RFR(S): 8245047: PPC64 fails jcstress Unsafe (?) memory ordering tests due to C2 (?) bug

[Doerr, Martin]

Hi,

acquire barriers are missing for load*_reversed nodes on PPC64 (introduced by JDK-8179527 in JDK 10).
Aleksey has reported the issue:
https://bugs.openjdk.java.net/browse/JDK-8245047

Here's my proposed fix:
http://cr.openjdk.java.net/~mdoerr/8245047_ppc64_load_reversed_acquire/webrev.00/

Please review. I'd appreciate retesting, too, if possible.

Best regards,
Martin