RFR(S): 8087341: C2 doesn't optimize redundant memory operations with G1

[Roland Westrelin]

Hi Andrew,

> I think this looks ok -- not sure until I try it out. However, I /am/
> fairly sure it is going to cause a problem for the AArch64 code which
> optimizes volatile loads and stores. That's because it change the
> characteristic shape of the subgraph searched for by the predicates
> which decide whether to i) generate loads + membars or ii) plant stlr or
> ladr instructions.
> 
> I'll look into this asap.

Thanks for looking at this. I’ll wait to hear back from you until I move forward with this change.

Roland.