The c2 compiler inserts MemBarAcquire/Release nodes to enforce memory ordering in various places. Some order a certain load/store with other operations. inline_unsafe_fence() inserts MemBars that do not correspont to a memory operation. So far, the same nodes were used.
This change introduces MemBarFenceAcquire/Release to use where no dedicated load/store is ordered. With this change, these nodes can be matched differently, what is needed on PPC64.
This is preparation for PPC64 integration: http://openjdk.java.net/jeps/175
This and following ppc64 changes will go into staging repository first and tested there: http://hg.openjdk.java.net/ppc-aix-port/stage/
Extend Load and Store nodes to know about memory ordering.