Re: your patch enabling Arm64's GCS extension

[Srinath Parvathaneni <srinath.parvathaneni@arm.com>]

Hi Jan,

On 2/12/2024 7:39 AM, Jan Beulich wrote:
> Srinath,
>
> may I ask against what specification this was written? There are two
> aspects I can't bring in line with what DDI0596 from December has, i.e.
> even newer than the patch (dating back to October):
>
> 1) gcspopcx, gcspopx, and gcspushx supposedly all have an optional
>     register operand, which gas 2.42 doesn't accept.

My understanding from the following specs is that the above mentioned

instructions does not take any optional arguments and this is aligned with

LLVM compiler behaviour.

https://developer.arm.com/documentation/ddi0601/2023-12/AArch64-Instructions/GCSPUSHX--Guarded-Control-Stack-Push-exception-return-record?lang=en

However, I am unsure about the statement "The value in the register by 
<Xt> is ignored" in the

specs and need further clarification. I will discuss this internally and 
get back to you with an update.

> 2) gcsstr and gcssttr supposedly have a memory-form 2nd operand, i.e.
>     a register name enclosed in square brackets. Gas 2.42 expects a
>     plain register name instead.

I agree this is a coding bug, I will create a bugzilla ticket and work 
on fixing this issue.

Thank You.

Regards,

Srinath

> Despite being newer it's of course possible that documentation is what
> actually needs fixing. Can you please clarify which way it is?
>
> Thanks, Jan