linux-kernel - Re: [PATCH 4/5] lib/mpi: Fix for building for MIPS64 with Clang

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Date:   Mon, 12 Aug 2019 10:42:31 -0700
From:   Nick Desaulniers <ndesaulniers@...gle.com>
To:     Nathan Chancellor <natechancellor@...il.com>
Cc:     Ralf Baechle <ralf@...ux-mips.org>,
        Paul Burton <paul.burton@...s.com>,
        James Hogan <jhogan@...nel.org>, linux-mips@...r.kernel.org,
        LKML <linux-kernel@...r.kernel.org>,
        clang-built-linux <clang-built-linux@...glegroups.com>,
        Werner Koch <wk@...pg.org>
Subject: Re: [PATCH 4/5] lib/mpi: Fix for building for MIPS64 with Clang

On Sun, Aug 11, 2019 at 8:31 PM Nathan Chancellor
<natechancellor@...il.com> wrote:
>
> From: Werner Koch <wk@...pg.org>
>
> * mpi/longlong.h [MIPS64][__clang__]: Use the C version like we
> already do for 32 bit MIPS
>
> clang errors:
>
> lib/mpi/generic_mpih-mul1.c:37:24: error: invalid use of a cast in a
> inline asm context requiring an l-value: remove the cast or build with
> -fheinous-gnu-extensions

Reminds me of:
https://github.com/ClangBuiltLinux/linux/commit/7b7c1df2883dd4393592859758c3e76207da8b1d

>                 umul_ppmm(prod_high, prod_low, s1_ptr[j], s2_limb);
>                 ~~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> lib/mpi/longlong.h:652:20: note: expanded from macro 'umul_ppmm'
>         : "=l" ((USItype)(w0)), \
>                 ~~~~~~~~~~^~~
> lib/mpi/generic_mpih-mul1.c:37:3: error: invalid output constraint '=h'
> in asm
>                 umul_ppmm(prod_high, prod_low, s1_ptr[j], s2_limb);
>                 ^
> lib/mpi/longlong.h:653:7: note: expanded from macro 'umul_ppmm'
>              "=h" ((USItype)(w1)) \
>              ^
> 2 errors generated.
>
> Fixes: 5ce3e312ec5c ("crypto: GnuPG based MPI lib - header files (part 2)")
> Link: https://github.com/ClangBuiltLinux/linux/issues/605
> Link: https://github.com/gpg/libgcrypt/commit/e7ae0ae243c8978a67c802169183187d88557be8
> Signed-off-by: Werner Koch <wk@...pg.org>
> [nc: Added build error and tags to commit message
>      Modified subject line
>      Removed GnuPG-bug-id
>      Removed space between defined and (__clang__)]
> Signed-off-by: Nathan Chancellor <natechancellor@...il.com>
> ---
>  lib/mpi/longlong.h | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/lib/mpi/longlong.h b/lib/mpi/longlong.h
> index 8a1507fc94dd..5636e6a09f7a 100644
> --- a/lib/mpi/longlong.h
> +++ b/lib/mpi/longlong.h
> @@ -688,7 +688,8 @@ do {                                                                        \
>                  : "d" ((UDItype)(u)),                                  \
>                    "d" ((UDItype)(v)));                                 \
>  } while (0)
> -#elif (__GNUC__ >= 5) || (__GNUC__ >= 4 && __GNUC_MINOR__ >= 4)
> +#elif defined(__clang__) || (__GNUC__ >= 5) || (__GNUC__ == 4 && \
> +                                               __GNUC_MINOR__ >= 4)

So the minimum supported version of GCC to build the kernel is
currently 4.6, so we can clean up a lot more here.  I'd remove the
check, and delete the #elif and #else implementations.

>  #define umul_ppmm(w1, w0, u, v) \
>  do {                                                                   \
>         typedef unsigned int __ll_UTItype __attribute__((mode(TI)));    \
> --
> 2.23.0.rc2
>


-- 
Thanks,
~Nick Desaulniers