Re: [PATCH] arm64: Remove AArch64 X30 redundant register alias
From: Robin Murphy <robin.murphy@arm.com>
Date: 2021-07-14 11:40:36
On 2021-07-14 10:54, Marc Zyngier wrote:
On Tue, 13 Jul 2021 14:29:45 +0100, Naohiro Tamura [off-list ref] wrote:quoted
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 <redacted> --- 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.
Right, the built-in alias was only introduced a few years ago in binutils 2.29 (where it initially caused problems itself by being a bit overzealous[2]), but our current minimum version is 2.23, so we still need this for older but still-supported toolchains (e.g. I expect the Linaro GCC 7-based releases with binutils 2.28 are still being used). Robin. [2] https://www.spinics.net/lists/arm-kernel/msg599929.html
Thanks, M. [1] https://lore.kernel.org/linux-arm-kernel/20210526213128.GB20442@willie-the-truck (local)
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