RFR(S): 8206245: [lworld] C2 crashes when merging values with different types

[Tobias Hartmann]

Hi,

please review the following patch:
https://bugs.openjdk.java.net/browse/JDK-8206245
http://cr.openjdk.java.net/~thartmann/8206245/webrev.00/

1) We hit an assert in Parse::merge_common() with test67 because m is top() and phi is NULL (we are
merging into a dead path caused by an uncommon trap). The assert is too strong. I've removed it
because we are checking both m and n when calling as_ValueType() anyway.

2) We hit an assert with test67 because we are trying to push ValueTypePtrNodes of different types
merged by a Phi node through that phi. We should check if the input types are equal.

Thanks,
Tobias