RFR(M): 8212243: More gc interface tweaks for arraycopy and some other smaller changes in preparation for Shenandoah

[Roland Westrelin]

> To determine that, I wonder exactly what barriers you need here at the 
> write. All I know is what barriers you do not know (no SATB, no 
> write-resolve).

As I mentioned earlier, storing is:

1- b' = wb(b);
2- pre_barrier();
3- b'.f = wb(v);

1- is emitted at parse time when the arraycopy is parsed, 2- is not
needed so wb(v) is what we need.

Roland.