linux-kernel - Re: [PATCH] powerpc/32: Remove memory clobber asm constraint on dcbX() functions

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Message-ID: <20190506165314.GC8599@gate.crashing.org>
Date:   Mon, 6 May 2019 11:53:14 -0500
From:   Segher Boessenkool <segher@...nel.crashing.org>
To:     Christophe Leroy <christophe.leroy@....fr>
Cc:     linux-kernel@...r.kernel.org, Scott Wood <oss@...error.net>,
        Paul Mackerras <paulus@...ba.org>,
        linuxppc-dev@...ts.ozlabs.org
Subject: Re: [PATCH] powerpc/32: Remove memory clobber asm constraint on dcbX() functions

Hi!

On Mon, May 06, 2019 at 04:31:38PM +0000, Christophe Leroy wrote:
> However, I've tried your suggestion below and get unnexpected result.

> >you can do
> >
> >	__asm__ __volatile__ ("dcbf %0" : : "Z"(addr) : "memory");
> >
> >to save some insns here and there. ]

This should be "dcbf %y0".  Sorry.  And not addr -- it needs a mem there,
so deref addr as usual.


Segher