<i18n dev> RFR: 8366178: Implement JEP 526: Lazy Constants (Second Preview)

[Chen Liang]

On Thu, 2 Oct 2025 16:16:44 GMT, Kerman <duke at openjdk.org> wrote:

>> Implement JEP 526: Lazy Constants (Second Preview)
>> 
>> The lazy list/map implementations are broken out from `ImmutableCollections` to a separate class.
>> 
>> The old benchmarks are not moved/renamed to allow comparison with previous releases.
>> 
>> `java.util.Optional` is updated so that its field is annotated with `@Stable`.  This is to allow `Optional` instances to be held in lazy constants and still provide constant folding.
>
> src/java.base/share/classes/java/util/Optional.java line 74:
> 
>> 72:      * If non-null, the value; if null, indicates no value is present
>> 73:      */
>> 74:     @Stable
> 
> Shouldn’t this also add a null sentinel to allow the folding of the empty case? Or is that irrelevant because empty would be the terminator of a chain.

Usually a null sentinel is used when null indicates something different. I think maybe to allow folding the empty case, we should probably add a new annotation or a new element-value to indicate this status and properly handle it in C1/C2 (similar to the field trusting in ciField)

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

PR Review Comment: https://git.openjdk.org/jdk/pull/27605#discussion_r2403729792