From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: by sourceware.org (Postfix, from userid 48) id 6D6573857820; Wed, 19 Jan 2022 17:42:55 +0000 (GMT) DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org 6D6573857820 From: "jakub at gcc dot gnu.org" To: gcc-bugs@gcc.gnu.org Subject: [Bug tree-optimization/103063] [9/10/11/12 Regression] Wrong code while using -O3 since r7-2373-g69b806f6a60efcf1 Date: Wed, 19 Jan 2022 17:42:55 +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: 12.0 X-Bugzilla-Keywords: wrong-code X-Bugzilla-Severity: normal X-Bugzilla-Who: jakub at gcc dot gnu.org X-Bugzilla-Status: NEW X-Bugzilla-Resolution: X-Bugzilla-Priority: P2 X-Bugzilla-Assigned-To: unassigned at gcc dot gnu.org X-Bugzilla-Target-Milestone: 9.5 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 X-BeenThere: gcc-bugs@gcc.gnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Gcc-bugs mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 19 Jan 2022 17:42:55 -0000 https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D103063 --- Comment #5 from Jakub Jelinek --- ifcvt dump looks correct to me, in vect it seems the vectorizer thinks it c= an compute the number of iterations of the inner loop using: _33 =3D b_lsm.8_5 * 6; _34 =3D _33 / 6; niters.11_32 =3D _34 + 1; _42 =3D b_lsm.8_5 * 6; if (_42 <=3D 89) For b_lsm.8_5 =3D=3D 0 niters.11_32 is correctly 1, but for b_lsm.8_5 =3D= =3D 255 it gives 42 (i.e. (0x5fa & 0xff) / 6 + 1), while it should be 128, because the only [0,255] values for which (v*6) & 0xff =3D=3D 0 are 0 and 128.=