RFR: 8337237: Use FFM instead of Unsafe for Java 2D RenderBuffer class [v3]

[Jorn Vernee]

On Mon, 29 Jul 2024 17:09:49 GMT, Phil Race <prr at openjdk.org> wrote:

>> Migrate from using Unsafe to FFM's MemorySegment API for allocating and setting native memory.
>> This code is used by Metal, OpenGL and D3D, so I manually tested SwingSet2 and J2Demo as well as running all the usual tests.
>> I also did some micro-benchmarking on the performance of Unsafe vs MemorySegment.
>> The performance of either is more than sufficient for us .. ie they could be 10x slower and we wouldn't even notice.
>> But they are in the same ballpark, and if one or the other is clearly faster it is the new FFM code.
>
> Phil Race has updated the pull request incrementally with one additional commit since the last revision:
> 
>   8337237

Latest version looks good to me.

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Marked as reviewed by jvernee (Reviewer).

PR Review: https://git.openjdk.org/jdk/pull/20339#pullrequestreview-2208133485