Date: Wed, 31 Oct 2007 11:03:20 +0100 From: "Stephan F. Yaraghchi" <stephan@yaraghchi.org> To: "Kris Kennaway" <kris@freebsd.org> Cc: freebsd-current@freebsd.org Subject: Re: loader breaks with -O2 optimizations Message-ID: <25f52a3d0710310303w7138bf5ds92698f1b6af2f655@mail.gmail.com> In-Reply-To: <47284E4F.5030008@FreeBSD.org> References: <25f52a3d0710300732x425f0c45vde1a29361096c018@mail.gmail.com> <47284E4F.5030008@FreeBSD.org>
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On 10/31/07, Kris Kennaway <kris@freebsd.org> wrote: > Stephan F. Yaraghchi wrote: > > After making world on a freshly installed 7.0-BETA1 > > the system does not boot anymore due to a broken loader: > > > > > > FreeBSD/i386 bootstrap loader, Revision 1.1 > > (root@bigblue, Tue Oct 30 11:26:32 CET 2007) > > Can't work out which disk we are booting from. > > Guessed BIOS device 0xffffffff not found by probes defaulting to disk0: > > > > panic: free: guard1 fail@ 0x6ded4 from > > /usr/src/sys/boot/i386/loader/../../common/module.c:959 > > > > --> Press a key on the console to reboot <-- > > > > > > I found out that the following line in my make.conf causes > > the problem: > > > > CFLAGS= -O2 -funroll-loops -pipe > > > > > > After changing down to -O1 and making /usr/src/sys/boot again > > the systems behaves properly at boot. > > > > Is this behavior intended? > > Maybe, what happens if you use just -O2 -pipe? -funroll-loops is not an > appropriate thing to be using globally anyway, unless your intention is > to randomly make some code slower. > > Kris > Hi Kris, I tried all possible combinations of these switches -- only -O2 led to the described behaviour. Anyway, it's very interesting to hear that adding these optimizations to make.conf is not recommended, even that -funroll-loops is possibly slowing down certain code. I'm sure many people use it since it's a common tuning tip found on the web. I read about it in Dru Lavigne's "BSD Hacks" (O'Reilly)... -- Stephan www.deine-stimme-gegen-armut.de
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