CompareAndSwapNode support

[Deneau, Tom]

In the HSAIL backend, we had support for CompareAndSwapNode.  (we had not pushed this out to the trunk yet).

As part of the merge with the new runtime infrastructure changes, I see that our CompareAndSwapNode  support is broken.
I'm trying to understand how to get it working again.

In the particular test I'm looking at the java code calls atomicInt.getAndAdd(constant)

First I noticed that we were getting Invoke nodes for things like getIntVolatile and compareAndSwapInt.
So I assumed the UnsafeSubstitutions needed to be enabled for our backend.

When I enabled these, I got the following error which doesn't mean anything to me...

java.lang.AssertionError: <unknown> has unexpected usage 20|LoadField#value of checkcast 19|GuardingPi at <unknown>
                at com.oracle.graal.replacements.NodeIntrinsificationPhase.checkCheckCastUsage(NodeIntrinsificationPhase.java:387)
                at com.oracle.graal.replacements.NodeIntrinsificationPhase.checkCheckCastUsage(NodeIntrinsificationPhase.java:382)
                at com.oracle.graal.replacements.NodeIntrinsificationPhase.cleanUpReturnCheckCast(NodeIntrinsificationPhase.java:328)
                at com.oracle.graal.replacements.NodeIntrinsificationPhase.run(NodeIntrinsificationPhase.java:67)

Any suggestions?

-- Tom