Track IR ordering of SelectionDAG nodes 3/4.

Remove the old IR ordering mechanism and switch to new one.  Fix unit
test failures.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@182704 91177308-0d34-0410-b5e6-96231b3b80d8

lib/Target/X86/X86ISelDAGToDAG.cpp

@@ -2335,9 +2335,6 @@ SDNode *X86DAGToDAGISel::Select(SDNode *Node) {
       DEBUG(dbgs() << "=> "; ResHi.getNode()->dump(CurDAG); dbgs() << '\n');
     }
 
-    // Propagate ordering to the last node, for now.
-    CurDAG->AssignOrdering(InFlag.getNode(), CurDAG->GetOrdering(Node));
-
     return NULL;
   }