[WIP] NumberToString operator in TF.

src/runtime/runtime-numbers.cc

 // Copyright 2014 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/runtime/runtime-utils.h"
 
 #include "src/arguments.h"
 #include "src/base/bits.h"
 #include "src/bootstrapper.h"
 #include "src/codegen.h"
@@ skipping 56 matching lines @@
   double value =
       StringToDouble(isolate->unicode_cache(), subject, ALLOW_TRAILING_JUNK,
                      std::numeric_limits<double>::quiet_NaN());
 
   return *isolate->factory()->NewNumber(value);
 }
 
 
 RUNTIME_FUNCTION(Runtime_NumberToString) {
   HandleScope scope(isolate);
-  DCHECK(args.length() == 1);
-  CONVERT_NUMBER_ARG_HANDLE_CHECKED(number, 0);
-
-  return *isolate->factory()->NumberToString(number);
+  DCHECK_LE(1, args.length());
+  DCHECK_GE(2, args.length());
+  CONVERT_NUMBER_ARG_HANDLE_CHECKED(value, 0);
+  if (args.length() == 1) return *isolate->factory()->NumberToString(value);
+  double value_number = value->Number();
+  CONVERT_INT32_ARG_CHECKED(radix, 1);
+  if (std::isnan(value_number)) return isolate->heap()->nan_string();
+  if (std::isinf(value_number)) {
+    return (value_number < 0.0) ? isolate->heap()->minus_infinity_string()
+                                : isolate->heap()->infinity_string();
+  }
+  char* const str = DoubleToRadixCString(value_number, radix);
+  Handle<String> result = isolate->factory()->NewStringFromAsciiChecked(str);
+  DeleteArray(str);
+  return *result;
 }
 
 
 RUNTIME_FUNCTION(Runtime_NumberToStringSkipCache) {
   HandleScope scope(isolate);
   DCHECK(args.length() == 1);
   CONVERT_NUMBER_ARG_HANDLE_CHECKED(number, 0);
 
   return *isolate->factory()->NumberToString(number, false);
 }
@@ skipping 126 matching lines @@
 
 RUNTIME_FUNCTION(Runtime_GetHoleNaNLower) {
   HandleScope scope(isolate);
   DCHECK(args.length() == 0);
   return *isolate->factory()->NewNumberFromUint(kHoleNanLower32);
 }
 
 
 }  // namespace internal
 }  // namespace v8