RFR: 8316645: RISC-V: Remove dependency on libatomic by adding cmpxchg 1b

Tue Sep 26 12:13:40 UTC 2023

Hi all, please consider.

latomic is used for non native atomic operation which causes problems with extra dependency.
This have been fixed in recent gcc, so latomic is no longer needed.

Added new gtest, passes t1 on vf2/qemu.

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

Commit messages:
 - Remove latomic, add cmpxchg 1 byte

Changes: https://git.openjdk.org/jdk/pull/15919/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=15919&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8316645
  Stats: 124 lines in 3 files changed: 118 ins; 6 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/15919.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/15919/head:pull/15919

PR: https://git.openjdk.org/jdk/pull/15919