From owner-freebsd-current  Tue Oct 15  8:15:17 2002
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 B20DD37B401; Tue, 15 Oct 2002 08:15:15 -0700 (PDT)
Received: from mailman.zeta.org.au (mailman.zeta.org.au [203.26.10.16])
	by mx1.FreeBSD.org (Postfix) with ESMTP
	id 3DFB143E3B; Tue, 15 Oct 2002 08:15:14 -0700 (PDT)
	(envelope-from bde@zeta.org.au)
Received: from bde.zeta.org.au (bde.zeta.org.au [203.2.228.102])
	by mailman.zeta.org.au (8.9.3/8.8.7) with ESMTP id BAA23318;
	Wed, 16 Oct 2002 01:14:57 +1000
Date: Wed, 16 Oct 2002 01:25:30 +1000 (EST)
From: Bruce Evans <bde@zeta.org.au>
X-X-Sender: bde@gamplex.bde.org
To: Steve Kargl <sgk@troutmask.apl.washington.edu>
Cc: Tim Robbins <tjr@FreeBSD.ORG>,
	Kris Kennaway <kris@obsecurity.org>,
	Andrew Gallatin <gallatin@cs.duke.edu>, Nate Lawson <nate@root.org>,
	<current@FreeBSD.ORG>
Subject: Re: X problems & 5.0... -RELEASE?
In-Reply-To: <20021015044028.GA17862@troutmask.apl.washington.edu>
Message-ID: <20021016005506.Y992-100000@gamplex.bde.org>
MIME-Version: 1.0
Content-Type: TEXT/PLAIN; charset=US-ASCII
Sender: owner-freebsd-current@FreeBSD.ORG
Precedence: bulk
List-ID: <freebsd-current.FreeBSD.ORG>
List-Archive: <http://docs.freebsd.org/mail/> (Web Archive)
List-Help: <mailto:majordomo@FreeBSD.ORG?subject=help> (List Instructions)
List-Subscribe: <mailto:majordomo@FreeBSD.ORG?subject=subscribe%20freebsd-current>
List-Unsubscribe: <mailto:majordomo@FreeBSD.ORG?subject=unsubscribe%20freebsd-current>
X-Loop: FreeBSD.ORG

On Mon, 14 Oct 2002, Steve Kargl wrote:

> On Tue, Oct 15, 2002 at 12:39:26PM +1000, Tim Robbins wrote:
> > On Mon, Oct 14, 2002 at 01:00:46PM -0700, Kris Kennaway wrote:
> >
> > [...]
> > > Did anyone test -current with the various FP test suites people posted
> > > about last week?

I run some of them occasionally (last ran ucbtest on June 18), but
they are perfectly irrelevant to this problem since they don't use
signals in any significant way.

> > Yes. I ran paranoia from http://cm.bell-labs.com/netlib/paranoia/ and
> > found that FP arithmethic is satisfactory when -O is not used, and no
> > -march or -mcpu options are used.
> >
> > However, compiling with -O causes a lot of failures.
>
> Are you using an intel cpu?  You need to add -ffloat-store
> to get the correct results due to the 80 bit FPU registers.
> Otherwise, intermediate results are stored with higher
> precision.

This is a well-known bug in gcc.  Intermediate results may be computed
with higher precision.  paranioa knows this and uses lots of assignments
to clip the results to double (or single) precision, aa is required to
work by C standards (very fuzzily in C90 and very clearly in C99).  This
doesn't actually work in the i386 gcc.  The -ffloat-store hack works
around this and gives much the same pessimizations as would a standards
conforming compiler.

Bruce


To Unsubscribe: send mail to majordomo@FreeBSD.org
with "unsubscribe freebsd-current" in the body of the message