[builtins] Remove STRING_ADD_LEFT and STRING_ADD_RIGHT builtins.

src/runtime.js

 // Copyright 2006-2008 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.
 
 // This files contains runtime support implemented in JavaScript.
 
 // CAUTION: Some of the functions specified in this file are called
 // directly from compiled code. These are the functions with names in
 // ALL CAPS. The compiled code passes the first argument in 'this'.
 
@@ skipping 132 matching lines @@
 
 // Strong mode COMPARE throws if an implicit conversion would be performed
 function COMPARE_STRONG(x, ncr) {
   if (IS_STRING(this) && IS_STRING(x)) return %_StringCompare(this, x);
   if (IS_NUMBER(this) && IS_NUMBER(x)) return %NumberCompare(this, x, ncr);
 
   throw %make_type_error(kStrongImplicitConversion);
 }
 
 
-
-/* -----------------------------------
-   - - -   A r i t h m e t i c   - - -
-   -----------------------------------
-*/
-
-// Left operand (this) is already a string.
-function STRING_ADD_LEFT(y) {
-  if (!IS_STRING(y)) {
-    if (IS_STRING_WRAPPER(y) && %_IsStringWrapperSafeForDefaultValueOf(y)) {
-      y = %_ValueOf(y);
-    } else {
-      y = IS_NUMBER(y)
-          ? %_NumberToString(y)
-          : %to_string_fun(%to_primitive(y, NO_HINT));
-    }
-  }
-  return %_StringAdd(this, y);
-}
-
-
-// Right operand (y) is already a string.
-function STRING_ADD_RIGHT(y) {
-  var x = this;
-  if (!IS_STRING(x)) {
-    if (IS_STRING_WRAPPER(x) && %_IsStringWrapperSafeForDefaultValueOf(x)) {
-      x = %_ValueOf(x);
-    } else {
-      x = IS_NUMBER(x)
-          ? %_NumberToString(x)
-          : %to_string_fun(%to_primitive(x, NO_HINT));
-    }
-  }
-  return %_StringAdd(x, y);
-}
-
-
 /* -----------------------------
    - - -   H e l p e r s   - - -
    -----------------------------
 */
 
 function APPLY_PREPARE(args) {
   var length;
 
   // First check that the receiver is callable.
   if (!IS_CALLABLE(this)) {
@@ skipping 331 matching lines @@
 $toString = ToString;
 
 %InstallToContext([
   "apply_prepare_builtin", APPLY_PREPARE,
   "compare_builtin", COMPARE,
   "compare_strong_builtin", COMPARE_STRONG,
   "concat_iterable_to_array_builtin", CONCAT_ITERABLE_TO_ARRAY,
   "equals_builtin", EQUALS,
   "reflect_apply_prepare_builtin", REFLECT_APPLY_PREPARE,
   "reflect_construct_prepare_builtin", REFLECT_CONSTRUCT_PREPARE,
-  "string_add_left_builtin", STRING_ADD_LEFT,
-  "string_add_right_builtin", STRING_ADD_RIGHT,
 ]);
 
 %InstallToContext([
   "concat_iterable_to_array", ConcatIterableToArray,
   "non_number_to_number", NonNumberToNumber,
   "non_string_to_string", NonStringToString,
   "to_integer_fun", ToInteger,
   "to_length_fun", ToLength,
   "to_number_fun", ToNumber,
   "to_primitive", ToPrimitive,
   "to_string_fun", ToString,
 ]);
 
 utils.Export(function(to) {
   to.ToBoolean = ToBoolean;
   to.ToLength = ToLength;
   to.ToNumber = ToNumber;
   to.ToPrimitive = ToPrimitive;
   to.ToString = ToString;
 });
 
 })