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

src/array.js

Index: src/array.js
diff --git a/src/array.js b/src/array.js
index 585d1da8427507f0ef0ea3cb12470d3c9bc21488..7fd2a06d87b439ba8fdd9d30e339476866a89948 100644
--- a/src/array.js
+++ b/src/array.js
@@ -90,7 +90,8 @@ 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)) {
@@ -203,7 +204,7 @@ function ConvertToLocaleString(e) {
 
 // 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)) {
@@ -233,7 +234,7 @@ function SmartSlice(array, start_i, del_count, len, deleted_elements) {
 
 // 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.
@@ -608,8 +609,8 @@ function ArrayShift() {
 
   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);
   }
@@ -648,10 +649,10 @@ function ArrayUnshift(arg1) {  // length == 1
   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);
   }
@@ -697,7 +698,7 @@ function ArraySlice(start, end) {
   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);
   }
@@ -813,8 +814,8 @@ function ArraySplice(start, delete_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);