RFR: 8369190: JavaFrameAnchor on AArch64 has unnecessary barriers and wrong store order in MacroAssembler [v4]

[Dean Long]

On Mon, 6 Oct 2025 16:38:51 GMT, Justin King <jcking at openjdk.org> wrote:

>> Remove unnecessary release barriers in `JavaFrameAnchor::{copy,clear}` and fix `MacroAssembler::set_last_Java_frame` to set `sp` last as expected by the profiler.
>
> Justin King has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Add comment to JavaFrameAnchor regarding no need for fencing
>   
>   Signed-off-by: Justin King <jcking at google.com>

src/hotspot/cpu/aarch64/javaFrameAnchor_aarch64.hpp line 60:

> 58:     //
> 59:     // No fencing required, the members are declared volatile so the compiler will not reorder and
> 60:     // the profiler always reads from the same thread and should observe the state in program order.

I don't think copy() is ever called.  Can we remove it?

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PR Review Comment: https://git.openjdk.org/jdk/pull/27645#discussion_r2409180328