From: Herbert Xu <herbert@gondor.apana.org.au>
To: Nathan Chancellor <natechancellor@gmail.com>
Cc: linux-crypto@vger.kernel.org, linux-kernel@vger.kernel.org,
clang-built-linux@googlegroups.com,
Dmitry Golovin <dima@golovin.in>
Subject: Re: [PATCH] lib/mpi: Fix 64-bit MIPS build with Clang
Date: Thu, 30 Apr 2020 15:30:04 +1000 [thread overview]
Message-ID: <20200430053004.GC11738@gondor.apana.org.au> (raw)
In-Reply-To: <20200421214703.47883-1-natechancellor@gmail.com>
On Tue, Apr 21, 2020 at 02:47:04PM -0700, Nathan Chancellor wrote:
> When building 64r6_defconfig with CONFIG_MIPS32_O32 disabled and
> CONFIG_CRYPTO_RSA enabled:
>
> 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
> umul_ppmm(prod_high, prod_low, s1_ptr[j], s2_limb);
> ~~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> lib/mpi/longlong.h:664:22: note: expanded from macro 'umul_ppmm'
> : "=d" ((UDItype)(w0))
> ~~~~~~~~~~^~~
> lib/mpi/generic_mpih-mul1.c:37:13: error: invalid use of a cast in a
> inline asm context requiring an l-value: remove the cast
> or build with -fheinous-gnu-extensions
> umul_ppmm(prod_high, prod_low, s1_ptr[j], s2_limb);
> ~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> lib/mpi/longlong.h:668:22: note: expanded from macro 'umul_ppmm'
> : "=d" ((UDItype)(w1))
> ~~~~~~~~~~^~~
> 2 errors generated.
>
> This special case for umul_ppmm for MIPS64r6 was added in
> commit bbc25bee37d2b ("lib/mpi: Fix umul_ppmm() for MIPS64r6"), due to
> GCC being inefficient and emitting a __multi3 intrinsic.
>
> There is no such issue with clang; with this patch applied, I can build
> this configuration without any problems and there are no link errors
> like mentioned in the commit above (which I can still reproduce with
> GCC 9.3.0 when that commit is reverted). Only use this definition when
> GCC is being used.
>
> This really should have been caught by commit b0c091ae04f67 ("lib/mpi:
> Eliminate unused umul_ppmm definitions for MIPS") when I was messing
> around in this area but I was not testing 64-bit MIPS at the time.
>
> Link: https://github.com/ClangBuiltLinux/linux/issues/885
> Reported-by: Dmitry Golovin <dima@golovin.in>
> Signed-off-by: Nathan Chancellor <natechancellor@gmail.com>
> ---
> lib/mpi/longlong.h | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
Patch applied. Thanks.
--
Email: Herbert Xu <herbert@gondor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt
prev parent reply other threads:[~2020-04-30 5:30 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-04-21 21:47 [PATCH] lib/mpi: Fix 64-bit MIPS build with Clang Nathan Chancellor
2020-04-30 5:30 ` Herbert Xu [this message]
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