RFR: 8315856: RISC-V: Use Zacas extension for cmpxchg [v5]

[Ludovic Henry]

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

Ludovic Henry has updated the pull request incrementally with one additional commit since the last revision:

  Fix narrow compxchg

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/16910/files
  - new: https://git.openjdk.org/jdk/pull/16910/files/942cb11f..0b0363da

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=16910&range=04
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=16910&range=03-04

  Stats: 2 lines in 1 file changed: 0 ins; 0 del; 2 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