Fix detection of do-while and for loops.

ICSharpCode.Decompiler/CSharp/StatementBuilder.cs

@@ -381,21 +381,25 @@ namespace ICSharpCode.Decompiler.CSharp
 
 		private static Block FindDoWhileConditionBlock(BlockContainer container, out ILInstruction condition)
 		{
-			var conditionGroup = new CaptureGroup();
-			var conditionBlockPattern = new Block {
-				Instructions = {
-					new IfInstruction(new AnyNode(conditionGroup), new Branch(container.EntryPoint)),
-					new Leave(container)
-				}
-			};
+			condition = null;
 			foreach (var b in container.Blocks) {
-				var match = conditionBlockPattern.Match(b);
-				if (match.Success) {
-					condition = match.Get(conditionGroup).Single();
-					return b;
+				if (b.Instructions.Last().MatchBranch(container.EntryPoint)) {
+					// potentially the do-while-condition block
+					int i = b.Instructions.Count - 2;
+					while (i >= 0 && b.Instructions[i] is IfInstruction ifInst
+						&& ifInst.TrueInst.MatchLeave(container) && ifInst.FalseInst.MatchNop())
+					{
+						if (condition == null)
+							condition = new LogicNot(ifInst.Condition);
+						else
+							condition = IfInstruction.LogicAnd(new LogicNot(ifInst.Condition), condition);
+						i--;
+					}
+					if (i == -1) {
+						return b;
+					}
 				}
 			}
-			condition = null;
 			return null;
 		}
 

ICSharpCode.Decompiler/IL/Instructions.cs

@@ -836,6 +836,7 @@ namespace ICSharpCode.Decompiler.IL
 		{
 		}
 		public override StackType ResultType { get { return StackType.I4; } }
+
 		public override void AcceptVisitor(ILVisitor visitor)
 		{
 			visitor.VisitLogicNot(this);

ICSharpCode.Decompiler/IL/Transforms/LoopingTransform.cs

@@ -39,13 +39,16 @@ namespace ICSharpCode.Decompiler.IL.Transforms
 			if (running)
 				throw new InvalidOperationException("LoopingBlockTransform already running. Transforms (and the CSharpDecompiler) are neither neither thread-safe nor re-entrant.");
 			running = true;
-			do {
-				block.ResetDirty();
-				block.RunTransforms(children, context);
-				if (block.IsDirty)
-					context.Step("Block is dirty; running another loop iteration.", block);
-			} while (block.IsDirty);
-			running = false;
+			try {
+				do {
+					block.ResetDirty();
+					block.RunTransforms(children, context);
+					if (block.IsDirty)
+						context.Step("Block is dirty; running another loop iteration.", block);
+				} while (block.IsDirty);
+			} finally {
+				running = false;
+			}
 		}
 
 		public IReadOnlyCollection<IBlockTransform> Transforms {

ICSharpCode.Decompiler/Util/CollectionExtensions.cs

@@ -19,7 +19,7 @@ namespace ICSharpCode.Decompiler.Util
 
 		public static IEnumerable<T> SkipLast<T>(this IReadOnlyCollection<T> input, int count)
 		{
-			return input.Skip(input.Count - count);
+			return input.Take(input.Count - count);
 		}
 		
 		public static T PopOrDefault<T>(this Stack<T> stack)