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From: Nick Desaulniers <ndesaulniers@google.com>
To: Fangrui Song <maskray@google.com>
Cc: Nathan Chancellor <nathan@kernel.org>,
	Masahiro Yamada <masahiroy@kernel.org>,
	Michal Marek <michal.lkml@markovi.net>,
	Linux Kbuild mailing list <linux-kbuild@vger.kernel.org>,
	LKML <linux-kernel@vger.kernel.org>,
	clang-built-linux <clang-built-linux@googlegroups.com>
Subject: Re: [PATCH 2/2] Makefile: Only specify '--prefix=' when building with clang + GNU as
Date: Tue, 2 Mar 2021 14:09:01 -0800	[thread overview]
Message-ID: <CAKwvOdmR_p-zbrTUmbObmCVKBcuNLpg_V3NqLeYsEK4xNHfYOA@mail.gmail.com> (raw)
In-Reply-To: <20210302220252.ulvlsfyp4ordwrky@google.com>

On Tue, Mar 2, 2021 at 2:02 PM Fangrui Song <maskray@google.com> wrote:
>
> On 2021-03-02, Nathan Chancellor wrote:
> >When building with LLVM_IAS=1, there is no point to specifying
> >'--prefix=' because that flag is only used to find the cross assembler,
> >which is clang itself when building with LLVM_IAS=1. All of the other
> >tools are invoked directly from PATH or a full path specified via the
> >command line, which does not depend on the value of '--prefix='.
> >
> >Sharing commands to reproduce issues becomes a little bit easier without
> >a '--prefix=' value because that '--prefix=' value is specific to a
> >user's machine due to it being an absolute path.
> >
> >Signed-off-by: Nathan Chancellor <nathan@kernel.org>
>
> Reviewed-by: Fangrui Song <maskray@google.com>
>
> clang can spawn GNU as (if -f?no-integrated-as is specified) and GNU
> objcopy (-f?no-integrated-as and -gsplit-dwarf and -g[123]).

But -g get's set via CONFIG_DEBUG_INFO and -gsplit-dwarf by
DEBUG_INFO_SPLIT.  So if we say:
$ ARCH=arm64 CROSS_COMPILE=aarch64-linux-gnu- make CC=clang LLVM_IAS=1

So cross compile, use clang, use the integrated assembler (ie. with
this change, don't set --prefix), with either of the two above
configs, which objcopy get's exec'd?

>
> With LLVM_IAS=1, these cases are ruled out.



-- 
Thanks,
~Nick Desaulniers

  reply	other threads:[~2021-03-02 22:56 UTC|newest]

Thread overview: 20+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-03-02 21:06 [PATCH 1/2] Makefile: Remove '--gcc-toolchain' flag Nathan Chancellor
2021-03-02 21:06 ` [PATCH 2/2] Makefile: Only specify '--prefix=' when building with clang + GNU as Nathan Chancellor
2021-03-02 22:02   ` Fangrui Song
2021-03-02 22:09     ` Nick Desaulniers [this message]
2021-03-02 22:40       ` Nick Desaulniers
2021-03-09 19:55   ` Masahiro Yamada
2021-03-09 19:58     ` Masahiro Yamada
2021-09-29 17:26   ` kernel test robot
2021-09-29 19:32   ` kernel test robot
2021-03-02 21:43 ` [PATCH 1/2] Makefile: Remove '--gcc-toolchain' flag Fangrui Song
2021-03-03  8:33   ` Masahiro Yamada
2021-03-02 22:33 ` Nick Desaulniers
2021-03-03  3:25 ` Sedat Dilek
2021-03-03 14:22   ` Sedat Dilek
2021-03-09 20:59 ` [PATCH v2 " Nathan Chancellor
2021-03-09 20:59   ` [PATCH v2 2/2] Makefile: Only specify '--prefix=' when building with clang + GNU as Nathan Chancellor
2021-03-09 21:15   ` [PATCH v2 1/2] Makefile: Remove '--gcc-toolchain' flag Fangrui Song
2021-03-15 16:21   ` Masahiro Yamada
2021-03-15 16:41     ` Sedat Dilek
2021-03-16 15:36       ` Masahiro Yamada

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