[lworld] RFR: 8325546: [lworld] Missing barrier in C1 compiled code on AArch64

[Tobias Hartmann]

Similar to [JDK-8264414](https://bugs.openjdk.org/browse/JDK-8264414), a membar is required after loading from a flat array to prevent a store that publishes the buffer reference to be executed before the initializing stores have completed.

Thanks,
Tobias

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Commit messages:
 - 8325546: [lworld] Missing barrier in C1 compiled code on AArch64

Changes: https://git.openjdk.org/valhalla/pull/1002/files
 Webrev: https://webrevs.openjdk.org/?repo=valhalla&pr=1002&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8325546
  Stats: 9 lines in 2 files changed: 9 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/valhalla/pull/1002.diff
  Fetch: git fetch https://git.openjdk.org/valhalla.git pull/1002/head:pull/1002

PR: https://git.openjdk.org/valhalla/pull/1002