RFR/RFC: Make OOM-during-evacuation race-free

[Roland Westrelin]

> Hmm. And we could still move around and manipulate the barrier as we do 
> now, and still have enough information (e.g. about locals) to allow 
> safepointing at the write-barrier? I simply don't know enough to tell this.

I think we would have enough information to allow safepointing. The
compiler needs to know what oops are live at a safepoint to compute the
oopmap and that's it. AFAIU, for that, debug info is not needed.

Roland.