Vector ICs: Like megamorphic keyed koads, use a dummy vector for stores

src/heap/heap.cc

Index: src/heap/heap.cc
diff --git a/src/heap/heap.cc b/src/heap/heap.cc
index bad4528ff4dee805a10f0d4532960276a8c29eb1..27c24f34b15fd5a9bedd121cad06463456da8f6b 100644
--- a/src/heap/heap.cc
+++ b/src/heap/heap.cc
@@ -3353,13 +3353,27 @@ void Heap::CreateInitialObjects() {
   // Number of queued microtasks stored in Isolate::pending_microtask_count().
   set_microtask_queue(empty_fixed_array());
 
-  FeedbackVectorSpec spec(0, Code::KEYED_LOAD_IC);
-  Handle<TypeFeedbackVector> dummy_vector =
-      factory->NewTypeFeedbackVector(&spec);
-  dummy_vector->Set(FeedbackVectorICSlot(0),
-                    *TypeFeedbackVector::MegamorphicSentinel(isolate()),
-                    SKIP_WRITE_BARRIER);
-  set_keyed_load_dummy_vector(*dummy_vector);
+  {
+    FeedbackVectorSpec spec(0, Code::KEYED_LOAD_IC);
+    Handle<TypeFeedbackVector> dummy_vector =
+        factory->NewTypeFeedbackVector(&spec);
+    dummy_vector->Set(FeedbackVectorICSlot(0),
+                      *TypeFeedbackVector::MegamorphicSentinel(isolate()),
+                      SKIP_WRITE_BARRIER);
+    set_keyed_load_dummy_vector(*dummy_vector);
+  }
+
+  if (FLAG_vector_stores) {
+    FeedbackVectorSpec spec(0, Code::KEYED_STORE_IC);
+    Handle<TypeFeedbackVector> dummy_vector =
+        factory->NewTypeFeedbackVector(&spec);
+    dummy_vector->Set(FeedbackVectorICSlot(0),
+                      *TypeFeedbackVector::MegamorphicSentinel(isolate()),
+                      SKIP_WRITE_BARRIER);
+    set_keyed_store_dummy_vector(*dummy_vector);
+  } else {
+    set_keyed_store_dummy_vector(empty_fixed_array());
+  }
 
   set_detached_contexts(empty_fixed_array());
   set_retained_maps(ArrayList::cast(empty_fixed_array()));