Supported folding of constant size allocation followed by dynamic size allocation.

src/hydrogen.h

Index: src/hydrogen.h
diff --git a/src/hydrogen.h b/src/hydrogen.h
index b3cb8ffc75dc3796ae288967b29c9c46f21a2e3e..2135289f236faa79a8abb7597ee22aeceef72a7e 100644
--- a/src/hydrogen.h
+++ b/src/hydrogen.h
@@ -1604,8 +1604,7 @@ class HGraphBuilder {
 
     HValue* EmitMapCode();
     HValue* EmitInternalMapCode();
-    HValue* EstablishEmptyArrayAllocationSize();
-    HValue* EstablishAllocationSize(HValue* length_node);
+    HValue* EstablishHeaderAllocationSize();
     HValue* AllocateArray(HValue* size_in_bytes, HValue* capacity,
                           HValue* length_field,  bool fill_with_hole);
 
@@ -1614,11 +1613,15 @@ class HGraphBuilder {
     AllocationSiteMode mode_;
     HValue* allocation_site_payload_;
     HValue* constructor_function_;
-    HInnerAllocatedObject* elements_location_;
+    HValue* elements_location_;
   };
 
+  HValue* BuildCalculateElementsSize(ElementsKind kind,
+                                     HValue* capacity);
+
   HValue* BuildAllocateElements(ElementsKind kind,
-                                HValue* capacity);
+                                HValue* size_in_bytes,
+                                PretenureFlag pretenure);
 
   void BuildInitializeElementsHeader(HValue* elements,
                                      ElementsKind kind,
@@ -1628,15 +1631,14 @@ class HGraphBuilder {
                                                            HValue* capacity);
 
   // array must have been allocated with enough room for
-  // 1) the JSArray, 2) a AllocationMemento if mode requires it,
-  // 3) a FixedArray or FixedDoubleArray.
-  // A pointer to the Fixed(Double)Array is returned.
-  HInnerAllocatedObject* BuildJSArrayHeader(HValue* array,
-                                            HValue* array_map,
-                                            AllocationSiteMode mode,
-                                            ElementsKind elements_kind,
-                                            HValue* allocation_site_payload,
-                                            HValue* length_field);
+  // 1) the JSArray, 2) a AllocationMemento if mode requires it.
+  // Initially the array elements storage is initialized with empty array.
+  void BuildJSArrayHeader(HValue* array,
+                          HValue* array_map,
+                          AllocationSiteMode mode,
+                          ElementsKind elements_kind,
+                          HValue* allocation_site_payload,
+                          HValue* length_field);
 
   HValue* BuildGrowElementsCapacity(HValue* object,
                                     HValue* elements,