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

[Dean Long]

On Tue, 7 Oct 2025 08:30:11 GMT, Andrew Haley <aph at openjdk.org> wrote:

>>> I don't think copy() is ever called. Can we remove it?
>> 
>> Sure.
>
>> > I don't think copy() is ever called. Can we remove it?
>> 
>> Sure.
> 
> Ah no. `copy()` is called after the anchor is constructed.

I missed that because I had commented out the JavaFrameAnchor(JavaFrameAnchor *src) ctor, thinking it was the only use, and it still builds.

I tried to research what this comment is about:
    // Hack Alert: Temporary bugfix for 4717480/4721647
and my conclusion is that it seems to be left over from an earlier safepoint implementation where the VM thread could look at the anchor of other threads while they were still running.  I don't think we do that anymore.

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PR Review Comment: https://git.openjdk.org/jdk/pull/27645#discussion_r2411926281