On Mon, Jan 07, 2019 at 05:54:27PM +0000, Will Deacon wrote:
> On Wed, Jan 02, 2019 at 03:57:54PM -0500, Michael S. Tsirkin wrote:
> > We don't really care whether the variable is in-register
> > or in-memory. Relax the constraint accordingly.
> >
> > Signed-off-by: Michael S. Tsirkin <mst@xxxxxxxxxx>
> > ---
> > include/linux/compiler.h | 2 +-
> > 1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/include/linux/compiler.h b/include/linux/compiler.h
> > index 1ad367b4cd8d..6601d39e8c48 100644
> > --- a/include/linux/compiler.h
> > +++ b/include/linux/compiler.h
> > @@ -154,7 +154,7 @@ void ftrace_likely_update(struct ftrace_likely_data *f, int val,
> > #ifndef OPTIMIZER_HIDE_VAR
> > /* Make the optimizer believe the variable can be manipulated arbitrarily. */
> > #define OPTIMIZER_HIDE_VAR(var) \
> > - __asm__ ("" : "=r" (var) : "0" (var))
> > + __asm__ ("" : "=rm" (var) : "0" (var))
> > #endif
>
> I think this can break for architectures with write-back addressing modes
> such as arm, where the "m" constraint is assumed to be evaluated precisely
> once in the asm block.
>
> Will
Thanks, I'll drop this patch.
