Add benchmarking for custom string comparer

osu.Game.Benchmarks/BenchmarkStringComparison.cs

@@ -0,0 +1,48 @@
+// Copyright (c) ppy Pty Ltd <contact@ppy.sh>. Licensed under the MIT Licence.
+// See the LICENCE file in the repository root for full licence text.
+
+using System;
+using System.Collections.Generic;
+using BenchmarkDotNet.Attributes;
+using osu.Game.Utils;
+
+namespace osu.Game.Benchmarks
+{
+    public class BenchmarkStringComparison
+    {
+        private string[] strings = null!;
+
+        [GlobalSetup]
+        public void GlobalSetUp()
+        {
+            strings = new string[10000];
+
+            for (int i = 0; i < strings.Length; ++i)
+                strings[i] = Guid.NewGuid().ToString();
+
+            for (int i = 0; i < strings.Length; ++i)
+            {
+                if (i % 2 == 0)
+                    strings[i] = strings[i].ToUpperInvariant();
+            }
+        }
+
+        [Benchmark]
+        public void OrdinalIgnoreCase() => compare(StringComparer.OrdinalIgnoreCase);
+
+        [Benchmark]
+        public void OrdinalSortByCase() => compare(OrdinalSortByCaseStringComparer.INSTANCE);
+
+        [Benchmark]
+        public void InvariantCulture() => compare(StringComparer.InvariantCulture);
+
+        private void compare(IComparer<string> comparer)
+        {
+            for (int i = 0; i < strings.Length; ++i)
+            {
+                for (int j = i + 1; j < strings.Length; ++j)
+                    _ = comparer.Compare(strings[i], strings[j]);
+            }
+        }
+    }
+}