Use SAR for positive divident by a power-of two constant divisor.

runtime/vm/intermediate_language.h

 // Copyright (c) 2013, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #ifndef VM_INTERMEDIATE_LANGUAGE_H_
 #define VM_INTERMEDIATE_LANGUAGE_H_
 
 #include "vm/allocation.h"
 #include "vm/ast.h"
 #include "vm/growable_array.h"
@@ skipping 3863 matching lines @@
   void set_overflow(bool overflow) {
     overflow_ = overflow;
   }
 
   void PrintTo(BufferFormatter* f) const;
 
   virtual void InferRange();
 
   virtual Definition* Canonicalize(FlowGraphOptimizer* optimizer);
 
+  // Returns true if right is a Smi constant which absolute value is
+  // a power of two.
+  bool RightIsPowerOfTwoConstant() const;
+
  private:
   const Token::Kind op_kind_;
   InstanceCallInstr* instance_call_;
   bool overflow_;
 
   DISALLOW_COPY_AND_ASSIGN(BinarySmiOpInstr);
 };
 
 
 // Handles both Smi operations: BIT_OR and NEGATE.
@@ skipping 582 matching lines @@
   ForwardInstructionIterator* current_iterator_;
 
  private:
   DISALLOW_COPY_AND_ASSIGN(FlowGraphVisitor);
 };
 
 
 }  // namespace dart
 
 #endif  // VM_INTERMEDIATE_LANGUAGE_H_