linux-kernel - Re: building csky with CC=clang

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Message-ID: <20201222214323.655tjdqdvxhw3722@google.com>
Date:   Tue, 22 Dec 2020 13:43:23 -0800
From:   Fangrui Song <maskray@...gle.com>
To:     Nick Desaulniers <ndesaulniers@...gle.com>
Cc:     Guo Ren <guoren@...nel.org>, linux-csky@...r.kernel.org,
        clang-built-linux <clang-built-linux@...glegroups.com>,
        Arnd Bergmann <arnd@...nel.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: building csky with CC=clang

On 2020-12-22, 'Nick Desaulniers' via Clang Built Linux wrote:
>Hello!
>I was playing with some of LLVM's experimental backends (m68k) and saw
>there was a CSKY backend. I rebuilt LLVM to support CSKY, but I ran
>into trouble building the kernel before even getting to the compiler
>invocation:
>
>$ ARCH=csky CROSS_COMPILE=csky-linux-gnu- make CC=clang -j71 defconfig
>...
>scripts/Kconfig.include:40: linker 'csky-linux-gnu-ld' not found
>
>My distro doesn't package binutils-csky-linux-gnu, is there
>documentation on how to build the kernel targeting CSKY, starting with
>building GNU binutils configured with CSKY emulation?

Note also that the llvm/lib/Target/CSKY has not been fully upstreamed
yet. It is a WIP https://lists.llvm.org/pipermail/llvm-dev/2020-August/144481.html
I will not expect clang csky to work currently.
(The latest committed LLVM patch is https://reviews.llvm.org/D93372
Normally committing an important piece of a large patch series like this should take
a bit longer time longer after someone in the community accepted it
https://llvm.org/docs/CodeReview.html#can-code-be-reviewed-after-it-is-committed )

I do want to raise the recent LLVM M68k target. Its patches ([M67k] (Patch */8))
are very organized and the main proposer shares updates to llvm-dev regularly.
There is a lot from the process where the C-SKY target can learn from.