Add CSV benchmarks for string.Split

src/benchmarks/micro/MicroBenchmarks.csproj

@@ -116,6 +116,9 @@
     <None Update="libraries\System.IO.Compression\TestData\**">
       <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
     </None>
+    <None Update="libraries\System.Runtime\TestData\**">
+      <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
+    </None>
     <None Update="libraries\System.Text.RegularExpressions\TestData\**">
       <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
     </None>

src/benchmarks/micro/libraries/System.Runtime/Perf.String.cs

@@ -3,6 +3,7 @@
 // See the LICENSE file in the project root for more information.
 
 using System.Collections.Generic;
+using System.IO;
 using System.Linq;
 using BenchmarkDotNet.Attributes;
 using MicroBenchmarks;
@@ -292,6 +293,48 @@ public int IndexerCheckPathLength()
             return counter;
         }
 
+        // Retrieved from https://data.cms.gov/sites/default/files/2024-05/b492c960-aea2-4f4e-a5f6-258c726b1a58/TMEDTREND_PUBLIC_240528.csv on Jan 22, 2025
+        private static readonly Lazy<string[]> s_csvShortText = new Lazy<string[]>(() => ReadInputFile("TMEDTREND_PUBLIC_240528.csv"));
+        // Retrieved from https://data.transportation.gov/api/views/kbvr-tyu5/rows.csv on Jan 22, 2025
+        private static readonly Lazy<string[]> s_csvShortMixed = new Lazy<string[]>(() => ReadInputFile("motor_fuel_sales.csv"));
+        // Retrieved from https://www.census.gov/econ/bfs/csv/date_table.csv on Jan 22, 2025
+        private static readonly Lazy<string[]> s_csvShortDates = new Lazy<string[]>(() => ReadInputFile("date_table.csv"));
+        // Retrieved from https://www.usda.gov/sites/default/files/documents/ai_inventory.csv on Jan 22, 2025
+        private static readonly Lazy<string[]> s_csvLongText = new Lazy<string[]>(() => ReadInputFile("ai_inventory.csv"));
+        // Retrieved from https://www.epa.gov/sites/production/files/2014-05/tri_2012_nd.csv on Jan 22, 2025
+        private static readonly Lazy<string[]> s_csvLongMixed = new Lazy<string[]>(() => ReadInputFile("tri_2012_nd.csv"));
+        // Retrieved from https://data.cdc.gov/api/views/dxpw-cm5u/rows.csv on Jan 22, 2025
+        private static readonly Lazy<string[]> s_csvLongNumbers = new Lazy<string[]>(() => ReadInputFile("500_cities.csv"));
+        private static volatile int s_splitCsvFieldCount;
+
+        public static IEnumerable<object[]> CsvCorpus()
+        {
+            yield return new object[] { "Short Text", s_csvShortText.Value };
+            yield return new object[] { "Short Mixed", s_csvShortMixed.Value };
+            yield return new object[] { "Short Dates", s_csvShortDates.Value };
+            yield return new object[] { "Long Text", s_csvLongText.Value };
+            yield return new object[] { "Long Mixed", s_csvLongMixed.Value };
+            yield return new object[] { "Long Numbers", s_csvLongNumbers.Value };
+        }
+
+        public static string[] ReadInputFile(string name)
+            => File.ReadAllLines(Path.Combine(AppContext.BaseDirectory, "libraries", "System.Runtime", "TestData", name));
+
+        [Benchmark]
+        [ArgumentsSource(nameof(CsvCorpus))]
+        public string[] Split_Csv(string testName, string[] lines)
+        {
+            string[] split = null;
+            int fieldCount = 0;
+            for (int i = 0; i < lines.Length; i++)
+            {
+                split = lines[i].Split(',');
+                fieldCount ^= split.Length;
+            }
+            s_splitCsvFieldCount = fieldCount;
+            return split;
+        }
+
         [System.Runtime.CompilerServices.MethodImpl(System.Runtime.CompilerServices.MethodImplOptions.NoInlining)]
         private static char getStringCharNoInline(string str, int index)
         {

src/benchmarks/micro/libraries/System.Runtime/TestData/THIRD-PARTY-NOTICES.TXT

@@ -0,0 +1,34 @@
+The CSV files in this directory are sourced from public U.S. government
+data portals and are in the public domain under U.S. law (17 U.S.C. § 105).
+
+TMEDTREND_PUBLIC_240528.csv
+  Source: https://data.cms.gov/sites/default/files/2024-05/b492c960-aea2-4f4e-a5f6-258c726b1a58/TMEDTREND_PUBLIC_240528.csv
+  Retrieved: January 22, 2025
+  Provider: Centers for Medicare & Medicaid Services (CMS)
+
+motor_fuel_sales.csv
+  Source: https://data.transportation.gov/api/views/kbvr-tyu5/rows.csv
+  Original name: Monthly Motor Fuel Sales Reported by States, Selected Data from FHWA Monthly Motor Fuel Report
+  Retrieved: January 22, 2025
+  Provider: U.S. Department of Transportation
+
+date_table.csv
+  Source: https://www.census.gov/econ/bfs/csv/date_table.csv
+  Retrieved: January 22, 2025
+  Provider: U.S. Census Bureau
+
+ai_inventory.csv
+  Source: https://www.usda.gov/sites/default/files/documents/ai_inventory.csv
+  Retrieved: January 22, 2025
+  Provider: U.S. Department of Agriculture (USDA)
+
+tri_2012_nd.csv
+  Source: https://www.epa.gov/sites/production/files/2014-05/tri_2012_nd.csv
+  Retrieved: January 22, 2025
+  Provider: U.S. Environmental Protection Agency (EPA)
+
+500_cities.csv
+  Source: https://data.cdc.gov/api/views/dxpw-cm5u/rows.csv
+  Original name: 500 Cities: City-level Data (GIS Friendly Format), 2019 release
+  Retrieved: January 22, 2025
+  Provider: Centers for Disease Control and Prevention (CDC)