Revert change to always call builtins for Array functions....

src/builtins.cc

Index: src/builtins.cc
===================================================================
--- src/builtins.cc	(revision 4073)
+++ src/builtins.cc	(working copy)
@@ -319,24 +319,6 @@
 }
 
 
-static bool IsJSArrayWithFastElements(Object* receiver,
-                                      FixedArray** elements) {
-  if (!receiver->IsJSArray()) {
-    return false;
-  }
-
-  JSArray* array = JSArray::cast(receiver);
-
-  HeapObject* elms = HeapObject::cast(array->elements());
-  if (elms->map() != Heap::fixed_array_map()) {
-    return false;
-  }
-
-  *elements = FixedArray::cast(elms);
-  return true;
-}
-
-
 static Object* CallJsBuiltin(const char* name,
                              BuiltinArguments<NO_EXTRA_ARGUMENTS> args) {
   HandleScope handleScope;
@@ -364,12 +346,8 @@
 
 
 BUILTIN(ArrayPush) {
-  Object* receiver = *args.receiver();
-  FixedArray* elms = NULL;
-  if (!IsJSArrayWithFastElements(receiver, &elms)) {
-    return CallJsBuiltin("ArrayPush", args);
-  }
-  JSArray* array = JSArray::cast(receiver);
+  JSArray* array = JSArray::cast(*args.receiver());
+  ASSERT(array->HasFastElements());
 
   int len = Smi::cast(array->length())->value();
   int to_add = args.length() - 1;
@@ -381,6 +359,7 @@
   ASSERT(to_add <= (Smi::kMaxValue - len));
 
   int new_length = len + to_add;
+  FixedArray* elms = FixedArray::cast(array->elements());
 
   if (new_length > elms->length()) {
     // New backing storage is needed.
@@ -411,17 +390,14 @@
 
 
 BUILTIN(ArrayPop) {
-  Object* receiver = *args.receiver();
-  FixedArray* elms = NULL;
-  if (!IsJSArrayWithFastElements(receiver, &elms)) {
-    return CallJsBuiltin("ArrayPop", args);
-  }
-  JSArray* array = JSArray::cast(receiver);
+  JSArray* array = JSArray::cast(*args.receiver());
+  ASSERT(array->HasFastElements());
 
   int len = Smi::cast(array->length())->value();
   if (len == 0) return Heap::undefined_value();
 
   // Get top element
+  FixedArray* elms = FixedArray::cast(array->elements());
   Object* top = elms->get(len - 1);
 
   // Set the length.
@@ -444,18 +420,18 @@
 
 
 BUILTIN(ArrayShift) {
-  Object* receiver = *args.receiver();
-  FixedArray* elms = NULL;
-  if (!IsJSArrayWithFastElements(receiver, &elms)
-      || !ArrayPrototypeHasNoElements()) {
+  if (!ArrayPrototypeHasNoElements()) {
     return CallJsBuiltin("ArrayShift", args);
   }
-  JSArray* array = JSArray::cast(receiver);
+
+  JSArray* array = JSArray::cast(*args.receiver());
   ASSERT(array->HasFastElements());
 
   int len = Smi::cast(array->length())->value();
   if (len == 0) return Heap::undefined_value();
 
+  FixedArray* elms = FixedArray::cast(array->elements());
+
   // Get first element
   Object* first = elms->get(0);
   if (first->IsTheHole()) {
@@ -475,13 +451,11 @@
 
 
 BUILTIN(ArrayUnshift) {
-  Object* receiver = *args.receiver();
-  FixedArray* elms = NULL;
-  if (!IsJSArrayWithFastElements(receiver, &elms)
-      || !ArrayPrototypeHasNoElements()) {
+  if (!ArrayPrototypeHasNoElements()) {
     return CallJsBuiltin("ArrayUnshift", args);
   }
-  JSArray* array = JSArray::cast(receiver);
+
+  JSArray* array = JSArray::cast(*args.receiver());
   ASSERT(array->HasFastElements());
 
   int len = Smi::cast(array->length())->value();
@@ -495,6 +469,8 @@
   // we should never hit this case.
   ASSERT(to_add <= (Smi::kMaxValue - len));
 
+  FixedArray* elms = FixedArray::cast(array->elements());
+
   if (new_length > elms->length()) {
     // New backing storage is needed.
     int capacity = new_length + (new_length >> 1) + 16;
@@ -527,13 +503,11 @@
 
 
 BUILTIN(ArraySlice) {
-  Object* receiver = *args.receiver();
-  FixedArray* elms = NULL;
-  if (!IsJSArrayWithFastElements(receiver, &elms)
-      || !ArrayPrototypeHasNoElements()) {
+  if (!ArrayPrototypeHasNoElements()) {
     return CallJsBuiltin("ArraySlice", args);
   }
-  JSArray* array = JSArray::cast(receiver);
+
+  JSArray* array = JSArray::cast(*args.receiver());
   ASSERT(array->HasFastElements());
 
   int len = Smi::cast(array->length())->value();
@@ -584,6 +558,8 @@
   if (result->IsFailure()) return result;
   FixedArray* result_elms = FixedArray::cast(result);
 
+  FixedArray* elms = FixedArray::cast(array->elements());
+
   AssertNoAllocation no_gc;
   CopyElements(&no_gc, result_elms, 0, elms, k, result_len);
 
@@ -597,13 +573,11 @@
 
 
 BUILTIN(ArraySplice) {
-  Object* receiver = *args.receiver();
-  FixedArray* elms = NULL;
-  if (!IsJSArrayWithFastElements(receiver, &elms)
-      || !ArrayPrototypeHasNoElements()) {
+  if (!ArrayPrototypeHasNoElements()) {
     return CallJsBuiltin("ArraySplice", args);
   }
-  JSArray* array = JSArray::cast(receiver);
+
+  JSArray* array = JSArray::cast(*args.receiver());
   ASSERT(array->HasFastElements());
 
   int len = Smi::cast(array->length())->value();
@@ -644,6 +618,8 @@
   }
   int actual_delete_count = Min(Max(delete_count, 0), len - actual_start);
 
+  FixedArray* elms = FixedArray::cast(array->elements());
+
   JSArray* result_array = NULL;
   if (actual_delete_count == 0) {
     Object* result = AllocateEmptyJSArray();