RFR(S): 8229422: Taskqueue: Outdated selection of weak memory model platforms

[Doerr, Martin]

Hi everybody,

thanks a lot for reviewing it, Thomas, David and Derek!

@Derek & Andrew:
I've created a webrev which provides full control for platform maintainers:
http://cr.openjdk.java.net/~mdoerr/8229422_multi-copy-atomic/webrev.01/

It also allows making the IRIW stuff switchable in platform code which was desired by
https://bugs.openjdk.java.net/browse/JDK-8165058

As an example, I've added an experimental switch for PPC64 "SupportIRIW" which was already on Michihiro's wish list (CC'ed).

So if you prefer this implementation for arm/aarch64, too, we can go forward with webrev.01.

This webrev doesn't contain functional changes except for s390 (taskqueue) and PPC64 (experimental switch added).
Both platforms maintained by us, anyway. 😊

I'll request reviews from runtime and compiler mailing lists later.

Best regards,
Martin