linux-kernel - Re: [PATCH] x86/crc32: improve crc32c

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Message-ID: <20250212201022.GB128826@sol.localdomain>
Date: Wed, 12 Feb 2025 12:10:22 -0800
From: Eric Biggers <ebiggers@...nel.org>
To: linux-kernel@...r.kernel.org
Cc: linux-crypto@...r.kernel.org, Ard Biesheuvel <ardb@...nel.org>,
	x86@...nel.org
Subject: Re: [PATCH] x86/crc32: improve crc32c_arch() code generation with
 clang

On Mon, Feb 10, 2025 at 01:07:41PM -0800, Eric Biggers wrote:
> From: Eric Biggers <ebiggers@...gle.com>
> 
> crc32c_arch() is affected by
> https://github.com/llvm/llvm-project/issues/20571 where clang
> unnecessarily spills the inputs to "rm"-constrained operands to the
> stack.  Replace "rm" with ASM_INPUT_RM which partially works around this
> by expanding to "r" when the compiler is clang.  This results in better
> code generation with clang, though still not optimal.
> 
> Signed-off-by: Eric Biggers <ebiggers@...gle.com>
> ---
> 
> This applies to
> https://git.kernel.org/pub/scm/linux/kernel/git/ebiggers/linux.git/log/?h=crc-next

Applied to crc-next.

- Eric