Simplify SelectionDAG::getNode so that a big switch stmt is not #ifndef  NDEBUG.  This is in response to a really nasty bug I introduced that  Dale tracked down, hopefully this won't happen in the future.   Many thanks Dale.
Simplify SelectionDAG::getNode so that a big switch stmt is not #ifndef 
NDEBUG.  This is in response to a really nasty bug I introduced that 
Dale tracked down, hopefully this won't happen in the future.  
Many thanks Dale.


git-svn-id: 0ff597fd157e6f4fc38580e8d64ab130330d2411@46254 91177308-0d34-0410-b5e6-96231b3b80d8

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