Add some benchmarks for array deabstraction

See dotnet/runtime#108913

Author: AndyAyersMS

src/benchmarks/micro/runtime/DeAbstraction/Array.cs

@@ -0,0 +1,162 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using BenchmarkDotNet.Attributes;
+using MicroBenchmarks;
+using System.Collections.Generic;
+using System.Linq;
+using System.Runtime.CompilerServices;
+using System.Threading;
+
+[MemoryDiagnoser]
+ [BenchmarkCategory(Categories.Runtime)]
+public class ArrayDeAbstraction
+{
+    static readonly int[] s_ro_array;
+    static int[] s_array;
+    int[] m_array;
+
+    static int[] newArr() => new int[512];
+
+    [GlobalSetup]
+    public void Setup()
+    {
+        m_array = newArr();;
+    }
+
+    static ArrayDeAbstraction()
+    {
+        s_ro_array = newArr();
+        s_array = newArr();
+    }
+
+    static IEnumerable<int> get_static_readonly_array() => s_ro_array;
+    static IEnumerable<int> get_static_array() => s_array;
+    IEnumerable<int> get_member_array() => m_array;
+    [MethodImpl(MethodImplOptions.NoInlining)]
+    IEnumerable<int> get_opaque_array() => m_array;
+
+    [Benchmark(Baseline = true)]
+    public int foreach_static_readonly_array()
+    {
+        int sum = 0;
+        foreach (int i in s_ro_array) sum += i;
+        return sum;
+    }
+
+    [Benchmark]
+    public int foreach_static_readonly_array_via_local()
+    {
+        int[] e = s_ro_array;
+        int sum = 0;
+        foreach (int i in e) sum += i;
+        return sum;
+    }
+
+    [Benchmark]
+    public int foreach_static_readonly_array_via_interface()
+    {
+        IEnumerable<int> e = s_ro_array;
+        int sum = 0;
+        foreach (int i in e) sum += i;
+        return sum;
+    }
+
+    [Benchmark]
+    public int foreach_static_readonly_array_via_interface_property()
+    {
+        var e = get_static_readonly_array();
+        int sum = 0;
+        foreach (int i in e) sum += i;
+        return sum;
+    }
+
+    [Benchmark]
+    public int foreach_static_array()
+    {
+        int sum = 0;
+        foreach (int i in s_array) sum += i;
+        return sum;
+    }
+
+    [Benchmark]
+    public int foreach_static_array_via_local()
+    {
+        int[] e = s_array;
+        int sum = 0;
+        foreach (int i in e) sum += i;
+        return sum;
+    }
+
+    [Benchmark]
+    public int foreach_static_array_via_interface()
+    {
+        IEnumerable<int> e = s_array;
+        int sum = 0;
+        foreach (int i in e) sum += i;
+        return sum;
+    }
+
+    [Benchmark]
+    public int foreach_static_array_via_interface_property()
+    {
+        IEnumerable<int> e = get_static_array();
+        int sum = 0;
+        foreach (int i in e) sum += i;
+        return sum;
+    }
+
+    [Benchmark]
+    public int foreach_member_array()
+    {
+        int sum = 0;
+        foreach (int i in m_array) sum += i;
+        return sum;
+    }
+
+    [Benchmark]
+    public int foreach_member_array_via_local()
+    {
+        int[] e = m_array;
+        int sum = 0;
+        foreach (int i in e) sum += i;
+        return sum;
+    }
+
+    [Benchmark]
+    public int foreach_member_array_via_interface()
+    {
+        IEnumerable<int> e = m_array;
+        int sum = 0;
+        foreach (int i in e) sum += i;
+        return sum;
+    }
+
+    [Benchmark]
+    public int foreach_member_array_via_interface_property()
+    {
+        IEnumerable<int> e = get_member_array();
+        int sum = 0;
+        foreach (int i in e) sum += i;
+        return sum;
+    }
+
+    [Benchmark]
+    public int foreach_opaque_array_via_interface()
+    {
+        IEnumerable<int> e = get_opaque_array();
+        int sum = 0;
+        foreach (int i in e) sum += i;
+        return sum;
+    }
+
+    [Benchmark]
+    public int sum_static_array_via_local()
+    {
+        int[] a = s_array;
+        IEnumerable<int> e = a;
+        return e.Sum();
+    }
+}
+