RFR: 8359435: AArch64: add support for SB instruction to MacroAssembler::spin_wait [v2]

[Evgeny Astigeevich]

On Tue, 24 Jun 2025 16:40:42 GMT, Aleksey Shipilev <shade at openjdk.org> wrote:

>> Evgeny Astigeevich has updated the pull request incrementally with two additional commits since the last revision:
>> 
>>  - Add SB detection
>>  - Add support for SB to MacroAssembler::spin_wait
>
> test/hotspot/jtreg/compiler/onSpinWait/TestOnSpinWaitAArch64.java line 36:
> 
>> 34:  * @run driver compiler.onSpinWait.TestOnSpinWaitAArch64 c2 isb 3
>> 35:  * @run driver compiler.onSpinWait.TestOnSpinWaitAArch64 c2 yield 1
>> 36:  * @run driver compiler.onSpinWait.TestOnSpinWaitAArch64 c2 sb
> 
> Since we are touching up the test: maybe just say `sb 1` explicitly, and then read `spinWaitInstCount` from `args[2]` unconditionally?

Done

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PR Review Comment: https://git.openjdk.org/jdk/pull/25801#discussion_r2166778973