From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: by sourceware.org (Postfix, from userid 48) id 9D6403858409; Sat, 11 Feb 2023 18:05:12 +0000 (GMT) DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org 9D6403858409 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gcc.gnu.org; s=default; t=1676138712; bh=/2mPZnLeJwMi+XVxkBWB1TjQt/QQIovgJmHfZM19l+A=; h=From:To:Subject:Date:In-Reply-To:References:From; b=Nj7gNemoenCeout7HupQ9qugQdCTRzxlDqChSO4ZRWZMq/Oxn87hZgBALAI5Hqy6N phyN0/I5bvuSStUtz9E8hXUyniIowk5FMPzx9KlpB9AOOXFMFWtGWqW6YeRCMpqv2M /4P6MSUyzT+ev75aRb8Z3KdmXeo3dECi/W93UChE= From: "bergner at gcc dot gnu.org" To: gcc-bugs@gcc.gnu.org Subject: [Bug tree-optimization/108757] We do not simplify (a - (N*M)) / N + M -> a / N Date: Sat, 11 Feb 2023 18:05:12 +0000 X-Bugzilla-Reason: CC X-Bugzilla-Type: changed X-Bugzilla-Watch-Reason: None X-Bugzilla-Product: gcc X-Bugzilla-Component: tree-optimization X-Bugzilla-Version: 13.0 X-Bugzilla-Keywords: missed-optimization X-Bugzilla-Severity: enhancement X-Bugzilla-Who: bergner at gcc dot gnu.org X-Bugzilla-Status: NEW 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: In-Reply-To: References: 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: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D108757 --- Comment #7 from Peter Bergner --- (In reply to Segher Boessenkool from comment #6) > No? Take a=3D59 as counterexample: >=20 > (a - (N*M)) / N + M =3D (59 - 2*30)/30 + 2 =3D ~0UL/30 + 2 For unsigned integers, isn't having a < N*M UB so we're free to do as we wi= sh for either the optimized and non-optimized sequences? Meaning, can't we as= sume here that a >=3D N*M?=