[jdk21u] RFR: 8316566: RISC-V: Zero extended narrow oop passed to Atomic::cmpxchg

[Robbin Ehn]

8316566: RISC-V: Zero extended narrow oop passed to Atomic::cmpxchg

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Commit messages:
 - Backport 2d154fcd0de0612f58abbc5027f409b9b2eb0dc2

Changes: https://git.openjdk.org/jdk21u/pull/210/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk21u&pr=210&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8316566
  Stats: 1 line in 1 file changed: 0 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/jdk21u/pull/210.diff
  Fetch: git fetch https://git.openjdk.org/jdk21u.git pull/210/head:pull/210

PR: https://git.openjdk.org/jdk21u/pull/210