RFR: 8261649: AArch64: Optimize LSE atomics in C++ code [v2]

[Andrew Haley]

On Thu, 18 Feb 2021 09:15:12 GMT, Andrew Haley <aph at openjdk.org> wrote:

>> src/hotspot/cpu/aarch64/stubGenerator_aarch64.cpp line 5651:
>> 
>>> 5649:     __ mov(prev, compare_val);
>>> 5650:     __ lse_cas(prev, exchange_val, ptr, size, acquire, release, /*not_pair*/true);
>>> 5651:     if (acquire && release) {
>> 
>> These two flags are only ever passed as true,true or false,false. Does any other combination make sense? If not then should you not be using a single flag? or at least asserting (pro tem) that they are both equal?
>
> Today HotSpot only really supports mo_conservative and mo_relaxed, but there are many places in HotSpot where release on its own would make sense; I think Aleksey  recently found some. Having said that, it would be clearer here to expose mo_conservative as well. I'll do so.

Clearer now?

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PR: https://git.openjdk.java.net/jdk/pull/2611