benchmark: add util.format benchmark

PR-URL: https://github.com/nodejs/node/pull/5360
Reviewed-By: James M Snell <jasnell@gmail.com>

benchmark/util/format.js

@@ -0,0 +1,40 @@
+'use strict';
+
+const util = require('util');
+const common = require('../common');
+const v8 = require('v8');
+const bench = common.createBenchmark(main, {
+  n: [1e6]
+, type: ['string',
+         'number',
+         'object',
+         'unknown',
+         'no-replace']
+});
+
+const inputs = {
+  'string': ['Hello, my name is %s', 'fred'],
+  'number': ['Hi, I was born in %d', 1942],
+  'object': ['An error occurred %j', {msg: 'This is an error', code: 'ERR'}],
+  'unknown': ['hello %a', 'test'],
+  'no-replace': [1, 2]
+};
+
+function main(conf) {
+  const n = conf.n | 0;
+  const type = conf.type;
+
+  const input = inputs[type];
+
+  v8.setFlagsFromString('--allow_natives_syntax');
+
+  util.format(input[0], input[1]);
+  eval('%OptimizeFunctionOnNextCall(util.format)');
+  util.format(input[0], input[1]);
+
+  bench.start();
+  for (var i = 0; i < n; i++) {
+    util.format(input[0], input[1]);
+  }
+  bench.end(n);
+}