[regexp] Use consistent map checks for fast paths

src/builtins/builtins-regexp.cc

 // Copyright 2016 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/builtins/builtins-utils.h"
 #include "src/builtins/builtins.h"
 
 #include "src/code-factory.h"
 #include "src/regexp/jsregexp.h"
 #include "src/regexp/regexp-utils.h"
@@ skipping 1272 matching lines @@
 
   Factory* factory = isolate->factory();
 
   Handle<Object> string_obj = args.atOrUndefined(isolate, 1);
   Handle<Object> limit_obj = args.atOrUndefined(isolate, 2);
 
   Handle<String> string;
   ASSIGN_RETURN_FAILURE_ON_EXCEPTION(isolate, string,
                                      Object::ToString(isolate, string_obj));
 
+  if (RegExpUtils::IsUnmodifiedRegExp(isolate, recv)) {
+    RETURN_RESULT_OR_FAILURE(
+        isolate,
+        RegExpSplit(isolate, Handle<JSRegExp>::cast(recv), string, limit_obj));
+  }
+
   Handle<JSFunction> regexp_fun = isolate->regexp_function();
   Handle<Object> ctor;
   ASSIGN_RETURN_FAILURE_ON_EXCEPTION(
       isolate, ctor, SpeciesConstructor(isolate, recv, regexp_fun));
 
-  if (recv->IsJSRegExp() && *ctor == *regexp_fun) {
-    Handle<Object> exec;
-    ASSIGN_RETURN_FAILURE_ON_EXCEPTION(
-        isolate, exec, JSObject::GetProperty(
-                           recv, factory->NewStringFromAsciiChecked("exec")));
-    if (RegExpUtils::IsBuiltinExec(exec)) {
-      RETURN_RESULT_OR_FAILURE(
-          isolate, RegExpSplit(isolate, Handle<JSRegExp>::cast(recv), string,
-                               limit_obj));
-    }
-  }
-
   Handle<Object> flags_obj;
   ASSIGN_RETURN_FAILURE_ON_EXCEPTION(
       isolate, flags_obj, JSObject::GetProperty(recv, factory->flags_string()));
 
   Handle<String> flags;
   ASSIGN_RETURN_FAILURE_ON_EXCEPTION(isolate, flags,
                                      Object::ToString(isolate, flags_obj));
 
   Handle<String> u_str = factory->LookupSingleCharacterStringFromCode('u');
   const bool unicode = (String::IndexOf(isolate, flags, u_str, 0) >= 0);
@@ skipping 375 matching lines @@
   a->Bind(&if_matched);
   {
     Node* result = ConstructNewResultFromMatchInfo(isolate, a, context,
                                                    match_indices, string);
     a->Return(result);
   }
 }
 
 }  // namespace internal
 }  // namespace v8