HSubAllocatedObject instruction allows hydrogen code to carve up

src/x64/lithium-x64.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 170 matching lines @@
   V(TypeofIsAndBranch)                          \
   V(UnaryMathOperation)                         \
   V(UnknownOSRValue)                            \
   V(ValueOf)                                    \
   V(ForInPrepareMap)                            \
   V(ForInCacheArray)                            \
   V(CheckMapValue)                              \
   V(LoadFieldByIndex)                           \
   V(DateField)                                  \
   V(WrapReceiver)                               \
-  V(Drop)
+  V(Drop)                                       \
+  V(SubAllocatedObject)
 
 
 #define DECLARE_CONCRETE_INSTRUCTION(type, mnemonic)              \
   virtual Opcode opcode() const { return LInstruction::k##type; } \
   virtual void CompileToNative(LCodeGen* generator);              \
   virtual const char* Mnemonic() const { return mnemonic; }       \
   static L##type* cast(LInstruction* instr) {                     \
     ASSERT(instr->Is##type());                                    \
     return reinterpret_cast<L##type*>(instr);                     \
   }
@@ skipping 1385 matching lines @@
 
   int count() const { return count_; }
 
   DECLARE_CONCRETE_INSTRUCTION(Drop, "drop")
 
  private:
   int count_;
 };
 
 
+class LSubAllocatedObject: public LTemplateInstruction<1, 1, 0> {
+ public:
+  explicit LSubAllocatedObject(LOperand* base_object) {
+    inputs_[0] = base_object;
+  }
+
+  LOperand* base_object() { return inputs_[0]; }
+  int offset() { return hydrogen()->offset(); }
+
+  virtual void PrintDataTo(StringStream* stream);
+
+  DECLARE_CONCRETE_INSTRUCTION(SubAllocatedObject, "sub-allocated-object")
+  DECLARE_HYDROGEN_ACCESSOR(SubAllocatedObject)
+};
+
+
 class LThisFunction: public LTemplateInstruction<1, 0, 0> {
  public:
   DECLARE_CONCRETE_INSTRUCTION(ThisFunction, "this-function")
   DECLARE_HYDROGEN_ACCESSOR(ThisFunction)
 };
 
 
 class LContext: public LTemplateInstruction<1, 0, 0> {
  public:
   DECLARE_CONCRETE_INSTRUCTION(Context, "context")
@@ skipping 1023 matching lines @@
 
   DISALLOW_COPY_AND_ASSIGN(LChunkBuilder);
 };
 
 #undef DECLARE_HYDROGEN_ACCESSOR
 #undef DECLARE_CONCRETE_INSTRUCTION
 
 } }  // namespace v8::int
 
 #endif  // V8_X64_LITHIUM_X64_H_