Re: [PATCH] powerpc/math-emu: Fix building with clang

[Nick Desaulniers <ndesaulniers@google.com>]

On Thu, Nov 1, 2018 at 8:37 PM Joel Stanley <joel@jms.id.au> wrote:
>
>   make CC=clang-8 ARCH=powerpc CROSS_COMPILE=powerpc-linux-gnu-  ppc44x_defconfig
>   make CC=clang-8 ARCH=powerpc CROSS_COMPILE=powerpc-linux-gnu-
>
>   ...
>
>   arch/powerpc/math-emu/fnmsub.c:46:2: error: invalid use of a cast in a
>   inline asm context requiring an l-value: remove the cast or build with
>   -fheinous-gnu-extensions
>           FP_ADD_D(R, T, B);
>           ^~~~~~~~~~~~~~~~~
>   ./include/math-emu/double.h:110:27: note: expanded from macro 'FP_ADD_D'
>   #define FP_ADD_D(R,X,Y)                 _FP_ADD(D,2,R,X,Y)
>                                           ^~~~~~~~~~~~~~~~~~
>   ./include/math-emu/op-common.h:367:34: note: expanded from macro '_FP_ADD'
>   #define _FP_ADD(fs, wc, R, X, Y) _FP_ADD_INTERNAL(fs, wc, R, X, Y, '+')
>                                    ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>   ./include/math-emu/op-common.h:264:4: note: expanded from macro '_FP_ADD_INTERNAL'
>             _FP_FRAC_ADD_##wc(R, X, Y);                                        \
>             ^~~~~~~~~~~~~~~~~~~~~~~~~~
>   note: (skipping 1 expansions in backtrace; use -fmacro-backtrace-limit=0 to see all)

^^^ Hi Joel, would you mind recompiling with
`-fmacro-backtrace-limit=0` hacked in and including the full
backtrace?  I'm curious if there's a more appropriate fix, but can't
tell where the inline asm is that clang is complaining about.

>   ./include/math-emu/op-2.h:94:27: note: expanded from macro '_FP_FRAC_ADD_2'
>     __FP_FRAC_ADD_2(R##_f1, R##_f0, X##_f1, X##_f0, Y##_f1, Y##_f0)
>     ~~~~~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>
> Link: https://github.com/ClangBuiltLinux/linux/issues/260
> Signed-off-by: Joel Stanley <joel@jms.id.au>
> ---
>  arch/powerpc/math-emu/Makefile | 4 ++++
>  1 file changed, 4 insertions(+)
>
> diff --git a/arch/powerpc/math-emu/Makefile b/arch/powerpc/math-emu/Makefile
> index 494df26c5988..b9cb797445ac 100644
> --- a/arch/powerpc/math-emu/Makefile
> +++ b/arch/powerpc/math-emu/Makefile
> @@ -18,3 +18,7 @@ CFLAGS_fabs.o = -fno-builtin-fabs
>  CFLAGS_math.o = -fno-builtin-fabs
>
>  ccflags-y = -I. -Iinclude/math-emu -w
> +
> +ifdef CONFIG_CC_IS_CLANG
> +ccflags-y += -fheinous-gnu-extensions
> +endif
> --
> 2.19.1
>


-- 
Thanks,
~Nick Desaulniers