[8u] backport of 8054478 and 8066045

[Roland Westrelin]

8u backport request. 8054478 was pushed to jdk9 last week. 8066045 is a trivial fix because of a few failures 8054478 caused during nightly testing.

8054478 doesn’t apply cleanly to 8u.
https://bugs.openjdk.java.net/browse/JDK-8054478
http://hg.openjdk.java.net/jdk9/hs-comp/hotspot/rev/49dd956bc8c0

Webrev with the change merged into 8u:
http://cr.openjdk.java.net/~roland/8054478/webrev.8u/

(castnode.[ch]pp don’t exist in 8u, allocation of node with new needs to be passed Compile object)

8066045 applies cleanly
https://bugs.openjdk.java.net/browse/JDK-8066045
http://hg.openjdk.java.net/jdk9/hs-comp/hotspot/rev/8394c315d83a

Note: 8054478 causes a performance regression:
https://bugs.openjdk.java.net/browse/JDK-8065965

Roland.