[builtins] Simplify String constructor code.

src/x64/macro-assembler-x64.h

 // 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.
 
 #ifndef V8_X64_MACRO_ASSEMBLER_X64_H_
 #define V8_X64_MACRO_ASSEMBLER_X64_H_
 
 #include "src/assembler.h"
 #include "src/bailout-reason.h"
 #include "src/base/flags.h"
@@ skipping 741 matching lines @@
   // Reconstruct a raw integer with pointer size from two integers masquerading
   // as smis on the top of stack.
   void PopRegisterAsTwoSmis(Register dst, Register scratch = kScratchRegister);
 
   void Test(const Operand& dst, Smi* source);
 
 
   // ---------------------------------------------------------------------------
   // String macros.
 
-  // Generate code to do a lookup in the number string cache. If the number in
-  // the register object is found in the cache the generated code falls through
-  // with the result in the result register. The object and the result register
-  // can be the same. If the number is not found in the cache the code jumps to
-  // the label not_found with only the content of register object unchanged.
-  void LookupNumberStringCache(Register object,
-                               Register result,
-                               Register scratch1,
-                               Register scratch2,
-                               Label* not_found);
-
   // If object is a string, its map is loaded into object_map.
   void JumpIfNotString(Register object,
                        Register object_map,
                        Label* not_string,
                        Label::Distance near_jump = Label::kFar);
 
 
   void JumpIfNotBothSequentialOneByteStrings(
       Register first_object, Register second_object, Register scratch1,
       Register scratch2, Label* on_not_both_flat_one_byte,
@@ skipping 861 matching lines @@
     masm->popfq();                                                           \
   }                                                                          \
   masm->
 #else
 #define ACCESS_MASM(masm) masm->
 #endif
 
 } }  // namespace v8::internal
 
 #endif  // V8_X64_MACRO_ASSEMBLER_X64_H_