linux-kernel - Re: asm volatile [Was: [RFC] div64

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Message-ID: <20070308182357.nnpvhqqj5qqk2vsx@m.safari.iki.fi>
Date:	Thu, 8 Mar 2007 20:23:57 +0200
From:	Sami Farin <7atbggg02@...akemail.com>
To:	linux-kernel@...r.kernel.org, netdev@...r.kernel.org
Subject: Re: asm volatile [Was: [RFC] div64_64 support]

On Wed, Mar 07, 2007 at 00:24:35 +0200, Sami Farin wrote:
> On Tue, Mar 06, 2007 at 23:53:49 +0200, Sami Farin wrote:
> ...
> > And I found bug in gcc-4.1.2, it gave 0 for ncubic results
> > when doing 1000 loops test... gcc-4.0.3 works.
> 
> Found it.
> 
> --- cbrt-test.c~	2007-03-07 00:20:54.735248105 +0200
> +++ cbrt-test.c	2007-03-07 00:21:03.964864343 +0200
> @@ -209,7 +209,7 @@
>  
>  	__asm__("bsrl %1,%0\n\t"
>  		"cmovzl %2,%0"
> -		: "=&r" (r) : "rm" (x), "rm" (-1));
> +		: "=&r" (r) : "rm" (x), "rm" (-1) : "memory");
>  	return r+1;
>  }
>  
> Now Linux 2.6 does not have "memory" in fls, maybe it causes
> some gcc funnies some people are seeing.

It also works without "memory" if I do "__asm__ volatile".

Why some functions have volatile and some have not in include/asm-*/*.h ?

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