RFR: 8325821: [REDO] use "dmb.ishst+dmb.ishld" for release barrier [v6]

[kuaiwei]

On Fri, 31 May 2024 11:56:26 GMT, kuaiwei <duke at openjdk.org> wrote:

>> src/hotspot/cpu/aarch64/macroAssembler_aarch64.hpp line 153:
>> 
>>> 151:     Assembler::bind(L);
>>> 152:     code()->clear_last_insn();
>>> 153:     code()->set_last_label(pc());
>> 
>> OK, so we have added `_last_label` to shared code in `codeBuffer`, but only update it in aarch64. This would be surprising for other platforms. On the other hand, this is what we already do with `_last_insn` -- only implementing it for specific platforms. Probably fine, but it would be nice to strengthen this with asserts, maybe in separate PR.
>
> It reminds me it could be applied to riscv. It also need merge membar. I will move this part to a new PR.

I need _last_label in this patch. I need it to check previous 2 instructions and they are not cross block boundary. I will create a new PR for RISCV only.

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PR Review Comment: https://git.openjdk.org/jdk/pull/19278#discussion_r1623854892