Fix Runtime_ArrayConcat to handle FAST_DOUBLE_ELEMENTS

src/runtime.cc

Index: src/runtime.cc
diff --git a/src/runtime.cc b/src/runtime.cc
index 08b944a8a1b00fdc3908d9f66d4ea74a76c20245..d8cf3df9cc134d9a1b71487ac22cbdf119b57bd2 100644
--- a/src/runtime.cc
+++ b/src/runtime.cc
@@ -9695,6 +9695,7 @@ static uint32_t EstimateElementCount(Handle<JSArray> array) {
   uint32_t length = static_cast<uint32_t>(array->length()->Number());
   int element_count = 0;
   switch (array->GetElementsKind()) {
+    case FAST_SMI_ONLY_ELEMENTS:

[danno, 2011/11/04 10:02:04]

Add all of the other elements kinds explicitly to the case that either are
UNREACHABLE or return length, remove the default. 

     case FAST_ELEMENTS: {
       // Fast elements can't have lengths that are not representable by
       // a 32-bit signed integer.
@@ -9796,6 +9797,11 @@ static void CollectElementIndices(Handle<JSObject> object,
       }
       break;
     }
+    case FAST_DOUBLE_ELEMENTS: {
+      // TODO(1810): Decide if it's worthwhile to implement this.
+      UNREACHABLE();
+      break;
+    }
     case DICTIONARY_ELEMENTS: {
       Handle<NumberDictionary> dict(NumberDictionary::cast(object->elements()));
       uint32_t capacity = dict->Capacity();
@@ -9926,6 +9932,11 @@ static bool IterateElements(Isolate* isolate,
       }
       break;
     }
+    case FAST_DOUBLE_ELEMENTS: {
+      // TODO(1810): Decide if it's worthwhile to implement this.
+      UNREACHABLE();
+      break;
+    }
     case DICTIONARY_ELEMENTS: {
       Handle<NumberDictionary> dict(receiver->element_dictionary());
       List<uint32_t> indices(dict->Capacity() / 2);
@@ -10036,6 +10047,13 @@ RUNTIME_FUNCTION(MaybeObject*, Runtime_ArrayConcat) {
       uint32_t element_estimate;
       if (obj->IsJSArray()) {
         Handle<JSArray> array(Handle<JSArray>::cast(obj));
+        // TODO(1810): Find out if it's worthwhile to properly support
+        // arbitrary ElementsKinds. For now, pessimistically transition to
+        // FAST_ELEMENTS.
+        if (array->HasFastDoubleElements()) {
+          array = Handle<JSArray>::cast(
+              TransitionElementsKind(array, FAST_ELEMENTS));
+        }
         length_estimate =
             static_cast<uint32_t>(array->length()->Number());
         element_estimate =