From owner-freebsd-hackers@FreeBSD.ORG Mon Jan 26 21:57:39 2009 Return-Path: Delivered-To: freebsd-hackers@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id 3162710656C4 for ; Mon, 26 Jan 2009 21:57:39 +0000 (UTC) (envelope-from jhb@freebsd.org) Received: from cyrus.watson.org (cyrus.watson.org [65.122.17.42]) by mx1.freebsd.org (Postfix) with ESMTP id 762508FC24 for ; Mon, 26 Jan 2009 21:57:37 +0000 (UTC) (envelope-from jhb@freebsd.org) Received: from server.baldwin.cx (pool-98-109-39-197.nwrknj.fios.verizon.net [98.109.39.197]) by cyrus.watson.org (Postfix) with ESMTPSA id 02FCD46B0C; Mon, 26 Jan 2009 16:57:36 -0500 (EST) Received: from localhost (john@localhost [127.0.0.1]) (authenticated bits=0) by server.baldwin.cx (8.14.3/8.14.3) with ESMTP id n0QLvJkB080649; Mon, 26 Jan 2009 16:57:30 -0500 (EST) (envelope-from jhb@freebsd.org) From: John Baldwin To: freebsd-hackers@freebsd.org Date: Mon, 26 Jan 2009 16:51:28 -0500 User-Agent: KMail/1.9.7 References: <20071220093950.GA79196@server.vk2pj.dyndns.org> <20071221181125.0B6F25B42@mail.bitblocks.com> <20071221201633.GM57756@deviant.kiev.zoral.com.ua> In-Reply-To: <20071221201633.GM57756@deviant.kiev.zoral.com.ua> MIME-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit Content-Disposition: inline Message-Id: <200901261651.29116.jhb@freebsd.org> X-Greylist: Sender succeeded SMTP AUTH authentication, not delayed by milter-greylist-2.0.2 (server.baldwin.cx [127.0.0.1]); Mon, 26 Jan 2009 16:57:31 -0500 (EST) X-Virus-Scanned: ClamAV 0.94.2/8905/Mon Jan 26 12:29:36 2009 on server.baldwin.cx X-Virus-Status: Clean X-Spam-Status: No, score=-4.4 required=4.2 tests=ALL_TRUSTED,AWL,BAYES_00 autolearn=ham version=3.1.3 X-Spam-Checker-Version: SpamAssassin 3.1.3 (2006-06-01) on server.baldwin.cx Cc: Kostik Belousov , Carl Shapiro Subject: Re: critical floating point incompatibility X-BeenThere: freebsd-hackers@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Technical Discussions relating to FreeBSD List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Mon, 26 Jan 2009 21:57:46 -0000 On Friday 21 December 2007 3:16:33 pm Kostik Belousov wrote: > On Fri, Dec 21, 2007 at 10:11:24AM -0800, Bakul Shah wrote: > > Peter Jeremy wrote: > > > On Wed, Dec 19, 2007 at 09:40:34PM -0800, Carl Shapiro wrote: > > > >The default setting of the x87 floating point control word on the i386 > > > >port is 0x127F. Among other things, this value sets the precision > > > >control to double precision. The default setting of the x87 floating > > > >point control word on the AMD64 is 0x37F. > > > ... > > > >It seems clear that the right thing to do is to set the floating point > > > >environment to the i386 default for i386 binaries. Is the current > > > >behavior intended? > > > > > > I believe this is an oversight. See the thread beginning > > > http://lists.freebsd.org/pipermail/freebsd-stable/2007-November/037947.html > > > > >From reading Bruce's last message in that thread, seems to me > > may be default for 64bit binaries should be the same as on > > i386. Anyone wanting different behavior can always call > > fpsetprec() etc. > > > > I think the fix is to change __INITIAL_FPUCW__ in > > /sys/amd64/include/fpu.h to 0x127F like on i386. > I think this shall be done for 32-bit processes only, or we get into > another ABI breaking nightmare. How about something like this: (Carl, can you please test this?) http://www.FreeBSD.org/~jhb/patches/amd64_fpu_i386.patch --- //depot/vendor/freebsd/src/sys/amd64/amd64/fpu.c 2006/06/19 22:39:16 +++ //depot/user/jhb/acpipci/amd64/amd64/fpu.c 2009/01/26 21:47:49 @@ -391,6 +391,7 @@ { struct pcb *pcb; register_t s; + u_short control; if (PCPU_GET(fpcurthread) == curthread) { printf("fpudna: fpcurthread == curthread %d times\n", @@ -421,6 +422,10 @@ * explicitly load sanitized registers. */ fxrstor(&fpu_cleanstate); + if (pcb->pcb_flags & PCB_32BIT) { + control = __INITIAL_FPUCW_I386__; + fldcw(&control); + } pcb->pcb_flags |= PCB_FPUINITDONE; } else fxrstor(&pcb->pcb_save); --- //depot/vendor/freebsd/src/sys/amd64/include/fpu.h 2004/04/05 21:30:47 +++ //depot/user/jhb/acpipci/amd64/include/fpu.h 2009/01/26 21:47:49 @@ -92,6 +92,7 @@ * SSE2 based math. For FreeBSD/amd64, we go with the default settings. */ #define __INITIAL_FPUCW__ 0x037F +#define __INITIAL_FPUCW_I386__ 0x127F #define __INITIAL_MXCSR__ 0x1F80 #define __INITIAL_MXCSR_MASK__ 0xFFBF -- John Baldwin