When a hazard recognizer needs noops to be inserted, do so.  This represents
noops as null pointers in the instruction sequence.

llvm-svn: 26564
diff --git a/llvm/lib/CodeGen/SelectionDAG/ScheduleDAG.cpp b/llvm/lib/CodeGen/SelectionDAG/ScheduleDAG.cpp
index 611abc3..c9455a0 100644
--- a/llvm/lib/CodeGen/SelectionDAG/ScheduleDAG.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/ScheduleDAG.cpp
@@ -370,6 +370,10 @@
   NI->VRBase = VRBase;
 }
 
+void ScheduleDAG::EmitNoop() {
+  TII->insertNoop(*BB, BB->end());
+}
+
 /// EmitAll - Emit all nodes in schedule sorted order.
 ///
 void ScheduleDAG::EmitAll() {