RFR: 8338995: New Object to ObjectMonitor mapping: PPC64 implementation [v3]

[Martin Doerr]

> PPC64 implementation of [JDK-8315884](https://bugs.openjdk.org/browse/JDK-8315884).

Martin Doerr has updated the pull request incrementally with two additional commits since the last revision:

 - Remove empty line.
 - Improve register usage and readability.

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/20922/files
  - new: https://git.openjdk.org/jdk/pull/20922/files/6dc7d495..571601f7

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=20922&range=02
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=20922&range=01-02

  Stats: 16 lines in 1 file changed: 9 ins; 1 del; 6 mod
  Patch: https://git.openjdk.org/jdk/pull/20922.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/20922/head:pull/20922

PR: https://git.openjdk.org/jdk/pull/20922