RFR: 8359435: AArch64: add support for SB instruction to MacroAssembler::spin_wait

[Andrew Haley]

On Sat, 14 Jun 2025 16:00:55 GMT, Andrew Haley <aph at openjdk.org> wrote:

>> FWIW, I don't mind the SB assembler support to go under this, separate PR. We sometimes do it to split the work in the series of atomic commits, where the commit like this should certainly be non-regressing. The actual use of SB (spin-pauses) can then come under separate RFE, and would require much more work (and have associated risk).
>> 
>> So, it would be tad less confusing if we had a dependent RFE for using SB in spin pauses, so it was obvious why do we need it.
>
>> So, it would be tad less confusing if we had a dependent RFE for using SB in spin pauses, so it was obvious why do we need it.
> 
> Huh? The least confusing is when the SB support goes in the PR where it is used. That really is obvious, without any dependency chain.

> Looks okay to me. @theRealAph should also take a look.

I'm still waiting for a use for this thing. Then we'll be able to see it in action.

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PR Comment: https://git.openjdk.org/jdk/pull/25801#issuecomment-3005256762