Implemented a very simple loop detection.

ICSharpCode.Decompiler/DominanceLoopDetector.cs

@@ -0,0 +1,80 @@
+// <file>
+//     <copyright see="prj:///doc/copyright.txt"/>
+//     <license see="prj:///doc/license.txt"/>
+//     <author name="Daniel Grunwald"/>
+//     <version>$Revision$</version>
+// </file>
+using System;
+using System.Collections.Generic;
+using System.IO;
+using System.Linq;
+using ICSharpCode.Decompiler.FlowAnalysis;
+
+namespace ICSharpCode.Decompiler
+{
+	/// <summary>
+	/// Description of DominanceLoopDetector.
+	/// </summary>
+	public class DominanceLoopDetector
+	{
+		public static ControlStructure DetectLoops(ControlFlowGraph g)
+		{
+			ControlStructure root = new ControlStructure(
+				new HashSet<ControlFlowNode>(g.Nodes),
+				g.EntryPoint
+			);
+			DetectLoops(g, root);
+			g.ResetVisited();
+			return root;
+		}
+		
+		static void DetectLoops(ControlFlowGraph g, ControlStructure current)
+		{
+			g.ResetVisited();
+			FindLoops(current, current.EntryPoint);
+			foreach (ControlStructure loop in current.Children)
+				DetectLoops(g, loop);
+		}
+		
+		static void FindLoops(ControlStructure current, ControlFlowNode node)
+		{
+			if (node.Visited)
+				return;
+			node.Visited = true;
+			if (current.Nodes.Contains(node)
+			    && node.DominanceFrontier.Contains(node)
+			    && node != current.EntryPoint)
+			{
+				HashSet<ControlFlowNode> loopContents = new HashSet<ControlFlowNode>();
+				FindLoopContents(current, loopContents, node, node);
+				current.Nodes.ExceptWith(loopContents);
+				current.Children.Add(new ControlStructure(loopContents, node));
+			}
+			foreach (var edge in node.Outgoing) {
+				FindLoops(current, edge.Target);
+			}
+		}
+		
+		static void FindLoopContents(ControlStructure current, HashSet<ControlFlowNode> loopContents, ControlFlowNode loopHead, ControlFlowNode node)
+		{
+			if (current.Nodes.Contains(node) && loopHead.Dominates(node) && loopContents.Add(node)) {
+				foreach (var edge in node.Incoming) {
+					FindLoopContents(current, loopContents, loopHead, edge.Source);
+				}
+			}
+		}
+	}
+	
+	public class ControlStructure
+	{
+		public List<ControlStructure> Children = new List<ControlStructure>();
+		public HashSet<ControlFlowNode> Nodes;
+		public ControlFlowNode EntryPoint;
+		
+		public ControlStructure(HashSet<ControlFlowNode> nodes, ControlFlowNode entryPoint)
+		{
+			this.Nodes = nodes;
+			this.EntryPoint = entryPoint;
+		}
+	}
+}

ICSharpCode.Decompiler/FlowAnalysis/ControlFlowEdge.cs

@@ -23,9 +23,23 @@ namespace ICSharpCode.Decompiler.FlowAnalysis
 	public enum JumpType
 	{
 		Normal,
+		/// <summary>
+		/// Jump to exception handler (an exception occurred)
+		/// </summary>
 		JumpToExceptionHandler,
+		/// <summary>
+		/// Jump from try block to leave target:
+		/// This is not a real jump, as the finally handler is executed first!
+		/// </summary>
 		LeaveTry,
-		MutualProtection
+		/// <summary>
+		/// Jump from one catch block to its sibling
+		/// </summary>
+		MutualProtection,
+		/// <summary>
+		/// non-determistic jump at end finally (to any of the potential leave targets)
+		/// </summary>
+		EndFinally
 	}
 	
 	public sealed class ControlFlowEdge

ICSharpCode.Decompiler/FlowAnalysis/ControlFlowGraphBuilder.cs

@@ -32,6 +32,7 @@ namespace ICSharpCode.Decompiler.FlowAnalysis
 			return new ControlFlowGraphBuilder(methodBody).Build();
 		}
 		
+		bool copyFinallyBlocks = false;
 		MethodBody methodBody;
 		int[] offsets; // array index = instruction index; value = IL offset
 		bool[] hasIncomingJumps; // array index = instruction index
@@ -39,7 +40,6 @@ namespace ICSharpCode.Decompiler.FlowAnalysis
 		ControlFlowNode entryPoint;
 		ControlFlowNode regularExit;
 		ControlFlowNode exceptionalExit;
-		//Stack<> activeExceptionHandlers = new Stack<ExceptionHandler>();
 		
 		private ControlFlowGraphBuilder(MethodBody methodBody)
 		{
@@ -69,7 +69,10 @@ namespace ICSharpCode.Decompiler.FlowAnalysis
 			CreateNodes();
 			CreateRegularControlFlow();
 			CreateExceptionalControlFlow();
+			if (copyFinallyBlocks)
 				CopyFinallyBlocksIntoLeaveEdges();
+			else
+				TransformLeaveEdges();
 			return new ControlFlowGraph(nodes.ToArray());
 		}
 		
@@ -242,6 +245,28 @@ namespace ICSharpCode.Decompiler.FlowAnalysis
 			}
 		}
 		
+		
+		void TransformLeaveEdges()
+		{
+			for (int i = nodes.Count - 1; i >= 0; i--) {
+				ControlFlowNode node = nodes[i];
+				if (node.End != null && node.Outgoing.Count == 1 && node.Outgoing[0].Type == JumpType.LeaveTry) {
+					Debug.Assert(node.End.OpCode == OpCodes.Leave);
+					
+					ControlFlowNode target = node.Outgoing[0].Target;
+					// remove the edge
+					target.Incoming.Remove(node.Outgoing[0]);
+					node.Outgoing.Clear();
+					
+					ControlFlowNode handler = FindInnermostExceptionHandler(node.End.Offset);
+					Debug.Assert(handler.NodeType == ControlFlowNodeType.FinallyOrFaultHandler);
+					
+					CreateEdge(node, handler, JumpType.Normal);
+					CreateEdge(handler.EndFinallyOrFaultNode, target, JumpType.EndFinally);
+				}
+			}
+		}
+		
 		/// <summary>
 		/// Creates a copy of all nodes pointing to 'end' and replaces those references with references to 'newEnd'.
 		/// Nodes pointing to the copied node are copied recursively to update those references, too.

ICSharpCode.Decompiler/FlowAnalysis/ControlFlowNode.cs

@@ -174,11 +174,26 @@ namespace ICSharpCode.Decompiler.FlowAnalysis
 //				writer.WriteLine();
 //				writer.Write("ImmediateDominator: #{0}", ImmediateDominator.BlockIndex);
 //			}
+			if (DominanceFrontier != null && DominanceFrontier.Any()) {
+				writer.WriteLine();
+				writer.Write("DominanceFrontier: " + string.Join(",", DominanceFrontier.OrderBy(d => d.BlockIndex).Select(d => d.BlockIndex.ToString())));
+			}
 			foreach (Instruction inst in this.Instructions) {
 				writer.WriteLine();
 				inst.WriteTo(writer);
 			}
 			return writer.ToString();
 		}
+		
+		public bool Dominates(ControlFlowNode node)
+		{
+			ControlFlowNode tmp = node;
+			while (tmp != null) {
+				if (tmp == this)
+					return true;
+				tmp = tmp.ImmediateDominator;
+			}
+			return false;
+		}
 	}
 }

ICSharpCode.Decompiler/ICSharpCode.Decompiler.csproj

@@ -50,6 +50,7 @@
   </ItemGroup>
   <ItemGroup>
     <Compile Include="CecilExtensions.cs" />
+    <Compile Include="DominanceLoopDetector.cs" />
     <Compile Include="FlowAnalysis\ControlFlowEdge.cs" />
     <Compile Include="FlowAnalysis\ControlFlowGraph.cs" />
     <Compile Include="FlowAnalysis\ControlFlowGraphBuilder.cs" />

ILSpy/Decompiler/CSharpLanguage.cs

@@ -17,7 +17,11 @@
 // DEALINGS IN THE SOFTWARE.
 
 using System;
+using System.IO;
+using ICSharpCode.Decompiler;
+using ICSharpCode.Decompiler.FlowAnalysis;
 using Mono.Cecil;
+using Mono.Cecil.Rocks;
 
 namespace ICSharpCode.ILSpy.Decompiler
 {
@@ -30,8 +34,9 @@ namespace ICSharpCode.ILSpy.Decompiler
 			get { return "C#"; }
 		}
 		
-		public override void Decompile(MethodDefinition methodDefinition, ITextOutput output)
+		public override void Decompile(MethodDefinition method, ITextOutput output)
 		{
+			throw new NotImplementedException();
 		}
 	}
 }

ILSpy/Disassembler/ILLanguage.cs

@@ -17,7 +17,11 @@
 // DEALINGS IN THE SOFTWARE.
 
 using System;
+using System.Linq;
+using ICSharpCode.Decompiler;
+using ICSharpCode.Decompiler.FlowAnalysis;
 using Mono.Cecil;
+using Mono.Cecil.Rocks;
 
 namespace ICSharpCode.ILSpy.Disassembler
 {
@@ -27,8 +31,18 @@ namespace ICSharpCode.ILSpy.Disassembler
 			get { return "IL"; }
 		}
 		
+		bool detectControlStructure = true;
+		
 		public override void Decompile(MethodDefinition method, ITextOutput output)
 		{
+			if (detectControlStructure) {
+				method.Body.SimplifyMacros();
+				var cfg = ControlFlowGraphBuilder.Build(method.Body);
+				cfg.ComputeDominance();
+				cfg.ComputeDominanceFrontier();
+				var s = DominanceLoopDetector.DetectLoops(cfg);
+				WriteStructure(output, s);
+			} else {
 				foreach (var inst in method.Body.Instructions) {
 					inst.WriteTo(output);
 					output.WriteLine();
@@ -40,4 +54,25 @@ namespace ICSharpCode.ILSpy.Disassembler
 				}
 			}
 		}
+		
+		void WriteStructure(ITextOutput output, ControlStructure s)
+		{
+			output.WriteComment("// loop start");
+			output.WriteLine();
+			output.Indent();
+			foreach (var node in s.Nodes.Concat(s.Children.Select(c => c.EntryPoint)).OrderBy(n => n.BlockIndex)) {
+				if (s.Nodes.Contains(node)) {
+					foreach (var inst in node.Instructions) {
+						inst.WriteTo(output);
+						output.WriteLine();
+					}
+				} else {
+					WriteStructure(output, s.Children.Single(c => c.EntryPoint == node));
+				}
+			}
+			output.Unindent();
+			output.WriteComment("// loop end");
+			output.WriteLine();
+		}
+	}
 }

ILSpy/MainWindow.xaml.cs

@@ -124,7 +124,10 @@ namespace ICSharpCode.ILSpy
 			MethodTreeNode node = treeView.SelectedItem as MethodTreeNode;
 			if (node != null && node.MethodDefinition.HasBody) {
 				node.MethodDefinition.Body.SimplifyMacros();
-				ShowGraph(node.MethodDefinition.Name + "-cfg", ControlFlowGraphBuilder.Build(node.MethodDefinition.Body).ExportGraph());
+				var cfg = ControlFlowGraphBuilder.Build(node.MethodDefinition.Body);
+				cfg.ComputeDominance();
+				cfg.ComputeDominanceFrontier();
+				ShowGraph(node.MethodDefinition.Name + "-cfg", cfg.ExportGraph());
 			}
 		}