stuff isn't good enough to simplify this.
>=20
> If we want to simplify directly to false, I would expect a match.pd patte=
rn
> using tree_expr_nonnegative_p to work in this case (conversion from a
> smaller unsigned). By the way, maybe tree_single_nonnegative_warnv_p could
> try looking at get_range_info before forwarding to
> gimple_stmt_nonnegative_warnv_p.

Oh I filed PR 111959 (and will be submitting a patch later today) for that.=