[string] Add a perf test for String.p.split

Bug: v8:7103
Change-Id: I86e208de38aad1d41c65d39b94996012efa1346b
Reviewed-on: https://chromium-review.googlesource.com/1045949
Commit-Queue: Jakob Gruber <jgruber@chromium.org>
Reviewed-by: Jakob Gruber <jgruber@chromium.org>
Cr-Commit-Position: refs/heads/master@{#53063}

test/js-perf-test/JSTests.json

@@ -237,6 +237,24 @@
             {"name": "StringIndexOfNonConstant"}
           ]
         },
+        {
+          "name": "StringSplit",
+          "main": "run.js",
+          "resources": [ "string-split.js" ],
+          "test_flags": [ "string-split" ],
+          "results_regexp": "^%s\\-Strings\\(Score\\): (.+)$",
+          "run_count": 1,
+          "tests": [
+            {"name": "ShortSubjectEmptySeparator"},
+            {"name": "LongSubjectEmptySeparator"},
+            {"name": "ShortTwoBytesSubjectEmptySeparator"},
+            {"name": "LongTwoBytesSubjectEmptySeparator"},
+            {"name": "ShortSubject"},
+            {"name": "LongSubject"},
+            {"name": "ShortTwoBytesSubject"},
+            {"name": "LongTwoBytesSubject"}
+          ]
+        },
         {
           "name": "StringAt",
           "main": "run.js",

test/js-perf-test/Strings/string-split.js

+// Copyright 2018 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.
+
+new BenchmarkSuite('ShortSubjectEmptySeparator', [5], [
+  new Benchmark('ShortSubjectEmptySeparator', true, false, 0,
+  ShortSubjectEmptySeparator),
+]);
+
+new BenchmarkSuite('LongSubjectEmptySeparator', [1000], [
+  new Benchmark('LongSubjectEmptySeparator', true, false, 0,
+  LongSubjectEmptySeparator),
+]);
+
+new BenchmarkSuite('ShortTwoBytesSubjectEmptySeparator', [5], [
+  new Benchmark('ShortTwoBytesSubjectEmptySeparator', true, false, 0,
+  ShortTwoBytesSubjectEmptySeparator),
+]);
+
+new BenchmarkSuite('LongTwoBytesSubjectEmptySeparator', [1000], [
+  new Benchmark('LongTwoBytesSubjectEmptySeparator', true, false, 0,
+  LongTwoBytesSubjectEmptySeparator),
+]);
+
+new BenchmarkSuite('ShortSubject', [5], [
+  new Benchmark('ShortSubject', true, false, 0,
+  ShortSubject),
+]);
+
+new BenchmarkSuite('LongSubject', [1000], [
+  new Benchmark('LongSubject', true, false, 0,
+  LongSubject),
+]);
+
+new BenchmarkSuite('ShortTwoBytesSubject', [5], [
+  new Benchmark('ShortTwoBytesSubject', true, false, 0,
+  ShortTwoBytesSubject),
+]);
+
+new BenchmarkSuite('LongTwoBytesSubject', [1000], [
+  new Benchmark('LongTwoBytesSubject', true, false, 0,
+  LongTwoBytesSubject),
+]);
+
+const shortString = "ababaabcdeaaaaaab";
+const shortTwoBytesString = "\u0429\u0428\u0428\u0429\u0429\u0429\u0428\u0429\u0429";
+// Use Array.join to create a flat string
+const longString = new Array(0x500).fill("abcde").join('');
+const longTwoBytesString = new Array(0x500).fill("\u0427\u0428\u0429\u0430").join('');
+
+function ShortSubjectEmptySeparator() {
+  shortString.split('');
+}
+
+function LongSubjectEmptySeparator() {
+  longString.split('');
+}
+
+function ShortTwoBytesSubjectEmptySeparator() {
+  shortTwoBytesString.split('');
+}
+
+function LongTwoBytesSubjectEmptySeparator() {
+  longTwoBytesString.split('');
+}
+
+function ShortSubject() {
+  shortString.split('a');
+}
+
+function LongSubject() {
+  longString.split('a');
+}
+
+function ShortTwoBytesSubject() {
+  shortTwoBytesString.split('\u0428');
+}
+
+function LongTwoBytesSubject() {
+  longTwoBytesString.split('\u0428');
+}