RFR: 8315841: RISC-V: Check for hardware TSO support [v4]

[Ludovic Henry]

On Thu, 7 Sep 2023 12:26:51 GMT, Robbin Ehn <rehn at openjdk.org> wrote:

>> Ludovic Henry has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   fixup! 8315841: RISC-V: Check for hardware TSO support
>
> src/hotspot/cpu/riscv/macroAssembler_riscv.hpp line 381:
> 
>> 379:   void fence(uint32_t predecessor, uint32_t successor) {
>> 380:     if (UseZtso) {
>> 381:       if (pred_succ_to_membar_mask(predecessor, successor) & StoreLoad) {
> 
> This should be "(pred_succ_to_membar_mask(predecessor, successor) & StoreLoad) == 0".

Not AFAIU, as we would then _not_ generate `StoreLoad` barriers which are the only one TSO doesn't guarantee.

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PR Review Comment: https://git.openjdk.org/jdk/pull/15613#discussion_r1318565637