Make HCapturedObjects non-deletable for DCE.

src/hydrogen-instructions.h

 // Copyright 2012 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 3240 matching lines @@
   }
 
  protected:
   virtual void InternalSetOperandAt(int index,
                                     HValue* value) V8_FINAL V8_OVERRIDE {
     values_[index] = value;
   }
 
   // List of values tracked by this marker.
   ZoneList<HValue*> values_;
-
- private:
-  virtual bool IsDeletable() const V8_FINAL V8_OVERRIDE { return true; }
 };
 
 
 class HArgumentsObject V8_FINAL : public HDematerializedObject {
  public:
   static HArgumentsObject* New(Zone* zone, HValue* context, int count) {
     return new(zone) HArgumentsObject(count, zone);
   }
 
   // The values contain a list of all elements in the arguments object
   // including the receiver object, which is skipped when materializing.
   const ZoneList<HValue*>* arguments_values() const { return &values_; }
   int arguments_count() const { return values_.length(); }
 
   void AddArgument(HValue* argument, Zone* zone) {
     values_.Add(NULL, zone);  // Resize list.
     SetOperandAt(values_.length() - 1, argument);
   }
 
   DECLARE_CONCRETE_INSTRUCTION(ArgumentsObject)
 
  private:
   HArgumentsObject(int count, Zone* zone)
       : HDematerializedObject(count, zone) {
     set_representation(Representation::Tagged());
     SetFlag(kIsArguments);
   }
+
+  virtual bool IsDeletable() const V8_FINAL V8_OVERRIDE { return true; }
 };
 
 
 class HCapturedObject V8_FINAL : public HDematerializedObject {
  public:
   HCapturedObject(int length, int id, Zone* zone)
       : HDematerializedObject(length, zone), capture_id_(id) {
     set_representation(Representation::Tagged());
     values_.AddBlock(NULL, length, zone);  // Resize list.
   }
@@ skipping 16 matching lines @@
 
   // Replay effects of this instruction on the given environment.
   void ReplayEnvironment(HEnvironment* env);
 
   virtual void PrintDataTo(StringStream* stream) V8_OVERRIDE;
 
   DECLARE_CONCRETE_INSTRUCTION(CapturedObject)
 
  private:
   int capture_id_;
+
+  // Note that we cannot DCE captured objects as they are used to replay
+  // the environment. This method is here as an explicit reminder.
+  // TODO(mstarzinger): Turn HSimulates into full snapshots maybe?
+  virtual bool IsDeletable() const V8_FINAL V8_OVERRIDE { return false; }
 };
 
 
 class HConstant V8_FINAL : public HTemplateInstruction<0> {
  public:
   DECLARE_INSTRUCTION_FACTORY_P1(HConstant, int32_t);
   DECLARE_INSTRUCTION_FACTORY_P2(HConstant, int32_t, Representation);
   DECLARE_INSTRUCTION_FACTORY_P1(HConstant, double);
   DECLARE_INSTRUCTION_FACTORY_P1(HConstant, Handle<Object>);
   DECLARE_INSTRUCTION_FACTORY_P1(HConstant, ExternalReference);
@@ skipping 3856 matching lines @@
   virtual bool IsDeletable() const V8_OVERRIDE { return true; }
 };
 
 
 #undef DECLARE_INSTRUCTION
 #undef DECLARE_CONCRETE_INSTRUCTION
 
 } }  // namespace v8::internal
 
 #endif  // V8_HYDROGEN_INSTRUCTIONS_H_