The component mirror now is an oop in ArrayKlass metadata, which is written once during initialization but has GC code to walk it in metadata during collections. There are also has compiler intrinsics to make getComponentType faster since it's a call inside the jvm.

Moving this field could allow us to remove the special compiler intrinsic code, and it's the second to last oop that metadata points to.

This field is could only be present in java/lang/Class instances and be overlaid on an injected field for InstanceKlasses so not add any space to the mirrors.