From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 12945 invoked by alias); 12 Oct 2006 15:03:44 -0000 Received: (qmail 12914 invoked by uid 48); 12 Oct 2006 15:03:34 -0000 Date: Thu, 12 Oct 2006 15:03:00 -0000 Message-ID: <20061012150334.12913.qmail@sourceware.org> X-Bugzilla-Reason: CC References: Subject: [Bug middle-end/29440] 4.2 20061007 experimental misscompiles libavcodec/h264.o In-Reply-To: Reply-To: gcc-bugzilla@gcc.gnu.org To: gcc-bugs@gcc.gnu.org From: "poirierg at gmail dot com" Mailing-List: contact gcc-bugs-help@gcc.gnu.org; run by ezmlm Precedence: bulk List-Archive: List-Post: List-Help: Sender: gcc-bugs-owner@gcc.gnu.org X-SW-Source: 2006-10/txt/msg01031.txt.bz2 List-Id: ------- Comment #6 from poirierg at gmail dot com 2006-10-12 15:03 ------- (In reply to comment #4) > (In reply to comment #3) > > Does it work when compiled with -O0 instead of -O4? How about -O1? > > > > Besies above, I noticed that the asm in get_cabac looks to be clobbering memory > > but is not marked as such. > > > > Andrew, this testcase violates aliasing rules. > > h264.c: In function 'filter_mb_fast': > h264.c:7074: warning: dereferencing type-punned pointer will break > strict-aliasing rules For what it's worth, the code around line 7074 compiled correctly with snapshot 4.2-20060909 and has been in FFmpeg since Mon Aug 28 09:33:01 2006 UTC, so IMHO it shouldn't be the cause of the problem I'm reporting today. However, if you have a suggestion to improve this code, I'm all ears Guillaume -- http://gcc.gnu.org/bugzilla/show_bug.cgi?id=29440