Make sure transitioned arrays efficiently call builtin Array functions

src/x64/lithium-codegen-x64.cc

Index: src/x64/lithium-codegen-x64.cc
diff --git a/src/x64/lithium-codegen-x64.cc b/src/x64/lithium-codegen-x64.cc
index 6239acb51531d1f39ecfd1e247315736e82c3e29..bafe74eec5e52c2c9bc3566963e354da497dd531 100644
--- a/src/x64/lithium-codegen-x64.cc
+++ b/src/x64/lithium-codegen-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:
@@ -3747,13 +3747,23 @@ void LCodeGen::DoCheckFunction(LCheckFunction* instr) {
 }
 
 
+void LCodeGen::DoCheckMapCommon(Register reg,
+                                Handle<Map> map,
+                                CompareMapMode mode,
+                                LEnvironment* env) {
+  Label success;
+  __ CompareMap(reg, map, &success, mode);
+  DeoptimizeIf(not_equal, env);
+  __ bind(&success);
+}
+
+
 void LCodeGen::DoCheckMap(LCheckMap* instr) {
   LOperand* input = instr->InputAt(0);
   ASSERT(input->IsRegister());
   Register reg = ToRegister(input);
-  __ Cmp(FieldOperand(reg, HeapObject::kMapOffset),
-         instr->hydrogen()->map());
-  DeoptimizeIf(not_equal, instr->environment());
+  Handle<Map> map = instr->hydrogen()->map();
+  DoCheckMapCommon(reg, map, instr->hydrogen()->mode(), instr->environment());
 }
 
 
@@ -3819,9 +3829,8 @@ void LCodeGen::DoCheckPrototypeMaps(LCheckPrototypeMaps* instr) {
 
   // Check prototype maps up to the holder.
   while (!current_prototype.is_identical_to(holder)) {
-    __ Cmp(FieldOperand(reg, HeapObject::kMapOffset),
-           Handle<Map>(current_prototype->map()));
-    DeoptimizeIf(not_equal, instr->environment());
+    DoCheckMapCommon(reg, Handle<Map>(current_prototype->map()),
+                     ALLOW_ELEMENT_TRANSITION_MAPS, instr->environment());
     current_prototype =
         Handle<JSObject>(JSObject::cast(current_prototype->GetPrototype()));
     // Load next prototype object.
@@ -3829,9 +3838,8 @@ void LCodeGen::DoCheckPrototypeMaps(LCheckPrototypeMaps* instr) {
   }
 
   // Check the holder map.
-  __ Cmp(FieldOperand(reg, HeapObject::kMapOffset),
-         Handle<Map>(current_prototype->map()));
-  DeoptimizeIf(not_equal, instr->environment());
+    DoCheckMapCommon(reg, Handle<Map>(current_prototype->map()),
+                     ALLOW_ELEMENT_TRANSITION_MAPS, instr->environment());
 }