DetectPinnedRegions: Support special case where pinned pointer is unused and the compiler optimized out the StopGCTracking-conversion.

ICSharpCode.Decompiler.Tests/TestCases/Pretty/UnsafeCode.cs

@@ -419,13 +419,32 @@ namespace ICSharpCode.Decompiler.Tests.TestCases.Pretty
 				UsePointer(ptr);
 			}
 		}
+#endif
 
+#if CS73
 		//public unsafe void FixedCustomReferenceType(CustomPinnable mem)
 		//{
-		//	fixed (int* ptr = mem) {
+		//	fixed (int* ptr = mem)
+		//	{
 		//		UsePointer(ptr);
 		//	}
 		//}
+
+		public unsafe void FixedCustomReferenceTypeNoPointerUse(CustomPinnable mem)
+		{
+			fixed (int* ptr = mem)
+			{
+				Console.WriteLine("Hello World!");
+			}
+		}
+
+		public unsafe void FixedCustomReferenceTypeExplicitGetPinnableReference(CustomPinnable mem)
+		{
+			fixed (int* ptr = &mem.GetPinnableReference())
+			{
+				UsePointer(ptr);
+			}
+		}
 #endif
 
 		public unsafe string StackAlloc(int count)

ICSharpCode.Decompiler/CSharp/Transforms/PatternStatementTransform.cs

@@ -1168,7 +1168,8 @@ namespace ICSharpCode.Decompiler.CSharp.Transforms
 		}
 		#endregion
 
-		#region C# 7.3 pattern based fixed
+		#region C# 7.3 pattern based fixed (for value types)
+		// reference types are handled by DetectPinnedRegions.IsCustomRefPinPattern
 		static readonly Expression addressOfPinnableReference = new UnaryOperatorExpression {
 			Operator = UnaryOperatorType.AddressOf,
 			Expression = new InvocationExpression {
@@ -1186,7 +1187,11 @@ namespace ICSharpCode.Decompiler.CSharp.Transforms
 					var m = addressOfPinnableReference.Match(v.Initializer);
 					if (m.Success)
 					{
-						v.Initializer = m.Get<Expression>("target").Single().Detach();
+						Expression target = m.Get<Expression>("target").Single();
+						if (target.GetResolveResult().Type.IsReferenceType == false)
+						{
+							v.Initializer = target.Detach();
+						}
 					}
 				}
 			}

ICSharpCode.Decompiler/IL/ControlFlow/DetectPinnedRegions.cs

@@ -192,7 +192,10 @@ namespace ICSharpCode.Decompiler.IL.ControlFlow
 					}
 					block.Instructions[block.Instructions.Count - 2] = new StLoc(v, gpr)
 						.WithILRange(block.Instructions[block.Instructions.Count - 2]);
-					block.Instructions.Insert(block.Instructions.Count - 1, stlocPtr);
+					if (stlocPtr != null)
+					{
+						block.Instructions.Insert(block.Instructions.Count - 1, stlocPtr);
+					}
 					((Branch)block.Instructions.Last()).TargetBlock = targetBlock;
 					modified = true;
 				}
@@ -235,7 +238,16 @@ namespace ICSharpCode.Decompiler.IL.ControlFlow
 			if (!block.MatchIfAtEndOfBlock(out var ifCondition, out var trueInst, out var falseInst))
 				return false;
 			if (!ifCondition.MatchCompNotEqualsNull(out ldlocMem))
-				return false;
+			{
+				if (ifCondition.MatchCompEqualsNull(out ldlocMem))
+				{
+					(trueInst, falseInst) = (falseInst, trueInst);
+				}
+				else
+				{
+					return false;
+				}
+			}
 			if (!SemanticHelper.IsPure(ldlocMem.Flags))
 				return false;
 			if (!trueInst.MatchBranch(out Block notNullBlock) || notNullBlock.Parent != block.Parent)
@@ -243,21 +255,6 @@ namespace ICSharpCode.Decompiler.IL.ControlFlow
 			if (!falseInst.MatchBranch(out Block nullBlock) || nullBlock.Parent != block.Parent)
 				return false;
 
-			//  Block nullBlock (incoming: 1) {
-			//      stloc ptr(conv i4->u <zero extend>(ldc.i4 0))
-			//      br targetBlock
-			//  }
-			if (nullBlock.IncomingEdgeCount != 1)
-				return false;
-			if (nullBlock.Instructions.Count != 2)
-				return false;
-			if (!nullBlock.Instructions[0].MatchStLoc(out var ptr, out var nullPointerInst))
-				return false;
-			if (!nullPointerInst.MatchLdcI(0))
-				return false;
-			if (!nullBlock.Instructions[1].MatchBranch(out targetBlock))
-				return false;
-
 			//  Block notNullBlock (incoming: 1) {
 			//      stloc V_1(call GetPinnableReference(ldloc mem))
 			//      stloc ptr(conv ref->u (ldloc V_1))
@@ -265,7 +262,7 @@ namespace ICSharpCode.Decompiler.IL.ControlFlow
 			//  }
 			if (notNullBlock.IncomingEdgeCount != 1)
 				return false;
-			if (notNullBlock.Instructions.Count != 3)
+			if (notNullBlock.Instructions.Count < 2)
 				return false;
 			// stloc V_1(call GetPinnableReference(ldloc mem))
 			if (!notNullBlock.Instructions[0].MatchStLoc(out v, out var value))
@@ -281,13 +278,38 @@ namespace ICSharpCode.Decompiler.IL.ControlFlow
 				return false;
 			// stloc ptr(conv ref->u (ldloc V_1))
 			ptrAssign = notNullBlock.Instructions[1] as StLoc;
-			if (ptrAssign == null || ptrAssign.Variable != ptr)
-				return false;
-			if (!ptrAssign.Value.UnwrapConv(ConversionKind.StopGCTracking).MatchLdLoc(v))
-				return false;
-			// br targetBlock
-			if (!notNullBlock.Instructions[2].MatchBranch(targetBlock))
-				return false;
+			if (ptrAssign != null)
+			{
+				if (!ptrAssign.Value.UnwrapConv(ConversionKind.StopGCTracking).MatchLdLoc(v))
+					return false;
+				// br targetBlock
+				if (!notNullBlock.Instructions[2].MatchBranch(out targetBlock))
+					return false;
+
+				//  Block nullBlock (incoming: 1) {
+				//      stloc ptr(conv i4->u <zero extend>(ldc.i4 0))
+				//      br targetBlock
+				//  }
+				if (nullBlock.IncomingEdgeCount != 1)
+					return false;
+				if (nullBlock.Instructions.Count != 2)
+					return false;
+				if (!nullBlock.Instructions[0].MatchStLoc(ptrAssign.Variable, out var nullPointerInst))
+					return false;
+				if (!nullPointerInst.MatchLdcI(0))
+					return false;
+				if (!nullBlock.Instructions[1].MatchBranch(targetBlock))
+					return false;
+			}
+			else
+			{
+				// br targetBlock
+				if (!notNullBlock.Instructions[1].MatchBranch(out targetBlock))
+					return false;
+
+				if (targetBlock != nullBlock)
+					return false;
+			}
 			return true;
 		}