Small fixes to sealed vtables (#1175)

* Avoid double hashtable lookup * Avoid generating empty sealed vtables (basically, emitting a bunch of unreferenced symbol definitions in the object file)
dotnet · May 27, 2021 · d707f62 · d707f62
1 parent 5e1d0cc
commit d707f62
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Showing 2 changed files with 14 additions and 4 deletions.
diff --git a/src/coreclr/tools/aot/ILCompiler.Compiler/Compiler/DependencyAnalysis/SealedVTableNode.cs b/src/coreclr/tools/aot/ILCompiler.Compiler/Compiler/DependencyAnalysis/SealedVTableNode.cs
@@ -56,6 +56,12 @@ public int NumSealedVTableEntries
             }
         }
 
+        public override bool ShouldSkipEmittingObjectNode(NodeFactory factory)
+        {
+            BuildSealedVTableSlots(factory, relocsOnly: false);
+            return NumSealedVTableEntries == 0;
+        }
+
         /// <summary>
         /// Returns the slot of a method in the sealed vtable, or -1 if not found. This API should only be called after 
         /// successfully building the sealed vtable slots.

diff --git a/src/coreclr/tools/aot/ILCompiler.Compiler/Compiler/VirtualMethodCallHelper.cs b/src/coreclr/tools/aot/ILCompiler.Compiler/Compiler/VirtualMethodCallHelper.cs
@@ -15,10 +15,12 @@ public static int GetDefaultInterfaceMethodSlot(NodeFactory factory, MethodDesc
         {
             Debug.Assert(method.GetTypicalMethodDefinition().OwningType == interfaceOnDefinition.GetTypeDefinition());
 
+            SealedVTableNode sealedVTable = factory.SealedVTable(implType);
+
             // Ensure the sealed vtable is built before computing the slot
-            factory.SealedVTable(implType).BuildSealedVTableSlots(factory, relocsOnly: false /* GetVirtualMethodSlot is called in the final emission phase */);
+            sealedVTable.BuildSealedVTableSlots(factory, relocsOnly: false /* GetVirtualMethodSlot is called in the final emission phase */);
 
-            int sealedVTableSlot = factory.SealedVTable(implType).ComputeDefaultInterfaceMethodSlot(method, interfaceOnDefinition);
+            int sealedVTableSlot = sealedVTable.ComputeDefaultInterfaceMethodSlot(method, interfaceOnDefinition);
             if (sealedVTableSlot == -1)
                 return -1;
 
@@ -42,10 +44,12 @@ public static int GetVirtualMethodSlot(NodeFactory factory, MethodDesc method, T
                 // does not get any sealed vtable entries
                 Debug.Assert(!implType.IsArrayTypeWithoutGenericInterfaces());
 
+                SealedVTableNode sealedVTable = factory.SealedVTable(implType);
+
                 // Ensure the sealed vtable is built before computing the slot
-                factory.SealedVTable(implType).BuildSealedVTableSlots(factory, relocsOnly: false /* GetVirtualMethodSlot is called in the final emission phase */);
+                sealedVTable.BuildSealedVTableSlots(factory, relocsOnly: false /* GetVirtualMethodSlot is called in the final emission phase */);
 
-                int sealedVTableSlot = factory.SealedVTable(implType).ComputeSealedVTableSlot(method);
+                int sealedVTableSlot = sealedVTable.ComputeSealedVTableSlot(method);
                 if (sealedVTableSlot == -1)
                     return -1;