[riscv-port-jdk11u:riscv-port] RFR: 8316645: RISC-V: Remove dependency on libatomic by adding cmpxchg 1b

[Fei Yang]

On Thu, 7 Mar 2024 12:12:05 GMT, Robbin Ehn <rehn at openjdk.org> wrote:

> For CI builds it helps to remove this.
> [8317335](https://bugs.openjdk.org/browse/JDK-8317335) is not needed as there is no gtest for atomic in 11.

Could you please enable GHA for your fork? I think the GHA linux-cross-compile is back working again. Thanks.

src/hotspot/os_cpu/linux_riscv/atomic_linux_riscv.hpp line 75:

> 73:                                                 T compare_value,
> 74:                                                 T exchange_value,
> 75:                                                 atomic_memory_order order) const {

I see the parameter order is not consistent with the one in jdk11u:
`T Atomic::PlatformCmpxchg<byte_size>::operator()`.
So this might need more adaptations, otherwise I guess it won't build.
Also the original commit adds one `#undef FULL_COMPILER_ATOMIC_SUPPORT` at the end of the file, which is missing for this backport.

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Changes requested by fyang (Lead).

PR Review: https://git.openjdk.org/riscv-port-jdk11u/pull/10#pullrequestreview-1926794147
PR Review Comment: https://git.openjdk.org/riscv-port-jdk11u/pull/10#discussion_r1519056413