Add a few struct promotion related benchmarks

src/benchmarks/micro/runtime/Struct/FilteredSpanEnumerator.cs

@@ -0,0 +1,68 @@
+// 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;
+using System.Linq;
+using System.Runtime.CompilerServices;
+
+namespace Struct
+{
+    [BenchmarkCategory(Categories.Runtime, Categories.JIT)]
+    public class FilteredSpanEnumerator
+    {
+        private int[] _array;
+        private int[] _inds;
+
+        [GlobalSetup]
+        public void Setup()
+        {
+            _array = Enumerable.Range(0, 10000).ToArray();
+            _inds = Enumerable.Range(0, 10000).ToArray();
+        }
+
+        [Benchmark]
+        public int Sum()
+        {
+            int sum = 0;
+            foreach (int s in new FilteredSpanEnumerator<int>(_array, _inds))
+            {
+                sum += s;
+            }
+
+            return sum;
+        }
+    }
+
+    public ref struct FilteredSpanEnumerator<T>
+    {
+        private readonly ReadOnlySpan<T> arr;
+        private readonly int[] inds;
+
+        private T current;
+        private int i;
+
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public FilteredSpanEnumerator(ReadOnlySpan<T> arr, int[] inds) {
+            this.arr = arr;
+            this.inds = inds;
+            current = default;
+            i = 0;
+        }
+
+        public T Current => current;
+
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public bool MoveNext() {
+            if (i >= inds.Length)
+                return false;
+
+            current = arr[inds[i++]];
+            return true;
+        }
+
+        public FilteredSpanEnumerator<T> GetEnumerator() => this;
+    }
+}

src/benchmarks/micro/runtime/Struct/GSeq.cs

@@ -0,0 +1,215 @@
+// 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.Collections;
+using System.Linq;
+
+namespace Struct
+{
+    [BenchmarkCategory(Categories.Runtime, Categories.JIT)]
+    public class GSeq
+    {
+        private int[] _array;
+
+        [GlobalSetup]
+        public void Setup()
+        {
+            _array = Enumerable.Range(0, 10000).ToArray();
+        }
+
+        [Benchmark]
+        public int FilterSkipMapSum()
+        {
+            var arr = new ArrayEnumerator<int>(_array);
+            var filter = new FilterEnumerator<int, ArrayEnumerator<int>, FilterIsOdd>(arr, new FilterIsOdd());
+            var skip = new SkipEnumerator<int, FilterEnumerator<int, ArrayEnumerator<int>, FilterIsOdd>>(5, filter);
+            var map =
+                new MapEnumerator<int, int,
+                    SkipEnumerator<int, FilterEnumerator<int, ArrayEnumerator<int>, FilterIsOdd>>, Plus15Mapper>(
+                    skip,
+                    new Plus15Mapper());
+            return Fold2<int, int,
+                MapEnumerator<int, int,
+                    SkipEnumerator<int, FilterEnumerator<int, ArrayEnumerator<int>, FilterIsOdd>>,
+                    Plus15Mapper>, FoldPlus>(map, 0, new FoldPlus());
+        }
+
+        public static TOut Fold2<TIn, TOut, TEnumerator, TFolder>(TEnumerator enumerator, TOut initial,
+            TFolder folder)
+            where TEnumerator : struct, IEnumerator<TIn>
+            where TFolder : struct, IInvokable<TOut, TIn, TOut>
+        {
+            while (enumerator.MoveNext())
+                initial = folder.Invoke(initial, enumerator.Current);
+
+            return initial;
+        }
+    }
+
+    public interface IInvokable<TIn1, TOut>
+    {
+        TOut Invoke(TIn1 value);
+    }
+
+    public interface IInvokable<TIn1, TIn2, TOut>
+    {
+        TOut Invoke(TIn1 value1, TIn2 value2);
+    }
+
+
+    public readonly struct Plus15Mapper : IInvokable<int, int>
+    {
+        public int Invoke(int value) => value + 15;
+    }
+
+    public readonly struct FilterIsOdd : IInvokable<int, bool>
+    {
+        public bool Invoke(int value) => value % 2 == 1;
+    }
+
+    public readonly struct FoldPlus : IInvokable<int, int, int>
+    {
+        public int Invoke(int value1, int value2) => value1 + value2;
+    }
+
+    public struct ArrayEnumerator<T> : IEnumerator<T>
+    {
+        private readonly T[] _array;
+        private int _count;
+
+        public ArrayEnumerator(T[] array)
+        {
+            _array = array;
+            _count = -1;
+        }
+
+
+        public bool MoveNext()
+        {
+            _count++;
+            return (uint)_count < (uint)_array.Length;
+        }
+
+        public void Reset()
+        {
+        }
+
+        public T Current => _array[_count];
+
+        object IEnumerator.Current => Current;
+
+        public void Dispose()
+        {
+        }
+    }
+
+    public struct SkipEnumerator<T, TEnumerator> : IEnumerator<T>
+        where TEnumerator : struct, IEnumerator<T>
+    {
+        private TEnumerator _enumerator;
+        private int _skipCount;
+
+        public SkipEnumerator(int skipCount, TEnumerator enumerator)
+        {
+            _skipCount = skipCount;
+            _enumerator = enumerator;
+        }
+
+        public bool MoveNext()
+        {
+            while (_skipCount > 0)
+            {
+                if (!_enumerator.MoveNext())
+                    return false;
+                _skipCount--;
+            }
+
+            return _enumerator.MoveNext();
+        }
+
+        public void Reset()
+        {
+        }
+
+        public T Current => _enumerator.Current;
+
+        object IEnumerator.Current => Current;
+
+        public void Dispose()
+        {
+        }
+    }
+
+    public struct MapEnumerator<T, TOut, TEnumerator, TMapper> : IEnumerator<TOut>
+        where TEnumerator : struct, IEnumerator<T>
+        where TMapper : struct, IInvokable<T, TOut>
+    {
+        private TEnumerator _enumerator;
+        private TMapper _mapper;
+
+        public MapEnumerator(TEnumerator enumerator, TMapper mapper)
+        {
+            _enumerator = enumerator;
+            _mapper = mapper;
+        }
+
+        public bool MoveNext()
+        {
+            return _enumerator.MoveNext();
+        }
+
+        public void Reset()
+        {
+        }
+
+        public TOut Current => _mapper.Invoke(_enumerator.Current);
+
+        object IEnumerator.Current => Current;
+
+        public void Dispose()
+        {
+        }
+    }
+
+    public struct FilterEnumerator<T, TEnumerator, TFilter> : IEnumerator<T>
+        where TEnumerator : struct, IEnumerator<T>
+        where TFilter : struct, IInvokable<T, bool>
+    {
+        private TEnumerator _enumerator;
+        private TFilter _filter;
+
+        public FilterEnumerator(TEnumerator enumerator, TFilter filter)
+        {
+            _enumerator = enumerator;
+            _filter = filter;
+        }
+
+        public bool MoveNext()
+        {
+            while (_enumerator.MoveNext())
+            {
+                if (_filter.Invoke(_enumerator.Current))
+                    return true;
+            }
+
+            return false;
+        }
+
+        public void Reset()
+        {
+        }
+
+        public T Current => _enumerator.Current;
+
+        object IEnumerator.Current => Current;
+
+        public void Dispose()
+        {
+        }
+    }
+
+}

src/benchmarks/micro/runtime/Struct/SpanWrapper.cs

@@ -0,0 +1,62 @@
+// 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.Linq;
+using System;
+using System.Runtime.CompilerServices;
+
+namespace Struct
+{
+    [BenchmarkCategory(Categories.Runtime, Categories.JIT)]
+    public class SpanWrapper
+    {
+        private int[] _array;
+
+        [GlobalSetup]
+        public void Setup()
+        {
+            _array = Enumerable.Range(0, 10000).ToArray();
+        }
+
+        [Benchmark]
+        public int BaselineSum()
+        {
+            return SumSpan(_array);
+        }
+
+        [Benchmark]
+        public int WrapperSum()
+        {
+            return SumSpanWrapper(new SpanWrapper<int> { Span = _array });
+        }
+
+        [MethodImpl(MethodImplOptions.NoInlining)]
+        private int SumSpan(ReadOnlySpan<int> span)
+        {
+            int sum = 0;
+            foreach (int val in span)
+                sum += val;
+
+            return sum;
+        }
+
+        [MethodImpl(MethodImplOptions.NoInlining)]
+        private int SumSpanWrapper(SpanWrapper<int> spanWrapper)
+        {
+            int sum = 0;
+            foreach (int val in spanWrapper)
+                sum += val;
+
+            return sum;
+        }
+    }
+
+    public ref struct SpanWrapper<T>
+    {
+        public ReadOnlySpan<T> Span;
+        public ReadOnlySpan<T>.Enumerator GetEnumerator() => Span.GetEnumerator();
+    }
+}