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Message-ID: <AANLkTim-2XE=4MbfDLXkg+jj=P5wj2cVKBHemRHLZn2L@mail.gmail.com>
Date:	Mon, 15 Nov 2010 23:07:15 +0100
From:	Richard Guenther <richard.guenther@...il.com>
To:	Jeff Law <law@...hat.com>
Cc:	Andi Kleen <andi@...stfloor.org>,
	Andreas Schwab <schwab@...ux-m68k.org>, Jim <jim876@...all.nl>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	gcc@....gnu.org
Subject: Re: gcc 4.5.1 / as 2.20.51.0.11 miscompiling drivers/char/i8k.c ?

On Mon, Nov 15, 2010 at 7:45 PM, Jeff Law <law@...hat.com> wrote:
> On 11/08/10 03:49, Richard Guenther wrote:
>>
>> On Mon, Nov 8, 2010 at 12:03 AM, Andi Kleen<andi@...stfloor.org>  wrote:
>>>
>>> Andreas Schwab<schwab@...ux-m68k.org>  writes:
>>>>
>>>> The asm fails to mention that it modifies *regs.
>>>
>>> It has a memory clobber, that should be enough, no?
>>
>> No.  A memory clobber does not cover automatic storage.
>
> A memory clobber should clobber anything in memory, including autos in
> memory; if it doesn't, then that seems like a major problem.  I'd like to
> see the rationale behind not clobbering autos in memory.

Non-address taken automatic storage.  (note that we don't excercise this
in optimization yet)

It's difficult to model thins kind of non-aliased memory with this kind
of aliasing mechanism (apart from taking all asms as clobbering
everything as we currently do).

Richard.

> Jeff
>
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