From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 21105 invoked by alias); 28 Jan 2003 07:06:00 -0000 Mailing-List: contact gcc-prs-help@gcc.gnu.org; run by ezmlm Precedence: bulk List-Archive: List-Post: List-Help: Sender: gcc-prs-owner@gcc.gnu.org Received: (qmail 21091 invoked by uid 71); 28 Jan 2003 07:06:00 -0000 Date: Tue, 28 Jan 2003 07:06:00 -0000 Message-ID: <20030128070600.21090.qmail@sources.redhat.com> To: nobody@gcc.gnu.org Cc: gcc-prs@gcc.gnu.org, From: Jim Bray Subject: Re: optimization/8412: Code generation problem with -march=k6 Reply-To: Jim Bray X-SW-Source: 2003-01/txt/msg01571.txt.bz2 List-Id: The following reply was made to PR optimization/8412; it has been noted by GNATS. From: Jim Bray To: gcc-gnats@gcc.gnu.org, gcc-bugs@gcc.gnu.org, nobody@gcc.gnu.org, gcc-prs@gcc.gnu.org, alexander.puchmayr@jku.at Cc: Subject: Re: optimization/8412: Code generation problem with -march=k6 Date: 28 Jan 2003 01:59:40 -0500 I think I'm seeing this same bug, with gcc version 3.2.1 20021207 (Gentoo Linux 3.2.1-20021207) I've noticed considerable instability with multimedia things including xine, and have been studying an easily reproducible problem with xmms. I'd assumed it was 3dnow related, but testing has zeroed me in on a combination of -funroll-all-loops and -O[23]. Here are my crude notes to date. Not yet a good bug-report, The test is compiling and running xmms and doing a particular operation with it. My system is a k6-2. -finline-functions is used in all tests. CFLAGS='-march=k6-2 -g -O1' works. CFLAGS='-march=k6-2 -g -O1 -ffast-math' works. CFLAGS='-march=k6-2 -g -O1 -ffast-math -funroll-all-loops' works. CFLAGS='-march=k6-2 -g -O2 -ffast-math -funroll-all-loops' FAILS. CFLAGS='-march=k6-2 -g -O2 -ffast-math' works. CFLAGS='-march=k6-2 -O2 -ffast-math' works. The xmms configuration normally uses -funroll-all-loops, and I was seeing consistent failure with any variant of -m{cpu,arch}= {k6,k6-2} -O[23], which is not reflected above. The problem went away when the k6-specific flags were removed. I did not start getting any k6-specific build successes until I started dropping below -O2 and -funroll-all-loops. I did some studying of this with gdb, which seemed to be zeroing me into an area of code which became an unrolled loop. Bug I 'sent email to interested parties' from: http://gcc.gnu.org/cgi-bin/gnatsweb.pl?cmd=view%20audit-trail&database=gcc&pr=8412 -- Jim Bray