RFR: 8260369: [PPC64] Add support for JDK-8200555 [v4]

[Martin Doerr]

> I'd like to add the PPC64 part of JDK-8200555 "OopHandle should use Access API". This will be required to support ShenandoahGC and zGC.
> 
> I have to change register usage. That's what makes this change a bit larger.

Martin Doerr has updated the pull request incrementally with one additional commit since the last revision:

  feedback from Niklas

-------------

Changes:
  - all: https://git.openjdk.java.net/jdk/pull/2358/files
  - new: https://git.openjdk.java.net/jdk/pull/2358/files/be66f4e5..32e919d6

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=2358&range=03
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=2358&range=02-03

  Stats: 31 lines in 2 files changed: 1 ins; 0 del; 30 mod
  Patch: https://git.openjdk.java.net/jdk/pull/2358.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/2358/head:pull/2358

PR: https://git.openjdk.java.net/jdk/pull/2358