Date: Sat, 27 Jul 2013 10:23:36 +0300 From: Andriy Gapon <avg@FreeBSD.org> To: freebsd-arch@FreeBSD.org Subject: Re: amd64: -O2 even with DEBUG Message-ID: <51F37578.2080405@FreeBSD.org> In-Reply-To: <20130726185425.GS26412@funkthat.com> References: <51F221D4.8040308@FreeBSD.org> <20130726185425.GS26412@funkthat.com>
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on 26/07/2013 21:54 John-Mark Gurney said the following: > Andriy Gapon wrote this message on Fri, Jul 26, 2013 at 10:14 +0300: >> I wonder why amd64 is distinguished to have -O2 in COPTFLAGS even when DEBUG is >> defined. For all other archs it's -O for that case. >> >> Perhaps, this was discussed / explained in the past, but I would appreciate it >> being said again (or even written as a comment in kern.pre.mk). > > It's probably because at least gcc produces terrible amd64 code w/o > it... It will constantly reload the register it uses to do relative > loads w/ the same value even though nothing changed... makes performance > suck... Well, we are talking about the DEBUG case. So I am not sure if better performance has more importance than better debugging. And I believe that -O2 does make debugging harder. -- Andriy Gapon
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