Add some tests that validate debug info through ETW events

src/tests/JIT/Directed/debugging/debuginfo/README.txt

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+This directory contains tests for debugging information generated by the JIT.
+The tests are written in IL inside the tests.il file by creating a method in the
+DebugInfoMethods class and marking them with the ExpectedILMappings attribute.
+In that attribute, the IL offsets at which mappings are expected to be generated
+can be specified for both debug (DebuggableAttribute with
+DisableOptimizations) and optimized builds.
+
+To debug these tests, run the 'tester' project, which will JIT all methods in
+tests.il in both debug and release (you may need to turn off tiered
+compilation).
+
+* attribute.cs/csproj: Project containing ExpectedILMappingsAttribute, to avoid
+  circular dependencies
+
+* tests.il: File containing the tests marked with ExpectedILMappings
+
+* tests_d.ilproj/tests_r.ilproj: Both these projects just add tests.il, the only
+  difference is that the former has DebuggableAttribute with
+  DisableOptimizations and the latter does not.
+
+* tester.cs/csproj: The orchestrator of the tests, references tests_d and
+  tests_r and jits the test methods using RuntimeHelpers.PrepareMethod, collects
+  the IL mappings emitted using runtime events, and validates that the mappings
+  match the data in ExpectedILMappings.

src/tests/JIT/Directed/debugging/debuginfo/attribute.cs

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+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+using System;
+
+[AttributeUsage(AttributeTargets.Method)]
+public class ExpectedILMappings : Attribute
+{
+    public int[] Debug { get; set; }
+    public int[] Opts { get; set; }
+}

src/tests/JIT/Directed/debugging/debuginfo/attribute.csproj

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+<Project Sdk="Microsoft.NET.Sdk">
+  <PropertyGroup>
+    <OutputType>Library</OutputType>
+    <Optimize>false</Optimize>
+    <CLRTestKind>BuildOnly</CLRTestKind>
+  </PropertyGroup>
+  <ItemGroup>
+    <Compile Include="$(MSBuildProjectName).cs" />
+  </ItemGroup>
+</Project>

src/tests/JIT/Directed/debugging/debuginfo/isdebug.il

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+#define DEBUG

src/tests/JIT/Directed/debugging/debuginfo/tester.cs

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+extern alias tests_d;
+extern alias tests_r;
+
+using System;
+using System.Collections.Generic;
+using System.Diagnostics;
+using System.Diagnostics.Tracing;
+using System.Linq;
+using System.Reflection;
+using System.Runtime.CompilerServices;
+using Microsoft.Diagnostics.Tools.RuntimeClient;
+using Microsoft.Diagnostics.Tracing;
+using Microsoft.Diagnostics.Tracing.Parsers;
+using Microsoft.Diagnostics.Tracing.Parsers.Clr;
+using Tracing.Tests.Common;
+using DebugInfoMethodsD = tests_d::DebugInfoMethods;
+using DebugInfoMethodsR = tests_r::DebugInfoMethods;
+
+public unsafe class DebugInfoTest
+{
+    public static unsafe int Main()
+    {
+        var keywords =
+            ClrTraceEventParser.Keywords.Jit | ClrTraceEventParser.Keywords.JittedMethodILToNativeMap;
+
+        var dotnetRuntimeProvider = new List<Provider>
+        {
+            new Provider("Microsoft-Windows-DotNETRuntime", eventLevel: EventLevel.Verbose, keywords: (ulong)keywords)
+        };
+
+        var config = new SessionConfiguration(1024, EventPipeSerializationFormat.NetTrace, dotnetRuntimeProvider);
+
+        return
+            IpcTraceTest.RunAndValidateEventCounts(
+                new Dictionary<string, ExpectedEventCount>(),
+                JitMethods,
+                config,
+                ValidateMappings);
+    }
+
+    private static void JitMethods()
+    {
+        ProcessType(typeof(DebugInfoMethodsD));
+        ProcessType(typeof(DebugInfoMethodsR));
+    }
+
+    private static void ProcessType(Type t)
+    {
+        foreach (MethodInfo mi in t.GetMethods())
+        {
+            if (mi.GetCustomAttribute<ExpectedILMappings>() != null)
+            {
+                RuntimeHelpers.PrepareMethod(mi.MethodHandle);
+            }
+        }
+    }
+
+    private static Func<int> ValidateMappings(EventPipeEventSource source)
+    {
+        List<(long MethodID, OptimizationTier Tier, (int ILOffset, int NativeOffset)[] Mappings)> methodsWithMappings = new();
+        Dictionary<long, OptimizationTier> methodTier = new();
+
+        source.Clr.MethodLoad += e => methodTier[e.MethodID] = e.OptimizationTier;
+        source.Clr.MethodLoadVerbose += e => methodTier[e.MethodID] = e.OptimizationTier;
+        source.Clr.MethodILToNativeMap += e =>
+        {
+            var mappings = new (int, int)[e.CountOfMapEntries];
+            for (int i = 0; i < mappings.Length; i++)
+                mappings[i] = (e.ILOffset(i), e.NativeOffset(i));
+
+            if (!methodTier.TryGetValue(e.MethodID, out OptimizationTier tier))
+                tier = OptimizationTier.Unknown;
+
+            methodsWithMappings.Add((e.MethodID, tier, mappings));
+        };
+
+        return () =>
+        {
+            int result = 100;
+            foreach ((long methodID, OptimizationTier tier, (int ILOffset, int NativeOffset)[] mappings) in methodsWithMappings)
+            {
+                MethodBase meth = s_getMethodBaseByHandle(null, (IntPtr)(void*)methodID);
+                ExpectedILMappings attrib = meth.GetCustomAttribute<ExpectedILMappings>();
+                if (attrib == null)
+                {
+                    continue;
+                }
+
+                string name = $"[{meth.DeclaringType.Assembly.GetName().Name}]{meth.DeclaringType.FullName}.{meth.Name}";
+
+                // If DebuggableAttribute is saying that the assembly must be debuggable, then verify debug mappings.
+                // Otherwise verify release mappings.
+                // This may seem a little strange since we do not use the tier at all -- however, we expect debug
+                // to never tier and in release, we expect the release mappings to be the "least common denominator",
+                // i.e. tier0 and tier1 mappings should both be a superset.
+                // Note that tier0 and MinOptJitted differs in mappings generated exactly due to DebuggableAttribute.
+                DebuggableAttribute debuggableAttrib = meth.DeclaringType.Assembly.GetCustomAttribute<DebuggableAttribute>();
+                bool debuggableMappings = debuggableAttrib != null && debuggableAttrib.IsJITOptimizerDisabled;
+
+                Console.WriteLine("{0}: Validate mappings for {1} codegen (tier: {2})", name, debuggableMappings ? "debuggable" : "optimized", tier);
+
+                int[] expected = debuggableMappings ? attrib.Debug : attrib.Opts;
+                if (expected == null)
+                {
+                    continue;
+                }
+
+                if (!ValidateSingle(expected, mappings))
+                {
+                    Console.WriteLine("  Validation failed: expected mappings at IL offsets {0}", string.Join(", ", expected.Select(il => $"{il:x3}")));
+                    Console.WriteLine("  Actual (IL <-> native):");
+                    foreach ((int ilOffset, int nativeOffset) in mappings)
+                    {
+                        string ilOffsetName = Enum.IsDefined((SpecialILOffset)ilOffset) ? ((SpecialILOffset)ilOffset).ToString() : $"{ilOffset:x3}";
+                        Console.WriteLine("    {0:x3} <-> {1:x3}", ilOffsetName, nativeOffset);
+                    }
+
+                    result = -1;
+                }
+            }
+
+            return result;
+        };
+    }
+
+    // Validate that all IL offsets we expected had mappings generated for them.
+    private static bool ValidateSingle(int[] expected, (int ILOffset, int NativeOffset)[] mappings)
+    {
+        return expected.All(il => mappings.Any(t => t.ILOffset == il));
+    }
+
+    private enum SpecialILOffset
+    {
+        NoMapping = -1,
+        Prolog = -2,
+        Epilog = -3,
+    }
+
+    static DebugInfoTest()
+    {
+        Type runtimeMethodHandleInternalType = typeof(RuntimeMethodHandle).Assembly.GetType("System.RuntimeMethodHandleInternal");
+        Type runtimeTypeType = typeof(RuntimeMethodHandle).Assembly.GetType("System.RuntimeType");
+        MethodInfo getMethodBaseMethod = runtimeTypeType.GetMethod("GetMethodBase", BindingFlags.NonPublic | BindingFlags.Static, new[] { runtimeTypeType, runtimeMethodHandleInternalType });
+        s_getMethodBaseByHandle = (delegate*<object, IntPtr, MethodBase>)getMethodBaseMethod.MethodHandle .GetFunctionPointer();
+    }
+
+    // Needed to go from MethodID -> MethodBase
+    private static readonly delegate*<object, IntPtr, MethodBase> s_getMethodBaseByHandle;
+}

src/tests/JIT/Directed/debugging/debuginfo/tester.csproj

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+<Project Sdk="Microsoft.NET.Sdk">
+  <PropertyGroup>
+    <OutputType>Exe</OutputType>
+    <DebugType>PdbOnly</DebugType>
+    <Optimize>True</Optimize>
+    <AllowUnsafeBlocks>True</AllowUnsafeBlocks>
+  </PropertyGroup>
+  <ItemGroup>
+    <ProjectReference Include="tests_d.ilproj" Aliases="tests_d" />
+    <ProjectReference Include="tests_r.ilproj" Aliases="tests_r" />
+    <ProjectReference Include="attribute.csproj" />
+    <ProjectReference Include="../../../../tracing/eventpipe/common/common.csproj" />
+    <Compile Include="$(MSBuildProjectName).cs" />
+  </ItemGroup>
+</Project>