From owner-svn-src-head@FreeBSD.ORG Wed Jan 5 15:02:53 2011 Return-Path: Delivered-To: svn-src-head@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id 7FC5E1065673; Wed, 5 Jan 2011 15:02:53 +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 4C9768FC13; Wed, 5 Jan 2011 15:02:53 +0000 (UTC) Received: from bigwig.baldwin.cx (66.111.2.69.static.nyinternet.net [66.111.2.69]) by cyrus.watson.org (Postfix) with ESMTPSA id E882046B09; Wed, 5 Jan 2011 10:02:52 -0500 (EST) Received: from jhbbsd.localnet (smtp.hudson-trading.com [209.249.190.9]) by bigwig.baldwin.cx (Postfix) with ESMTPSA id 19F6B8A009; Wed, 5 Jan 2011 10:02:52 -0500 (EST) From: John Baldwin To: Nathan Whitehorn Date: Wed, 5 Jan 2011 10:02:51 -0500 User-Agent: KMail/1.13.5 (FreeBSD/7.3-CBSD-20101102; KDE/4.4.5; amd64; ; ) References: <201101042051.p04KpSGk054564@svn.freebsd.org> <201101050928.30748.jhb@freebsd.org> <4D248540.3030602@freebsd.org> In-Reply-To: <4D248540.3030602@freebsd.org> MIME-Version: 1.0 Content-Type: Text/Plain; charset="utf-8" Content-Transfer-Encoding: 7bit Message-Id: <201101051002.51598.jhb@freebsd.org> X-Greylist: Sender succeeded SMTP AUTH, not delayed by milter-greylist-4.2.6 (bigwig.baldwin.cx); Wed, 05 Jan 2011 10:02:52 -0500 (EST) X-Virus-Scanned: clamav-milter 0.96.3 at bigwig.baldwin.cx X-Virus-Status: Clean X-Spam-Status: No, score=-1.9 required=4.2 tests=BAYES_00 autolearn=ham version=3.3.1 X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on bigwig.baldwin.cx Cc: Gleb Kurtsou , src-committers@freebsd.org, svn-src-all@freebsd.org, Dimitry Andric , svn-src-head@freebsd.org, Alexander Best Subject: Re: svn commit: r216977 - in head/libexec/rtld-elf: amd64 i386 X-BeenThere: svn-src-head@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: SVN commit messages for the src tree for head/-current List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 05 Jan 2011 15:02:53 -0000 On Wednesday, January 05, 2011 9:50:40 am Nathan Whitehorn wrote: > On 01/05/11 08:28, John Baldwin wrote: > > On Wednesday, January 05, 2011 8:36:06 am Dimitry Andric wrote: > >> On 2011-01-05 13:59, John Baldwin wrote: > >>>> Why not to add NO_HWFLOAT knob (or similar) into makefile > >>>> infrastructure. And set CFLAGS accordingly, depending on CC, arch, etc. > >>>> These flags are getting rather common in tree. > >>> It strikes me that we really want clang/gcc to have some sort of > >>> '-mno-hwfloat' so we don't keep having to add new flags in the future. > >> This is not just about floats, clang can also use SSE/AVX instructions > >> for e.g. memset(), memcpy() and the like, or even for structure > >> assignments. > > Yes, but the thing that all these extensions have in common is that they use > > FPU state (i.e. subject to DNA traps, managed via *SAVE and *RSTOR, etc.) > > and that is the problem with using them in boot code or rtld. What I would > > want a -mno-hwfloat flag to do is to disable use of anything that would > > require working FPU state handling. > > You would also want this to be cross-platform, in which case it's more > than floating point. E.g. on powerpc, you also want to disable both FP > and vector extensions, which use separate sets of instructions and > registers. I guess overriding CPU type to be something very old (386?) > potentially deoptimizes the code? Hmm, I don't know if this is generically MI, but at least for x86 having a single -mno-sse-xmm-mmx-anything-registers-please would be useful I think. -- John Baldwin