VectorICs: use a vector slot to aid in array literal processing.

src/compiler/js-generic-lowering.cc

Index: src/compiler/js-generic-lowering.cc
diff --git a/src/compiler/js-generic-lowering.cc b/src/compiler/js-generic-lowering.cc
index eac05657861f4661b1ac688ed0f3c358b9372be1..94b1c4e9da9be2950ffd5099ddc0d33a79e7a730 100644
--- a/src/compiler/js-generic-lowering.cc
+++ b/src/compiler/js-generic-lowering.cc
@@ -332,14 +332,10 @@ void JSGenericLowering::LowerJSStoreProperty(Node* node) {
   CallDescriptor::Flags flags = AdjustFrameStatesForCall(node);
   const StorePropertyParameters& p = StorePropertyParametersOf(node->op());
   LanguageMode language_mode = p.language_mode();
-  // We have a special case where we do keyed stores but don't have a type
-  // feedback vector slot allocated to support it. In this case, install
-  // the megamorphic keyed store stub which needs neither vector nor slot.
-  bool use_vector_slot = FLAG_vector_stores && p.feedback().index() != -1;
   Callable callable = CodeFactory::KeyedStoreICInOptimizedCode(
-      isolate(), language_mode,
-      (use_vector_slot || !FLAG_vector_stores) ? UNINITIALIZED : MEGAMORPHIC);
-  if (use_vector_slot) {
+      isolate(), language_mode, UNINITIALIZED);
+  if (FLAG_vector_stores) {
+    DCHECK(p.feedback().index() != -1);
     node->InsertInput(zone(), 3, jsgraph()->SmiConstant(p.feedback().index()));
   } else {
     node->RemoveInput(3);