From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 6148 invoked by alias); 2 Feb 2012 08:57:17 -0000 Received: (qmail 6139 invoked by uid 22791); 2 Feb 2012 08:57:16 -0000 X-SWARE-Spam-Status: No, hits=-2.9 required=5.0 tests=ALL_TRUSTED,AWL,BAYES_00 X-Spam-Check-By: sourceware.org Received: from localhost (HELO gcc.gnu.org) (127.0.0.1) by sourceware.org (qpsmtpd/0.43rc1) with ESMTP; Thu, 02 Feb 2012 08:57:03 +0000 From: "rguenther at suse dot de" To: gcc-bugs@gcc.gnu.org Subject: [Bug middle-end/51994] [4.6/4.7 Regression] git-1.7.8.3 miscompiled due to negative bitpos from get_inner_reference Date: Thu, 02 Feb 2012 08:57:00 -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-Keywords: wrong-code X-Bugzilla-Severity: normal X-Bugzilla-Who: rguenther at suse dot de X-Bugzilla-Status: ASSIGNED X-Bugzilla-Priority: P3 X-Bugzilla-Assigned-To: ebotcazou at gcc dot gnu.org X-Bugzilla-Target-Milestone: 4.6.3 X-Bugzilla-Changed-Fields: Message-ID: In-Reply-To: References: X-Bugzilla-URL: http://gcc.gnu.org/bugzilla/ Auto-Submitted: auto-generated Content-Type: text/plain; charset="UTF-8" MIME-Version: 1.0 Mailing-List: contact gcc-bugs-help@gcc.gnu.org; run by ezmlm Precedence: bulk List-Id: List-Archive: List-Post: List-Help: Sender: gcc-bugs-owner@gcc.gnu.org X-SW-Source: 2012-02/txt/msg00190.txt.bz2 http://gcc.gnu.org/bugzilla/show_bug.cgi?id=51994 --- Comment #34 from rguenther at suse dot de 2012-02-02 08:56:04 UTC --- On Wed, 1 Feb 2012, ebotcazou at gcc dot gnu.org wrote: > http://gcc.gnu.org/bugzilla/show_bug.cgi?id=51994 > > --- Comment #32 from Eric Botcazou 2012-02-01 16:34:30 UTC --- > > The base object can be an indirect reference, so yes, there doesn't have > > to be an overall positive offset (well, yes, to the _real_ object, > > but we don't see that). > > If this is an indirect reference, there is no base object by definition. So > I'm not sure we should care in get_inner_reference and, in any case, I'm not > sure what to do. Probably avoid sending MEM_REF to get_inner_reference in this > case, > after all it's clearly not a handled_component_p-like thing. Well, you can have component refs wrapped around a MEM_REF (or formerly an INDIRECT_REF). The only difference now is that the MEM_REF may have a (negative) constant offset embedded. Now, only if the MEM_REF is based on an ADDR_EXPR (and thus a real object) we factor in its (possibly negative) offset to bitpos. So, hum - now I don't see as easily that we can get a negative bitpos from a not undefined input ... (maybe except for the Ada fat pointer case). So your patch is probably ok (can you try verifying we don't get (too much) codegen differences on a bootstrap?) Richard.