RFR: 8362376: Use @Stable annotation in Java FDLIBM implementation

[Joe Darcy]

On Wed, 16 Jul 2025 18:32:13 GMT, John R Rose <jrose at openjdk.org> wrote:

> The effect of this PR is to make the affected array elements eligible for constant-folding by the JIT.
> 
> The contract of `@Stable` is private to the JDK, since it is a trusted annotation. The trusted user promises not to change the array elements after the JIT might have observed them.
> 
> If we had a frozen (immutable) array feature in the JVM this PR could be formulated using frozen array constants. But we are not there yet.

Yes; my intention was to allow HotSpot greater leeway to optimize the FDLIBM code. Under my limited performance testing, the change seemed to be performance neutral, but if it shouldn't cause a regression, I'd be comfortable pushing the change.

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PR Comment: https://git.openjdk.org/jdk/pull/26341#issuecomment-3079867240