Add support for static virtual methods (#66084)

Took the type system changes from #54063 and cleaned them up, added unit tests.

Hooked it up into JitInterface/ResolveConstraintMethodApprox. Using the pre-existing `ConstrainedMethodUseLookupResult` that wasn't currently getting emitted. We'll want to use it for its original purpose at some point, but I think we can make this work for both instance and static constrained calls.

Missing things:

* Support creating delegates to static virtual methods. This will need a RyuJIT/JitInterface change.
* Type loader support. If `MakeGeneric` needs static virtuals at runtime, it will throw.

But this is enough to get HttpClient working again. Fixes #65613. Contributes to dotnet/runtimelab#1665.

Author: MichalStrehovsky

src/coreclr/tools/Common/Compiler/TypeExtensions.cs

@@ -421,9 +421,11 @@ public static MethodDesc TryResolveConstraintMethodApprox(this TypeDesc constrai
         {
             forceRuntimeLookup = false;
 
+            bool isStaticVirtualMethod = interfaceMethod.Signature.IsStatic;
+
             // We can't resolve constraint calls effectively for reference types, and there's
             // not a lot of perf. benefit in doing it anyway.
-            if (!constrainedType.IsValueType)
+            if (!constrainedType.IsValueType && (!isStaticVirtualMethod || constrainedType.IsCanonicalDefinitionType(CanonicalFormKind.Any)))
             {
                 return null;
             }
@@ -466,10 +468,17 @@ public static MethodDesc TryResolveConstraintMethodApprox(this TypeDesc constrai
                                 potentialInterfaceMethod.GetTypicalMethodDefinition(), (InstantiatedType)potentialInterfaceType);
                         }
 
-                        method = canonType.ResolveInterfaceMethodToVirtualMethodOnType(potentialInterfaceMethod);
+                        if (isStaticVirtualMethod)
+                        {
+                            method = canonType.ResolveVariantInterfaceMethodToStaticVirtualMethodOnType(potentialInterfaceMethod);
+                        }
+                        else
+                        {
+                            method = canonType.ResolveInterfaceMethodToVirtualMethodOnType(potentialInterfaceMethod);
+                        }
 
                         // See code:#TryResolveConstraintMethodApprox_DoNotReturnParentMethod
-                        if (method != null && !method.OwningType.IsValueType)
+                        if (!isStaticVirtualMethod && method != null && !method.OwningType.IsValueType)
                         {
                             // We explicitly wouldn't want to abort if we found a default implementation.
                             // The above resolution doesn't consider the default methods.
@@ -500,7 +509,14 @@ public static MethodDesc TryResolveConstraintMethodApprox(this TypeDesc constrai
                             // We can resolve to exact method
                             MethodDesc exactInterfaceMethod = context.GetMethodForInstantiatedType(
                                 genInterfaceMethod.GetTypicalMethodDefinition(), (InstantiatedType)interfaceType);
-                            method = constrainedType.ResolveVariantInterfaceMethodToVirtualMethodOnType(exactInterfaceMethod);
+                            if (isStaticVirtualMethod)
+                            {
+                                method = constrainedType.ResolveVariantInterfaceMethodToStaticVirtualMethodOnType(exactInterfaceMethod);
+                            }
+                            else
+                            {
+                                method = constrainedType.ResolveVariantInterfaceMethodToVirtualMethodOnType(exactInterfaceMethod);
+                            }
                             isExactMethodResolved = method != null;
                         }
                     }
@@ -523,7 +539,14 @@ public static MethodDesc TryResolveConstraintMethodApprox(this TypeDesc constrai
                         if (genInterfaceMethod.OwningType != interfaceType)
                             exactInterfaceMethod = context.GetMethodForInstantiatedType(
                                 genInterfaceMethod.GetTypicalMethodDefinition(), (InstantiatedType)interfaceType);
-                        method = constrainedType.ResolveVariantInterfaceMethodToVirtualMethodOnType(exactInterfaceMethod);
+                        if (isStaticVirtualMethod)
+                        {
+                            method = constrainedType.ResolveVariantInterfaceMethodToStaticVirtualMethodOnType(exactInterfaceMethod);
+                        }
+                        else
+                        {
+                            method = constrainedType.ResolveVariantInterfaceMethodToVirtualMethodOnType(exactInterfaceMethod);
+                        }
                     }
                 }
             }
@@ -548,7 +571,7 @@ public static MethodDesc TryResolveConstraintMethodApprox(this TypeDesc constrai
             //#TryResolveConstraintMethodApprox_DoNotReturnParentMethod
             // Only return a method if the value type itself declares the method,
             // otherwise we might get a method from Object or System.ValueType
-            if (!method.OwningType.IsValueType)
+            if (!isStaticVirtualMethod && !method.OwningType.IsValueType)
             {
                 // Fall back to VSD
                 return null;

src/coreclr/tools/Common/TypeSystem/Common/MetadataVirtualMethodAlgorithm.cs

@@ -572,6 +572,16 @@ public override MethodDesc ResolveVariantInterfaceMethodToVirtualMethodOnType(Me
             return ResolveVariantInterfaceMethodToVirtualMethodOnType(interfaceMethod, (MetadataType)currentType);
         }
 
+        public override MethodDesc ResolveInterfaceMethodToStaticVirtualMethodOnType(MethodDesc interfaceMethod, TypeDesc currentType)
+        {
+            return ResolveInterfaceMethodToStaticVirtualMethodOnType(interfaceMethod, (MetadataType)currentType);
+        }
+
+        public override MethodDesc ResolveVariantInterfaceMethodToStaticVirtualMethodOnType(MethodDesc interfaceMethod, TypeDesc currentType)
+        {
+            return ResolveVariantInterfaceMethodToStaticVirtualMethodOnType(interfaceMethod, (MetadataType)currentType);
+        }
+
         //////////////////////// INTERFACE RESOLUTION
         //Interface function resolution
         //    Interface function resolution follows the following rules
@@ -588,6 +598,8 @@ public override MethodDesc ResolveVariantInterfaceMethodToVirtualMethodOnType(Me
         //    See current interface call resolution for details on how that happens.
         private static MethodDesc ResolveInterfaceMethodToVirtualMethodOnType(MethodDesc interfaceMethod, MetadataType currentType)
         {
+            Debug.Assert(!interfaceMethod.Signature.IsStatic);
+
             if (currentType.IsInterface)
                 return null;
 
@@ -657,6 +669,8 @@ private static MethodDesc ResolveInterfaceMethodToVirtualMethodOnType(MethodDesc
 
         public static MethodDesc ResolveVariantInterfaceMethodToVirtualMethodOnType(MethodDesc interfaceMethod, MetadataType currentType)
         {
+            Debug.Assert(!interfaceMethod.Signature.IsStatic);
+
             MetadataType interfaceType = (MetadataType)interfaceMethod.OwningType;
             bool foundInterface = IsInterfaceImplementedOnType(currentType, interfaceType);
             MethodDesc implMethod;
@@ -841,5 +855,108 @@ public static IEnumerable<MethodDesc> EnumAllVirtualSlots(MetadataType type)
                 } while (type != null);
             }
         }
+
+        /// <summary>
+        /// Try to resolve a given virtual static interface method on a given constrained type and its base types.
+        /// </summary>
+        /// <param name="interfaceMethod">Interface method to resolve</param>
+        /// <param name="currentType">Type to attempt virtual static method resolution on</param>
+        /// <returns>MethodDesc of the resolved virtual static method, null when not found (runtime lookup must be used)</returns>
+        public static MethodDesc ResolveInterfaceMethodToStaticVirtualMethodOnType(MethodDesc interfaceMethod, MetadataType currentType)
+        {
+            TypeDesc interfaceType = interfaceMethod.OwningType;
+
+            // Search for match on a per-level in the type hierarchy
+            for (MetadataType typeToCheck = currentType; typeToCheck != null; typeToCheck = typeToCheck.MetadataBaseType)
+            {
+                MethodDesc resolvedMethodOnType = TryResolveVirtualStaticMethodOnThisType(typeToCheck, interfaceMethod);
+                if (resolvedMethodOnType != null)
+                {
+                    return resolvedMethodOnType;
+                }
+            }
+            return null;
+        }
+
+        /// <summary>
+        /// Try to resolve a given virtual static interface method on a given constrained type and its base types.
+        /// </summary>
+        /// <param name="interfaceMethod">Interface method to resolve</param>
+        /// <param name="currentType">Type to attempt virtual static method resolution on</param>
+        /// <returns>MethodDesc of the resolved virtual static method, null when not found (runtime lookup must be used)</returns>
+        public static MethodDesc ResolveVariantInterfaceMethodToStaticVirtualMethodOnType(MethodDesc interfaceMethod, MetadataType currentType)
+        {
+            TypeDesc interfaceType = interfaceMethod.OwningType;
+
+            // Search for match on a per-level in the type hierarchy
+            for (MetadataType typeToCheck = currentType; typeToCheck != null; typeToCheck = typeToCheck.MetadataBaseType)
+            {
+                MethodDesc resolvedMethodOnType = TryResolveVirtualStaticMethodOnThisType(typeToCheck, interfaceMethod);
+                if (resolvedMethodOnType != null)
+                {
+                    return resolvedMethodOnType;
+                }
+
+                // Variant interface dispatch
+                foreach (DefType runtimeInterfaceType in typeToCheck.RuntimeInterfaces)
+                {
+                    if (runtimeInterfaceType == interfaceType)
+                    {
+                        // This is the variant interface check logic, skip this
+                        continue;
+                    }
+
+                    if (!runtimeInterfaceType.HasSameTypeDefinition(interfaceType))
+                    {
+                        // Variance matches require a typedef match
+                        // Equivalence isn't sufficient, and is uninteresting as equivalent interfaces cannot have static virtuals.
+                        continue;
+                    }
+
+                    if (runtimeInterfaceType.CanCastTo(interfaceType))
+                    {
+                        // Attempt to resolve on variance matched interface
+                        MethodDesc runtimeInterfaceMethod = runtimeInterfaceType.FindMethodOnExactTypeWithMatchingTypicalMethod(interfaceMethod);
+                        resolvedMethodOnType = TryResolveVirtualStaticMethodOnThisType(typeToCheck, runtimeInterfaceMethod);
+                        if (resolvedMethodOnType != null)
+                        {
+                            return resolvedMethodOnType;
+                        }
+                    }
+                }
+            }
+            return null;
+        }
+
+        /// <summary>
+        /// Try to resolve a given virtual static interface method on a given constrained type and return the resolved method or null when not found.
+        /// </summary>
+        /// <param name="constrainedType">Type to attempt method resolution on</param>
+        /// <param name="interfaceMethod">Method to resolve</param>
+        /// <returns>MethodDesc of the resolved method or null when not found (runtime lookup must be used)</returns>
+        private static MethodDesc TryResolveVirtualStaticMethodOnThisType(MetadataType constrainedType, MethodDesc interfaceMethod)
+        {
+            Debug.Assert(interfaceMethod.Signature.IsStatic);
+
+            MethodImplRecord[] possibleImpls = constrainedType.FindMethodsImplWithMatchingDeclName(interfaceMethod.Name);
+            if (possibleImpls == null)
+                return null;
+
+            MethodDesc interfaceMethodDefinition = interfaceMethod.GetMethodDefinition();
+            foreach (MethodImplRecord methodImpl in possibleImpls)
+            {
+                if (methodImpl.Decl == interfaceMethodDefinition)
+                {
+                    MethodDesc resolvedMethodImpl = methodImpl.Body;
+                    if (interfaceMethod != interfaceMethodDefinition)
+                    {
+                        resolvedMethodImpl = resolvedMethodImpl.MakeInstantiatedMethod(interfaceMethod.Instantiation);
+                    }
+                    return resolvedMethodImpl;
+                }
+            }
+
+            return null;
+        }
     }
 }

src/coreclr/tools/Common/TypeSystem/Common/TypeSystemHelpers.cs

@@ -205,6 +205,16 @@ public static MethodDesc ResolveVariantInterfaceMethodToVirtualMethodOnType(this
             return type.Context.GetVirtualMethodAlgorithmForType(type).ResolveVariantInterfaceMethodToVirtualMethodOnType(interfaceMethod, type);
         }
 
+        public static MethodDesc ResolveInterfaceMethodToStaticVirtualMethodOnType(this TypeDesc type, MethodDesc interfaceMethod)
+        {
+            return type.Context.GetVirtualMethodAlgorithmForType(type).ResolveInterfaceMethodToStaticVirtualMethodOnType(interfaceMethod, type);
+        }
+
+        public static MethodDesc ResolveVariantInterfaceMethodToStaticVirtualMethodOnType(this TypeDesc type, MethodDesc interfaceMethod)
+        {
+            return type.Context.GetVirtualMethodAlgorithmForType(type).ResolveVariantInterfaceMethodToStaticVirtualMethodOnType(interfaceMethod, type);
+        }
+
         public static DefaultInterfaceMethodResolution ResolveInterfaceMethodToDefaultImplementationOnType(this TypeDesc type, MethodDesc interfaceMethod, out MethodDesc implMethod)
         {
             return type.Context.GetVirtualMethodAlgorithmForType(type).ResolveInterfaceMethodToDefaultImplementationOnType(interfaceMethod, type, out implMethod);

src/coreclr/tools/Common/TypeSystem/Common/VirtualMethodAlgorithm.cs

@@ -24,6 +24,10 @@ public abstract class VirtualMethodAlgorithm
 
         public abstract MethodDesc ResolveVariantInterfaceMethodToVirtualMethodOnType(MethodDesc interfaceMethod, TypeDesc currentType);
 
+        public abstract MethodDesc ResolveInterfaceMethodToStaticVirtualMethodOnType(MethodDesc interfaceMethod, TypeDesc currentType);
+
+        public abstract MethodDesc ResolveVariantInterfaceMethodToStaticVirtualMethodOnType(MethodDesc interfaceMethod, TypeDesc currentType);
+
         public abstract DefaultInterfaceMethodResolution ResolveInterfaceMethodToDefaultImplementationOnType(MethodDesc interfaceMethod, TypeDesc currentType, out MethodDesc impl);
 
         /// <summary>

src/coreclr/tools/aot/ILCompiler.Compiler/Compiler/Compilation.cs

@@ -252,6 +252,10 @@ public bool NeedsRuntimeLookup(ReadyToRunHelperId lookupKind, object targetOfLoo
                 case ReadyToRunHelperId.FieldHandle:
                     return ((FieldDesc)targetOfLookup).OwningType.IsRuntimeDeterminedSubtype;
 
+                case ReadyToRunHelperId.ConstrainedDirectCall:
+                    return ((ConstrainedCallInfo)targetOfLookup).Method.IsRuntimeDeterminedExactMethod
+                        || ((ConstrainedCallInfo)targetOfLookup).ConstrainedType.IsRuntimeDeterminedSubtype;
+
                 default:
                     throw new NotImplementedException();
             }
@@ -643,4 +647,12 @@ public IEnumerable<TypeDesc> ConstructedEETypes
             }
         }
     }
+
+    public sealed class ConstrainedCallInfo
+    {
+        public readonly TypeDesc ConstrainedType;
+        public readonly MethodDesc Method;
+        public ConstrainedCallInfo(TypeDesc constrainedType, MethodDesc method)
+            => (ConstrainedType, Method) = (constrainedType, method);
+    }
 }

src/coreclr/tools/aot/ILCompiler.Compiler/Compiler/DependencyAnalysis/EETypeNode.cs

@@ -162,6 +162,10 @@ public override bool InterestingForDynamicDependencyAnalysis
                         {
                             Debug.Assert(method.IsVirtual);
 
+                            // Static interface methods don't participate in GVM analysis
+                            if (method.Signature.IsStatic)
+                                continue;
+
                             if (method.HasInstantiation)
                             {
                                 // We found a GVM on one of the implemented interfaces. Find if the type implements this method. 

src/coreclr/tools/aot/ILCompiler.Compiler/Compiler/DependencyAnalysis/GenericLookupResult.cs

@@ -1431,20 +1431,36 @@ public override ISymbolNode GetTarget(NodeFactory factory, GenericLookupResultCo
         {
             MethodDesc instantiatedConstrainedMethod = _constrainedMethod.GetNonRuntimeDeterminedMethodFromRuntimeDeterminedMethodViaSubstitution(dictionary.TypeInstantiation, dictionary.MethodInstantiation);
             TypeDesc instantiatedConstraintType = _constraintType.GetNonRuntimeDeterminedTypeFromRuntimeDeterminedSubtypeViaSubstitution(dictionary.TypeInstantiation, dictionary.MethodInstantiation);
-            MethodDesc implMethod = instantiatedConstrainedMethod;
+            MethodDesc implMethod;
 
-            if (implMethod.OwningType.IsInterface)
+            if (instantiatedConstrainedMethod.OwningType.IsInterface)
             {
-                implMethod = instantiatedConstraintType.GetClosestDefType().ResolveVariantInterfaceMethodToVirtualMethodOnType(implMethod);
+                if (instantiatedConstrainedMethod.Signature.IsStatic)
+                {
+                    implMethod = instantiatedConstraintType.GetClosestDefType().ResolveVariantInterfaceMethodToStaticVirtualMethodOnType(instantiatedConstrainedMethod);
+                }
+                else
+                {
+                    throw new NotImplementedException();
+                }
+            }
+            else
+            {
+                implMethod = instantiatedConstraintType.GetClosestDefType().FindVirtualFunctionTargetMethodOnObjectType(instantiatedConstrainedMethod);
             }
-
-            implMethod = instantiatedConstraintType.GetClosestDefType().FindVirtualFunctionTargetMethodOnObjectType(implMethod);
 
             // AOT use of this generic lookup is restricted to finding methods on valuetypes (runtime usage of this slot in universal generics is more flexible)
-            Debug.Assert(instantiatedConstraintType.IsValueType);
-            Debug.Assert(implMethod.OwningType == instantiatedConstraintType);
+            Debug.Assert(instantiatedConstraintType.IsValueType || (instantiatedConstrainedMethod.OwningType.IsInterface && instantiatedConstrainedMethod.Signature.IsStatic));
+            Debug.Assert(!instantiatedConstraintType.IsValueType || implMethod.OwningType == instantiatedConstraintType);
 
-            if (implMethod.HasInstantiation)
+            if (implMethod.Signature.IsStatic)
+            {
+                if (implMethod.GetCanonMethodTarget(CanonicalFormKind.Specific).IsSharedByGenericInstantiations)
+                    return factory.ExactCallableAddress(implMethod);
+                else
+                    return factory.MethodEntrypoint(implMethod);
+            }
+            else if (implMethod.HasInstantiation)
             {
                 return factory.ExactCallableAddress(implMethod);
             }
@@ -1467,7 +1483,8 @@ public override void AppendMangledName(NameMangler nameMangler, Utf8StringBuilde
 
         public override NativeLayoutVertexNode TemplateDictionaryNode(NodeFactory factory)
         {
-            return factory.NativeLayout.ConstrainedMethodUse(_constrainedMethod, _constraintType, _directCall);
+            return factory.NativeLayout.NotSupportedDictionarySlot;
+            //return factory.NativeLayout.ConstrainedMethodUse(_constrainedMethod, _constraintType, _directCall);
         }
 
         public override void WriteDictionaryTocData(NodeFactory factory, IGenericLookupResultTocWriter writer)

src/coreclr/tools/aot/ILCompiler.Compiler/Compiler/DependencyAnalysis/InterfaceDispatchMapNode.cs

@@ -111,6 +111,10 @@ public static bool MightHaveInterfaceDispatchMap(TypeDesc type, NodeFactory fact
 
                 foreach (MethodDesc slotMethod in slots)
                 {
+                    // Static interface methods don't go in the dispatch map
+                    if (slotMethod.Signature.IsStatic)
+                        continue;
+
                     MethodDesc declMethod = slotMethod;
 
                     Debug.Assert(!declMethod.Signature.IsStatic && declMethod.IsVirtual);