Basic support for tracking smi-only arrays on ia32.

src/elements.cc

Index: src/elements.cc
diff --git a/src/elements.cc b/src/elements.cc
index e4ecfe8dd63df799b4bd083f59b849808c6e5973..5e7a84e38b8377a6009a93ecc4967832f168dc19 100644
--- a/src/elements.cc
+++ b/src/elements.cc
@@ -227,7 +227,9 @@ class FastElementsAccessor
  public:
   static MaybeObject* DeleteCommon(JSObject* obj,
                                    uint32_t key) {
-    ASSERT(obj->HasFastElements() || obj->HasFastArgumentsElements());
+    ASSERT(obj->HasFastElements() ||
+           obj->HasFastSmiOnlyElements() ||
+           obj->HasFastArgumentsElements());
     Heap* heap = obj->GetHeap();
     FixedArray* backing_store = FixedArray::cast(obj->elements());
     if (backing_store->map() == heap->non_strict_arguments_elements_map()) {
@@ -596,6 +598,9 @@ ElementsAccessor* ElementsAccessor::ForArray(FixedArrayBase* array) {
 
 void ElementsAccessor::InitializeOncePerProcess() {
   static struct ConcreteElementsAccessors {
+    // Use the fast element handler for smi-only arrays. The implementation is
+    // currently identical.
+    FastElementsAccessor fast_smi_elements_handler;
     FastElementsAccessor fast_elements_handler;
     FastDoubleElementsAccessor fast_double_elements_handler;
     DictionaryElementsAccessor dictionary_elements_handler;
@@ -612,6 +617,7 @@ void ElementsAccessor::InitializeOncePerProcess() {
   } element_accessors;
 
   static ElementsAccessor* accessor_array[] = {
+    &element_accessors.fast_smi_elements_handler,
     &element_accessors.fast_elements_handler,
     &element_accessors.fast_double_elements_handler,
     &element_accessors.dictionary_elements_handler,
@@ -627,6 +633,9 @@ void ElementsAccessor::InitializeOncePerProcess() {
     &element_accessors.pixel_elements_handler
   };
 
+  STATIC_ASSERT((sizeof(accessor_array) / sizeof(*accessor_array)) ==
+                kElementsKindCount);
+
   elements_accessors_ = accessor_array;
 }