On Thu, 18 Dec 2025 00:03:10 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: > > Move the test to a core library purposed directory What I mean by stronger is that trusted final fields only ensure that their values are unchanged after initialization. Strict fields are unchanged unconditionally, there is only 1 observable state for a strict field of an object. As a result, in addition to constant folding, we can do load hoisting, too. So my question is why this annotation does not try to enforce a stronger invariant so that we can benefit from those invariants without having to wait for strict fields. ------------- PR Comment: https://git.openjdk.org/jdk/pull/28540#issuecomment-3668379612
