Upcall stubs currently use resolve_jobject which may generate a lot of code depending on the selected GC.
We can use resolve_global_jobject (introduced by JDK-8299089) because we know that the handle is created by JNIHandles::make_global in UL_MakeUpcallStub. That creates much shorter code.
An alternative solution was proposed during review of JDK-8303040: Move the jobject handling into UpcallLinker::on_entry which is called anyway. This helps for Shenandoah and ZGC which emit more code in resolve_global_jobject.