On Wed, Jul 10, 2019 at 10:33:31AM +0200, Arnd Bergmann wrote:
> On Wed, Jul 10, 2019 at 12:25 AM Russell King - ARM Linux admin
> <li...@armlinux.org.uk> wrote:
> >
> > On Tue, Jul 09, 2019 at 08:40:51PM +0200, Arnd Bergmann wrote:
> > > On Tue, Jul 9, 2019 at 8:08 PM 'Nick Desaulniers' via Clang Built
> > > Linux <clang-built-li...@googlegroups.com> wrote:
> > > > On Tue, Jul 9, 2019 at 1:41 AM Linus Walleij <linus.wall...@linaro.org>
> > > > wrote:
> > > >
> > > > > I guess this brings up the old question whether the compiler should
> > > > > be worked around or just considered immature, but as it happens this
> > > >
> > > > Definitely a balancing act; we prioritize work based on what's
> > > > feasible to work around vs must be implemented. A lot of my time is
> > > > going into validation of asm goto right now, but others are ramping up
> > > > on the integrated assembler (clang itself can be invoked as a
> > > > substitute for GNU AS; but there's not enough support to do `make
> > > > AS=clang` for the kernel just yet).
> > >
> > > Note that this bug is the same with both gas and AS=clang, which also
> > > indicates that clang implemented the undocumented .rep directive
> > > for compatibility.
> > >
> > > Overall I think we are at the point where building the kernel with clang-8
> > > is mature enough that we should work around bugs like this where it is
> > > easy enough rather than waiting for clang-9.
> >
> > While both assemblers seem to support both .rept and .rep, might it
> > be an idea to check what the clang-8 situation is with .rept ?
>
> Good idea. I tried this patch now:
>
> --- a/arch/arm/include/asm/mtd-xip.h
> +++ b/arch/arm/include/asm/mtd-xip.h
> @@ -15,6 +15,6 @@
> #include <mach/mtd-xip.h>
>
> /* fill instruction prefetch */
> -#define xip_iprefetch() do { asm volatile (".rep 8; nop;
> .endr"); } while (0)
> +#define xip_iprefetch() do { asm volatile (".rept 8; nop;
> .endr"); } while (0)
>
> #endif /* __ARM_MTD_XIP_H__ */
>
> Unfortunately that has no effect, clang treats them both the same way.
In any case, good to know.
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