[lworld] RFR: 8367792: [lworld] Remove the Unsafe remnants of old valhalla prototypes

[Jatin Bhateja]

On Wed, 17 Sep 2025 16:52:46 GMT, Chen Liang <liach at openjdk.org> wrote:

>> There are some remnants from previous iterations of value objects in Unsafe. We should aim to remove them for cleaner code in the future.
>
> The vector support prototype was last updated 5 months ago. makePrivateBuffer introduces significant complexity into core library code and JVM. Besides this complexity, the vector prototype also introduces "multifield", which is also uncertain.
> 
> I will reach out to Paul Sandoz and Jatin Bhateja to check on the status of this prototype - it hasn't been updated since the new lworld model, maybe our mainline hacks can continue to work after the vector classes are marked value.

Hi @liach, For now, vectorAPI fallback does make heavy use of unsafe APIs to explicit larval transitions.
There is a whole lot of discussion that went into the usage of the @multifield annotation for contiguous backing storage allocation. Sharing some links for your reference.

https://cr.openjdk.org/~jrose/values/multi-field.html
https://cr.openjdk.org/~jbhateja/Valhalla/Valhalla-VectorAPI-OracleF2F-3-Apr_2024.pptx

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PR Comment: https://git.openjdk.org/valhalla/pull/1593#issuecomment-3335219756