NullCheckOp

[Deneau, Tom]

I am trying to get null checks working on the hsail backend.
What is required of NullCheckOp in the HSAILLIRGenerator?
On Hsail, we can't support an implicit exception for this like amd64 does  so I think we would just want to end up with an explicit compare and branch if null to something that would be similar to the code emitted for a deoptimizing node.  How much of that does NullCheckOp have to do?

-- Tom