[lworld] RFR: 8368274: [lworld] Unsafe.compareAndExchangeFlatValue() wrongly assumes padding bytes are the same for identical value objects [v5]

[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 pull request now contains 10 commits:

 - Merge branch 'lworld' into fix/unsafe-flat-cas
 - Comment update
 - 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

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Changes: https://git.openjdk.org/valhalla/pull/1734/files
  Webrev: https://webrevs.openjdk.org/?repo=valhalla&pr=1734&range=04
  Stats: 81 lines in 2 files changed: 37 ins; 15 del; 29 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