linux-kernel - Re: gcc 4.5.1 / as 2.20.51.0.11 miscompiling drivers/char/i8k.c ?

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Message-ID: <877hgorrj1.fsf@basil.nowhere.org>
Date:	Mon, 08 Nov 2010 12:20:02 +0100
From:	Andi Kleen <andi@...stfloor.org>
To:	Richard Guenther <richard.guenther@...il.com>
Cc:	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 ?

Richard Guenther <richard.guenther@...il.com> writes:

> 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.

That's a separate problem.

> Btw, I can't see a testcase anywhere so I just assume Andreas got
> it right as usual.

An asm with live inputs and outputs should never be optimized
way. If 4.5.1 started doing that it's seriously broken.

-Andi

-- 
ak@...ux.intel.com -- Speaking for myself only.
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