RFR: 8315131: Clarify VarHandle set/get access on 32-bit platforms [v3]

[Raffaello Giulietti]

On Thu, 17 Jul 2025 23:15:44 GMT, John R Rose <jrose at openjdk.org> wrote:

>> Yep, to distinguish access and the encapsulated read-modify-write atomicity, I decided to avoid using "atomic"/"non-atomic" altogether - now it is just "make no atomicity guarantee"
>
> Not sure this is relevant, but isn't "opaque" access the way to request atomicity "by all means possible"?  So a user who cares can use `VH::getOpaque` if the requirement is atomicity aligned to `CAS`.
> 
> I still agree that it is good to specify the meaning of plain `VH::get` and `VH::set` as much as possible.

Opaque mode indeed ensures atomic access to primitive and reference variables.
In addition, it ensures coherence on that variable.

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PR Review Comment: https://git.openjdk.org/jdk/pull/26258#discussion_r2216902696