Narrow cases where Sparse/Smart versions of Array methods are used

src/array.js

 // Copyright 2012 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.
 
 "use strict";
 
 // This file relies on the fact that the following declarations have been made
 // in runtime.js:
 // var $Array = global.Array;
 
@@ skipping 72 matching lines @@
     }
   }
   return %StringBuilderConcat(elements, elements_length, '');
 }
 
 
 function UseSparseVariant(array, length, is_array, touched) {
   // Only use the sparse variant on arrays that are likely to be sparse and the
   // number of elements touched in the operation is relatively small compared to
   // the overall size of the array.
-  if (!is_array || length < 1000 || %IsObserved(array)) {
+  if (!is_array || length < 1000 || %IsObserved(array) ||
+      %HasComplexElements(array)) {
     return false;
   }
   if (!%_IsSmi(length)) {
     return true;
   }
   var elements_threshold = length >> 2;  // No more than 75% holes
   var estimated_elements = %EstimateNumberOfElements(array);
   return (estimated_elements < elements_threshold) &&
     (touched > estimated_elements * 4);
 }
@@ skipping 92 matching lines @@
     // must throw a TypeError if ToObject(e).toLocaleString isn't
     // callable.
     var e_obj = ToObject(e);
     return %ToString(e_obj.toLocaleString());
   }
 }
 
 
 // This function implements the optimized splice implementation that can use
 // special array operations to handle sparse arrays in a sensible fashion.
-function SmartSlice(array, start_i, del_count, len, deleted_elements) {
+function SparseSlice(array, start_i, del_count, len, deleted_elements) {
   // Move deleted elements to a new array (the return value from splice).
   var indices = %GetArrayKeys(array, start_i + del_count);
   if (IS_NUMBER(indices)) {
     var limit = indices;
     for (var i = start_i; i < limit; ++i) {
       var current = array[i];
       if (!IS_UNDEFINED(current) || i in array) {
         deleted_elements[i - start_i] = current;
       }
     }
   } else {
     var length = indices.length;
     for (var k = 0; k < length; ++k) {
       var key = indices[k];
       if (!IS_UNDEFINED(key)) {
         if (key >= start_i) {
           var current = array[key];
           if (!IS_UNDEFINED(current) || key in array) {
             deleted_elements[key - start_i] = current;
           }
         }
       }
     }
   }
 }
 
 
 // This function implements the optimized splice implementation that can use
 // special array operations to handle sparse arrays in a sensible fashion.
-function SmartMove(array, start_i, del_count, len, num_additional_args) {
+function SparseMove(array, start_i, del_count, len, num_additional_args) {
   // Bail out if no moving is necessary.
   if (num_additional_args === del_count) return;
   // Move data to new array.
   var new_array = new InternalArray(len - del_count + num_additional_args);
   var indices = %GetArrayKeys(array, len);
   if (IS_NUMBER(indices)) {
     var limit = indices;
     for (var i = 0; i < start_i && i < limit; ++i) {
       var current = array[i];
       if (!IS_UNDEFINED(current) || i in array) {
@@ skipping 354 matching lines @@
   if (ObjectIsSealed(array)) {
     throw MakeTypeError("array_functions_change_sealed",
                         ["Array.prototype.shift"]);
   }
 
   if (%IsObserved(array))
     return ObservedArrayShift.call(array, len);
 
   var first = array[0];
 
-  if (IS_ARRAY(array)) {
-    SmartMove(array, 0, 1, len, 0);
+  if (UseSparseVariant(array, len, IS_ARRAY(array), len)) {
+    SparseMove(array, 0, 1, len, 0);
   } else {
     SimpleMove(array, 0, 1, len, 0);
   }
 
   array.length = len - 1;
 
   return first;
 }
 
 function ObservedArrayUnshift() {
@@ skipping 18 matching lines @@
 
 function ArrayUnshift(arg1) {  // length == 1
   CHECK_OBJECT_COERCIBLE(this, "Array.prototype.unshift");
 
   if (%IsObserved(this))
     return ObservedArrayUnshift.apply(this, arguments);
 
   var array = TO_OBJECT_INLINE(this);
   var len = TO_UINT32(array.length);
   var num_arguments = %_ArgumentsLength();
-  var is_sealed = ObjectIsSealed(array);
 
-  if (IS_ARRAY(array) && !is_sealed && len > 0) {
-    SmartMove(array, 0, 0, len, num_arguments);
+  if (len > 0 && UseSparseVariant(array, len, IS_ARRAY(array), len) &&
+     !ObjectIsSealed(array)) {
+    SparseMove(array, 0, 0, len, num_arguments);
   } else {
     SimpleMove(array, 0, 0, len, num_arguments);
   }
 
   for (var i = 0; i < num_arguments; i++) {
     array[i] = %_Arguments(i);
   }
 
   var new_length = len + num_arguments;
   array.length = new_length;
@@ skipping 25 matching lines @@
     if (end_i > len) end_i = len;
   }
 
   var result = [];
 
   if (end_i < start_i) return result;
 
   if (UseSparseVariant(array, len, IS_ARRAY(array), end_i - start_i)) {
     %NormalizeElements(array);
     %NormalizeElements(result);
-    SmartSlice(array, start_i, end_i - start_i, len, result);
+    SparseSlice(array, start_i, end_i - start_i, len, result);
   } else {
     SimpleSlice(array, start_i, end_i - start_i, len, result);
   }
 
   result.length = end_i - start_i;
 
   return result;
 }
 
 
@@ skipping 95 matching lines @@
 
   var changed_elements = del_count;
   if (num_elements_to_add != del_count) {
     // If the slice needs to do a actually move elements after the insertion
     // point, then include those in the estimate of changed elements.
     changed_elements += len - start_i - del_count;
   }
   if (UseSparseVariant(array, len, IS_ARRAY(array), changed_elements)) {
     %NormalizeElements(array);
     %NormalizeElements(deleted_elements);
-    SmartSlice(array, start_i, del_count, len, deleted_elements);
-    SmartMove(array, start_i, del_count, len, num_elements_to_add);
+    SparseSlice(array, start_i, del_count, len, deleted_elements);
+    SparseMove(array, start_i, del_count, len, num_elements_to_add);
   } else {
     SimpleSlice(array, start_i, del_count, len, deleted_elements);
     SimpleMove(array, start_i, del_count, len, num_elements_to_add);
   }
 
   // Insert the arguments into the resulting array in
   // place of the deleted elements.
   var i = start_i;
   var arguments_index = 2;
   var arguments_length = %_ArgumentsLength();
@@ skipping 740 matching lines @@
   ));
 
   SetUpLockedPrototype(InternalPackedArray, $Array(), $Array(
     "join", getFunction("join", ArrayJoin),
     "pop", getFunction("pop", ArrayPop),
     "push", getFunction("push", ArrayPush)
   ));
 }
 
 SetUpArray();