[js-perf-test] Add RegExp microbenchmarks

test/js-perf-test/RegExp/base_exec.js

+// Copyright 2016 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.
+
+load("base.js");
+
+var str;
+var re;
+
+function Exec() {
+  re.exec(str);
+}
+
+function Exec1Setup() {
+  re = /[Cz]/;
+  str = createHaystack();
+}
+
+function Exec2Setup() {
+  re = /[Cz]/g;
+  str = createHaystack();
+}
+
+function Exec3Setup() {
+  re = /([Cz])/y;
+  str = createHaystack();
+}
+
+function Exec4Setup() {
+  re = /[cZ]/;
+  str = createHaystack();
+}
+
+function Exec5Setup() {
+  re = /[cZ]/g;
+  str = createHaystack();
+}
+
+function Exec6Setup() {
+  re = /([cZ])/y;
+  str = createHaystack();
+}
+
+function Exec7Setup() {
+  re = /[Cz]/gy;
+  re.lastIndex = 2 ** 32;
+  str = createHaystack();
+}
+
+var benchmarks = [ [Exec, Exec1Setup],
+                   [Exec, Exec2Setup],
+                   [Exec, Exec3Setup],
+                   [Exec, Exec4Setup],
+                   [Exec, Exec5Setup],
+                   [Exec, Exec6Setup],
+                   [Exec, Exec7Setup],
+                 ];