Revert of [stubs] Port SubStringStub to TurboFan

src/code-stubs.cc

 // Copyright 2012 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/code-stubs.h"
 
 #include <sstream>
 
 #include "src/ast/ast.h"
 #include "src/bootstrapper.h"
@@ skipping 2670 matching lines @@
     result_var.Bind(assembler->ChangeFloat64ToTagged(fdec_result));
     assembler->Goto(&end);
   }
 
   assembler->Bind(&end);
   assembler->UpdateFeedback(var_type_feedback.value(), type_feedback_vector,
                             slot_id);
   return result_var.value();
 }
 
-// ES6 section 21.1.3.19 String.prototype.substring ( start, end )
-compiler::Node* SubStringStub::Generate(CodeStubAssembler* assembler,
-                                        compiler::Node* string,
-                                        compiler::Node* from,
-                                        compiler::Node* to,
-                                        compiler::Node* context) {
-  return assembler->SubString(context, string, from, to);
-}
-
 // ES6 section 7.1.13 ToObject (argument)
 void ToObjectStub::GenerateAssembly(CodeStubAssembler* assembler) const {
   typedef compiler::Node Node;
   typedef CodeStubAssembler::Label Label;
   typedef CodeStubAssembler::Variable Variable;
 
   Label if_number(assembler, Label::kDeferred), if_notsmi(assembler),
       if_jsreceiver(assembler), if_noconstructor(assembler, Label::kDeferred),
       if_wrapjsvalue(assembler);
 
@@ skipping 3607 matching lines @@
 
   if (type == MachineType::Pointer()) {
     return Representation::External();
   }
 
   return Representation::Tagged();
 }
 
 }  // namespace internal
 }  // namespace v8