[lworld] RFR: 8341844: [lworld] Test crashing in genzgc in ZBarrier::mark_from_old_slow_path(zaddress)+0x4c [v2]

[David Simms]

> Generational zgc requires a store barrier in addition to the load barrier.
> load barrier followed by bulk copy isn't enough

David Simms has updated the pull request incrementally with two additional commits since the last revision:

 - Correct atomicity requirement assertion
 - Sanity checking Xint with the pickiest GC

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

Changes:
  - all: https://git.openjdk.org/valhalla/pull/1321/files
  - new: https://git.openjdk.org/valhalla/pull/1321/files/672d282d..94a02c6d

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=valhalla&pr=1321&range=01
 - incr: https://webrevs.openjdk.org/?repo=valhalla&pr=1321&range=00-01

  Stats: 22 lines in 2 files changed: 21 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/valhalla/pull/1321.diff
  Fetch: git fetch https://git.openjdk.org/valhalla.git pull/1321/head:pull/1321

PR: https://git.openjdk.org/valhalla/pull/1321