From owner-freebsd-current@FreeBSD.ORG  Tue May 20 11:03:42 2003
Return-Path: <owner-freebsd-current@FreeBSD.ORG>
Delivered-To: freebsd-current@freebsd.org
Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125])
	by hub.freebsd.org (Postfix) with ESMTP id B8A6E37B401
	for <freebsd-current@FreeBSD.ORG>;
	Tue, 20 May 2003 11:03:42 -0700 (PDT)
Received: from HAL9000.homeunix.com (12-233-57-131.client.attbi.com
	[12.233.57.131])
	by mx1.FreeBSD.org (Postfix) with ESMTP id 1502343F85
	for <freebsd-current@FreeBSD.ORG>;
	Tue, 20 May 2003 11:03:42 -0700 (PDT)	(envelope-from das@FreeBSD.ORG)
Received: from HAL9000.homeunix.com (localhost [127.0.0.1])
	by HAL9000.homeunix.com (8.12.9/8.12.5) with ESMTP id h4KI3fqN002474;
	Tue, 20 May 2003 11:03:41 -0700 (PDT)
	(envelope-from das@FreeBSD.ORG)
Received: (from das@localhost)
	by HAL9000.homeunix.com (8.12.9/8.12.5/Submit) id h4KI3aBe002473;
	Tue, 20 May 2003 11:03:36 -0700 (PDT)
	(envelope-from das@FreeBSD.ORG)
Date: Tue, 20 May 2003 11:03:36 -0700
From: David Schultz <das@FreeBSD.ORG>
To: Terry Lambert <tlambert2@mindspring.com>
Message-ID: <20030520180336.GB2372@HAL9000.homeunix.com>
Mail-Followup-To: Terry Lambert <tlambert2@mindspring.com>,
	Jon Lido <jlido@goof.com>, freebsd-current@freebsd.org
References: <200305201025.30296.jlido@goof.com>
	<3ECA526F.A6E4A085@mindspring.com>
Mime-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <3ECA526F.A6E4A085@mindspring.com>
cc: Jon Lido <jlido@goof.com>
cc: freebsd-current@FreeBSD.ORG
Subject: Re: gcc/libm floating-point bug?
X-BeenThere: freebsd-current@freebsd.org
X-Mailman-Version: 2.1.1
Precedence: list
List-Id: Discussions about the use of FreeBSD-current
	<freebsd-current.freebsd.org>
List-Unsubscribe: <http://lists.freebsd.org/mailman/listinfo/freebsd-current>,
	<mailto:freebsd-current-request@freebsd.org?subject=unsubscribe>
List-Archive: <http://lists.freebsd.org/pipermail/freebsd-current>
List-Post: <mailto:freebsd-current@freebsd.org>
List-Help: <mailto:freebsd-current-request@freebsd.org?subject=help>
List-Subscribe: <http://lists.freebsd.org/mailman/listinfo/freebsd-current>,
	<mailto:freebsd-current-request@freebsd.org?subject=subscribe>
X-List-Received-Date: Tue, 20 May 2003 18:03:43 -0000

On Tue, May 20, 2003, Terry Lambert wrote:
> Jon Lido wrote:
> > I've been running 5-CURRENT on my laptop for about a week now.  I believe I
> > may have found a bug in FreeBSD's gcc floating-point code generation, or
> > perhaps more likely, in the math library.
> [ ... ]
> > I know my floating point hardware is fine, since I used to run xmms and artsd
> > fine under Linux before I switched the machine to FreeBSD.
> > 
> > I'd appreciate any help with further isolating and reproducing the bug.  Has
> > anyone else experienced this problem?
> 
> There was a recent discussion about -mieee being set by
> default in one of the Makefiles, which leaked into the
> main code base.  It may be that you need the option, or
> you need to disable it (depending on when you downloaded
> you copy of -current).

That's for an Alpha-specific problem.  The i386-specific problem
is due to a bug gcc has that involves Pentium 4 code generation
and aliasing.  The latter can be fixed by removing
-march=pentium4, disabling optimization, or upgrading to gcc 3.3.
The former is intentional and not expected to change; gcc
generates non-standard FP math code on Alpha because it saves a
few instructions to deal with NaNs, etc.  We work around it by
setting -mieee in bsd.cpu.mk for Alpha.