Allocation folding integrated into the GVN phase.

src/hydrogen.h

Index: src/hydrogen.h
diff --git a/src/hydrogen.h b/src/hydrogen.h
index 6c1aba5db66d709231b996207965af7146b758e9..c582bcef7d9cd7af327d76764afa1bddb11b8f9e 100644
--- a/src/hydrogen.h
+++ b/src/hydrogen.h
@@ -332,6 +332,7 @@ class HGraph: public ZoneObject {
   HConstant* GetConstantHole();
   HConstant* GetConstantNull();
   HConstant* GetInvalidContext();
+  HConstant* GetConstantFreeSpaceMap();
 
   bool IsStandardConstant(HConstant* constant);
 
@@ -489,6 +490,7 @@ class HGraph: public ZoneObject {
   SetOncePointer<HConstant> constant_null_;
   SetOncePointer<HConstant> constant_invalid_context_;
   SetOncePointer<HArgumentsObject> arguments_object_;
+  SetOncePointer<HConstant> constant_free_space_map_;
 
   HOsrBuilder* osr_;