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From: Marc Zyngier <maz@kernel.org>
To: Naohiro Tamura <naohirot@fujitsu.com>
Cc: linux-arm-kernel@lists.infradead.org,
	Catalin Marinas <catalin.marinas@arm.com>,
	Will Deacon <will@kernel.org>, Ard Biesheuvel <ardb@kernel.org>,
	Mark Rutland <mark.rutland@arm.com>,
	Fuad Tabba <tabba@google.com>,
	Andrey Konovalov <andreyknvl@gmail.com>,
	David Brazdil <dbrazdil@google.com>
Subject: Re: [PATCH] arm64: Remove AArch64 X30 redundant register alias
Date: Wed, 14 Jul 2021 10:54:25 +0100	[thread overview]
Message-ID: <87lf696x0u.wl-maz@kernel.org> (raw)
In-Reply-To: <20210713132945.334534-1-naohirot@fujitsu.com>

On Tue, 13 Jul 2021 14:29:45 +0100,
Naohiro Tamura <naohirot@fujitsu.com> wrote:
> 
> This trivial patch is my first one to the kernel community.
> Please advice me if something is not right.
> 
> -- >8 --
> Subject: arm64: Remove AArch64 X30 redundant register alias
> 
> This patch removes a redundant AArch64 register alias of X30.
> According to the GNU as manual [1], "ip0, ip1, lr and fp are
> automatically defined to alias to X16, X17, X30 and X29
> respectively".
> 
> [1] https://sourceware.org/binutils/docs/as/AArch64-Directives.html
> 
> Signed-off-by: Naohiro Tamura <naohirot@fujitsu.com>
> ---
>  arch/arm64/include/asm/assembler.h | 5 -----
>  1 file changed, 5 deletions(-)
> 
> diff --git a/arch/arm64/include/asm/assembler.h b/arch/arm64/include/asm/assembler.h
> index 89faca0e740d..c66efc1b5406 100644
> --- a/arch/arm64/include/asm/assembler.h
> +++ b/arch/arm64/include/asm/assembler.h
> @@ -155,11 +155,6 @@ alternative_endif
>  9999:	x;					\
>  	_asm_extable	9999b, l
>  
> -/*
> - * Register aliases.
> - */
> -lr	.req	x30		// link register
> -
>  /*
>   * Vector entry
>   */

I seem to vaguely remember that this isn't always defined, see [1] for
a recent example. Dropping it altogether may end-up being pretty
disruptive.

Thanks,

	M.

[1] https://lore.kernel.org/linux-arm-kernel/20210526213128.GB20442@willie-the-truck

-- 
Without deviation from the norm, progress is not possible.

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  reply	other threads:[~2021-07-14  9:56 UTC|newest]

Thread overview: 4+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-07-13 13:29 [PATCH] arm64: Remove AArch64 X30 redundant register alias Naohiro Tamura
2021-07-14  9:54 ` Marc Zyngier [this message]
2021-07-14 11:38   ` Robin Murphy
2021-07-15  1:29     ` naohirot

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