Improve performance on virtual method processing (dotnet#100897)

The _virtual_methods cache had duplicates due to the Scope item in the tuple, which made ProcessVirtualMethods do significantly more work. This PR makes the cache a dictionary, with TryAdd's instead of Add to only add each method once. These changes made caused the overrides cache in TypeMapInfo to be modified during iteration, so a for loop is used instead of a foreach loop. This should be find since the list will always be append-only. I noticed we copy _typesWithInterfaces to an array for the same reason, though since that's also append-only we can iterate with a for loop there, too.

Fixes dotnet/sdk#40060.

src/tools/illink/src/linker/Linker.Steps/MarkStep.cs

@@ -60,7 +60,7 @@ protected LinkContext Context {
 		}
 
 		protected Queue<(MethodDefinition, DependencyInfo, MessageOrigin)> _methods;
-		protected HashSet<(MethodDefinition, MarkScopeStack.Scope)> _virtual_methods;
+		protected Dictionary<MethodDefinition, MarkScopeStack.Scope> _virtual_methods;
 		protected Queue<AttributeProviderPair> _assemblyLevelAttributes;
 		readonly List<AttributeProviderPair> _ivt_attributes;
 		protected Queue<(AttributeProviderPair, DependencyInfo, MarkScopeStack.Scope)> _lateMarkedAttributes;
@@ -220,7 +220,7 @@ internal DynamicallyAccessedMembersTypeHierarchy DynamicallyAccessedMembersTypeH
 		public MarkStep ()
 		{
 			_methods = new Queue<(MethodDefinition, DependencyInfo, MessageOrigin)> ();
-			_virtual_methods = new HashSet<(MethodDefinition, MarkScopeStack.Scope)> ();
+			_virtual_methods = new Dictionary<MethodDefinition, MarkScopeStack.Scope> ();
 			_assemblyLevelAttributes = new Queue<AttributeProviderPair> ();
 			_ivt_attributes = new List<AttributeProviderPair> ();
 			_lateMarkedAttributes = new Queue<(AttributeProviderPair, DependencyInfo, MarkScopeStack.Scope)> ();
@@ -588,10 +588,8 @@ void ProcessMarkedTypesWithInterfaces ()
 			// We may mark an interface type later on.  Which means we need to reprocess any time with one or more interface implementations that have not been marked
 			// and if an interface type is found to be marked and implementation is not marked, then we need to mark that implementation
 
-			// copy the data to avoid modified while enumerating error potential, which can happen under certain conditions.
-			var typesWithInterfaces = _typesWithInterfaces.ToArray ();
-
-			foreach ((var type, var scope) in typesWithInterfaces) {
+			for (int i = 0; i < _typesWithInterfaces.Count; i++) {
+				(var type, var scope) = _typesWithInterfaces[i];
 				// Exception, types that have not been flagged as instantiated yet.  These types may not need their interfaces even if the
 				// interface type is marked
 				// UnusedInterfaces optimization is turned off mark all interface implementations
@@ -609,7 +607,7 @@ void ProcessMarkedTypesWithInterfaces ()
 							continue;
 						foreach (var ov in baseMethods) {
 							if (ov.Base.DeclaringType is not null && ov.Base.DeclaringType.IsInterface && IgnoreScope (ov.Base.DeclaringType.Scope)) {
-								_virtual_methods.Add ((ov.Base, ScopeStack.CurrentScope));
+								_virtual_methods.TryAdd (ov.Base, ScopeStack.CurrentScope);
 							}
 						}
 					}
@@ -707,9 +705,10 @@ void ProcessVirtualMethod (MethodDefinition method)
 							MarkMethod (dimInfo.Override, new DependencyInfo (DependencyKind.Override, dimInfo.Base), ScopeStack.CurrentScope.Origin);
 					}
 				}
-				var overridingMethods = Annotations.GetOverrides (method);
+				List<OverrideInformation>? overridingMethods = (List<OverrideInformation>?)Annotations.GetOverrides (method);
 				if (overridingMethods is not null) {
-					foreach (OverrideInformation ov in overridingMethods) {
+					for (int i = 0; i < overridingMethods.Count; i++) {
+						OverrideInformation ov = overridingMethods[i];
 						if (IsInterfaceImplementationMethodNeededByTypeDueToInterface (ov))
 							MarkMethod (ov.Override, new DependencyInfo (DependencyKind.Override, ov.Base), ScopeStack.CurrentScope.Origin);
 					}
@@ -3267,7 +3266,7 @@ protected virtual void ProcessMethod (MethodDefinition method, in DependencyInfo
 			MarkMethodSpecialCustomAttributes (method);
 
 			if (method.IsVirtual)
-				_virtual_methods.Add ((method, ScopeStack.CurrentScope));
+				_virtual_methods.TryAdd (method, ScopeStack.CurrentScope);
 
 			MarkNewCodeDependencies (method);
 
@@ -3475,7 +3474,7 @@ void MarkBaseMethods (MethodDefinition method)
 				// This will produce warnings for all interface methods and virtual methods regardless of whether the interface, interface implementation, or interface method is kept or not.
 				if (ov.Base.DeclaringType.IsInterface && !method.DeclaringType.IsInterface) {
 					// These are all virtual, no need to check IsVirtual before adding to list
-					_virtual_methods.Add ((ov.Base, ScopeStack.CurrentScope));
+					_virtual_methods.TryAdd (ov.Base, ScopeStack.CurrentScope);
 					continue;
 				}
 

src/tools/illink/src/linker/Linker/Annotations.cs

@@ -719,7 +719,7 @@ public void EnqueueVirtualMethod (MethodDefinition method)
 				VirtualMethodsWithAnnotationsToValidate.Add (method);
 		}
 
-		internal List<(TypeReference, List<InterfaceImplementation>)>? GetRecursiveInterfaces (TypeDefinition type)
+		internal List<(TypeReference InterfaceType, List<InterfaceImplementation> ImplementationChain)>? GetRecursiveInterfaces (TypeDefinition type)
 		{
 			return TypeMapInfo.GetRecursiveInterfaces (type);
 		}

src/tools/illink/src/linker/Linker/TypeMapInfo.cs

@@ -66,7 +66,7 @@ public void EnsureProcessed (AssemblyDefinition assembly)
 		/// <summary>
 		/// Returns a list of all known methods that override <paramref name="method"/>. The list may be incomplete if other overrides exist in assemblies that haven't been processed by TypeMapInfo yet
 		/// </summary>
-		public IEnumerable<OverrideInformation>? GetOverrides (MethodDefinition method)
+		public List<OverrideInformation>? GetOverrides (MethodDefinition method)
 		{
 			EnsureProcessed (method.Module.Assembly);
 			override_methods.TryGetValue (method, out List<OverrideInformation>? overrides);
@@ -130,14 +130,15 @@ protected virtual void MapType (TypeDefinition type)
 				MapType (nested);
 		}
 
-		internal List<(TypeReference, List<InterfaceImplementation>)>? GetRecursiveInterfaces (TypeDefinition type)
+		internal List<(TypeReference InterfaceType, List<InterfaceImplementation> ImplementationChain)>? GetRecursiveInterfaces (TypeDefinition type)
 		{
+			EnsureProcessed(type.Module.Assembly);
 			if (interfaces.TryGetValue (type, out var value))
 				return value;
 			return null;
 		}
 
-		List<(TypeReference, List<InterfaceImplementation>)> GetRecursiveInterfaceImplementations (TypeDefinition type)
+		List<(TypeReference InterfaceType, List<InterfaceImplementation> ImplementationChain)> GetRecursiveInterfaceImplementations (TypeDefinition type)
 		{
 			List<(TypeReference, List<InterfaceImplementation>)> firstImplementationChain = new ();