Use range information for optimizing integer boxing and fix bug in range analysis.

runtime/vm/intermediate_language.h

Index: runtime/vm/intermediate_language.h
===================================================================
--- runtime/vm/intermediate_language.h	(revision 37654)
+++ runtime/vm/intermediate_language.h	(working copy)
@@ -1811,6 +1811,7 @@
             IsBinaryMintOp() ||
             IsUnaryMintOp() ||
             IsShiftMintOp() ||
+            IsBoxInteger() ||
             IsUnboxInteger();
   }
 
@@ -5096,12 +5097,15 @@
 
 class BoxIntegerInstr : public TemplateDefinition<1> {
  public:
-  explicit BoxIntegerInstr(Value* value) {
+  explicit BoxIntegerInstr(Value* value) : is_smi_(false) {
     SetInputAt(0, value);
   }
 
   Value* value() const { return inputs_[0]; }
 
+  bool is_smi() const { return is_smi_; }
+  void set_is_smi(bool is_smi) { is_smi_ = is_smi; }
+
   virtual bool CanDeoptimize() const { return false; }
 
   virtual intptr_t DeoptimizationTarget() const {
@@ -5115,7 +5119,10 @@
 
   DECLARE_INSTRUCTION(BoxInteger)
   virtual CompileType ComputeType() const;
+  virtual bool RecomputeType();
 
+  virtual void InferRange();
+
   virtual bool AllowsCSE() const { return true; }
   virtual EffectSet Effects() const { return EffectSet::None(); }
   virtual EffectSet Dependencies() const { return EffectSet::None(); }
@@ -5124,6 +5131,8 @@
   virtual bool MayThrow() const { return false; }
 
  private:
+  bool is_smi_;
+
   DISALLOW_COPY_AND_ASSIGN(BoxIntegerInstr);
 };
 
@@ -7139,6 +7148,8 @@
     return deopt_id_;
   }
 
+  virtual void InferRange();
+
   DECLARE_INSTRUCTION(ShiftMintOp)
 
   virtual bool AllowsCSE() const { return true; }