From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 15144 invoked by alias); 26 Sep 2011 08:06:59 -0000 Received: (qmail 15126 invoked by uid 22791); 26 Sep 2011 08:06:57 -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; Mon, 26 Sep 2011 08:06:43 +0000 From: "rguenther at suse dot de" To: gcc-bugs@gcc.gnu.org Subject: [Bug rtl-optimization/38644] [4.4/4.5/4.6/4.7 Regression] Optimization flag -O1 -fschedule-insns2 causes wrong code Date: Mon, 26 Sep 2011 08:11:00 -0000 X-Bugzilla-Reason: CC X-Bugzilla-Type: changed X-Bugzilla-Watch-Reason: None X-Bugzilla-Product: gcc X-Bugzilla-Component: rtl-optimization X-Bugzilla-Keywords: wrong-code X-Bugzilla-Severity: normal X-Bugzilla-Who: rguenther at suse dot de X-Bugzilla-Status: NEW X-Bugzilla-Priority: P2 X-Bugzilla-Assigned-To: unassigned at gcc dot gnu.org X-Bugzilla-Target-Milestone: 4.4.7 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: 2011-09/txt/msg01908.txt.bz2 http://gcc.gnu.org/bugzilla/show_bug.cgi?id=38644 --- Comment #51 from rguenther at suse dot de 2011-09-26 08:04:37 UTC --- On Mon, 12 Sep 2011, rearnsha at arm dot com wrote: > http://gcc.gnu.org/bugzilla/show_bug.cgi?id=38644 > > --- Comment #48 from Richard Earnshaw 2011-09-12 15:31:51 UTC --- > On 12/09/11 16:18, law at redhat dot com wrote: > > > A much simpler way to fix this is to emit a barrier just prior to > > mucking around with stack pointer in the epilogue. That's how targets > > have dealt with this exact issue for a couple decades. > > Simpler, but wrong. The compiler should not be generating unsafe code > by default. The problem is in the mid-end and expecting every port to > get this right in order to work-around a mid-end bug is just stupid > stupid stupid. > > The mid end should not be scheduling around stack moves unless it has > been explicitly told it is safe to do this. I don't understand why > there is so much resistance to fixing the problem properly. The middle-end does not treat stack moves specially, they are just memory accesses. Extra dependences have to be modeled accordingly. It's a hack to treat stack moves specially, not a proper fix.