HSubAllocatedObject instruction allows hydrogen code to carve up

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 104 matching lines @@
   V(ForceRepresentation)                       \
   V(FunctionLiteral)                           \
   V(GetCachedArrayIndex)                       \
   V(GlobalObject)                              \
   V(GlobalReceiver)                            \
   V(Goto)                                      \
   V(HasCachedArrayIndexAndBranch)              \
   V(HasInstanceTypeAndBranch)                  \
   V(InductionVariableAnnotation)               \
   V(In)                                        \
+  V(InnerAllocatedObject)                      \
   V(InstanceOf)                                \
   V(InstanceOfKnownGlobal)                     \
   V(InstanceSize)                              \
   V(InvokeFunction)                            \
   V(IsConstructCallAndBranch)                  \
   V(IsNilAndBranch)                            \
   V(IsObjectAndBranch)                         \
   V(IsStringAndBranch)                         \
   V(IsSmiAndBranch)                            \
   V(IsUndetectableAndBranch)                   \
@@ skipping 4542 matching lines @@
   virtual void PrintDataTo(StringStream* stream);
 
   DECLARE_CONCRETE_INSTRUCTION(Allocate)
 
  private:
   HType type_;
   Flags flags_;
 };
 
 
+class HInnerAllocatedObject: public HTemplateInstruction<1> {
+ public:
+  HInnerAllocatedObject(HValue* value, int offset)
+      : offset_(offset) {
+    ASSERT(value->IsAllocate());
+    SetOperandAt(0, value);
+    set_representation(Representation::Tagged());
+  }
+
+  HValue* base_object() { return OperandAt(0); }
+  int offset() { return offset_; }
+
+  virtual Representation RequiredInputRepresentation(int index) {
+    return Representation::Tagged();
+  }
+
+  virtual void PrintDataTo(StringStream* stream);
+
+  DECLARE_CONCRETE_INSTRUCTION(InnerAllocatedObject)
+
+ private:
+  int offset_;
+};
+
+
 inline bool StoringValueNeedsWriteBarrier(HValue* value) {
   return !value->type().IsBoolean()
       && !value->type().IsSmi()
       && !(value->IsConstant() && HConstant::cast(value)->ImmortalImmovable());
 }
 
 
 inline bool ReceiverObjectNeedsWriteBarrier(HValue* object,
                                             HValue* new_space_dominator) {
+  if (object->IsInnerAllocatedObject()) {
+    return ReceiverObjectNeedsWriteBarrier(
+        HInnerAllocatedObject::cast(object)->base_object(),
+        new_space_dominator);
+  }
   if (object != new_space_dominator) return true;
   if (object->IsFastLiteral()) return false;
   if (object->IsAllocateObject()) return false;
   if (object->IsAllocate()) {
     return !HAllocate::cast(object)->GuaranteedInNewSpace();
   }
   return true;
 }
 
 
@@ skipping 1461 matching lines @@
   virtual bool IsDeletable() const { return true; }
 };
 
 
 #undef DECLARE_INSTRUCTION
 #undef DECLARE_CONCRETE_INSTRUCTION
 
 } }  // namespace v8::internal
 
 #endif  // V8_HYDROGEN_INSTRUCTIONS_H_