[turbofan] Optimize certain chains of Branch into a Switch.

src/compiler/schedule.h

 // Copyright 2013 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef V8_COMPILER_SCHEDULE_H_
 #define V8_COMPILER_SCHEDULE_H_
 
 #include <iosfwd>
 
 #include "src/zone-containers.h"
@@ skipping 88 matching lines @@
   void ClearSuccessors() { successors_.clear(); }
   void AddSuccessor(BasicBlock* successor);
 
   // Nodes in the basic block.
   typedef Node* value_type;
   bool empty() const { return nodes_.empty(); }
   size_t size() const { return nodes_.size(); }
   Node* NodeAt(size_t index) { return nodes_[index]; }
   size_t NodeCount() const { return nodes_.size(); }
 
+  value_type& front() { return nodes_.front(); }
+  value_type const& front() const { return nodes_.front(); }
+
   typedef NodeVector::iterator iterator;
   iterator begin() { return nodes_.begin(); }
   iterator end() { return nodes_.end(); }
 
   typedef NodeVector::const_iterator const_iterator;
   const_iterator begin() const { return nodes_.begin(); }
   const_iterator end() const { return nodes_.end(); }
 
   typedef NodeVector::reverse_iterator reverse_iterator;
   reverse_iterator rbegin() { return nodes_.rbegin(); }
@@ skipping 166 matching lines @@
   DISALLOW_COPY_AND_ASSIGN(Schedule);
 };
 
 std::ostream& operator<<(std::ostream&, const Schedule&);
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_COMPILER_SCHEDULE_H_