Use in-object fields instead of private symbols for regexp slots.

src/bootstrapper.cc

 // Copyright 2014 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/bootstrapper.h"
 
 #include "src/accessors.h"
 #include "src/api-natives.h"
 #include "src/code-stubs.h"
 #include "src/extensions/externalize-string-extension.h"
@@ skipping 1205 matching lines @@
         InstallFunction(global, "RegExp", JS_REGEXP_TYPE, JSRegExp::kSize,
                         isolate->initial_object_prototype(),
                         Builtins::kIllegal);
     native_context()->set_regexp_function(*regexp_fun);
 
     DCHECK(regexp_fun->has_initial_map());
     Handle<Map> initial_map(regexp_fun->initial_map());
 
     DCHECK_EQ(0, initial_map->GetInObjectProperties());
 
-    PropertyAttributes final =
-        static_cast<PropertyAttributes>(DONT_ENUM | DONT_DELETE | READ_ONLY);
-    Map::EnsureDescriptorSlack(initial_map, 5);
+    Map::EnsureDescriptorSlack(initial_map, 1);
 
-    {
-      // ES6 21.2.3.2.1
-      DataDescriptor field(factory->regexp_source_symbol(),
-                           JSRegExp::kSourceFieldIndex, final,
-                           Representation::Tagged());
-      initial_map->AppendDescriptor(&field);
-    }
-    {
-      DataDescriptor field(factory->regexp_flags_symbol(),
-                           JSRegExp::kFlagsFieldIndex, final,
-                           Representation::Smi());
-      initial_map->AppendDescriptor(&field);
-    }
-    {
-      // ECMA-262, section 15.10.7.5.
-      PropertyAttributes writable =
-          static_cast<PropertyAttributes>(DONT_ENUM | DONT_DELETE);
-      DataDescriptor field(factory->last_index_string(),
-                           JSRegExp::kLastIndexFieldIndex, writable,
-                           Representation::Tagged());
-      initial_map->AppendDescriptor(&field);
-    }
+    // ECMA-262, section 15.10.7.5.
+    PropertyAttributes writable =
+        static_cast<PropertyAttributes>(DONT_ENUM | DONT_DELETE);
+    DataDescriptor field(factory->last_index_string(),
+                         JSRegExp::kLastIndexFieldIndex, writable,
+                         Representation::Tagged());
+    initial_map->AppendDescriptor(&field);
 
     static const int num_fields = JSRegExp::kInObjectFieldCount;
     initial_map->SetInObjectProperties(num_fields);
     initial_map->set_unused_property_fields(0);
     initial_map->set_instance_size(initial_map->instance_size() +
                                    num_fields * kPointerSize);
   }
 
   // Initialize the embedder data slot.
   Handle<FixedArray> embedder_data = factory->NewFixedArray(3);
@@ skipping 1983 matching lines @@
 }
 
 
 // Called when the top-level V8 mutex is destroyed.
 void Bootstrapper::FreeThreadResources() {
   DCHECK(!IsActive());
 }
 
 }  // namespace internal
 }  // namespace v8