Revert of Replace PushIfAbsent by a Stack object and move StringBuilderJoin to JS

src/runtime/runtime-array.cc

 // Copyright 2014 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "src/runtime/runtime-utils.h"
 
 #include "src/arguments.h"
 #include "src/conversions-inl.h"
 #include "src/elements.h"
 #include "src/factory.h"
@@ skipping 70 matching lines @@
 RUNTIME_FUNCTION(Runtime_TransitionElementsKind) {
   HandleScope scope(isolate);
   RUNTIME_ASSERT(args.length() == 2);
   CONVERT_ARG_HANDLE_CHECKED(JSArray, array, 0);
   CONVERT_ARG_HANDLE_CHECKED(Map, map, 1);
   JSObject::TransitionElementsKind(array, map->elements_kind());
   return *array;
 }
 
 
+// Push an object unto an array of objects if it is not already in the
+// array.  Returns true if the element was pushed on the stack and
+// false otherwise.
+RUNTIME_FUNCTION(Runtime_PushIfAbsent) {
+  HandleScope scope(isolate);
+  DCHECK(args.length() == 2);
+  CONVERT_ARG_HANDLE_CHECKED(JSArray, array, 0);
+  CONVERT_ARG_HANDLE_CHECKED(JSReceiver, element, 1);
+  RUNTIME_ASSERT(array->HasFastSmiOrObjectElements());
+  int length = Smi::cast(array->length())->value();
+  FixedArray* elements = FixedArray::cast(array->elements());
+  for (int i = 0; i < length; i++) {
+    if (elements->get(i) == *element) return isolate->heap()->false_value();
+  }
+
+  // Strict not needed. Used for cycle detection in Array join implementation.
+  RETURN_FAILURE_ON_EXCEPTION(
+      isolate, JSObject::AddDataElement(array, length, element, NONE));
+  JSObject::ValidateElements(array);
+  return isolate->heap()->true_value();
+}
+
+
 // Moves all own elements of an object, that are below a limit, to positions
 // starting at zero. All undefined values are placed after non-undefined values,
 // and are followed by non-existing element. Does not change the length
 // property.
 // Returns the number of non-undefined elements collected.
 // Returns -1 if hole removal is not supported by this method.
 RUNTIME_FUNCTION(Runtime_RemoveArrayHoles) {
   HandleScope scope(isolate);
   DCHECK(args.length() == 2);
   CONVERT_ARG_HANDLE_CHECKED(JSReceiver, object, 0);
@@ skipping 373 matching lines @@
   CONVERT_ARG_HANDLE_CHECKED(Object, original_array, 0);
   Handle<Object> constructor;
   ASSIGN_RETURN_FAILURE_ON_EXCEPTION(
       isolate, constructor,
       Object::ArraySpeciesConstructor(isolate, original_array));
   return *constructor;
 }
 
 }  // namespace internal
 }  // namespace v8