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From: Arnd Bergmann <arnd@kernel.org>
To: Nick Desaulniers <ndesaulniers@google.com>
Cc: Masahiro Yamada <masahiroy@kernel.org>,
	Miguel Ojeda <ojeda@kernel.org>,
	Fangrui Song <maskray@google.com>,
	Michal Marek <michal.lkml@markovi.net>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	Linux Kbuild mailing list <linux-kbuild@vger.kernel.org>,
	clang-built-linux <clang-built-linux@googlegroups.com>,
	Geert Uytterhoeven <geert@linux-m68k.org>,
	Christoph Hellwig <hch@infradead.org>,
	Linus Torvalds <torvalds@linux-foundation.org>,
	Nathan Chancellor <nathan@kernel.org>
Subject: Re: [PATCH v3 2/2] Makefile: infer CROSS_COMPILE from SRCARCH for CC=clang LLVM_IAS=1
Date: Thu, 29 Jul 2021 21:40:12 +0200	[thread overview]
Message-ID: <CAK8P3a2=mLvHfOthgyMgtv1v=nqY=oEMnj1EdJfFW-AwOrMh9g@mail.gmail.com> (raw)
In-Reply-To: <20210729165039.23896-3-ndesaulniers@google.com>

On Thu, Jul 29, 2021 at 6:50 PM 'Nick Desaulniers' via Clang Built
Linux <clang-built-linux@googlegroups.com> wrote:
>
> We get constant feedback that the command line invocation of make is too
> long. CROSS_COMPILE is helpful when a toolchain has a prefix of the
> target triple, or is an absolute path outside of $PATH, but it's mostly
> redundant for a given SRCARCH. SRCARCH itself is derived from ARCH
> (normalized for a few different targets).
>
> If CROSS_COMPILE is not set, simply set --target= for CLANG_FLAGS,
> KBUILD_CFLAGS, and KBUILD_AFLAGS based on $SRCARCH.
>
> Previously, we'd cross compile via:
> $ ARCH=arm64 CROSS_COMPILE=aarch64-linux-gnu- make LLVM=1 LLVM_IAS=1
> Now:
> $ ARCH=arm64 make LLVM=1 LLVM_IAS=1
>
> For native builds (not involving cross compilation) we now explicitly
> specify a target triple rather than rely on the implicit host triple.
>
> Link: https://github.com/ClangBuiltLinux/linux/issues/1399
> Suggested-by: Arnd Bergmann <arnd@kernel.org>
> Suggested-by: Nathan Chancellor <nathan@kernel.org>
> Suggested-by: Masahiro Yamada <masahiroy@kernel.org>
> Signed-off-by: Nick Desaulniers <ndesaulniers@google.com>

Looks good to me,

Acked-by: Arnd Bergmann <arnd@arndb.de>

> +else
> +$(error Specify CROSS_COMPILE or add '--target=' option to scripts/Makefile.clang)
> +endif # SRCARCH
> +endif # LLVM_IAS

Now in theory I suppose we could just have the fallback use
--target="$(SRCARCH)-linux-gnu"
to avoid having to change this for every new architecture. I think in
most cases, this
would just work, even though a lot of the one you listed have
different patterns.

       Arnd

  reply	other threads:[~2021-07-29 19:40 UTC|newest]

Thread overview: 9+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-07-29 16:50 [PATCH v3 0/2] " Nick Desaulniers
2021-07-29 16:50 ` [PATCH v3 1/2] Makefile: move initial clang flag handling into scripts/Makefile.clang Nick Desaulniers
2021-07-29 16:50 ` [PATCH v3 2/2] Makefile: infer CROSS_COMPILE from SRCARCH for CC=clang LLVM_IAS=1 Nick Desaulniers
2021-07-29 19:40   ` Arnd Bergmann [this message]
2021-07-29 21:00   ` Nathan Chancellor
2021-07-30  0:19     ` Nick Desaulniers
2021-07-30  6:50       ` Miguel Ojeda
2021-07-30 15:15       ` Masahiro Yamada
2021-07-30 15:10     ` Masahiro Yamada

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