RFR: 8345322: RISC-V: Add concurrent gtests for cmpxchg variants [v4]

[Robbin Ehn]

On Thu, 12 Dec 2024 02:08:57 GMT, Fei Yang <fyang at openjdk.org> wrote:

>> So one case is shenandoah CAS:ing a narrow oop.
>> Narrow oop are zero extended (MASM::set_narrow_oop) which means expected, exchange values should be zero extended. Hence I think we have yet another cmpxchg bug.
>
> Sorry, I withdraw my previous comment. I think we are fine here.
> I double checked and found that the the zero-extension is there in `MacroAssembler::load_reserved` for `uint32` type [1].
> 
> [1] https://github.com/openjdk/jdk/blob/master/src/hotspot/cpu/riscv/macroAssembler_riscv.cpp#L3693

I found an issue in the gtest using uint32_t.

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PR Review Comment: https://git.openjdk.org/jdk/pull/22574#discussion_r1882135012