RFR: 8315856: RISC-V: Use Zacas extension for cmpxchg [v2]

[Ludovic Henry]

> 8315856: RISC-V: Use Zacas extension for cmpxchg

Ludovic Henry has updated the pull request with a new target base due to a merge or a rebase. The pull request now contains three commits:

 - review
 - Merge branch 'master' of github.com:openjdk/jdk into upstream-zacas
 - 8315856: RISC-V: Use Zacas extension for cmpxchg

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Changes: https://git.openjdk.org/jdk/pull/16910/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=16910&range=01
  Stats: 197 lines in 5 files changed: 166 ins; 4 del; 27 mod
  Patch: https://git.openjdk.org/jdk/pull/16910.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/16910/head:pull/16910

PR: https://git.openjdk.org/jdk/pull/16910