switch the sched unit map over to use a DenseMap instead of std::map.  This
speeds up isel as a whole time by 2.6%.

llvm-svn: 33810
diff --git a/llvm/lib/CodeGen/SelectionDAG/ScheduleDAGList.cpp b/llvm/lib/CodeGen/SelectionDAG/ScheduleDAGList.cpp
index d21ef34..dbbf3f9 100644
--- a/llvm/lib/CodeGen/SelectionDAG/ScheduleDAGList.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/ScheduleDAGList.cpp
@@ -328,7 +328,7 @@
     LatencyPriorityQueue() : Queue(latency_sort(this)) {
     }
     
-    void initNodes(std::map<SDNode*, SUnit*> &sumap,
+    void initNodes(DenseMap<SDNode*, SUnit*> &sumap,
                    std::vector<SUnit> &sunits) {
       SUnits = &sunits;
       // Calculate node priorities.