From 48a8351e27fad3d1c399efa1121cd066c54a4081 Mon Sep 17 00:00:00 2001
From: Siegfried Pammer <siegfriedpammer@gmail.com>
Date: Mon, 27 Jun 2022 16:10:42 +0200
Subject: [PATCH] Use Unsafe.SizeOf when taking the size of a managed type.

---
 .../TestCases/ILPretty/Unsafe.cs              |  8 ++++----
 .../CSharp/ExpressionBuilder.cs               | 19 ++++++++++++++++---
 .../TypeSystem/TypeSystemExtensions.cs        |  3 +++
 3 files changed, 23 insertions(+), 7 deletions(-)

diff --git a/ICSharpCode.Decompiler.Tests/TestCases/ILPretty/Unsafe.cs b/ICSharpCode.Decompiler.Tests/TestCases/ILPretty/Unsafe.cs
index 1a126fd9c..c853317bc 100644
--- a/ICSharpCode.Decompiler.Tests/TestCases/ILPretty/Unsafe.cs
+++ b/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)]
diff --git a/ICSharpCode.Decompiler/CSharp/ExpressionBuilder.cs b/ICSharpCode.Decompiler/CSharp/ExpressionBuilder.cs
index 6c1d6f9be..b278907bf 100644
--- a/ICSharpCode.Decompiler/CSharp/ExpressionBuilder.cs
+++ b/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))
-				.WithILInstruction(inst)
-				.WithRR(new SizeOfResolveResult(compilation.FindType(KnownTypeCode.Int32), inst.Type, null));
+			if (inst.Type.IsUnmanagedType(allowGenerics: settings.IntroduceUnmanagedConstraint))
+			{
+				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)
diff --git a/ICSharpCode.Decompiler/TypeSystem/TypeSystemExtensions.cs b/ICSharpCode.Decompiler/TypeSystem/TypeSystemExtensions.cs
index f714be673..122f794e6 100644
--- a/ICSharpCode.Decompiler/TypeSystem/TypeSystemExtensions.cs
+++ b/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;