Hydrogen support for context allocated harmony bindings.

src/hydrogen-instructions.h

Index: src/hydrogen-instructions.h
diff --git a/src/hydrogen-instructions.h b/src/hydrogen-instructions.h
index c9a4bf062d3a7c3c6b4c79d36d4abe4959c6d8e2..35fc363b46efba3057ce880ae6fa916a915f21a7 100644
--- a/src/hydrogen-instructions.h
+++ b/src/hydrogen-instructions.h
@@ -3447,14 +3447,20 @@ class HStoreGlobalGeneric: public HTemplateInstruction<3> {
 
 class HLoadContextSlot: public HUnaryOperation {
  public:
-  HLoadContextSlot(HValue* context , int slot_index)
-      : HUnaryOperation(context), slot_index_(slot_index) {
+  HLoadContextSlot(HValue* context , Variable* var)
+      : HUnaryOperation(context), var_(var) {
+    ASSERT(var_->IsContextSlot());
     set_representation(Representation::Tagged());
     SetFlag(kUseGVN);
     SetFlag(kDependsOnContextSlots);
   }
 
-  int slot_index() const { return slot_index_; }
+  int slot_index() const { return var_->index(); }
+  Variable* var() const { return var_; }
+
+  bool RequiresHoleCheck() {
+    return var_->mode() == LET || var_->mode() == CONST_HARMONY;
+  }
 
   virtual Representation RequiredInputRepresentation(int index) {
     return Representation::Tagged();
@@ -3471,14 +3477,23 @@ class HLoadContextSlot: public HUnaryOperation {
   }
 
  private:
-  int slot_index_;
+  Variable* var_;
 };
 
 
 class HStoreContextSlot: public HTemplateInstruction<2> {
  public:
-  HStoreContextSlot(HValue* context, int slot_index, HValue* value)
-      : slot_index_(slot_index) {
+  // Indicates whether this store to the context is an initializing store or
+  // a proper assignment. Non-initializing assignments to harmony bindings
+  // perform a hole check.
+  enum Mode {
+    kInitialize,
+    kAssign
+  };
+
+  HStoreContextSlot(HValue* context, Variable* var, Mode mode, HValue* value)
+      : var_(var), mode_(mode) {
+    ASSERT(var->IsContextSlot());
     SetOperandAt(0, context);
     SetOperandAt(1, value);
     SetFlag(kChangesContextSlots);
@@ -3486,12 +3501,19 @@ class HStoreContextSlot: public HTemplateInstruction<2> {
 
   HValue* context() { return OperandAt(0); }
   HValue* value() { return OperandAt(1); }
-  int slot_index() const { return slot_index_; }
+  int slot_index() const { return var_->index(); }
+  Variable* var() const { return var_; }
+  Mode mode() const { return mode_; }
 
   bool NeedsWriteBarrier() {
     return StoringValueNeedsWriteBarrier(value());
   }
 
+  bool RequiresHoleCheck() {
+    return mode_ == kAssign &&
+        (var_->mode() == LET || var_->mode() == CONST_HARMONY);
+  }
+
   virtual Representation RequiredInputRepresentation(int index) {
     return Representation::Tagged();
   }
@@ -3501,7 +3523,8 @@ class HStoreContextSlot: public HTemplateInstruction<2> {
   DECLARE_CONCRETE_INSTRUCTION(StoreContextSlot)
 
  private:
-  int slot_index_;
+  Variable* var_;
+  Mode mode_;
 };