RFR: rework CAS support

[Roman Kennke]

Am 12.09.2018 um 13:22 schrieb Roland Westrelin:
> 
>> Excellent! This should reduce our upstream diff considerably. And the
>> new stuff to support new C2 nodes should be ok too. Patch looks good,
>> please push if it passes tier3_gc_shenandoah.
> 
> Except for:
> 
> #  Internal Error (/home/rwestrel/shenandoah/src/hotspot/share/gc/shenandoah/shenandoahHeap.cpp:80), pid=40463, tid=40517
> #  Error: Shenandoah assert_not_forwarded failed; Object should not be forwarded
> 
> with AllocIntArrays, it does pass tier3_gc_shenandoah.

Yes, I'm working on this (fix is already RFR'ed). Please push.

Thanks,
Roman