RFR: 8261492: Shenandoah: reconsider forwardee accesses memory ordering [v2]

[Martin Doerr]

On Fri, 12 Feb 2021 10:56:34 GMT, Aleksey Shipilev <shade at openjdk.org> wrote:

>> Thanks for your reply. Yeah, I got your point regarding C++. But we use load-consume a lot in our self-made assembly code which should be ok.
>> I guess the shenandoahBarrierSetAssembler_aarch64.cpp part you're changing is not very perfomance sensitive?
>
>> I guess the shenandoahBarrierSetAssembler_aarch64.cpp part you're changing is not very perfomance sensitive?
> 
> Yes, it is not supposed to be: CAS failure path when GC is relocating the objects.

I'd prefer using load-consume with comment in assembly code and acquire in C++ code. That would be consistent with other code. But that's just my opinion. I'll leave the aarch64 maintainers free to decide.

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PR: https://git.openjdk.java.net/jdk/pull/2496