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From: Nick Desaulniers <ndesaulniers@google.com>
To: Masahiro Yamada <masahiroy@kernel.org>
Cc: Miguel Ojeda <ojeda@kernel.org>,
	Fangrui Song <maskray@google.com>,
	Michal Marek <michal.lkml@markovi.net>,
	Arnd Bergmann <arnd@kernel.org>,
	linux-kernel@vger.kernel.org, linux-kbuild@vger.kernel.org,
	clang-built-linux@googlegroups.com,
	Geert Uytterhoeven <geert@linux-m68k.org>,
	Christoph Hellwig <hch@infradead.org>,
	Linus Torvalds <torvalds@linux-foundation.org>,
	Nick Desaulniers <ndesaulniers@google.com>
Subject: [PATCH v5 0/3] infer --target from SRCARCH for CC=clang
Date: Fri, 30 Jul 2021 14:57:05 -0700	[thread overview]
Message-ID: <20210730215708.276437-1-ndesaulniers@google.com> (raw)

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 ARCH.

Instead, let's infer it from SRCARCH, and move some flag handling into a
new file included from the top level Makefile.

Changes v4 -> v5:
* Include previously missing first patch!

Changes v3 -> v4:
* Remove the requirement that LLVM_IAS=1 be set, as per Masahiro.
* Remove the Documentation/ change from patch 2, as per Masahiro and
  Nathan.
* Add Documentation/ change as patch 3, from Masahiro.
* Reword commit message of patch 2, as per Nathan.
* Change patch 2 oneline to refer to --target and CC=clang (not
  CROSS_COMPILE).
* Carry Arnd's and Nathan's AB/RB/TB tags, confirmed ok on IRC+discord.

Changes v2 -> v3:
* Remove requirement that LLVM=1 be set. Instead, if building with just
  CC=clang LLVM_IAS=1 instead of LLVM=1 LLVM_IAS=1, you should use
  LD=ld.lld explicitly, or LD=aarch64-linux-gnu-ld. (As per Masahiro)
  Example:

  $ ARCH=arm64 make CC=clang LLVM_IAS=1 LD=ld.lld OBJCOPY=llvm-objcopy \
    STRIP=llvm-strip -j72 defconfig all

  (It's still preferable to use LLVM=1 IMO, but this is maximally
  flexible.)
* Change oneliner from LLVM=1 to CC=clang.
* Update Docs slightly.

Changes v1 -> v2:
* patch 1/2 untouched.
* Fix typos in commit message as per Geert and Masahiro.
* Use SRCARCH instead of ARCH, simplifying x86 handling, as per
  Masahiro. Add his sugguested by tag.
* change commit oneline from 'drop' to 'infer.'
* Add detail about explicit host --target and relationship of ARCH to
  SRCARCH, as per Masahiro.

Nick Desaulniers (3):
  Makefile: move initial clang flag handling into scripts/Makefile.clang
  Makefile: infer --target from ARCH for CC=clang
  Documentation/llvm: update CROSS_COMPILE inferencing

 Documentation/kbuild/llvm.rst | 17 +++++++++++++++
 MAINTAINERS                   |  1 +
 Makefile                      | 15 +------------
 scripts/Makefile.clang        | 40 +++++++++++++++++++++++++++++++++++
 4 files changed, 59 insertions(+), 14 deletions(-)
 create mode 100644 scripts/Makefile.clang


base-commit: 27932b6a2088eac7a5afa5471963b926cfbb4de7
-- 
2.32.0.554.ge1b32706d8-goog


             reply	other threads:[~2021-07-30 21:57 UTC|newest]

Thread overview: 8+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-07-30 21:57 Nick Desaulniers [this message]
2021-07-30 21:57 ` [PATCH v5 1/3] Makefile: move initial clang flag handling into scripts/Makefile.clang Nick Desaulniers
2021-07-30 21:57 ` [PATCH v5 2/3] Makefile: infer --target from ARCH for CC=clang Nick Desaulniers
2021-07-30 21:57 ` [PATCH v5 3/3] Documentation/llvm: update CROSS_COMPILE inferencing Nick Desaulniers
2021-07-30 23:12   ` Fangrui Song
2021-07-31  0:04     ` Masahiro Yamada
2021-08-02 18:30       ` Nick Desaulniers
2021-08-02 17:57     ` Nick Desaulniers

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