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

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Message-ID: <4CE17C4B.1070305@xs4all.nl>
Date:	Mon, 15 Nov 2010 19:30:35 +0100
From:	Jim Bos <jim876@...all.nl>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
CC:	Jakub Jelinek <jakub@...hat.com>, Andi Kleen <andi@...stfloor.org>,
	James Cloos <cloos@...loos.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Andreas Schwab <schwab@...hat.com>,
	Michael Matz <matz@...e.de>,
	Dave Korn <dave.korn.cygwin@...il.com>,
	Richard Guenther <richard.guenther@...il.com>, gcc@....gnu.org
Subject: Re: gcc 4.5.1 / as 2.20.51.0.11 miscompiling drivers/char/i8k.c ?

On 11/15/2010 07:08 PM, Linus Torvalds wrote:
> On Mon, Nov 15, 2010 at 9:40 AM, Jim Bos <jim876@...all.nl> wrote:
>>
>> Hmm, that doesn't work.
>>
>> [ Not sure if you read to whole thread but initial workaround was to
>> change the asm(..) to asm volatile(..) which did work. ]
> 
> Since I have a different gcc than yours (and I'm not going to compile
> my own), have you posted your broken .s file anywhere? In fact, with
> the noinline (and the removal of the "+m" thing - iow just the patch
> you tried), what does just the "i8k_smm" function assembly look like
> for you after you've done a "make drivers/char/i8k.s"?
> 
> If the asm just doesn't exist AT ALL, that's just odd. Because every
> single call-site of i8k_smm() clearly looks at the return value. So
> the volatile really shouldn't make any difference from that
> standpoint. Odd.
> 
>                        Linus
> 

Attached version with plain 2.6.36 source and version with the committed
patch, i.e with the '"+m" (*regs)'


_
Jim



View attachment "i8k.s-2.6.36" of type "text/plain" (22373 bytes)

View attachment "i8k.s-2.6.36+patch" of type "text/plain" (22949 bytes)