RFR (XS): 7181658 CTW: assert(t->meet(t0) == t) failed: Not monotonic

[Vladimir Ivanov]

http://cr.openjdk.java.net/~vlivanov/7181658/webrev.00

7181658 CTW: assert(t->meet(t0) == t) failed: Not monotonic

One of node equivalence checks in CmpUNode::sub doesn't respect 
ConstraintCast nodes, which could lead to missed optimization 
opportunities. In this particular case it also breaks monotonicity 
assumption of CCP analysis due to a discrepancy in logic between 2 cases.

I haven't been able to come up with a reduced regression test due to 
some tricky symbol resolution orderings which provoke the bug - even 
when the method bytecode is effectively the same! :-)

Testing: failing test, CTW (full testlist)

Best regards,
Vladimir Ivanov