[riscv-port-jdk11u:riscv-port] RFR: 8292867: RISC-V: Simplify weak CAS return value handling

[Gui Cao]

On Fri, 13 Sep 2024 03:53:53 GMT, Dingli Zhang <dzhang at openjdk.org> wrote:

> Please review this backport to riscv-port-jdk11u.
> Backport of [JDK-8292867](https://bugs.openjdk.org/browse/JDK-8292867). Applies cleanly.
> 
> Testing:
> 
> - Tier1 passed without new failure on lp4a (release).

LGTM.

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

Marked as reviewed by gcao (Committer).

PR Review: https://git.openjdk.org/riscv-port-jdk11u/pull/31#pullrequestreview-2304327628