Various minor improvements of sort.

src/array.js

 // Copyright 2006-2008 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 632 matching lines @@
   
   // Return the deleted elements.
   return deleted_elements;
 };
 
 
 function ArraySort(comparefn) {
   // In-place QuickSort algorithm.
   // For short (length <= 22) arrays, insertion sort is used for efficiency.
 
+  var custom_compare = IS_FUNCTION(comparefn);
+  
   function Compare(x,y) {
-    if (IS_UNDEFINED(x)) {
-      if (IS_UNDEFINED(y)) return 0;
-      return 1;
-    }
-    if (IS_UNDEFINED(y)) return -1;
-
-    if (IS_FUNCTION(comparefn)) {
+    if (custom_compare) {
       return comparefn.call(null, x, y);
     }
     if (%_IsSmi(x) && %_IsSmi(y)) {
       return %SmiLexicographicCompare(x, y);
     }
     x = ToString(x);
     y = ToString(y);
     if (x == y) return 0;
     else return x < y ? -1 : 1;
   };
@@ skipping 13 matching lines @@
           min = max = mid;
           break;
         }
         if (order < 0) {
           min = mid + 1;
         } else {
           max = mid;
         }
       }
       // place element at position min==max.
-      for (var j = min; j < i; j++) {
-        var tmp = a[j];
-        a[j] = element;
-        element = tmp;
+      for (var j = i; j > min; j--) {
+        a[j] = a[j - 1];
       }
-      a[i] = element;
+      a[min] = element;
     }
   }
-  
+
   function QuickSort(a, from, to) {
     // Insertion sort is faster for short arrays.
     if (to - from <= 22) { 
       InsertionSort(a, from, to);
       return;
     }
     var pivot_index = $floor($random() * (to - from)) + from;
     var pivot = a[pivot_index];
     // Issue 95: Keep the pivot element out of the comparisons to avoid
     // infinite recursion if comparefn(pivot, pivot) != 0.
@@ skipping 23 matching lines @@
     high_start++;
     QuickSort(a, from, low_end);
     QuickSort(a, high_start, to);
   }
 
   var old_length = ToUint32(this.length);
 
   %RemoveArrayHoles(this);
 
   var length = ToUint32(this.length);
+
+  // Move undefined elements to the end of the array.
+  for (var i = 0; i < length; ) {
+    if (IS_UNDEFINED(this[i])) {
+      length--;
+      this[i] = this[length];
+      this[length] = undefined;
+    } else {
+      i++;
+    }
+  }
+
   QuickSort(this, 0, length);
 
   // We only changed the length of the this object (in
   // RemoveArrayHoles) if it was an array.  We are not allowed to set
   // the length of the this object if it is not an array because this
   // might introduce a new length property.
   if (IS_ARRAY(this)) {
     this.length = old_length;
   }
 
@@ skipping 191 matching lines @@
     ArrayEvery: 1,
     ArrayMap: 1,
     ArrayIndexOf: 1,
     ArrayLastIndexOf: 1,
     ArrayPush: 1
   });
 };
 
 
 SetupArray();