RFR(XS): 8227384: C2 compilation fails with "graph should be schedulable" when running with -XX:-EliminateLocks

[Roland Westrelin]

Hi Dean,

> this category of "it can never happen in the current code" justification 
> always worries me.  I guess you could say it's my pet peeve.  What 
> happens if in the future C2 does decide to eliminate CastPPs early?  How 
> much time are we going to spend to find the breakage?  I hope the answer 
> is that an assert will fire and we will detect it immediately.  Or, if 
> because of the removed control, the load does float to where it 
> shouldn't, what's the worst that can happen?  SEGV?  Or an unexpected 
> NullPointerException?

Removing CastPPs early was done because it helped performance at the
time but it was inherently broken so I don't expect C2 will ever go
back. Anyway, as Jamsheed pointer out, I was wrong about the reason for
pinning the load.

Roland.