Optimize conditional branches that have same true/false targets.

runtime/vm/flow_graph_optimizer.h

Index: runtime/vm/flow_graph_optimizer.h
===================================================================
--- runtime/vm/flow_graph_optimizer.h	(revision 27294)
+++ runtime/vm/flow_graph_optimizer.h	(working copy)
@@ -246,6 +246,16 @@
   // by range analysis.
   static void OptimizeBranches(FlowGraph* graph);
 
+  // Eliminate branches that have the same true- and false-target: For example,
+  // this occurs after expressions like
+  //
+  // if (a == null) || (b == null) {

[Kevin Millikin (Google), 2013/09/27 11:03:43]

You need more parentheses in the comment :)

[Florian Schneider, 2013/09/30 12:19:23]

Less is more :)

Done.

+  //   ...
+  // }
+  //
+  // where b is known to be null.
+  static void RemoveRedundantBranches(FlowGraph* graph);
+
   // Used to initialize the abstract value of definitions.
   static RawObject* Unknown() { return Object::unknown_constant().raw(); }
 
@@ -253,6 +263,7 @@
   void Analyze();
   void VisitBranches();
   void Transform();
+  void EliminateRedundantBranches();
 
   void SetReachable(BlockEntryInstr* block);
   void SetValue(Definition* definition, const Object& value);