From mboxrd@z Thu Jan  1 00:00:00 1970
From: Kyle McMartin <kyle@mcmartin.ca>
Subject: Re: ldcw inline assembler patch
Date: Mon, 16 Jun 2008 17:57:26 -0400
Message-ID: <20080616215726.GD18358@phobos.i.cabal.ca>
References: <4853E587.9020802@gmx.de> <119aab440806161350w4d15c14ex735377b78f697fd8@mail.gmail.com> <4856D5E4.7090206@gmx.de> <119aab440806161454v49c15f47k75dbf27215d4a978@mail.gmail.com>
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Cc: Helge Deller <deller@gmx.de>, linux-parisc@vger.kernel.org,
	John David Anglin <dave.anglin@nrc.ca>
To: Carlos O'Donell <carlos@systemhalted.org>
Return-path: <linux-parisc-owner@vger.kernel.org>
In-Reply-To: <119aab440806161454v49c15f47k75dbf27215d4a978@mail.gmail.com>
List-ID: <linux-parisc.vger.kernel.org>
List-Id: linux-parisc.vger.kernel.org

On Mon, Jun 16, 2008 at 05:54:24PM -0400, Carlos O'Donell wrote:
> On Mon, Jun 16, 2008 at 5:06 PM, Helge Deller <deller@gmx.de> wrote:
> > So, your proposal is (copy-and-pasted in here) the following ?
> >
> > diff --git a/include/asm-parisc/system.h b/include/asm-parisc/system.h
> > index ee80c92..daeae39 100644
> > --- a/include/asm-parisc/system.h
> > +++ b/include/asm-parisc/system.h
> > @@ -169,7 +169,7 @@ static inline void set_eiem(unsigned long val)
> >  #define __ldcw(a) ({                                           \
> >        unsigned __ret;                                         \
> >        __asm__ __volatile__(__LDCW " 0(%1),%0"                 \
> > -               : "=r" (__ret) : "r" (a));                      \
> > +               : "=r" (__ret) : "r" (a) : "memory" );          \
> >        __ret;                                                  \
> >  })
> 
> Yes. The asm should clobber memory thus forcing the compiler to avoid
> memory temporaries.
> 

It shouldn't need to, since we're only ever accessing one word (the one
specified in the operand.)

Otherwise basically every inline asm everywhere ever is going to need a
memory clobber, and that's just BROKEN.

r, Kyle