RFR: 8351565: Implement JEP 502: Stable Values (Preview) [v41]

[Maurizio Cimadamore]

On Fri, 4 Apr 2025 09:14:22 GMT, Per Minborg <pminborg at openjdk.org> wrote:

>> Implement JEP 502.
>> 
>> The PR passes tier1-tier3 tests.
>
> Per Minborg has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Address comments on docs

src/java.base/share/classes/java/lang/StableValue.java line 407:

> 405:  * The _content_ of a set stable value is treated as a constant by the JVM, provided that
> 406:  * the reference to the stable value is also constant (e.g. in cases where the
> 407:  * stable value itself is stored in a `static final` field).

watch out for the markdown quotes :-)

src/java.base/share/classes/java/lang/StableValue.java line 411:

> 409:  * This means that, at least in some cases, access to the content of a stable value
> 410:  * enjoys the same constant-folding optimizations that are available when accessing
> 411:  * `static final` fields.

We probably need to extra para that says something about stable suppliers/functions etc. E.g. since these are cleanly built on top of SV, if these are constants (again, stored in `static final` field) their access can be constant-folded. E.g. make it clear that this property is compositional. It doesn't just hold for a single constant SV, but also for another constant objects that wraps a SV.

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PR Review Comment: https://git.openjdk.org/jdk/pull/23972#discussion_r2028542265
PR Review Comment: https://git.openjdk.org/jdk/pull/23972#discussion_r2028544663