RFR: 8369190: JavaFrameAnchor on AArch64 appears to be missing barriers

[Justin King]

On Mon, 6 Oct 2025 15:30:13 GMT, Andrew Haley <aph at openjdk.org> wrote:

>> Add store barrier at the appropriate place in `JavaFrameAnchor::copy`. Move `sp` store to be last in `MacroAssembler::set_last_Java_frame`. Add `dmb ISHST` to `MacroAssembler::set_last_Java_frame` and `MacroAssembler::reset_last_Java_frame`.
>
> src/hotspot/cpu/aarch64/javaFrameAnchor_aarch64.hpp line 43:
> 
>> 41:   void clear(void) {
>> 42:     // Must clear sp first and place a store-store barrier (dmb ISHST) immediately after,
>> 43:     // to ensure ACGT does not observe a corrupted frame.
> 
> What is ACGT that you want to slow down AArch64 HotSpot for it?

`AsyncGetCallTrace`, meant `AGCT`.

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PR Review Comment: https://git.openjdk.org/jdk/pull/27645#discussion_r2407078098