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

src/ast/ast.h

Index: src/ast/ast.h
diff --git a/src/ast/ast.h b/src/ast/ast.h
index 2d9833aee1eb2b8f7aa3b8e3de1acf2fb2967720..df59db8f562bcbff4842de01c9033f80745f63c1 100644
--- a/src/ast/ast.h
+++ b/src/ast/ast.h
@@ -1264,6 +1264,7 @@ class MaterializedLiteral : public Expression {
   void set_is_simple(bool is_simple) {
     bit_field_ = IsSimpleField::update(bit_field_, is_simple);
   }
+
   friend class CompileTimeValue;
 
   void set_depth(int depth) {
@@ -1353,6 +1354,11 @@ class ObjectLiteralProperty final : public LiteralProperty {
 
   void set_receiver_type(Handle<Map> map) { receiver_type_ = map; }
 
+  bool IsNullPrototype() const {
+    return IsPrototype() && value()->IsNullLiteral();
+  }
+  bool IsPrototype() const { return kind() == PROTOTYPE; }
+
  private:
   friend class AstNodeFactory;
 
@@ -1390,7 +1396,9 @@ class ObjectLiteral final : public MaterializedLiteral {
   bool has_rest_property() const {
     return HasRestPropertyField::decode(bit_field_);
   }
-
+  bool has_null_prototype() const {
+    return HasNullPrototypeField::decode(bit_field_);
+  }
   // Decide if a property should be in the object boilerplate.
   static bool IsBoilerplateProperty(Property* property);
 
@@ -1420,12 +1428,9 @@ class ObjectLiteral final : public MaterializedLiteral {
   // Assemble bitfield of flags for the CreateObjectLiteral helper.
   int ComputeFlags(bool disable_mementos = false) const {
     int flags = fast_elements() ? kFastElements : kNoFlags;
-    if (has_shallow_properties()) {
-      flags |= kShallowProperties;
-    }
-    if (disable_mementos) {
-      flags |= kDisableMementos;
-    }
+    if (has_shallow_properties()) flags |= kShallowProperties;
+    if (disable_mementos) flags |= kDisableMementos;
+    if (has_null_prototype()) flags |= kHasNullPrototype;
     return flags;
   }
 
@@ -1434,7 +1439,7 @@ class ObjectLiteral final : public MaterializedLiteral {
     kFastElements = 1,
     kShallowProperties = 1 << 1,
     kDisableMementos = 1 << 2,
-    kHasRestProperty = 1 << 3,
+    kHasNullPrototype = 1 << 3,
   };
 
   struct Accessors: public ZoneObject {
@@ -1470,12 +1475,23 @@ class ObjectLiteral final : public MaterializedLiteral {
     bit_field_ |= FastElementsField::encode(false) |
                   HasElementsField::encode(false) |
                   MayStoreDoublesField::encode(false) |
-                  HasRestPropertyField::encode(has_rest_property);
+                  HasRestPropertyField::encode(has_rest_property) |
+                  HasNullPrototypeField::encode(false);
   }
 
   static int parent_num_ids() { return MaterializedLiteral::num_ids(); }
   int local_id(int n) const { return base_id() + parent_num_ids() + n; }
 
+  void set_fast_elements(bool fast_elements) {
+    bit_field_ = FastElementsField::update(bit_field_, fast_elements);
+  }
+  void set_has_elements(bool has_elements) {
+    bit_field_ = HasElementsField::update(bit_field_, has_elements);
+  }
+  void set_has_null_protoype(bool has_null_prototype) {
+    bit_field_ = HasNullPrototypeField::update(bit_field_, has_null_prototype);
+  }
+
   uint32_t boilerplate_properties_;
   Handle<BoilerplateDescription> constant_properties_;
   ZoneList<Property*>* properties_;
@@ -1488,6 +1504,8 @@ class ObjectLiteral final : public MaterializedLiteral {
       : public BitField<bool, HasElementsField::kNext, 1> {};
   class HasRestPropertyField
       : public BitField<bool, MayStoreDoublesField::kNext, 1> {};
+  class HasNullPrototypeField
+      : public BitField<bool, HasRestPropertyField::kNext, 1> {};
 };