Add pretenuring support to HAllocateObject.

src/hydrogen-instructions.h

Index: src/hydrogen-instructions.h
diff --git a/src/hydrogen-instructions.h b/src/hydrogen-instructions.h
index f16efe6de83276be38aaf9b299f32586385761f0..4a22d7c1492bc4746986bd8ddef3234f74131c20 100644
--- a/src/hydrogen-instructions.h
+++ b/src/hydrogen-instructions.h
@@ -4840,8 +4840,14 @@ class HLoadGlobalGeneric: public HTemplateInstruction<2> {
 
 class HAllocateObject: public HTemplateInstruction<1> {
  public:
-  HAllocateObject(HValue* context, Handle<JSFunction> constructor)
-      : constructor_(constructor) {
+  enum Flags {
+    CAN_ALLOCATE_IN_NEW_SPACE = 1 << 0,
+    CAN_ALLOCATE_IN_OLD_POINTER_SPACE = 1 << 1
+  };
+
+  HAllocateObject(HValue* context, Handle<JSFunction> constructor, Flags flags)
+      : constructor_(constructor),
+        flags_(flags) {
     SetOperandAt(0, context);
     set_representation(Representation::Tagged());
     SetGVNFlag(kChangesNewSpacePromotion);
@@ -4869,6 +4875,22 @@ class HAllocateObject: public HTemplateInstruction<1> {
   }
   virtual HType CalculateInferredType();
 
+  static Flags DefaultFlags() {

[mvstanton, 2013/05/23 12:47:46]

It would be nice if these ~20 lines could be shared with the similar lines in
HAllocate. If it is straightforward to make a base class for those two hydrogen
instructions, I would say do it. 

+    return CAN_ALLOCATE_IN_NEW_SPACE;
+  }
+
+  bool CanAllocateInNewSpace() const {
+    return (flags_ & CAN_ALLOCATE_IN_NEW_SPACE) != 0;
+  }
+
+  bool CanAllocateInOldPointerSpace() const {
+    return (flags_ & CAN_ALLOCATE_IN_OLD_POINTER_SPACE) != 0;
+  }
+
+  bool GuaranteedInNewSpace() const {
+    return CanAllocateInNewSpace() && !CanAllocateInOldPointerSpace();
+  }
+
   DECLARE_CONCRETE_INSTRUCTION(AllocateObject)
 
  private:
@@ -4877,6 +4899,7 @@ class HAllocateObject: public HTemplateInstruction<1> {
 
   Handle<JSFunction> constructor_;
   Handle<Map> constructor_initial_map_;
+  Flags flags_;
 };
 
 
@@ -4999,7 +5022,9 @@ inline bool ReceiverObjectNeedsWriteBarrier(HValue* object,
         new_space_dominator);
   }
   if (object != new_space_dominator) return true;
-  if (object->IsAllocateObject()) return false;
+  if (object->IsAllocateObject()) {
+    return !HAllocateObject::cast(object)->GuaranteedInNewSpace();
+  }
   if (object->IsAllocate()) {
     return !HAllocate::cast(object)->GuaranteedInNewSpace();
   }