Re: [PATCH] [POWERPC] Improve (in|out)_beXX() asm code

David Miller
2008-05-20T22:53:44Z

From: Scott Wood <scottwood@freescale.com>
Date: Tue, 20 May 2008 17:43:58 -0500

> David Miller wrote:
> > The __volatile__ in the asm construct disallows movement of the
> > inline asm relative to statements surrounding it.
> >
> > The only reason barrier() in kernel.h needs a memory clobber is
> > because of a bug in ancient versions of gcc. In fact, I think
> > that memory clobber might even be removable.
>
> Current versions of GCC seem quite happy to move non-asm memory accesses
> around a volatile asm without a memory clobber; see the test Trent posted.

Indeed, and even the GCC manual is clear about this.