[8u20] RFR (XS) 8039050: Crash in C2 compiler at Node::rematerialize

[Vladimir Kozlov]

8u20 backport request. These changes were pushed into jdk9 yesterday and 
nightly testing shows no problems. I will wait one more night and push 
it tomorrow morning if approved.

Changes from jdk9 applied to 8u without conflicts.

http://hg.openjdk.java.net/jdk9/hs-comp/hotspot/rev/218bc7e588be
https://bugs.openjdk.java.net/browse/JDK-8039050

Thanks,
Vladimir