Recognize leaf functions: skip stack check and populating the pc slot, store the pc slot lazily in …

runtime/vm/flow_graph_optimizer.h

Index: runtime/vm/flow_graph_optimizer.h
===================================================================
--- runtime/vm/flow_graph_optimizer.h	(revision 9089)
+++ runtime/vm/flow_graph_optimizer.h	(working copy)
@@ -46,6 +46,25 @@
   DISALLOW_COPY_AND_ASSIGN(FlowGraphOptimizer);
 };
 
+
+// Analyze the generated flow graph. Currently only if it is a leaf
+// method, i.e., does not contain any calls to runtime or other Dart code.
+class FlowGraphAnalyzer : public ValueObject {
+ public:
+  explicit FlowGraphAnalyzer(const GrowableArray<BlockEntryInstr*>& blocks);
+  virtual ~FlowGraphAnalyzer() {}
+
+  void Analyze();
+
+  bool is_leaf() const { return is_leaf_; }
+
+ private:
+  const GrowableArray<BlockEntryInstr*>& blocks_;
+  bool is_leaf_;
+
+  DISALLOW_COPY_AND_ASSIGN(FlowGraphAnalyzer);
+};
+
 }  // namespace dart
 
 #endif  // VM_FLOW_GRAPH_OPTIMIZER_H_