Improve decompiler performance.

ICSharpCode.Decompiler/CSharp/Resolver/CSharpConversions.cs

@@ -112,7 +112,12 @@ namespace ICSharpCode.Decompiler.CSharp.Resolver
 					if (c != Conversion.None) return c;
 				}
 			} else {
-				c = ImplicitConversion(resolveResult.Type, toType, allowUserDefined);
+				if (allowUserDefined) {
+					// if allowUserDefined is true, we might as well use the cache
+					c = ImplicitConversion(resolveResult.Type, toType);
+				} else {
+					c = ImplicitConversion(resolveResult.Type, toType, allowUserDefined);
+				}
 				if (c != Conversion.None) return c;
 			}
 			if (resolveResult.Type.Kind == TypeKind.Dynamic)

ICSharpCode.Decompiler/IL/ControlFlow/YieldReturnDecompiler.cs

@@ -409,7 +409,7 @@ namespace ICSharpCode.Decompiler.IL.ControlFlow
 		#region Analyze MoveNext() and generate new body
 		BlockContainer AnalyzeMoveNext()
 		{
-			context.Stepper.StartGroup("AnalyzeMoveNext");
+			context.StepStartGroup("AnalyzeMoveNext");
 			MethodDefinition moveNextMethod = enumeratorType.Methods.FirstOrDefault(m => m.Name == "MoveNext");
 			ILFunction moveNextFunction = CreateILAst(moveNextMethod);
 
@@ -450,7 +450,7 @@ namespace ICSharpCode.Decompiler.IL.ControlFlow
 			moveNextFunction.Variables.Clear();
 			// release references from old moveNextFunction to instructions that were moved over to newBody
 			moveNextFunction.ReleaseRef();
-			context.Stepper.EndGroup();
+			context.StepEndGroup();
 			return newBody;
 		}
 
@@ -458,7 +458,7 @@ namespace ICSharpCode.Decompiler.IL.ControlFlow
 		{
 			// Roslyn may optimize MoveNext() by copying fields from the iterator class into local variables
 			// at the beginning of MoveNext(). Undo this optimization.
-			context.Stepper.StartGroup("PropagateCopiesOfFields");
+			context.StepStartGroup("PropagateCopiesOfFields");
 			var mutableFields = body.Descendants.OfType<LdFlda>().Where(ldflda => ldflda.Parent.OpCode != OpCode.LdObj).Select(ldflda => ldflda.Field).ToHashSet();
 			for (int i = 0; i < body.EntryPoint.Instructions.Count; i++) {
 				if (body.EntryPoint.Instructions[i] is StLoc store
@@ -482,7 +482,7 @@ namespace ICSharpCode.Decompiler.IL.ControlFlow
 					break; // unknown instruction
 				}
 			}
-			context.Stepper.EndGroup();
+			context.StepEndGroup();
 		}
 
 		/// <summary>
@@ -718,7 +718,7 @@ namespace ICSharpCode.Decompiler.IL.ControlFlow
 		void ReconstructTryFinallyBlocks(ILFunction iteratorFunction)
 		{
 			BlockContainer newBody = (BlockContainer)iteratorFunction.Body;
-			context.Stepper.Step("Reconstuct try-finally blocks");
+			context.Step("Reconstuct try-finally blocks", newBody);
 			var blockState = new int[newBody.Blocks.Count];
 			blockState[0] = -1;
 			var stateToContainer = new Dictionary<int, BlockContainer>();

ICSharpCode.Decompiler/IL/Instructions/Block.cs

@@ -215,10 +215,10 @@ namespace ICSharpCode.Decompiler.IL
 			this.CheckInvariant(ILPhase.Normal);
 			foreach (var transform in transforms) {
 				context.CancellationToken.ThrowIfCancellationRequested();
-				context.Stepper.StartGroup(transform.GetType().Name);
+				context.StepStartGroup(transform.GetType().Name);
 				transform.Run(this, context);
 				this.CheckInvariant(ILPhase.Normal);
-				context.Stepper.EndGroup();
+				context.StepEndGroup();
 			}
 		}
 

ICSharpCode.Decompiler/IL/Instructions/ILFunction.cs

@@ -114,13 +114,13 @@ namespace ICSharpCode.Decompiler.IL
 			foreach (var transform in transforms) {
 				context.CancellationToken.ThrowIfCancellationRequested();
 				if (transform is BlockILTransform blockTransform) {
-					context.Stepper.StartGroup(blockTransform.ToString());
+					context.StepStartGroup(blockTransform.ToString());
 				} else {
-					context.Stepper.StartGroup(transform.GetType().Name);
+					context.StepStartGroup(transform.GetType().Name);
 				}
 				transform.Run(this, context);
 				this.CheckInvariant(ILPhase.Normal);
-				context.Stepper.EndGroup(keepIfEmpty: true);
+				context.StepEndGroup(keepIfEmpty: true);
 			}
 		}
 

ICSharpCode.Decompiler/IL/Transforms/BlockTransform.cs

@@ -83,7 +83,7 @@ namespace ICSharpCode.Decompiler.IL.Transforms
 		void VisitBlock(ControlFlowNode cfgNode, BlockTransformContext context)
 		{
 			Block block = (Block)cfgNode.UserData;
-			context.Stepper.StartGroup(block.Label, block);
+			context.StepStartGroup(block.Label, block);
 
 			context.ControlFlowNode = cfgNode;
 			context.Block = block;
@@ -99,7 +99,7 @@ namespace ICSharpCode.Decompiler.IL.Transforms
 			context.ControlFlowNode = cfgNode;
 			context.Block = block;
 			block.RunTransforms(PostOrderTransforms, context);
-			context.Stepper.EndGroup();
+			context.StepEndGroup();
 		}
 	}
 }

ICSharpCode.Decompiler/IL/Transforms/IILTransform.cs

@@ -62,5 +62,17 @@ namespace ICSharpCode.Decompiler.IL.Transforms
 		{
 			Stepper.Step(description, near);
 		}
+		
+		[Conditional("STEP")]
+		internal void StepStartGroup(string description, ILInstruction near = null)
+		{
+			Stepper.StartGroup(description, near);
+		}
+
+		[Conditional("STEP")]
+		internal void StepEndGroup(bool keepIfEmpty = false)
+		{
+			Stepper.EndGroup(keepIfEmpty);
+		}
 	}
 }