From owner-cvs-src@FreeBSD.ORG  Fri Mar 18 06:16:53 2005
Return-Path: <owner-cvs-src@FreeBSD.ORG>
Delivered-To: cvs-src@freebsd.org
Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125])
	by hub.freebsd.org (Postfix) with ESMTP
	id 6D4DA16A4CE; Fri, 18 Mar 2005 06:16:53 +0000 (GMT)
Received: from VARK.MIT.EDU (VARK.MIT.EDU [18.95.3.179])
	by mx1.FreeBSD.org (Postfix) with ESMTP
	id 0900F43D3F; Fri, 18 Mar 2005 06:16:53 +0000 (GMT)
	(envelope-from das@FreeBSD.ORG)
Received: from VARK.MIT.EDU (localhost [127.0.0.1])
	by VARK.MIT.EDU (8.13.3/8.13.1) with ESMTP id j2I6GlP4040997;
	Fri, 18 Mar 2005 01:16:47 -0500 (EST)
	(envelope-from das@FreeBSD.ORG)
Received: (from das@localhost)
	by VARK.MIT.EDU (8.13.3/8.13.1/Submit) id j2I6GlxO040996;
	Fri, 18 Mar 2005 01:16:47 -0500 (EST)
	(envelope-from das@FreeBSD.ORG)
Date: Fri, 18 Mar 2005 01:16:47 -0500
From: David Schultz <das@FreeBSD.ORG>
To: Alexey Dokuchaev <danfe@FreeBSD.ORG>
Message-ID: <20050318061647.GA40922@VARK.MIT.EDU>
Mail-Followup-To: Alexey Dokuchaev <danfe@FreeBSD.ORG>,
	src-committers@FreeBSD.ORG, cvs-src@FreeBSD.ORG, cvs-all@FreeBSD.ORG
References: <200503172221.j2HMLkfq017761@repoman.freebsd.org>
	<20050318055212.GA70385@FreeBSD.org>
Mime-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <20050318055212.GA70385@FreeBSD.org>
cc: cvs-src@FreeBSD.ORG
cc: src-committers@FreeBSD.ORG
cc: cvs-all@FreeBSD.ORG
Subject: Re: cvs commit: src/lib/msun/i387 fenv.c fenv.h
X-BeenThere: cvs-src@freebsd.org
X-Mailman-Version: 2.1.1
Precedence: list
List-Id: CVS commit messages for the src tree <cvs-src.freebsd.org>
List-Unsubscribe: <http://lists.freebsd.org/mailman/listinfo/cvs-src>,
	<mailto:cvs-src-request@freebsd.org?subject=unsubscribe>
List-Archive: <http://lists.freebsd.org/pipermail/cvs-src>
List-Post: <mailto:cvs-src@freebsd.org>
List-Help: <mailto:cvs-src-request@freebsd.org?subject=help>
List-Subscribe: <http://lists.freebsd.org/mailman/listinfo/cvs-src>,
	<mailto:cvs-src-request@freebsd.org?subject=subscribe>
X-List-Received-Date: Fri, 18 Mar 2005 06:16:53 -0000

On Fri, Mar 18, 2005, Alexey Dokuchaev wrote:
> On Thu, Mar 17, 2005 at 10:21:46PM +0000, David Schultz wrote:
> > das         2005-03-17 22:21:46 UTC
> > 
> >   FreeBSD src repository
> > 
> >   Modified files:
> >     lib/msun/i387        fenv.c fenv.h 
> >   Log:
> >   Make the fenv.h routines work for programs that use SSE for
> >   floating-point arithmetic on i386.  Now I'm going to make excuses
> >   for why this code is kinda scary:
> >   
> >   - To avoid breaking the ABI with 5.3-RELEASE, we can't change
> >     sizeof(fenv_t).  I stuck the saved mxcsr in some discontiguous
> >     reserved bits in the existing structure.
> 
> Why do you care about ABI compatibility between 6-CURRENT and 5.3-RELEASE?
> If you plan to MFC this code at some point, you could use your current
> approach in RELENG_5.  This would, of course, mean you'd have to maintain
> two different code sets, but still.

The reasons are manifold.  For one, I would like the complicated
version to get exposure in -CURRENT before I MFC it.  Further,
this only adds a few extra instructions, so it's not a big deal,
particularly compared to the code to support older processors.
You're right that I could just bump the libm version number and
break the ABI, but that inconveniences people, so I would like to
avoid it when possible.