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Subject: Re: [PATCH] MIPS: Add comment about CONFIG_MIPS32_O32 in
 loongson3_defconfig when build with Clang
To:     "Maciej W. Rozycki" <macro@orcam.me.uk>,
        Tiezhu Yang <yangtiezhu@loongson.cn>
Cc:     Thomas Bogendoerfer <tsbogend@alpha.franken.de>,
        Nathan Chancellor <nathan@kernel.org>,
        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>
References: <1614820544-10686-1-git-send-email-yangtiezhu@loongson.cn>
 <alpine.DEB.2.21.2103042356150.51127@angie.orcam.me.uk>
From:   Jiaxun Yang <jiaxun.yang@flygoat.com>
Message-ID: <d4802e65-52a0-f927-3e7c-80044c5bba80@flygoat.com>
Date:   Fri, 5 Mar 2021 10:22:47 +0800
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?? 2021/3/5 ????7:08, Maciej W. Rozycki д??:
> On Thu, 4 Mar 2021, Tiezhu Yang wrote:
> 
>> This is a known bug [2] with Clang, as Simon Atanasyan said,
>> "There is no plan on support O32 for MIPS64 due to lack of
>> resources".
> 
>   Huh?  Is that a joke?  From the o32 psABI's point of view a MIPS64 CPU is
> exactly the same as a MIPS32 one (for whatever ISA revision), so there's
> nothing to support there really other than the CPU/ISA name.

Clang treat MIPS32 as a different backend so we may need some extra 
effort....

TBH it is a toolchain issue and kernel workaround seems bogus.

 From my point view we can "s/mips64r2/mips32r2" when doing syscall checks
to workaround clang issue instead of disable it for kernel.

Thanks.

- Jiaxun

> 
>   As much as I dislike all the hacks the Clang community seems to come up
> with for the shortcomings of their tool there has to be a saner workaround
> available rather than forcibly disabling support for the o32 ABI with
> CONFIG_64BIT kernels, but the report is missing the compiler invocation
> line triggering the issue (V=1 perhaps?), which should be included with
> any commit description anyway, so I can't suggest anything based on the
> limited information provided.
> 
>    Maciej
>