Building the Linux kernel with Clang and LLVM
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From: Nathan Chancellor <nathan@kernel.org>
To: Rong Xu <xur@google.com>, Han Shen <shenhan@google.com>
Cc: llvm@lists.linux.dev, linux-kbuild@vger.kernel.org
Subject: Build breakage from renamed '-split-machine-functions' plugin option
Date: Fri, 9 Oct 2026 22:45:01 +0100	[thread overview]
Message-ID: <20261009214501.GA905361@ax162> (raw)

Hi Rong and Han,

LLVM recently landed a commit renaming the '-split-machine-functions'
plugin option to '-function-splitting=all':

  https://github.com/llvm/llvm-project/commit/3e6acc87c58843e551d6e8e4bf06c26712b04622

This breaks builds with CONFIG_AUTOFDO and CONFIG_LTO_CLANG_THIN with:

  ld.lld: error: -plugin-opt=-: ld.lld: Unknown command line argument '-split-machine-functions'.  Try: 'ld.lld --help'

Obviously, we can handle this rename but I noticed that the combination
of '-flto -fsplit-machine-functions' should add the corresponding
'-plugin-opt=' since LLVM 15:

  https://github.com/llvm/llvm-project/commit/72acd042bad35f78232f17addc02196a7af1a6e9

So is this even necessary? Should we just remove

  KBUILD_LDFLAGS += -plugin-opt=-split-machine-functions

from scripts/Makefile.autofdo and rely on '-fsplit-machine-functions' to
do the right thing or am I missing something here?

-- 
Cheers,
Nathan

             reply	other threads:[~2026-10-09 21:45 UTC|newest]

Thread overview: 3+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2026-10-09 21:45 Nathan Chancellor [this message]
     [not found] ` <CAF1bQ=Qq66JuvYrbR-7GgegZuWPSjxDOgerUSD2NOp9W0BauZw@mail.gmail.com>
2026-10-10 18:49   ` Build breakage from renamed '-split-machine-functions' plugin option Rong Xu
2026-10-10 18:50   ` Rong Xu

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