[PATCH] powerpc: workaround clang codegen bug in dcbz

[Arnd Bergmann]

On Tue, Jul 30, 2019 at 7:07 PM Segher Boessenkool
<segher at kernel.crashing.org> wrote:
>
> On Tue, Jul 30, 2019 at 11:16:37AM -0500, Segher Boessenkool wrote:
> > in_le32 and friends?  Yeah, huh.  If LLVM copies that to the stack as
> > well, its (not byte reversing) read will be atomic just fine, so things
> > will still work correctly.
> >
> > The things defined with DEF_MMIO_IN_D (instead of DEF_MMIO_IN_X) do not
> > look like they will work correctly if an update form address is chosen,
> > but that won't happen because the constraint is "m" instead of "m<>",
> > making the %Un pretty useless (it will always be the empty string).
>
> Btw, this is true since GCC 4.8; before 4.8, plain "m" *could* have an
> automodify (autoinc, autodec, etc.) side effect.  What is the minimum
> GCC version required, these days?

gcc-4.6, but an architecture can require a higher version.

         Arnd