RFR(M): 8181211: C2: Use profiling data to optimize on/off heap unsafe accesses

[Roland Westrelin]

> It was a nice property that VarHandles avoided the profile pollution
> of mixed memory buffer usage but that was not the primary reason for
> the feature. So i would say mildly concerned :-) and robust unsafe
> access is far more important.

Thanks for the feedback, Paul.

Roland.