[bootstrapper] Ensure RegExp constructor has fast properties.

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/base/ieee754.h"
 #include "src/code-stubs.h"
@@ skipping 2419 matching lines @@
       function->shared()->set_native(true);
       native_context()->set(Context::REGEXP_INTERNAL_MATCH, *function);
     }
 
     // Create the last match info. One for external use, and one for internal
     // use when we don't want to modify the externally visible match info.
     Handle<RegExpMatchInfo> last_match_info = factory->NewRegExpMatchInfo();
     native_context()->set_regexp_last_match_info(*last_match_info);
     Handle<RegExpMatchInfo> internal_match_info = factory->NewRegExpMatchInfo();
     native_context()->set_regexp_internal_match_info(*internal_match_info);
+
+    // Force the RegExp constructor to fast properties, so that we can use the
+    // fast paths for various things like
+    //
+    //   x instanceof RegExp
+    //
+    // etc. We should probably come up with a more principled approach once
+    // the JavaScript builtins are gone.
+    JSObject::MigrateSlowToFast(regexp_fun, 0, "Bootstrapping");
   }
 
   {  // -- E r r o r
     InstallError(isolate, global, factory->Error_string(),
                  Context::ERROR_FUNCTION_INDEX);
     InstallMakeError(isolate, isolate->builtins()->MakeError(),
                      Context::MAKE_ERROR_INDEX);
   }
 
   {  // -- E v a l E r r o r
@@ skipping 2815 matching lines @@
 }
 
 
 // Called when the top-level V8 mutex is destroyed.
 void Bootstrapper::FreeThreadResources() {
   DCHECK(!IsActive());
 }
 
 }  // namespace internal
 }  // namespace v8