Make sure transitioned arrays efficiently call builtin Array functions

src/x64/macro-assembler-x64.cc

Index: src/x64/macro-assembler-x64.cc
diff --git a/src/x64/macro-assembler-x64.cc b/src/x64/macro-assembler-x64.cc
index 10e423b5b9537f9b7841f2aa2f17c5eccc8b7cec..3aa78e9bee8b56da0b58cb9cff1baa7e193be211 100644
--- a/src/x64/macro-assembler-x64.cc
+++ b/src/x64/macro-assembler-x64.cc
@@ -1,4 +1,4 @@
-// Copyright 2011 the V8 project authors. All rights reserved.
+// 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:
@@ -2739,15 +2739,48 @@ void MacroAssembler::StoreNumberToDoubleElements(
 }
 
 
+void MacroAssembler::CompareMap(Register obj,
+                                Handle<Map> map,
+                                Label* early_success,
+                                CompareMapMode mode) {
+  Cmp(FieldOperand(obj, HeapObject::kMapOffset), map);
+  if (mode == ALLOW_ELEMENT_TRANSITION_MAPS) {
+    Map* transitioned_fast_element_map(
+        map->LookupElementsTransitionMap(FAST_ELEMENTS, NULL));
+    ASSERT(transitioned_fast_element_map == NULL ||
+           map->elements_kind() != FAST_ELEMENTS);
+    if (transitioned_fast_element_map != NULL) {
+      j(equal, early_success, Label::kNear);
+      Cmp(FieldOperand(obj, HeapObject::kMapOffset),
+          Handle<Map>(transitioned_fast_element_map));
+    }
+
+    Map* transitioned_double_map(
+        map->LookupElementsTransitionMap(FAST_DOUBLE_ELEMENTS, NULL));
+    ASSERT(transitioned_double_map == NULL ||
+           map->elements_kind() == FAST_SMI_ONLY_ELEMENTS);
+    if (transitioned_double_map != NULL) {
+      j(equal, early_success, Label::kNear);
+      Cmp(FieldOperand(obj, HeapObject::kMapOffset),
+          Handle<Map>(transitioned_double_map));
+    }
+  }
+}
+
+
 void MacroAssembler::CheckMap(Register obj,
                               Handle<Map> map,
                               Label* fail,
-                              SmiCheckType smi_check_type) {
+                              SmiCheckType smi_check_type,
+                              CompareMapMode mode) {
   if (smi_check_type == DO_SMI_CHECK) {
     JumpIfSmi(obj, fail);
   }
-  Cmp(FieldOperand(obj, HeapObject::kMapOffset), map);
+
+  Label success;
+  CompareMap(obj, map, &success, mode);
   j(not_equal, fail);
+  bind(&success);
 }