[lworld] RFR: 8357373: [lworld] jdk/valhalla/valuetypes/ObjectMethods.java fails with -XX:+UseAtomicValueFlattening [v2]

[Roger Riggs]

> This test failing with VM options prompted a refatoring and cleanup of the test (and renaming to be more appropriate).
> The test is re-enabled with a 4 combinations of command line flags.
> 
> Refactored test to verify that hashcode changed with each change to a field. Previously, the test tried to compute the hashCode for the value class. That was fragile in the presence of the VM changing the layout information. Check the hashCodes are equal for objects that are `.equals`. Renamed to 'ValueObjectMethodsTest`.

Roger Riggs has updated the pull request incrementally with one additional commit since the last revision:

  Correct check for identityHashCode

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

Changes:
  - all: https://git.openjdk.org/valhalla/pull/1771/files
  - new: https://git.openjdk.org/valhalla/pull/1771/files/e8be456c..cf21f7d4

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=valhalla&pr=1771&range=01
 - incr: https://webrevs.openjdk.org/?repo=valhalla&pr=1771&range=00-01

  Stats: 1 line in 1 file changed: 0 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/valhalla/pull/1771.diff
  Fetch: git fetch https://git.openjdk.org/valhalla.git pull/1771/head:pull/1771

PR: https://git.openjdk.org/valhalla/pull/1771