RFR(S): 8211153: [lworld] TestNativeClone.java fails with "Error mixing types: valuetype[1]:{int} and NULL" when executed with -Xcomp

[Tobias Hartmann]

Hi,

please review the following patch:
https://bugs.openjdk.java.net/browse/JDK-8211153
http://cr.openjdk.java.net/~thartmann/8211153/webrev.00/

The test calls Object.clone() on a value type receiver and C2 emits a virtual call for that. We
assert because VirtualCallGenerator::generate tries to null check the ValueTypeNode.

The fix also contains an unrelated refactoring of ciInstanceKlass::compute_nonstatic_fields_impl().

Thanks,
Tobias