[lworld] RFR: 8295735: [lworld] Missing membar after buffer initialization in method handle return

[Tobias Hartmann]

A missing membar after buffer initialization in C2's handling of scalarized returns from method handle intrinsics leads to incorrect execution and crashes with compiler/valhalla/inlinetypes/TestBufferTearing.java on aarch64.

Thanks,
Tobias

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Commit messages:
 - Undo incorrect refactoring
 - 8295735: [lworld] Missing membar after buffer initialization in method handle return

Changes: https://git.openjdk.org/valhalla/pull/799/files
 Webrev: https://webrevs.openjdk.org/?repo=valhalla&pr=799&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8295735
  Stats: 11 lines in 1 file changed: 11 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/valhalla/pull/799.diff
  Fetch: git fetch https://git.openjdk.org/valhalla pull/799/head:pull/799

PR: https://git.openjdk.org/valhalla/pull/799