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

src/heap/heap.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "src/v8.h"
 
 #include "src/accessors.h"
 #include "src/api.h"
 #include "src/base/bits.h"
 #include "src/base/once.h"
@@ skipping 3335 matching lines @@
   set_symbol_registry(Smi::FromInt(0));
 
   // Allocate object to hold object observation state.
   set_observation_state(*factory->NewJSObjectFromMap(
       factory->NewMap(JS_OBJECT_TYPE, JSObject::kHeaderSize)));
 
   // Microtask queue uses the empty fixed array as a sentinel for "empty".
   // 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()));
 
   set_weak_object_to_code_table(
       *WeakHashTable::New(isolate(), 16, USE_DEFAULT_MINIMUM_CAPACITY,
                           TENURED));
 
   Handle<SeededNumberDictionary> slow_element_dictionary =
       SeededNumberDictionary::New(isolate(), 0, TENURED);
@@ skipping 3459 matching lines @@
     *object_type = "CODE_TYPE";                                                \
     *object_sub_type = "CODE_AGE/" #name;                                      \
     return true;
     CODE_AGE_LIST_COMPLETE(COMPARE_AND_RETURN_NAME)
 #undef COMPARE_AND_RETURN_NAME
   }
   return false;
 }
 }  // namespace internal
 }  // namespace v8