From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 2855 invoked by alias); 28 Dec 2010 20:43:09 -0000 Received: (qmail 2847 invoked by uid 22791); 28 Dec 2010 20:43:09 -0000 X-SWARE-Spam-Status: No, hits=-1.8 required=5.0 tests=AWL,BAYES_00,DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,FREEMAIL_FROM,RFC_ABUSE_POST,TW_TM X-Spam-Check-By: sourceware.org Received: from mail-iy0-f175.google.com (HELO mail-iy0-f175.google.com) (209.85.210.175) by sourceware.org (qpsmtpd/0.43rc1) with ESMTP; Tue, 28 Dec 2010 20:43:04 +0000 Received: by iyj18 with SMTP id 18so8875496iyj.20 for ; Tue, 28 Dec 2010 12:43:03 -0800 (PST) MIME-Version: 1.0 Received: by 10.231.34.201 with SMTP id m9mr13613696ibd.81.1293568982824; Tue, 28 Dec 2010 12:43:02 -0800 (PST) Received: by 10.231.35.134 with HTTP; Tue, 28 Dec 2010 12:43:02 -0800 (PST) In-Reply-To: References: Date: Tue, 28 Dec 2010 21:38:00 -0000 Message-ID: Subject: Re: [PR debug/46931] don't crash propagating removed DEFs into debug stmts From: Richard Guenther To: Alexandre Oliva Cc: gcc-patches@gcc.gnu.org Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable X-IsSubscribed: yes Mailing-List: contact gcc-patches-help@gcc.gnu.org; run by ezmlm Precedence: bulk List-Id: List-Archive: List-Post: List-Help: Sender: gcc-patches-owner@gcc.gnu.org X-SW-Source: 2010-12/txt/msg01909.txt.bz2 On Tue, Dec 28, 2010 at 9:26 PM, Alexandre Oliva wrote: > On Dec 26, 2010, Richard Guenther wrote: > >> Yeah. =A0But wasn't there a correctness problem with propagating as well? > >> the the debug info will refer to the wrong value of i. =A0Remember that >> we can have overlapping life ranges for SSA names but not for the >> decls for which we emit debug info. > > The value expressions in debug stmts refer to the SSA names, so there's > no problem, at least in this regard. =A0The overlapping ranges, if > expanded to different pseudos, it will get the correct RTL expressions; > if no longer available at a point, it should not get any RTL expression > (although it would in theory be possible to do better, looking for some > equivalence). > > Now, I don't think the latter has been actually verified, especially > after the change that made us go straight from SSA to RTL, so if you > have evidence that we're doing it wrong, I'd love to see it. I don't have evidence, it's just what I seem to remember (for some reason). Btw, we can have memory operands on the RHS of debug stmts? For those propagating wouldn't be valid as they are not in SSA form. Richard. >>> Regstrapping your proposed patch now. > >> It's ok to commit if it works (with your testcase). > > Here's what I installed. > > > > -- > Alexandre Oliva, freedom fighter =A0 =A0http://FSFLA.org/~lxoliva/ > You must be the change you wish to see in the world. -- Gandhi > Be Free! -- http://FSFLA.org/ =A0 FSF Latin America board member > Free Software Evangelist =A0 =A0 =A0Red Hat Brazil Compiler Engineer > >