Re: register x18

Reply: tuexen_a_freebsd.org: "Re: register x18"
In reply to: Michael Tuexen : "register x18"
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From: Mark Millard via freebsd-arm <freebsd-arm_at_freebsd.org>
Date: Fri, 16 Jul 2021 02:06:47 UTC


On 2021-Jul-15, at 17:40, Michael Tuexen <tuexen at freebsd.org> wrote:

> Dear all,
> 
> register x18 seems to be special. What is it used for in FreeBSD?
> 
> Best regards
> Michael

https://developer.arm.com/documentation/den0024/a/The-ABI-for-ARM-64-bit-Architecture/Register-use-in-the-AArch64-Procedure-Call-Standard/Parameters-in-general-purpose-registers

reports:

QUOTE
	• X18 is the platform register and is reserved for the use of platform ABIs. This is an additional temporary register on platforms that don't assign a special meaning to it.
END QUOTE

So, special, yes. But I do not know what the "platform ABI" usage
for it might be on FreeBSD. So, for the most part, this does not
well-answer your question. Sorry.

===
Mark Millard
marklmi at yahoo.com
( dsl-only.net went
away in early 2018-Mar)