From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <gcc-bugzilla@gcc.gnu.org>
Received: by sourceware.org (Postfix, from userid 48)
	id E12D23857C4A; Thu,  7 Mar 2024 07:32:00 +0000 (GMT)
DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org E12D23857C4A
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gcc.gnu.org;
	s=default; t=1709796720;
	bh=94aj77VwLQXQo9CqTdDedC2Aog6w08qb6vIdZI6TYGs=;
	h=From:To:Subject:Date:In-Reply-To:References:From;
	b=JSXUWyN7+qsTwYtb6YHl9v9HuESsko0p2l9HUbzQgzkFvA8rKnbQmtTi0q+yTlNCc
	 KiGSEM3I1k93MLUA8Xkv3T5VPkd4tWfg7hRBCcVu8YP30B/J5kfLSp90EIZFotquzQ
	 o1ecmFoFIZayjOCDJxjshV6MfXiiSnnM1dtb01Ko=
From: "rguenther at suse dot de" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug middle-end/105533] UBSAN: gcc/expmed.cc:3272:26: runtime error:
 signed integer overflow: -9223372036854775808 - 1 cannot be represented in
 type 'long int'
Date: Thu, 07 Mar 2024 07:32:00 +0000
X-Bugzilla-Reason: CC
X-Bugzilla-Type: changed
X-Bugzilla-Watch-Reason: None
X-Bugzilla-Product: gcc
X-Bugzilla-Component: middle-end
X-Bugzilla-Version: 13.0
X-Bugzilla-Keywords: 
X-Bugzilla-Severity: normal
X-Bugzilla-Who: rguenther at suse dot de
X-Bugzilla-Status: UNCONFIRMED
X-Bugzilla-Resolution: 
X-Bugzilla-Priority: P3
X-Bugzilla-Assigned-To: unassigned at gcc dot gnu.org
X-Bugzilla-Target-Milestone: ---
X-Bugzilla-Flags: 
X-Bugzilla-Changed-Fields: 
Message-ID: <bug-105533-4-IpOJoVFr2J@http.gcc.gnu.org/bugzilla/>
In-Reply-To: <bug-105533-4@http.gcc.gnu.org/bugzilla/>
References: <bug-105533-4@http.gcc.gnu.org/bugzilla/>
Content-Type: text/plain; charset="UTF-8"
Content-Transfer-Encoding: quoted-printable
X-Bugzilla-URL: http://gcc.gnu.org/bugzilla/
Auto-Submitted: auto-generated
MIME-Version: 1.0
List-Id: <gcc-bugs.sourceware.org>

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D105533

--- Comment #10 from rguenther at suse dot de <rguenther at suse dot de> ---
On Wed, 6 Mar 2024, jakub at gcc dot gnu.org wrote:

> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D105533
>=20
> Jakub Jelinek <jakub at gcc dot gnu.org> changed:
>=20
>            What    |Removed                     |Added
> -------------------------------------------------------------------------=
---
>                  CC|                            |rguenth at gcc dot gnu.o=
rg
>=20
> --- Comment #7 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
> The second UB is on
> #2  ao_ref_init_from_vn_reference (ref=3D<optimized out>, set=3D1, base_s=
et=3D1,
> type=3D<optimized out>, ops=3D...) at ../../gcc/tree-ssa-sccvn.cc:1224
> 1224                offset +=3D op->off << LOG2_BITS_PER_UNIT;
> where op->off is negative.
> Isn't this just an unnecessary optimization?  I mean can't we just do
>                     offset +=3D op->off * BITS_PER_UNIT;
> BITS_PER_UNIT is a constant 8 on all targets we support...

It's a habit from dealing with offset_int (but this is poly_int64)
where the multiply is possibly a lot more costly than a shift.

So yeah, a multiply is fine I guess.=