RFR(S): 8228416: [lworld] C2 compilation fails with assert(raw_val == __null) failed: val may not be null

[Tobias Hartmann]

Hi,

please review the following patch:
https://bugs.openjdk.java.net/browse/JDK-8228416
http://cr.openjdk.java.net/~thartmann/8228416/webrev.00/

When allocating an array without a statically known type (for example, through reflection), we only
set raw_default_value but not default_value which triggers an assert during macro expansion of the
AllocateArrayNode. Both values should be initialized.

This only happens with -XX:-UseCompressedClassPointers because the code paths in
PhaseMacroExpand::generate_clear_array are different due to different alignment restrictions.

Thanks,
Tobias