[lworld] RFR: 8364483: [lworld] Pre-register migrated classes in class loaders [v3]

[Dan Heidinga]

On Tue, 19 Aug 2025 02:07:59 GMT, Roger Riggs <rriggs at openjdk.org> wrote:

> The official list of migrated classes is in `make/modules/java.base/gensrc/GensrcValueClasses.gmk`.
> How are all these copies of the list of files kept in sync?

This is a temporary measure to make up for classfiles that don't have a `LoadedDescriptors` attribute yet.  Those classes - in user class loaders - won't "know" at link time that the box classes have migrated to be values and therefore won't benefit from the calling convention optimizations.  This PR lets us make those classloaders aware of the changed nature of the boxing classes early and ensures they get the benefits of Valhalla.  The other migrated classes are included because "why not" and so keeping the lists in sync isn't a priority.

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PR Comment: https://git.openjdk.org/valhalla/pull/1520#issuecomment-3200789475