[hydrogen] don't bailout assignments to consts

src/hydrogen-instructions.h

 // Copyright 2011 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 3459 matching lines @@
     return (slot_index() == b->slot_index());
   }
 
  private:
   int slot_index_;
 };
 
 
 class HStoreContextSlot: public HTemplateInstruction<2> {
  public:
+  enum Check {
+    kEmpty,
+    kIsHoleCheck
+  };
+
   HStoreContextSlot(HValue* context, int slot_index, HValue* value)
-      : slot_index_(slot_index) {
+      : slot_index_(slot_index), check_(kEmpty) {
     SetOperandAt(0, context);
     SetOperandAt(1, value);
     SetFlag(kChangesContextSlots);
   }
 
+  void ForceIsHoleCheck() {
+    check_ = kIsHoleCheck;
+  }
+
   HValue* context() { return OperandAt(0); }
   HValue* value() { return OperandAt(1); }
   int slot_index() const { return slot_index_; }
+  bool RequiresHoleCheck() const { return check_ == kIsHoleCheck; }
 
   bool NeedsWriteBarrier() {
     return StoringValueNeedsWriteBarrier(value());
   }
 
   virtual Representation RequiredInputRepresentation(int index) {
     return Representation::Tagged();
   }
 
   virtual void PrintDataTo(StringStream* stream);
 
   DECLARE_CONCRETE_INSTRUCTION(StoreContextSlot)
 
  private:
   int slot_index_;
+  Check check_;
 };
 
 
 class HLoadNamedField: public HUnaryOperation {
  public:
   HLoadNamedField(HValue* object, bool is_in_object, int offset)
       : HUnaryOperation(object),
         is_in_object_(is_in_object),
         offset_(offset) {
     set_representation(Representation::Tagged());
@@ skipping 914 matching lines @@
 
   DECLARE_CONCRETE_INSTRUCTION(In)
 };
 
 #undef DECLARE_INSTRUCTION
 #undef DECLARE_CONCRETE_INSTRUCTION
 
 } }  // namespace v8::internal
 
 #endif  // V8_HYDROGEN_INSTRUCTIONS_H_