[14] RFR(XS): 8220416: Comparison of klass pointers is not optimized any more

[Christian Hagedorn]

Hi

Please review the following patch:
https://bugs.openjdk.java.net/browse/JDK-8220416
http://cr.openjdk.java.net/~chagedorn/8220416/webrev.00/

This enables the dead klass pointer optimization again. The same dead 
optimization can be found in CmpNNode::sub. However, this method is 
never executed since CmpNNodes are only created in 
final_graph_reshaping() after which we do not apply (I)GVN anymore.

After completing and testing my change I noticed that Roland has already 
included this ticket in his change for JDK-6312651 [1] that is currently 
out for review. I think it still makes sense to fix this in a separate 
change.

Thank you!

Best regards,
Christian


[1] 
http://cr.openjdk.java.net/~roland/6312651/webrev.04/src/hotspot/share/opto/subnode.cpp.sdiff.html