From owner-freebsd-arm@FreeBSD.ORG Tue Oct 7 04:24:33 2014 Return-Path: Delivered-To: freebsd-arm@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [8.8.178.115]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by hub.freebsd.org (Postfix) with ESMTPS id C0009EEB for ; Tue, 7 Oct 2014 04:24:33 +0000 (UTC) Received: from h2.funkthat.com (gate2.funkthat.com [208.87.223.18]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (Client CN "funkthat.com", Issuer "funkthat.com" (not verified)) by mx1.freebsd.org (Postfix) with ESMTPS id 90D34C90 for ; Tue, 7 Oct 2014 04:24:32 +0000 (UTC) Received: from h2.funkthat.com (localhost [127.0.0.1]) by h2.funkthat.com (8.14.3/8.14.3) with ESMTP id s974OVKg017315 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=NO); Mon, 6 Oct 2014 21:24:32 -0700 (PDT) (envelope-from jmg@h2.funkthat.com) Received: (from jmg@localhost) by h2.funkthat.com (8.14.3/8.14.3/Submit) id s974OUiD017314; Mon, 6 Oct 2014 21:24:30 -0700 (PDT) (envelope-from jmg) Date: Mon, 6 Oct 2014 21:24:30 -0700 From: John-Mark Gurney To: Andrew Turner Subject: Re: [RFC] Add and armv7hf TARGET_ARCH Message-ID: <20141007042430.GH1852@funkthat.com> Mail-Followup-To: Andrew Turner , freebsd-arm@freebsd.org References: <20141006134626.59cc5573@bender.lan> <20141006173045.GE1852@funkthat.com> <20141006224124.494267e0@bender.lan> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20141006224124.494267e0@bender.lan> User-Agent: Mutt/1.4.2.3i X-Operating-System: FreeBSD 7.2-RELEASE i386 X-PGP-Fingerprint: 54BA 873B 6515 3F10 9E88 9322 9CB1 8F74 6D3F A396 X-Files: The truth is out there X-URL: http://resnet.uoregon.edu/~gurney_j/ X-Resume: http://resnet.uoregon.edu/~gurney_j/resume.html X-TipJar: bitcoin:13Qmb6AeTgQecazTWph4XasEsP7nGRbAPE X-to-the-FBI-CIA-and-NSA: HI! HOW YA DOIN? can i haz chizburger? X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.2.2 (h2.funkthat.com [127.0.0.1]); Mon, 06 Oct 2014 21:24:32 -0700 (PDT) Cc: freebsd-arm@freebsd.org X-BeenThere: freebsd-arm@freebsd.org X-Mailman-Version: 2.1.18-1 Precedence: list List-Id: "Porting FreeBSD to ARM processors." List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Tue, 07 Oct 2014 04:24:33 -0000 Andrew Turner wrote this message on Mon, Oct 06, 2014 at 22:41 +0100: > On Mon, 6 Oct 2014 10:30:45 -0700 > John-Mark Gurney wrote: > > > Andrew Turner wrote this message on Mon, Oct 06, 2014 at 13:46 +0100: > > > I'm interested in peoples opinion on creating a new TARGET_ARCH to > > > target ARMv7 SoCs. This will target all the current Cortex-A chips > > > we support but not the Raspberry Pi. My intention with this is to > > > have it become the tier 1 arm platform. > > > > > > This platform will support 32-bit Cortex-A based SoCs with a VFP > > > unit. As it would be targeting ARMv7 we could look at supporting > > > Thumb-2. > > > > > > As the VFP unit is optional and future SoCs without it will only be > > > supported by the armv6 TARGET_ARCH, however I would expect almost > > > all ARMv7 designs to include it. > > > > So, what are the specific pros of having a new arch? I see you talk > > about Thumb-2 support, but are there other advantages? Will we get > > significant performance boosts? What? > > We would get a significant speed improvement for anything that uses > floating-point. I haven't done extensive tests, but Ian was getting > around 30x-34x improvement by using the vfp on one benchmark [1]. I've > seen a sight improvement of around 3-5 MFlops on his numbers on my > board. > > I expect there to be a slight performance improvement from being able > to use the newer ARMv7 instructions, however this will be less > pronounced than the above floating-point improvement. > > There are also a number of NEON optimised libc functions we could make > use of, for example [2]. While we may be able to use them on armv6 it > becomes simpler if we can assume we have a NEON unit. Don't we already have armv6hf for hardware float? What is the difference between armv6hf and armv7hf? or is this 30x-34x improvement over armv6hf? > > Also, what impact will this have on trying to get binary packages > > for other arm archs? i.e. will this significantly take away > > resources? If we do this split, why would we want to build binary > > packages for RPI? > > This would depend on how we expect to build them. If the packages are > cross built it would mean having two machines to build packages on > rather than one. If we have native package building I could see > managing two clusters could be difficult. > > Andrew > > [1] > https://lists.freebsd.org/pipermail/freebsd-arm/2014-February/007555.html > [2] > https://android.googlesource.com/platform/bionic/+/master/libc/arch-arm/bionic/memcpy.S -- John-Mark Gurney Voice: +1 415 225 5579 "All that I will do, has been done, All that I have, has not."