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Subject: Re: [PATCH] MIPS: Add comment about CONFIG_MIPS32_O32 in
 loongson3_defconfig when build with Clang
To:     Nathan Chancellor <nathan@kernel.org>
References: <1614820544-10686-1-git-send-email-yangtiezhu@loongson.cn>
 <20210304020244.pza6xd4ixziysrom@archlinux-ax161>
Cc:     Thomas Bogendoerfer <tsbogend@alpha.franken.de>,
        Nick Desaulniers <ndesaulniers@google.com>,
        linux-mips@vger.kernel.org, linux-kernel@vger.kernel.org,
        clang-built-linux@googlegroups.com,
        Xuefeng Li <lixuefeng@loongson.cn>
From:   Tiezhu Yang <yangtiezhu@loongson.cn>
Message-ID: <958c5df5-76aa-9161-9519-07a03ee864a0@loongson.cn>
Date:   Thu, 4 Mar 2021 11:48:09 +0800
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On 03/04/2021 10:02 AM, Nathan Chancellor wrote:
> On Thu, Mar 04, 2021 at 09:15:44AM +0800, Tiezhu Yang wrote:
>> When build kernel with Clang [1]:
>>
>> $ make CC=clang loongson3_defconfig
>> $ make CC=clang

[snip]

> I think this might be a better solution. I know that I personally never
> read defconfig files if a build fails.
>
> If CONFIG_MIPS32_O32 is broken with clang and the MIPS backend
> maintainer has said that it will not be supported due to lack of
> resources, then the config should not even be selectable in my opinion.
>
> Cheers,
> Nathan
>
> diff --git a/arch/mips/Kconfig b/arch/mips/Kconfig
> index d89efba3d8a4..ed35318a759d 100644
> --- a/arch/mips/Kconfig
> +++ b/arch/mips/Kconfig
> @@ -3315,6 +3315,8 @@ config SYSVIPC_COMPAT
>   config MIPS32_O32
>   	bool "Kernel support for o32 binaries"
>   	depends on 64BIT
> +	# https://bugs.llvm.org/show_bug.cgi?id=38063
> +	depends on $(success,$(CC) $(CLANG_FLAGS) -march=mips64 -o32 -c -x c /dev/null -o /dev/null)
>   	select ARCH_WANT_OLD_COMPAT_IPC
>   	select COMPAT
>   	select MIPS32_COMPAT

Hi Nathan,

Thank you very much for your reply and suggestion, maybe the following
change is simple, clear and better? If yes, I will send v2 later.

diff --git a/arch/mips/Kconfig b/arch/mips/Kconfig
index 3a38d27..f6ba59f 100644
--- a/arch/mips/Kconfig
+++ b/arch/mips/Kconfig
@@ -3318,6 +3318,8 @@ config SYSVIPC_COMPAT
  config MIPS32_O32
         bool "Kernel support for o32 binaries"
         depends on 64BIT
+       # https://bugs.llvm.org/show_bug.cgi?id=38063
+       depends on !CC_IS_CLANG
         select ARCH_WANT_OLD_COMPAT_IPC
         select COMPAT
         select MIPS32_COMPAT

Thanks,
Tiezhu