[9] RFR(S): 8134739: compiler/loopopts/superword/TestVectorizationWithInvariant crashes in loop opts

[Tobias Hartmann]

Hi,

please review the following patch.

https://bugs.openjdk.java.net/browse/JDK-8134739
http://cr.openjdk.java.net/~thartmann/8134739/webrev.00

Problem:
The VM crashes during loop optimizations in CountedLoopEndNode::loopnode() because CountedLoopEndNode::phi() does not return a PhiNode but a SubINode. The problem is that the phi (2432 PhiNode) was replaced by the final value of the last loop iteration (2881 SubINode) to collapse the empty loop in IdealLoopTree::policy_do_remove_empty_loop(). See before [1] and after [2].

Solution:
CountedLoopEndNode::phi() should check if the node really is a PhiNode and return NULL otherwise.

Testing:
- Failing test
- JPRT

Thanks,
Tobias

[1] https://bugs.openjdk.java.net/secure/attachment/52878/emptyLoop1.png
[2] https://bugs.openjdk.java.net/secure/attachment/52879/emptyLoop2.png