RFR: 8359936: StableValues can release the underlying function after complete computation [v3]

[ExE Boss]

On Thu, 19 Jun 2025 09:59:41 GMT, Per Minborg <pminborg at openjdk.org> wrote:

>> This PR proposes to release the underlying function if a stable function or collection has invoked its underlying supplier exhaustively so that it can be collected.
>> 
>> This PR passes tier1, tier2, and tier3 testing on multiple platforms.
>
> Per Minborg has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains eight additional commits since the last revision:
> 
>  - Merge branch 'master' into sv-release-supplier2
>  - Fix performance regression
>  - Clean up
>  - Fix bug
>  - Simplify
>  - Revert to records
>  - Make code more like the old one
>  - Add removable underlying functions

src/java.base/share/classes/jdk/internal/lang/stable/StableSupplier.java line 46:

> 44:     @Override
> 45:     public T get() {
> 46:         return delegate.orElseSet(underlyingHolder.underlying(), underlyingHolder);

By avoiding reading from `underlyingHolder` when the `StableValue` is already set, this can avoid the overhead of a field read from `underlyingHolder`:
Suggestion:

        final Object t = delegate.wrappedContentsAcquire();
        if (t != null) {
            return unwrap(t);
        }
        return delegate.orElseSet(underlyingHolder.underlying(), underlyingHolder);

-------------

PR Review Comment: https://git.openjdk.org/jdk/pull/25878#discussion_r2156730614