RFR: 8325821: [REDO] use "dmb.ishst+dmb.ishld" for release barrier [v3]

[kuaiwei]

On Tue, 21 May 2024 03:01:09 GMT, kuaiwei <duke at openjdk.org> wrote:

>> src/hotspot/cpu/aarch64/aarch64.ad line 7841:
>> 
>>> 7839:   ins_encode %{
>>> 7840:     __ block_comment("membar_release");
>>> 7841:     __ membar(Assembler::StoreStore);
>> 
>> Do we need to respect `AlwaysMergeDMB`here?
>
> Yes, usually they can be merged in macroAssembler. but  it can help to reduce the possibility of unmerged case. Thanks to point it.

I checked code again. They will be merged if enable AlwaysMergeDMB. So we can skip the check.

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PR Review Comment: https://git.openjdk.org/jdk/pull/19278#discussion_r1611045449