[lworld] RFR: 8368274: [lworld] Unsafe.compareAndExchangeFlatValue() wrongly assumes padding bytes are the same for identical value objects [v3]

[Chen Liang]

> Use the raw value get as witness, because the flat value get may ignore garbage value and cause infinite loop as a result. Waiting for a test case.

Chen Liang has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains eight additional commits since the last revision:

 - Merge branch 'lworld' of https://github.com/openjdk/valhalla into fix/unsafe-flat-cas
 - Remove test as permitted
 - Fixes, VHTMHAV now passes
 - Merge branch 'lworld' of https://github.com/openjdk/valhalla into fix/unsafe-flat-cas
 - A test
 - Merge branch 'lworld' of https://github.com/openjdk/valhalla into fix/unsafe-flat-cas
 - Merge branch 'lworld' of https://github.com/openjdk/valhalla into fix/unsafe-flat-cas
 - Attempt to fix garbage cas

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

Changes:
  - all: https://git.openjdk.org/valhalla/pull/1734/files
  - new: https://git.openjdk.org/valhalla/pull/1734/files/0b95903f..c1659649

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=valhalla&pr=1734&range=02
 - incr: https://webrevs.openjdk.org/?repo=valhalla&pr=1734&range=01-02

  Stats: 23028 lines in 2478 files changed: 5555 ins; 2720 del; 14753 mod
  Patch: https://git.openjdk.org/valhalla/pull/1734.diff
  Fetch: git fetch https://git.openjdk.org/valhalla.git pull/1734/head:pull/1734

PR: https://git.openjdk.org/valhalla/pull/1734