Date: Mon, 15 Nov 2010 23:46:45 +0100
From: Jakub Jelinek <jakub@redhat.com>
To: Andi Kleen <andi@firstfloor.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>, Jim Bos <jim876@xs4all.nl>,
        James Cloos <cloos@jhcloos.com>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Andreas Schwab <schwab@redhat.com>, Michael Matz <matz@suse.de>,
        Dave Korn <dave.korn.cygwin@gmail.com>,
        Richard Guenther <richard.guenther@gmail.com>, gcc@gcc.gnu.org
Subject: Re: gcc 4.5.1 / as 2.20.51.0.11 miscompiling drivers/char/i8k.c ?
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On Mon, Nov 15, 2010 at 11:43:22PM +0100, Andi Kleen wrote:
> > testcase shows that in 4.1/4.2/4.3/4.4 this is miscompiled only when using
> > -fno-ipa-reference, in 4.5 it is miscompiled always when optimizing
> > unless -fno-ipa-pure-const (as 4.5 added local-pure-const pass which is run
> > before ipa-reference) and in 4.6 this has been fixed by Honza when
> > doing ipa cleanups.
> 
> Maybe it would be better to simply change the kernel Makefiles to pass
> -fno-ipa-pure-const instead of adding volatiles everywhere.

If you do this, please do it for 4.5.[012] only.  If you disable all gcc
passes that ever had any bugs in it, you'd need to disable most of them if
not all.

	Jakub
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