Use Unsafe.SizeOf when taking the size of a managed type.

ICSharpCode.Decompiler.Tests/TestCases/ILPretty/Unsafe.cs

@@ -207,9 +207,9 @@ namespace System.Runtime.CompilerServices
 		}
 
 		[MethodImpl(MethodImplOptions.AggressiveInlining)]
-		public unsafe static int SizeOf<T>()
+		public static int SizeOf<T>()
 		{
-			return sizeof(T);
+			return Unsafe.SizeOf<T>();
 		}
 
 		[MethodImpl(MethodImplOptions.AggressiveInlining)]
@@ -307,7 +307,7 @@ namespace System.Runtime.CompilerServices
 		[MethodImpl(MethodImplOptions.AggressiveInlining)]
 		public unsafe static void* Add<T>(void* source, int elementOffset)
 		{
-			return (byte*)source + (nint)elementOffset * (nint)sizeof(T);
+			return (byte*)source + (nint)elementOffset * (nint)Unsafe.SizeOf<T>();
 		}
 
 		[MethodImpl(MethodImplOptions.AggressiveInlining)]
@@ -343,7 +343,7 @@ namespace System.Runtime.CompilerServices
 		[MethodImpl(MethodImplOptions.AggressiveInlining)]
 		public unsafe static void* Subtract<T>(void* source, int elementOffset)
 		{
-			return (byte*)source - (nint)elementOffset * (nint)sizeof(T);
+			return (byte*)source - (nint)elementOffset * (nint)Unsafe.SizeOf<T>();
 		}
 
 		[MethodImpl(MethodImplOptions.AggressiveInlining)]

ICSharpCode.Decompiler/CSharp/ExpressionBuilder.cs

@@ -648,9 +648,22 @@ namespace ICSharpCode.Decompiler.CSharp
 
 		protected internal override TranslatedExpression VisitSizeOf(SizeOf inst, TranslationContext context)
 		{
-			return new SizeOfExpression(ConvertType(inst.Type))
+			if (inst.Type.IsUnmanagedType(allowGenerics: settings.IntroduceUnmanagedConstraint))
-				.WithILInstruction(inst)
+			{
-				.WithRR(new SizeOfResolveResult(compilation.FindType(KnownTypeCode.Int32), inst.Type, null));
+				return new SizeOfExpression(ConvertType(inst.Type))
+					.WithILInstruction(inst)
+					.WithRR(new SizeOfResolveResult(compilation.FindType(KnownTypeCode.Int32), inst.Type, null));
+			}
+			else
+			{
+				return CallUnsafeIntrinsic(
+					name: "SizeOf",
+					arguments: Array.Empty<Expression>(),
+					returnType: compilation.FindType(KnownTypeCode.Int32),
+					inst: inst,
+					typeArguments: new[] { inst.Type }
+				);
+			}
 		}
 
 		protected internal override TranslatedExpression VisitLdTypeToken(LdTypeToken inst, TranslationContext context)

ICSharpCode.Decompiler/TypeSystem/TypeSystemExtensions.cs

@@ -290,13 +290,16 @@ namespace ICSharpCode.Decompiler.TypeSystem
 					{
 						if (types.Contains(f.Type))
 						{
+							types.Remove(type);
 							return false;
 						}
 						if (!IsUnmanagedTypeInternal(f.Type))
 						{
+							types.Remove(type);
 							return false;
 						}
 					}
+					types.Remove(type);
 					return true;
 				}
 				return false;