RFR (xs) 8027616: Off by one error in putback for compressed oops nashorn performance impr,ovement

[Coleen Phillimore]

Summary: Should compare bounds greater than or equal 4G when deciding if 
shift is
  needed or CDS area + compressed class space are within 4G of each other.

open webrev at http://cr.openjdk.java.net/~coleenp/8027616/
bug link https://bugs.openjdk.java.net/browse/JDK-8027616

Tested with jtreg tests for metaspace and compressed class pointers.

Thanks,
Coleen