[stubs] Port StringAddStub to TF

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 1512 matching lines @@
       a->Bind(&if_replaceisempty);
       {
         // TODO(jgruber): We could skip many of the checks that using SubString
         // here entails.
 
         Node* const first_part =
             a->SubString(context, subject_string, subject_start, match_start);
         Node* const second_part =
             a->SubString(context, subject_string, match_end, subject_end);
 
-        Node* const result = a->StringConcat(context, first_part, second_part);
+        Node* const result = a->StringAdd(context, first_part, second_part);
         var_result.Bind(result);
         a->Goto(&out);
       }
 
       a->Bind(&if_replaceisnotempty);
       {
         Node* const first_part =
             a->SubString(context, subject_string, subject_start, match_start);
         Node* const second_part = replace_string;
         Node* const third_part =
             a->SubString(context, subject_string, match_end, subject_end);
 
-        Node* result = a->StringConcat(context, first_part, second_part);
-        result = a->StringConcat(context, result, third_part);
+        Node* result = a->StringAdd(context, first_part, second_part);
+        result = a->StringAdd(context, result, third_part);
 
         var_result.Bind(result);
         a->Goto(&out);
       }
     }
   }
 
   a->Bind(&out);
   return var_result.value();
 }
@@ skipping 100 matching lines @@
   a->Bind(&if_matched);
   {
     Node* result = ConstructNewResultFromMatchInfo(isolate, a, context,
                                                    match_indices, string);
     a->Return(result);
   }
 }
 
 }  // namespace internal
 }  // namespace v8