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

[Andrew Haley]

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>

Good.

Although in the end we don't need a fence, you prompted me to measure the difference between a releasing store (STLR) and a DMB ST; STR and to my surprise STLR is way faster, at least on Apple hardware.

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Marked as reviewed by aph (Reviewer).

PR Review: https://git.openjdk.org/jdk/pull/27645#pullrequestreview-3305930035