Date: Fri, 18 Mar 2005 01:16:47 -0500 From: David Schultz <das@FreeBSD.ORG> To: Alexey Dokuchaev <danfe@FreeBSD.ORG> Cc: cvs-all@FreeBSD.ORG Subject: Re: cvs commit: src/lib/msun/i387 fenv.c fenv.h Message-ID: <20050318061647.GA40922@VARK.MIT.EDU> In-Reply-To: <20050318055212.GA70385@FreeBSD.org> References: <200503172221.j2HMLkfq017761@repoman.freebsd.org> <20050318055212.GA70385@FreeBSD.org>
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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.
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