Request for reviews (XS): 6875577

[Vladimir Kozlov]

http://cr.openjdk.java.net/~kvn/6875577/webrev.00

Fixed 6875577: CTW fails with /hotspot/src/share/vm/opto/memnode.cpp

Problem:
do_null_check checks for unloaded klass only for instances.
In the test case C2 tries to generate Object.clone() intrinsic
for array with unloaded element's klass.

Solution:
Fix do_null_check to check for unloaded klass for all oop pointers.
Add check for stopped() state into PreserveReexecuteState destructor
and assert into its contructor.
Add assert to check that allocation's CheckCastPP node used in
arraycopy has more precise type then Object. Otherwise it will
fold with new CheckCastPP node and incorrect graph will be generated.

Reviewed by:

Fix verified (y/n): y, test

Other testing:
JPRT