Implement function pointer type support (#85031)

Implements function pointer type support in the compiler, runtime, and reflection stack.

Contributes to #71883.

* Introduce a new kind of `MethodTable` for function pointers in the compiler.
* Remove function pointer type blocking from various places in the compiler.
* Generate a new summary table so we can construct/deconstruct function pointer types at runtime.
* Update metadata format so that we can capture calling conventions and distinguish managed/unmanaged function pointers in metadata.
* Update `MethodTable` reader.
* Update casting logic in the runtime.
* Update BCL (arrays, TypedReference, etc.)
* Update reflection stack: representation of the type, parsing metadata, invoke, field get/set
* Enable applicable tests.

Not implemented yet: the modified type stuff, runtime type loader support.

src/coreclr/nativeaot/Common/src/Internal/Runtime/MethodTable.cs

@@ -483,7 +483,7 @@ internal bool IsString
             get
             {
                 // String is currently the only non-array type with a non-zero component size.
-                return ComponentSize == StringComponentSize.Value && !IsArray && !IsGenericTypeDefinition;
+                return ComponentSize == StringComponentSize.Value && IsCanonical;
             }
         }
 
@@ -720,6 +720,14 @@ internal bool IsParameterizedType
             }
         }
 
+        internal bool IsFunctionPointerType
+        {
+            get
+            {
+                return Kind == EETypeKind.FunctionPointerEEType;
+            }
+        }
+
         // The parameterized type shape defines the particular form of parameterized type that
         // is being represented.
         // Currently, the meaning is a shape of 0 indicates that this is a Pointer,
@@ -945,6 +953,9 @@ internal IntPtr FinalizerCode
                         return null;
                 }
 
+                // Function pointers naturally set the base type field to null.
+                Debug.Assert(!IsFunctionPointerType || (!IsRelatedTypeViaIAT && _relatedType._pBaseType == null));
+
                 Debug.Assert(IsCanonical);
 
                 if (IsRelatedTypeViaIAT)
@@ -957,6 +968,7 @@ internal IntPtr FinalizerCode
             {
                 Debug.Assert(IsDynamicType);
                 Debug.Assert(!IsParameterizedType);
+                Debug.Assert(!IsFunctionPointerType);
                 Debug.Assert(IsCanonical);
                 _uFlags &= (uint)~EETypeFlags.RelatedTypeViaIATFlag;
                 _relatedType._pBaseType = value;

src/coreclr/nativeaot/Runtime.Base/src/System/Runtime/MethodTable.Runtime.cs

@@ -45,43 +45,6 @@ internal IntPtr GetClasslibFunction(ClassLibFunctionId id)
             return (IntPtr)InternalCalls.RhpGetClasslibFunctionFromEEType((MethodTable*)Unsafe.AsPointer(ref this), id);
         }
 
-        // Returns an address in the module most closely associated with this MethodTable that can be handed to
-        // EH.GetClasslibException and use to locate the compute the correct exception type. In most cases
-        // this is just the MethodTable pointer itself, but when this type represents a generic that has been
-        // unified at runtime (and thus the MethodTable pointer resides in the process heap rather than a specific
-        // module) we need to do some work.
-        internal unsafe MethodTable* GetAssociatedModuleAddress()
-        {
-            fixed (MethodTable* pThis = &this)
-            {
-                if (!IsDynamicType)
-                    return pThis;
-
-                // There are currently four types of runtime allocated EETypes, arrays, pointers, byrefs, and generic types.
-                // Arrays/Pointers/ByRefs can be handled by looking at their element type.
-                if (IsParameterizedType)
-                    return pThis->RelatedParameterType->GetAssociatedModuleAddress();
-
-                if (!IsGeneric)
-                {
-                    // No way to resolve module information for a non-generic dynamic type.
-                    return null;
-                }
-
-                // Generic types are trickier. Often we could look at the parent type (since eventually it
-                // would derive from the class library's System.Object which is definitely not runtime
-                // allocated). But this breaks down for generic interfaces. Instead we fetch the generic
-                // instantiation information and use the generic type definition, which will always be module
-                // local. We know this lookup will succeed since we're dealing with a unified generic type
-                // and the unification process requires this metadata.
-                MethodTable* pGenericType = pThis->GenericDefinition;
-
-                Debug.Assert(pGenericType != null, "Generic type expected");
-
-                return pGenericType;
-            }
-        }
-
         /// <summary>
         /// Return true if type is good for simple casting : canonical, no related type via IAT, no generic variance
         /// </summary>

src/coreclr/nativeaot/Runtime.Base/src/System/Runtime/RuntimeExports.cs

@@ -30,6 +30,8 @@ public static unsafe object RhNewObject(MethodTable* pEEType)
                 !pEEType->IsInterface &&
                 !pEEType->IsArray &&
                 !pEEType->IsString &&
+                !pEEType->IsPointerType &&
+                !pEEType->IsFunctionPointerType &&
                 !pEEType->IsByRefLike;
             if (!isValid)
                 Debug.Assert(false);
@@ -394,7 +396,7 @@ internal static unsafe IntPtr RhGetRuntimeHelperForType(MethodTable* pEEType, Ru
                         return (IntPtr)(delegate*<MethodTable*, object, object>)&TypeCast.IsInstanceOfArray;
                     else if (pEEType->IsInterface)
                         return (IntPtr)(delegate*<MethodTable*, object, object>)&TypeCast.IsInstanceOfInterface;
-                    else if (pEEType->IsParameterizedType)
+                    else if (pEEType->IsParameterizedType || pEEType->IsFunctionPointerType)
                         return (IntPtr)(delegate*<MethodTable*, object, object>)&TypeCast.IsInstanceOf; // Array handled above; pointers and byrefs handled here
                     else
                         return (IntPtr)(delegate*<MethodTable*, object, object>)&TypeCast.IsInstanceOfClass;
@@ -404,7 +406,7 @@ internal static unsafe IntPtr RhGetRuntimeHelperForType(MethodTable* pEEType, Ru
                         return (IntPtr)(delegate*<MethodTable*, object, object>)&TypeCast.CheckCastArray;
                     else if (pEEType->IsInterface)
                         return (IntPtr)(delegate*<MethodTable*, object, object>)&TypeCast.CheckCastInterface;
-                    else if (pEEType->IsParameterizedType)
+                    else if (pEEType->IsParameterizedType || pEEType->IsFunctionPointerType)
                         return (IntPtr)(delegate*<MethodTable*, object, object>)&TypeCast.CheckCast; // Array handled above; pointers and byrefs handled here
                     else
                         return (IntPtr)(delegate*<MethodTable*, object, object>)&TypeCast.CheckCastClass;

src/coreclr/nativeaot/Runtime.Base/src/System/Runtime/TypeCast.cs

@@ -52,6 +52,7 @@ public static unsafe object IsInstanceOfClass(MethodTable* pTargetType, object o
             MethodTable* pObjType = obj.GetMethodTable();
 
             Debug.Assert(!pTargetType->IsParameterizedType, "IsInstanceOfClass called with parameterized MethodTable");
+            Debug.Assert(!pTargetType->IsFunctionPointerType, "IsInstanceOfClass called with function pointer MethodTable");
             Debug.Assert(!pTargetType->IsInterface, "IsInstanceOfClass called with interface MethodTable");
 
             // Quick check if both types are good for simple casting: canonical, no related type via IAT, no generic variance
@@ -251,6 +252,7 @@ private static unsafe bool IsInstanceOfInterfaceViaIDynamicInterfaceCastable(Met
         internal static unsafe bool ImplementsInterface(MethodTable* pObjType, MethodTable* pTargetType, EETypePairList* pVisited)
         {
             Debug.Assert(!pTargetType->IsParameterizedType, "did not expect parameterized type");
+            Debug.Assert(!pTargetType->IsFunctionPointerType, "did not expect function pointer type");
             Debug.Assert(pTargetType->IsInterface, "IsInstanceOfInterface called with non-interface MethodTable");
 
             int numInterfaces = pObjType->NumInterfaces;
@@ -536,22 +538,30 @@ internal static unsafe bool AreTypesAssignableInternalUncached(MethodTable* pSou
                 if (pSourceType->IsParameterizedType
                     && (pTargetType->ParameterizedTypeShape == pSourceType->ParameterizedTypeShape))
                 {
+                    MethodTable* pSourceRelatedParameterType = pSourceType->RelatedParameterType;
                     // Source type is also a parameterized type. Are the parameter types compatible?
-                    if (pSourceType->RelatedParameterType->IsPointerType)
+                    if (pSourceRelatedParameterType->IsPointerType)
                     {
                         // If the parameter types are pointers, then only exact matches are correct.
                         // As we've already called AreTypesEquivalent at the start of this function,
                         // return false as the exact match case has already been handled.
                         // int** is not compatible with uint**, nor is int*[] oompatible with uint*[].
                         return false;
                     }
-                    else if (pSourceType->RelatedParameterType->IsByRefType)
+                    else if (pSourceRelatedParameterType->IsByRefType)
                     {
                         // Only allow exact matches for ByRef types - same as pointers above. This should
                         // be unreachable and it's only a defense in depth. ByRefs can't be parameters
                         // of any parameterized type.
                         return false;
                     }
+                    else if (pSourceRelatedParameterType->IsFunctionPointerType)
+                    {
+                        // If the parameter types are function pointers, then only exact matches are correct.
+                        // As we've already called AreTypesEquivalent at the start of this function,
+                        // return false as the exact match case has already been handled.
+                        return false;
+                    }
                     else
                     {
                         // Note that using AreTypesAssignableInternal with AssignmentVariation.AllowSizeEquivalence
@@ -565,6 +575,13 @@ internal static unsafe bool AreTypesAssignableInternalUncached(MethodTable* pSou
                 // Can't cast a non-parameter type to a parameter type or a parameter type of different shape to a parameter type
                 return false;
             }
+
+            if (pTargetType->IsFunctionPointerType)
+            {
+                // Function pointers only cast if source and target are equivalent types.
+                return false;
+            }
+
             if (pSourceType->IsArray)
             {
                 // Target type is not an array. But we can still cast arrays to Object or System.Array.
@@ -574,6 +591,10 @@ internal static unsafe bool AreTypesAssignableInternalUncached(MethodTable* pSou
             {
                 return false;
             }
+            else if (pSourceType->IsFunctionPointerType)
+            {
+                return false;
+            }
 
             //
             // Handle cast to other (non-interface, non-array) cases.
@@ -829,9 +850,11 @@ internal static unsafe bool IsDerived(MethodTable* pDerivedType, MethodTable* pB
         {
             Debug.Assert(!pDerivedType->IsArray, "did not expect array type");
             Debug.Assert(!pDerivedType->IsParameterizedType, "did not expect parameterType");
+            Debug.Assert(!pDerivedType->IsFunctionPointerType, "did not expect function pointer");
             Debug.Assert(!pBaseType->IsArray, "did not expect array type");
             Debug.Assert(!pBaseType->IsInterface, "did not expect interface type");
             Debug.Assert(!pBaseType->IsParameterizedType, "did not expect parameterType");
+            Debug.Assert(!pBaseType->IsFunctionPointerType, "did not expect function pointer");
             Debug.Assert(pBaseType->IsCanonical || pBaseType->IsGenericTypeDefinition, "unexpected MethodTable");
             Debug.Assert(pDerivedType->IsCanonical || pDerivedType->IsGenericTypeDefinition, "unexpected MethodTable");
 
@@ -879,7 +902,7 @@ public static unsafe object IsInstanceOf(MethodTable* pTargetType, object obj)
                 return IsInstanceOfArray(pTargetType, obj);
             else if (pTargetType->IsInterface)
                 return IsInstanceOfInterface(pTargetType, obj);
-            else if (pTargetType->IsParameterizedType)
+            else if (pTargetType->IsParameterizedType || pTargetType->IsFunctionPointerType)
                 return null; // We handled arrays above so this is for pointers and byrefs only.
             else
                 return IsInstanceOfClass(pTargetType, obj);
@@ -921,13 +944,13 @@ public static unsafe object CheckCast(MethodTable* pTargetType, object obj)
                 return CheckCastArray(pTargetType, obj);
             else if (pTargetType->IsInterface)
                 return CheckCastInterface(pTargetType, obj);
-            else if (pTargetType->IsParameterizedType)
-                return CheckCastNonArrayParameterizedType(pTargetType, obj);
+            else if (pTargetType->IsParameterizedType || pTargetType->IsFunctionPointerType)
+                return CheckCastNonboxableType(pTargetType, obj);
             else
                 return CheckCastClass(pTargetType, obj);
         }
 
-        private static unsafe object CheckCastNonArrayParameterizedType(MethodTable* pTargetType, object obj)
+        private static unsafe object CheckCastNonboxableType(MethodTable* pTargetType, object obj)
         {
             // a null value can be cast to anything
             if (obj == null)

src/coreclr/nativeaot/System.Private.CoreLib/src/CompatibilitySuppressions.xml

@@ -572,6 +572,10 @@
     <DiagnosticId>CP0001</DiagnosticId>
     <Target>T:Internal.Metadata.NativeFormat.ScopeReferenceHandle</Target>
   </Suppression>
+  <Suppression>
+    <DiagnosticId>CP0001</DiagnosticId>
+    <Target>T:Internal.Metadata.NativeFormat.SignatureCallingConvention</Target>
+  </Suppression>
   <Suppression>
     <DiagnosticId>CP0001</DiagnosticId>
     <Target>T:Internal.Metadata.NativeFormat.SingleCollection</Target>

src/coreclr/nativeaot/System.Private.CoreLib/src/Internal/Reflection/Core/Execution/ExecutionDomain.cs

@@ -152,6 +152,23 @@ public Type GetPointerTypeForHandle(RuntimeTypeHandle typeHandle)
             return targetTypeHandle.GetTypeForRuntimeTypeHandle().GetPointerType(typeHandle);
         }
 
+        public Type GetFunctionPointerTypeForHandle(RuntimeTypeHandle typeHandle)
+        {
+            ExecutionEnvironment.GetFunctionPointerTypeComponents(typeHandle, out RuntimeTypeHandle returnTypeHandle,
+                                                                              out RuntimeTypeHandle[] parameterHandles,
+                                                                              out bool isUnmanaged);
+
+            RuntimeTypeInfo returnType = returnTypeHandle.GetTypeForRuntimeTypeHandle();
+            int count = parameterHandles.Length;
+            RuntimeTypeInfo[] parameterTypes = new RuntimeTypeInfo[count];
+            for (int i = 0; i < count; i++)
+            {
+                parameterTypes[i] = parameterHandles[i].GetTypeForRuntimeTypeHandle();
+            }
+
+            return RuntimeFunctionPointerTypeInfo.GetFunctionPointerTypeInfo(returnType, parameterTypes, isUnmanaged, typeHandle);
+        }
+
         public Type GetByRefTypeForHandle(RuntimeTypeHandle typeHandle)
         {
             RuntimeTypeHandle targetTypeHandle;

src/coreclr/nativeaot/System.Private.CoreLib/src/Internal/Reflection/Core/Execution/ExecutionEnvironment.cs

@@ -64,6 +64,9 @@ public abstract class ExecutionEnvironment
 
         public abstract bool TryGetMultiDimArrayTypeForElementType(RuntimeTypeHandle elementTypeHandle, int rank, out RuntimeTypeHandle arrayTypeHandle);
 
+        public abstract bool TryGetFunctionPointerTypeForComponents(RuntimeTypeHandle returnTypeHandle, RuntimeTypeHandle[] parameterHandles, bool isUnmanaged, out RuntimeTypeHandle functionPointerTypeHandle);
+        public abstract void GetFunctionPointerTypeComponents(RuntimeTypeHandle functionPointerHandle, out RuntimeTypeHandle returnTypeHandle, out RuntimeTypeHandle[] parameterHandles, out bool isUnmanaged);
+
         public abstract bool TryGetPointerTypeForTargetType(RuntimeTypeHandle targetTypeHandle, out RuntimeTypeHandle pointerTypeHandle);
         public abstract bool TryGetPointerTypeTargetType(RuntimeTypeHandle pointerTypeHandle, out RuntimeTypeHandle targetTypeHandle);
 

src/coreclr/nativeaot/System.Private.CoreLib/src/Internal/Reflection/Core/NonPortable/RuntimeTypeUnifier.cs

@@ -106,6 +106,10 @@ public static Type GetRuntimeTypeBypassCache(EETypePtr eeType)
             {
                 return callbacks.GetPointerTypeForHandle(runtimeTypeHandle);
             }
+            else if (eeType.IsFunctionPointer)
+            {
+                return callbacks.GetFunctionPointerTypeForHandle(runtimeTypeHandle);
+            }
             else if (eeType.IsByRef)
             {
                 return callbacks.GetByRefTypeForHandle(runtimeTypeHandle);

src/coreclr/nativeaot/System.Private.CoreLib/src/Internal/Runtime/Augments/ReflectionExecutionDomainCallbacks.cs

@@ -37,6 +37,7 @@ public abstract class ReflectionExecutionDomainCallbacks
         public abstract Type GetArrayTypeForHandle(RuntimeTypeHandle typeHandle);
         public abstract Type GetMdArrayTypeForHandle(RuntimeTypeHandle typeHandle, int rank);
         public abstract Type GetPointerTypeForHandle(RuntimeTypeHandle typeHandle);
+        public abstract Type GetFunctionPointerTypeForHandle(RuntimeTypeHandle typeHandle);
         public abstract Type GetByRefTypeForHandle(RuntimeTypeHandle typeHandle);
         public abstract Type GetConstructedGenericTypeForHandle(RuntimeTypeHandle typeHandle);
 

src/coreclr/nativeaot/System.Private.CoreLib/src/Internal/Runtime/Augments/RuntimeAugments.cs

@@ -473,7 +473,7 @@ public static bool IsInstanceOfInterface(object obj, RuntimeTypeHandle interface
         public static bool TryGetBaseType(RuntimeTypeHandle typeHandle, out RuntimeTypeHandle baseTypeHandle)
         {
             EETypePtr eeType = typeHandle.ToEETypePtr();
-            if (eeType.IsGenericTypeDefinition || eeType.IsPointer || eeType.IsByRef)
+            if (eeType.IsGenericTypeDefinition || eeType.IsPointer || eeType.IsByRef || eeType.IsFunctionPointer)
             {
                 baseTypeHandle = default(RuntimeTypeHandle);
                 return false;
@@ -490,7 +490,7 @@ public static bool TryGetBaseType(RuntimeTypeHandle typeHandle, out RuntimeTypeH
         public static IEnumerable<RuntimeTypeHandle> TryGetImplementedInterfaces(RuntimeTypeHandle typeHandle)
         {
             EETypePtr eeType = typeHandle.ToEETypePtr();
-            if (eeType.IsGenericTypeDefinition || eeType.IsPointer || eeType.IsByRef)
+            if (eeType.IsGenericTypeDefinition || eeType.IsPointer || eeType.IsByRef || eeType.IsFunctionPointer)
                 return null;
 
             LowLevelList<RuntimeTypeHandle> implementedInterfaces = new LowLevelList<RuntimeTypeHandle>();
@@ -637,6 +637,11 @@ public static bool IsUnmanagedPointerType(RuntimeTypeHandle typeHandle)
             return typeHandle.ToEETypePtr().IsPointer;
         }
 
+        public static bool IsFunctionPointerType(RuntimeTypeHandle typeHandle)
+        {
+            return typeHandle.ToEETypePtr().IsFunctionPointer;
+        }
+
         public static bool IsByRefType(RuntimeTypeHandle typeHandle)
         {
             return typeHandle.ToEETypePtr().IsByRef;
@@ -659,6 +664,8 @@ public static bool CanPrimitiveWiden(RuntimeTypeHandle srcType, RuntimeTypeHandl
                 return false;
             if (srcEEType.IsPointer || dstEEType.IsPointer)
                 return false;
+            if (srcEEType.IsFunctionPointer || dstEEType.IsFunctionPointer)
+                return false;
             if (srcEEType.IsByRef || dstEEType.IsByRef)
                 return false;
 

src/coreclr/nativeaot/System.Private.CoreLib/src/System.Private.CoreLib.csproj

@@ -154,6 +154,8 @@
     <Compile Include="System\Reflection\Metadata\AssemblyExtensions.cs" />
     <Compile Include="System\Reflection\Metadata\MetadataUpdater.cs" />
     <Compile Include="System\Reflection\ModifiedType.NativeAot.cs" />
+    <Compile Include="System\Reflection\Runtime\TypeInfos\RuntimeFunctionPointerTypeInfo.cs" />
+    <Compile Include="System\Reflection\Runtime\TypeInfos\RuntimeFunctionPointerTypeInfo.UnificationKey.cs" />
     <Compile Include="System\Runtime\InteropServices\CriticalHandle.NativeAot.cs" />
     <Compile Include="System\Activator.NativeAot.cs" />
     <Compile Include="System\AppContext.NativeAot.cs" />