Date: Wed, 13 Sep 2006 03:08:23 -0700
From: Pete Slagle <freebsd-stable@voidcaptain.com>
To: olli@lurza.secnetix.de
Cc: freebsd-stable@Freebsd.org
Subject: Re: optimization levels for 6-STABLE build{kernel,world}
Message-ID: <4507D897.4030502@voidcaptain.com>
In-Reply-To: <200609130905.k8D95idk062789@lurza.secnetix.de>
References: <200609130905.k8D95idk062789@lurza.secnetix.de>
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Oliver Fromme wrote: > Marc G. Fournier <freebsd@hub.org> 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. /etc/make.conf on most of my 6.1 machines contains (in part) this: CFLAGS= -O2 -pipe -fno-strict-aliasing COPTFLAGS= -O2 -pipe I no longer remember exactly why, but at some point I must have understood or assumed that to be the recommendation. Just to be completely clear, are you saying that this CFLAGS= -O2 -pipe -fno-strict-aliasing COPTFLAGS= -O2 -pipe -fno-strict-aliasing would be better in the general case?
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