From owner-freebsd-arch@FreeBSD.ORG Sun Jan 13 22:54:02 2013 Return-Path: Delivered-To: freebsd-arch@freebsd.org Received: from mx1.freebsd.org (mx1.FreeBSD.org [8.8.178.115]) by hub.freebsd.org (Postfix) with ESMTP id CA2FD960 for ; Sun, 13 Jan 2013 22:54:02 +0000 (UTC) (envelope-from nwhitehorn@freebsd.org) Received: from agogare.doit.wisc.edu (agogare.doit.wisc.edu [144.92.197.211]) by mx1.freebsd.org (Postfix) with ESMTP id A2CAE311 for ; Sun, 13 Jan 2013 22:54:02 +0000 (UTC) MIME-version: 1.0 Content-transfer-encoding: 7BIT Content-type: text/plain; CHARSET=US-ASCII Received: from avs-daemon.smtpauth2.wiscmail.wisc.edu by smtpauth2.wiscmail.wisc.edu (Sun Java(tm) System Messaging Server 7u2-7.05 32bit (built Jul 30 2009)) id <0MGL0060069W4C00@smtpauth2.wiscmail.wisc.edu> for freebsd-arch@freebsd.org; Sun, 13 Jan 2013 16:53:56 -0600 (CST) Received: from wanderer.tachypleus.net (c-24-63-204-107.hsd1.ct.comcast.net [24.63.204.107]) by smtpauth2.wiscmail.wisc.edu (Sun Java(tm) System Messaging Server 7u2-7.05 32bit (built Jul 30 2009)) with ESMTPSA id <0MGL004YO69UFK00@smtpauth2.wiscmail.wisc.edu> for freebsd-arch@freebsd.org; Sun, 13 Jan 2013 16:53:55 -0600 (CST) Date: Sun, 13 Jan 2013 14:53:54 -0800 From: Nathan Whitehorn Subject: Re: how long to keep support for gcc on x86? In-reply-to: <20130113224800.GS1410@funkthat.com> Sender: whitehorn@wisc.edu To: freebsd-arch@freebsd.org Message-id: <50F33B02.6040303@freebsd.org> X-Spam-Report: AuthenticatedSender=yes, SenderIP=24.63.204.107 X-Spam-PmxInfo: Server=avs-13, Version=5.6.1.2065439, Antispam-Engine: 2.7.2.376379, Antispam-Data: 2013.1.13.224528, SenderIP=24.63.204.107 References: <20130112233147.GK1410@funkthat.com> <20130113014242.GA61609@troutmask.apl.washington.edu> <20130113053725.GL1410@funkthat.com> <20130113202952.GO1410@funkthat.com> <20130113224800.GS1410@funkthat.com> User-Agent: Mozilla/5.0 (X11; FreeBSD amd64; rv:17.0) Gecko/20130112 Thunderbird/17.0.2 X-BeenThere: freebsd-arch@freebsd.org X-Mailman-Version: 2.1.14 Precedence: list List-Id: Discussion related to FreeBSD architecture List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Sun, 13 Jan 2013 22:54:02 -0000 On 01/13/13 14:48, John-Mark Gurney wrote: > Peter Wemm wrote this message on Sun, Jan 13, 2013 at 14:26 -0800: >> On Sun, Jan 13, 2013 at 12:29 PM, John-Mark Gurney wrote: >>> Adrian Chadd wrote this message on Sat, Jan 12, 2013 at 23:44 -0800: >>>> >>>> People are still ironing out kinks/differences with clang. Anyone >>>> saying otherwise is likely pushing an agenda. :-) >>>> >>>> Thus I think adding clang-only code to the system right now is very, >>>> very premature. There still seem to be reasons to run systems on GCC >>>> instead of clang. >>>> >>>> If you have a need for new instruction support, perhaps look at adding >>>> it to our base GCC for the time being? >>> >>> I did look at it briefly, but I don't know gcc's internals, and it would >>> take me 5+ hours to do it, while someone who does know gcc would take >>> abount a half an hour (just a guess)... I don't have the free time I >>> used to, otherwise I would of done it by now.. >> >> It seems to me that since clang is the default compiler for the >> platforms that have AES-NI that the following could be done: >> >> * get the inline AES-NI stuff in and debugged and solid. >> * .. without breaking the existing gcc-compatible code >> * once the support is solid, decide what the appropriate thing to do for gcc is. >> >> .. so long as the existing code doesn't get broken. >> >> Trying to do backwards compatibility port to gcc with a moving target >> has potential to be a work multiplier. > > I already have a gcc compatible version of an improved AES-NI for > amd64... The real question is, do I improve things further by using > intrinsics which means we can share code between amd64 and i386 and get > great performance from both, or do I simply make a seperate version > for i386 that is gcc compatible, but not as good performance... > > Though a lot of this last little bit of performance questions isn't too > useful since the overhead of the crypto framework and geom introduces > a significant overhead already... > > I'm not too interesting in creating AES-NI v2 module and having two > versions that do the same thing just because of a compiler issue... > > So I'm going to go with the plan of making an i386 and gcc compatible > version... it'll still be a 4x+ performance over the existing code... > This also means we could back port it to 9-stable if we wanted to... > > Thanks for the input... > This also raises the interesting question of whether we want to bother supporting things like AES-NI on i386 at all. It's a legacy/embedded architecture at this point, in my opinion, and the people who run it probably don't care about fancy new features like this. A related question is whether we want to have any clang-only features in the kernel... -Nathan