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List:       linux-kernel
Subject:    Re: [PATCH] make atomic_t volatile on all architectures
From:       Linus Torvalds <torvalds () linux-foundation ! org>
Date:       2007-08-12 9:54:16
Message-ID: alpine.LFD.0.999.0708120251570.30176 () woody ! linux-foundation ! org
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On Sun, 12 Aug 2007, Martin Schwidefsky wrote:
> 
> The duplication "=m" and "m" with the same constraint is rather 
> annoying.

It's not only annoying, it causes gcc to generate bad code too. At least 
certain versions of gcc will generate the address *twice*, even if there 
is obviously only one address used.

If you have problems with "+m", you are often actually better off using 
just "m" and then adding a memory clobber. But that has other code 
generation downsides.

			Linus
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