Introduce faster swapping primitives.

src/runtime.cc

 // Copyright 2006-2009 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:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 7730 matching lines @@
   CONVERT_CHECKED(JSArray, array, args[0]);
   HeapObject* elements = array->elements();
   if (elements->IsDictionary()) {
     return Smi::FromInt(NumberDictionary::cast(elements)->NumberOfElements());
   } else {
     return array->length();
   }
 }
 
 
+static Object* Runtime_SwapElements(Arguments args) {
+  HandleScope handle_scope;
+
+  ASSERT_EQ(3, args.length());
+
+  Handle<Object> object = args.at<Object>(0);
+  Handle<Object> key1 = args.at<Object>(1);
+  Handle<Object> key2 = args.at<Object>(2);
+
+  uint32_t index1, index2;
+  // That must be the most common case.
+  if (object->IsJSObject()
+      && Array::IndexFromObject(*key1, &index1)
+      && Array::IndexFromObject(*key2, &index2)) {
+    Handle<JSObject> jsobject = Handle<JSObject>::cast(object);
+    Handle<Object> tmp1 = GetElement(jsobject, index1);
+    Handle<Object> tmp2 = GetElement(jsobject, index2);
+
+    SetElement(jsobject, index1, tmp2);
+    SetElement(jsobject, index2, tmp1);
+  } else {
+    Handle<Object> tmp1 = GetProperty(object, key1);
+    Handle<Object> tmp2 = GetProperty(object, key2);
+
+    SetProperty(object, key1, tmp2, NONE);
+    SetProperty(object, key2, tmp1, NONE);
+  }
+
+  return Heap::undefined_value();
+}
+
+
 // Returns an array that tells you where in the [0, length) interval an array
 // might have elements.  Can either return keys or intervals.  Keys can have
 // gaps in (undefined).  Intervals can also span over some undefined keys.
 static Object* Runtime_GetArrayKeys(Arguments args) {
   ASSERT(args.length() == 2);
   HandleScope scope;
   CONVERT_ARG_CHECKED(JSObject, array, 0);
   CONVERT_NUMBER_CHECKED(uint32_t, length, Uint32, args[1]);
   if (array->elements()->IsDictionary()) {
     // Create an array and get all the keys into it, then remove all the
@@ skipping 2440 matching lines @@
   } else {
     // Handle last resort GC and make sure to allow future allocations
     // to grow the heap without causing GCs (if possible).
     Counters::gc_last_resort_from_js.Increment();
     Heap::CollectAllGarbage(false);
   }
 }
 
 
 } }  // namespace v8::internal