HSubAllocatedObject instruction allows hydrogen code to carve up

src/x64/lithium-x64.h

Index: src/x64/lithium-x64.h
diff --git a/src/x64/lithium-x64.h b/src/x64/lithium-x64.h
index 22a1f96ddf8445f2521fdb32c331fad739564513..a46c3a17bc0419b30bf9d252a9415a87a0b5f4d1 100644
--- a/src/x64/lithium-x64.h
+++ b/src/x64/lithium-x64.h
@@ -188,7 +188,8 @@ class LCodeGen;
   V(LoadFieldByIndex)                           \
   V(DateField)                                  \
   V(WrapReceiver)                               \
-  V(Drop)
+  V(Drop)                                       \
+  V(SubAllocatedObject)
 
 
 #define DECLARE_CONCRETE_INSTRUCTION(type, mnemonic)              \
@@ -1594,6 +1595,22 @@ class LDrop: public LTemplateInstruction<0, 0, 0> {
 };
 
 
+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")