From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: by sourceware.org (Postfix, from userid 48) id 8DAD43852751; Tue, 30 Aug 2022 09:03:35 +0000 (GMT) DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org 8DAD43852751 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gcc.gnu.org; s=default; t=1661850215; bh=At28wlTRs+O6Y/OdTUQ3Zw94pzsX19RsNaldYAoNkvg=; h=From:To:Subject:Date:In-Reply-To:References:From; b=Rf7gpLEkK4S49qUp6f9s6wbLWM5znrr1P71/ydjk0UTGSTPaENN7bLO9G1pw19eCi 9FHRqlX/Q7A2mW9Vs3haFdvhgCMOWbe+wZnDmgRShKeplsU1q0vZGbmS/kMKrDRQep tqSx763tufgblaJJiOUaHEE2eEKWAOl2U8/DaA3s= From: "rguenth at gcc dot gnu.org" To: gcc-bugs@gcc.gnu.org Subject: [Bug tree-optimization/67194] [10/11/12/13 Regression] Missed jump thread and false positive from -Wuninitialized Date: Tue, 30 Aug 2022 09:03:34 +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: 4.8.0 X-Bugzilla-Keywords: diagnostic, missed-optimization X-Bugzilla-Severity: normal X-Bugzilla-Who: rguenth 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: 10.5 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 List-Id: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D67194 --- Comment #5 from Richard Biener --- For the second testcase the issue is the aliasing store *operand_loc =3D 0; which can invalidate the predicate value. Fixed with -fstrict-aliasing (or -O2). Nothing uninit analysis can do here. The first testcase has a similar issue at -O2 because of the union now containing rtx *. I don't see what we can do here - if there's no aliasing the code needs to = say that or be optimized in source.=