Merge pull request #5505 from dotnet/nmirror

Merge nmirror to master

5 files changed, 48 insertions, 5 deletions

diff --git a/src/ILCompiler.Compiler/src/Compiler/DependencyAnalysis/CanonicalEETypeNode.cs b/src/ILCompiler.Compiler/src/Compiler/DependencyAnalysis/CanonicalEETypeNode.cs
index 807f620b9..6e3bc9f58 100644
--- a/src/ILCompiler.Compiler/src/Compiler/DependencyAnalysis/CanonicalEETypeNode.cs
+++ b/src/ILCompiler.Compiler/src/Compiler/DependencyAnalysis/CanonicalEETypeNode.cs
@@ -46,7 +46,7 @@ namespace ILCompiler.DependencyAnalysis
 
             DefType closestDefType = _type.GetClosestDefType();
 
-            if (_type.RuntimeInterfaces.Length > 0 && !_type.IsArrayTypeWithoutGenericInterfaces())
+            if (InterfaceDispatchMapNode.MightHaveInterfaceDispatchMap(_type, factory))
                 dependencyList.Add(factory.InterfaceDispatchMap(_type), "Canonical interface dispatch map");
 
             dependencyList.Add(factory.VTable(closestDefType), "VTable");
diff --git a/src/ILCompiler.Compiler/src/Compiler/DependencyAnalysis/ConstructedEETypeNode.cs b/src/ILCompiler.Compiler/src/Compiler/DependencyAnalysis/ConstructedEETypeNode.cs
index 4dc900b3e..0dee4d7cb 100644
--- a/src/ILCompiler.Compiler/src/Compiler/DependencyAnalysis/ConstructedEETypeNode.cs
+++ b/src/ILCompiler.Compiler/src/Compiler/DependencyAnalysis/ConstructedEETypeNode.cs
@@ -80,7 +80,7 @@ namespace ILCompiler.DependencyAnalysis
 
             DefType closestDefType = _type.GetClosestDefType();
 
-            if (_type.RuntimeInterfaces.Length > 0 && !_type.IsArrayTypeWithoutGenericInterfaces())
+            if (InterfaceDispatchMapNode.MightHaveInterfaceDispatchMap(_type, factory))
             {
                 dependencyList.Add(factory.InterfaceDispatchMap(_type), "Interface dispatch map");
             }
diff --git a/src/ILCompiler.Compiler/src/Compiler/DependencyAnalysis/EETypeNode.cs b/src/ILCompiler.Compiler/src/Compiler/DependencyAnalysis/EETypeNode.cs
index dfe887c46..8df68bd1d 100644
--- a/src/ILCompiler.Compiler/src/Compiler/DependencyAnalysis/EETypeNode.cs
+++ b/src/ILCompiler.Compiler/src/Compiler/DependencyAnalysis/EETypeNode.cs
@@ -867,7 +867,7 @@ namespace ILCompiler.DependencyAnalysis
         /// </summary>
         protected internal virtual void ComputeOptionalEETypeFields(NodeFactory factory, bool relocsOnly)
         {
-            if (!relocsOnly && _type.RuntimeInterfaces.Length > 0 && !_type.IsArrayTypeWithoutGenericInterfaces() && factory.InterfaceDispatchMap(_type).Marked)
+            if (!relocsOnly && EmitVirtualSlotsAndInterfaces && InterfaceDispatchMapNode.MightHaveInterfaceDispatchMap(_type, factory))
             {
                 _optionalFieldsBuilder.SetFieldValue(EETypeOptionalFieldTag.DispatchMap, checked((uint)factory.InterfaceDispatchMapIndirection(Type).IndexFromBeginningOfArray));
             }
diff --git a/src/ILCompiler.Compiler/src/Compiler/DependencyAnalysis/InterfaceDispatchMapNode.cs b/src/ILCompiler.Compiler/src/Compiler/DependencyAnalysis/InterfaceDispatchMapNode.cs
index 71966e20f..b631efaff 100644
--- a/src/ILCompiler.Compiler/src/Compiler/DependencyAnalysis/InterfaceDispatchMapNode.cs
+++ b/src/ILCompiler.Compiler/src/Compiler/DependencyAnalysis/InterfaceDispatchMapNode.cs
@@ -15,12 +15,13 @@ namespace ILCompiler.DependencyAnalysis
     {
         TypeDesc _type;
 
-        public InterfaceDispatchMapNode(TypeDesc type)
+        public InterfaceDispatchMapNode(NodeFactory factory, TypeDesc type)
         {
             // Multidimensional arrays should not get a sealed vtable or a dispatch map. Runtime should use the 
             // sealed vtable and dispatch map of the System.Array basetype instead.
             // Pointer arrays also follow the same path
             Debug.Assert(!type.IsArrayTypeWithoutGenericInterfaces());
+            Debug.Assert(MightHaveInterfaceDispatchMap(type, factory));
 
             _type = type;
         }
@@ -62,6 +63,48 @@ namespace ILCompiler.DependencyAnalysis
             return result;
         }
 
+        /// <summary>
+        /// Gets a value indicating whether '<paramref name="type"/>' might have a non-empty dispatch map.
+        /// Note that this is only an approximation because we might not be able to take into account
+        /// whether the interface methods are actually used.
+        /// </summary>
+        public static bool MightHaveInterfaceDispatchMap(TypeDesc type, NodeFactory factory)
+        {
+            if (type.IsArrayTypeWithoutGenericInterfaces())
+                return false;
+
+            if (!type.IsArray && !type.IsDefType)
+                return false;
+
+            DefType defType = type.GetClosestDefType();
+
+            foreach (DefType interfaceType in defType.RuntimeInterfaces)
+            {
+                IEnumerable<MethodDesc> slots;
+
+                // If the vtable has fixed slots, we can query it directly.
+                // If it's a lazily built vtable, we might not be able to query slots
+                // just yet, so approximate by looking at all methods.
+                VTableSliceNode vtableSlice = factory.VTable(interfaceType);
+                if (vtableSlice.HasFixedSlots)
+                    slots = vtableSlice.Slots;
+                else
+                    slots = interfaceType.GetAllMethods();
+
+                foreach (MethodDesc declMethod in slots)
+                {
+                    if (declMethod.Signature.IsStatic)
+                        continue;
+
+                    var implMethod = defType.ResolveInterfaceMethodToVirtualMethodOnType(declMethod);
+                    if (implMethod != null)
+                        return true;
+                }
+            }
+
+            return false;
+        }
+
         void EmitDispatchMap(ref ObjectDataBuilder builder, NodeFactory factory)
         {
             var entryCountReservation = builder.ReserveInt();
diff --git a/src/ILCompiler.Compiler/src/Compiler/DependencyAnalysis/NodeFactory.cs b/src/ILCompiler.Compiler/src/Compiler/DependencyAnalysis/NodeFactory.cs
index 597b2d55a..35795ed02 100644
--- a/src/ILCompiler.Compiler/src/Compiler/DependencyAnalysis/NodeFactory.cs
+++ b/src/ILCompiler.Compiler/src/Compiler/DependencyAnalysis/NodeFactory.cs
@@ -379,7 +379,7 @@ namespace ILCompiler.DependencyAnalysis
 
             _interfaceDispatchMaps = new NodeCache<TypeDesc, InterfaceDispatchMapNode>((TypeDesc type) =>
             {
-                return new InterfaceDispatchMapNode(type);
+                return new InterfaceDispatchMapNode(this, type);
             });
 
             _sealedVtableNodes = new NodeCache<TypeDesc, SealedVTableNode>((TypeDesc type) =>