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

[Andrew Haley]

On Mon, 6 Oct 2025 12:35:44 GMT, Justin King <jcking 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?

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PR Review Comment: https://git.openjdk.org/jdk/pull/27645#discussion_r2407033608