From owner-freebsd-stable@FreeBSD.ORG Wed Sep 13 23:49:43 2006 Return-Path: X-Original-To: freebsd-stable@freebsd.org Delivered-To: freebsd-stable@freebsd.org Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125]) by hub.freebsd.org (Postfix) with ESMTP id 4F56416A47E for ; Wed, 13 Sep 2006 23:49:43 +0000 (UTC) (envelope-from kline@sage.thought.org) Received: from sage.thought.org (dsl231-043-140.sea1.dsl.speakeasy.net [216.231.43.140]) by mx1.FreeBSD.org (Postfix) with ESMTP id 8D56943D46 for ; Wed, 13 Sep 2006 23:49:42 +0000 (GMT) (envelope-from kline@sage.thought.org) Received: from sage.thought.org (kline@localhost [127.0.0.1]) by sage.thought.org (8.13.6/8.12.10) with ESMTP id k8DNnZqQ092125; Wed, 13 Sep 2006 16:49:35 -0700 (PDT) (envelope-from kline@sage.thought.org) Received: (from kline@localhost) by sage.thought.org (8.13.6/8.13.1/Submit) id k8DNnY37092124; Wed, 13 Sep 2006 16:49:34 -0700 (PDT) (envelope-from kline) Date: Wed, 13 Sep 2006 16:49:34 -0700 From: Gary Kline To: Stefan Lambrev Message-ID: <20060913234934.GA92067@thought.org> References: <200609130905.k8D95idk062789@lurza.secnetix.de> <4507CC9B.60704@sun-fish.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <4507CC9B.60704@sun-fish.com> X-Organization: Thought Unlimited. Public service Unix since 1986. X-Of_Interest: Observing twenty years of service to the Unix community User-Agent: Mutt/1.5.11 Cc: freebsd-stable@freebsd.org Subject: Re: optimization levels for 6-STABLE build{kernel,world} X-BeenThere: freebsd-stable@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Production branch of FreeBSD source code List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 13 Sep 2006 23:49:43 -0000 On Wed, Sep 13, 2006 at 12:17:15PM +0300, Stefan Lambrev wrote: > Hello, > > Oliver Fromme wrote: > >Marc G. Fournier wrote: > > > What are ppl currently using for CFLAGS/COPTFLAGS in /etc/make.conf for > > > building kernel/world? I know awhile back it wasn't recommended to go > > > above -O2, for instance, but suspect that has changed ... ? > > > >The best optimization is probably to not override the > >defaults at all, because they're already pretty optimal. > >In fact, by overriding the defaults there's a good chance > >to make things worse. :-) > > > >The default CFLAGS are "-O2 -pipe -fno-strict-aliasing". > >Anything above -O2 isn't supported, and using -O2 without > >-fno-strict-aliasing also isn't supported (and will create > >broken code for some programs). A common mistake is to > >specify CFLAGS="-O2 -pipe" and omit -fno-strict-aliasing. > >That'll shot you in the foot sooner or later. > > > >Best regards > > Oliver > > > > > May be default flags have to be set here: > /usr/src/share/examples/etc/make.conf ? > I'm asking because in this file I read: > > # CFLAGS controls the compiler settings used when compiling C code. > # Note that optimization settings other than -O and -O2 are not recommended > # or supported for compiling the world or the kernel - please revert any > # nonstandard optimization settings to "-O" or -O2 before submitting bug > # reports without patches to the developers. > # > #CFLAGS= -O -pipe > > May be "-fno-strict-aliasing" have to be added here then ? > A couple of things. Will having gcc unroll loops have any negative consequences? (I can't imagine how:: but better informed than to have something crash inexplicability.) With 6.X safe at -O2 and with -funroll-loops, that should be a slight gain, right? (It also will make an upgrade from 5.5 to 6.[12] that much more rational.) [Dumb] questions:: first, what does the compiler do with "-fno-strict-aliasing"? And is there any guess, any SWAG even, on when FreeBSD will safe with -O3?? thanks, people, gary > -- > Best Wishes, > Stefan Lambrev > ICQ# 24134177 > > _______________________________________________ > freebsd-stable@freebsd.org mailing list > http://lists.freebsd.org/mailman/listinfo/freebsd-stable > To unsubscribe, send any mail to "freebsd-stable-unsubscribe@freebsd.org" -- Gary Kline kline@thought.org www.thought.org Public service Unix