On Mon, 1 Dec 2025 18:27:34 GMT, Chen Liang <[email protected]> wrote:
>> Currently, the hotspot compiler (as in ciField) trusts final fields in >> hidden classes, record classes, and selected jdk packages. Some classes in >> the JDK wish to be trusted, but they cannot apply package-wide opt-in due to >> other legacy classes in the package, such as java.util. >> >> They currently can use `@Stable` as a workaround, but this is fragile >> because a stable final field may hold a trusted null, zero, or false value, >> which is currently treated as non-constant by ciField. >> >> We should add an annotation to opt-in for a whole class, mainly for legacy >> packages. This would benefit greatly some of our classes already using a lot >> of Stable, such as java.util.Optional, whose empty instance is now >> constant-foldable, as demonstrated in a new IR test. >> >> Paging @minborg who requested Optional folding for review. >> >> I think we can remove redundant Stable in a few other java.util classes >> after this patch is integrated. I plan to do that in subsequent patches. > > Chen Liang has updated the pull request incrementally with one additional > commit since the last revision: > > bracket styles This PR currently does not interact with JEP 500. However, as specified in `Field.set`, the result of setting a final field may be ignored, as Alan [commented](https://github.com/openjdk/jdk/pull/28540#discussion_r2573494589). So I don't think we need to rescind the current trusting even if users enable mutations. In addition, @DanHeidinga I made the same fault as you when I first saw `--enable-final-field-mutation=` - this actually represents the callers, instead of the target, of `Field.set`. The target of mutation is specified via `--add-opens`, if the target field is not public. ------------- PR Comment: https://git.openjdk.org/jdk/pull/28540#issuecomment-3598676839
