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From: Andreas Hindborg <a.hindborg@kernel.org>
To: "Gary Guo" <gary@garyguo.net>
Cc: "Miguel Ojeda" <ojeda@kernel.org>,  "Alex Gaynor"
 <alex.gaynor@gmail.com>,  "Boqun Feng" <boqun.feng@gmail.com>,
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 Baron <bjorn3_gh@protonmail.com>,  "Benno Lossin"
 <benno.lossin@proton.me>,  "Alice Ryhl" <aliceryhl@google.com>,  "Trevor
 Gross" <tmgross@umich.edu>,  "Nathan Chancellor" <nathan@kernel.org>,
  "Nick Desaulniers" <ndesaulniers@google.com>,  "Bill Wendling"
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 Yamada" <masahiroy@kernel.org>,  "Andrew Morton"
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 Heo" <tj@kernel.org>,  "Yoann Congal" <yoann.congal@smile.fr>,  "Roman
 Gushchin" <roman.gushchin@linux.dev>,  "Jens Axboe" <axboe@kernel.dk>,
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  "Mark Rutland" <mark.rutland@arm.com>,  "Vincent Guittot"
 <vincent.guittot@linaro.org>,  <rust-for-linux@vger.kernel.org>,
  <llvm@lists.linux.dev>,  <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH v2 1/3] kbuild: rust: add
 `CONFIG_RUSTC_CLANG_LLVM_COMPATIBLE`
In-Reply-To: <20250105194054.545201-2-gary@garyguo.net> (Gary Guo's message of
	"Sun, 05 Jan 2025 19:40:04 +0000")
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References: <20250105194054.545201-1-gary@garyguo.net>
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	<20250105194054.545201-2-gary@garyguo.net>
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Date: Tue, 07 Jan 2025 12:29:39 +0100
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"Gary Guo" <gary@garyguo.net> writes:

> This config detects if Rust and Clang have matching LLVM major version.
> All IR or bitcode operations (e.g. LTO) rely on LLVM major version to be
> matching, otherwise it may generate errors, or worse, miscompile silently
> due to change of IR semantics.
>
> It's usually suggested to use the exact same LLVM version, but this can
> be difficult to guarantee. Rust's suggestion [1] is also major-version only,
> so I think this check is sufficient for the kernel.
>
> Link: https://doc.rust-lang.org/rustc/linker-plugin-lto.html [1]
> Signed-off-by: Gary Guo <gary@garyguo.net>


Reviewed-by: Andreas Hindborg <a.hindborg@kernel.org>


Best regards,
Andreas Hindborg