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

[Roland Westrelin]

Here is a new fix:

http://cr.openjdk.java.net/~roland/8227384/webrev.01/

This time the fix makes sure the load of the mark word that causes the
graph to be unschedulable is properly eliminated. This is achieved by
proceeding with macro expansions in 2 steps: first all macro nodes
except allocations and then only allocations. A pass of igvn is perfomed
between the 2 steps. That's where the load from a newly allocated object
is eliminated by a new Ideal or Value transformation.

Roland.