RFR(S): 8207346: [lworld] C2 fails with "already heap allocated value types should be linked directly"

[Tobias Hartmann]

Hi,

please review the following patch:
https://bugs.openjdk.java.net/browse/JDK-8207346
http://cr.openjdk.java.net/~thartmann/8207346/webrev.00/

We hit an assert when trying to scalarize value types with safepoint usages because allocated value
types should be linked directly. The problem is that ArrayCopyNodes have debug information (added by
GraphKit::add_safepoint_edges()) but ArrayCopyNode::Ideal does not call SafePointNode::Ideal() which
checks for value type inputs and links them directly.

All tests pass.

Thanks,
Tobias