[ic] Cache weak cells containing prototypes in respective PrototypeInfo objects.

src/objects.cc

 // Copyright 2015 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/objects.h"
 
 #include <cmath>
 #include <iomanip>
 #include <memory>
 #include <sstream>
@@ skipping 12714 matching lines @@
       return cell;
     }
   }
   // Otherwise create a new cell.
   Handle<Cell> cell = isolate->factory()->NewCell(
       handle(Smi::FromInt(Map::kPrototypeChainValid), isolate));
   proto_info->set_validity_cell(*cell);
   return cell;
 }
 
+// static
+Handle<WeakCell> Map::GetOrCreatePrototypeWeakCell(Handle<JSObject> prototype,
+                                                   Isolate* isolate) {
+  DCHECK(!prototype.is_null());
+  Handle<PrototypeInfo> proto_info =
+      GetOrCreatePrototypeInfo(prototype, isolate);
+  Object* maybe_cell = proto_info->weak_cell();
+  // Return existing cell if it's already created.
+  if (maybe_cell->IsWeakCell()) {
+    Handle<WeakCell> cell(WeakCell::cast(maybe_cell), isolate);
+    DCHECK(!cell->cleared());
+    return cell;
+  }
+  // Otherwise create a new cell.
+  Handle<WeakCell> cell = isolate->factory()->NewWeakCell(prototype);
+  proto_info->set_weak_cell(*cell);
+  return cell;
+}
 
 // static
 void Map::SetPrototype(Handle<Map> map, Handle<Object> prototype,
                        PrototypeOptimizationMode proto_mode) {
   RuntimeCallTimerScope stats_scope(*map, &RuntimeCallStats::Map_SetPrototype);
 
   bool is_hidden = false;
   if (prototype->IsJSObject()) {
     Handle<JSObject> prototype_jsobj = Handle<JSObject>::cast(prototype);
     JSObject::OptimizeAsPrototype(prototype_jsobj, proto_mode);
@@ skipping 7450 matching lines @@
         ns, Accessors::ModuleNamespaceEntryInfo(isolate, name, attr))
         .Check();
   }
   JSObject::PreventExtensions(ns, THROW_ON_ERROR).ToChecked();
 
   return ns;
 }
 
 }  // namespace internal
 }  // namespace v8