Ensure slow properties for simple {__proto__:null} literals.

src/interpreter/bytecode-generator.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/interpreter/bytecode-generator.h"
 
 #include "src/ast/compile-time-value.h"
 #include "src/ast/scopes.h"
 #include "src/builtins/builtins-constructor.h"
 #include "src/code-stubs.h"
@@ skipping 1725 matching lines @@
                 ->LoadLiteral(Smi::FromInt(SLOPPY))
                 .StoreAccumulatorInRegister(args[3])
                 .CallRuntime(Runtime::kSetProperty, args);
             Register value = args[2];
             VisitSetHomeObject(value, literal, property);
           }
         }
         break;
       }
       case ObjectLiteral::Property::PROTOTYPE: {
+        if (property->IsNullPrototype()) break;
         DCHECK(property->emit_store());
         RegisterList args = register_allocator()->NewRegisterList(2);
         builder()->MoveRegister(literal, args[0]);
         VisitForRegisterValue(property->value(), args[1]);
         builder()->CallRuntime(Runtime::kInternalSetPrototype, args);
         break;
       }
       case ObjectLiteral::Property::GETTER:
         if (property->emit_store()) {
           accessor_table.lookup(key)->second->getter = property;
@@ skipping 29 matching lines @@
   // with the first computed property name and continues with all properties to
   // its right. All the code from above initializes the static component of the
   // object literal, and arranges for the map of the result to reflect the
   // static order in which the keys appear. For the dynamic properties, we
   // compile them into a series of "SetOwnProperty" runtime calls. This will
   // preserve insertion order.
   for (; property_index < expr->properties()->length(); property_index++) {
     ObjectLiteral::Property* property = expr->properties()->at(property_index);
     RegisterAllocationScope inner_register_scope(this);
 
-    if (property->kind() == ObjectLiteral::Property::PROTOTYPE) {
+    if (property->IsPrototype()) {
+      // __proto__:null is handled by CreateObjectLiteral.
+      if (property->IsNullPrototype()) continue;
       DCHECK(property->emit_store());
       RegisterList args = register_allocator()->NewRegisterList(2);
       builder()->MoveRegister(literal, args[0]);
       VisitForRegisterValue(property->value(), args[1]);
       builder()->CallRuntime(Runtime::kInternalSetPrototype, args);
       continue;
     }
 
     switch (property->kind()) {
       case ObjectLiteral::Property::CONSTANT:
@@ skipping 1713 matching lines @@
 }
 
 Runtime::FunctionId BytecodeGenerator::StoreKeyedToSuperRuntimeId() {
   return is_strict(language_mode()) ? Runtime::kStoreKeyedToSuper_Strict
                                     : Runtime::kStoreKeyedToSuper_Sloppy;
 }
 
 }  // namespace interpreter
 }  // namespace internal
 }  // namespace v8