Terminating all optimizations with exceptions

lib/NRefactory/Project/Src/Ast/NodeCollection.cs

@@ -60,13 +60,21 @@ namespace ICSharpCode.NRefactory.Ast
 		
 		public INode First {
 			get {
-				return this[0];
+				if (this.Count > 0) {
+					return this[0];
+				} else {
+					return null;
+				}
 			}
 		}
 		
 		public INode Last {
 			get {
-				return this[this.Count - 1];
+				if (this.Count > 0) {
+					return this[this.Count - 1];
+				} else {
+					return null;
+				}
 			}
 		}
 		

src/AstMetodBodyBuilder.cs

@@ -33,10 +33,16 @@ namespace Decompiler
 			
 			ByteCodeCollection body = new ByteCodeCollection(methodDef);
 			StackExpressionCollection exprCollection = new StackExpressionCollection(body);
-			exprCollection.Optimize();
+			try {
+				exprCollection.Optimize();
+			} catch (StopOptimizations) {
+			}
 			
 			MethodBodyGraph bodyGraph = new MethodBodyGraph(exprCollection);
-			bodyGraph.Optimize();
+			try {
+				bodyGraph.Optimize();
+			} catch (StopOptimizations) {
+			}
 			
 			List<string> intNames = new List<string>(new string[] {"i", "j", "k", "l", "m", "n", "o", "p", "q", "r", "s", "t"});
 			

src/ControlFlow/Node-Optimize.cs

@@ -22,7 +22,6 @@ namespace Decompiler.ControlFlow
 		Reset:
 			foreach(Node child in this.Childs) {
 				if (child.Predecessors.Count == 1) {
-					if (Options.ReduceGraph <= 0) return;
 					Node predecessor = child.Predecessors[0];
 					Node mergedNode;
 					if (child.Successors.Contains(predecessor)) {
@@ -36,7 +35,7 @@ namespace Decompiler.ControlFlow
 			}
 			// If the result is single acyclic node, eliminate it
 			if (this.Childs.Count == 1 && this.HeadChild is AcyclicGraph) {
-				if (Options.ReduceGraph-- <= 0) return;
+				Options.NotifyReducingGraph();
 				Node headChild = this.HeadChild;
 				this.Childs.Remove(this.HeadChild);
 				headChild.Childs.MoveTo(this);
@@ -103,18 +102,18 @@ namespace Decompiler.ControlFlow
 			falseNodes.RemoveRange(commonReachable);
 			
 			// Replace the basic block with condition node
-			if (Options.ReduceGraph-- <= 0) return;
+			Options.NotifyReducingGraph();
 			Node conditionParent = condition.Parent;
 			int conditionIndex = condition.Index; 
 			ConditionalNode conditionalNode = new ConditionalNode(condition);
 			conditionalNode.MoveTo(conditionParent, conditionIndex);
 			
-			if (Options.ReduceGraph-- <= 0) return;
+			Options.NotifyReducingGraph();
 			trueNodes.MoveTo(conditionalNode.TrueBody);
 			
-			if (Options.ReduceGraph-- <= 0) return;
 			// We can exit the 'true' part of Loop or MethodBody conviently using 'break' or 'return'
 			if (commonReachable.Count > 0 && (conditionalNode.Parent is Loop || conditionalNode.Parent is MethodBodyGraph)) {
+				Options.NotifyReducingGraph();
 				falseNodes.MoveTo(conditionalNode.FalseBody);
 			}
 			

src/ControlFlow/Node-Transforms.cs

@@ -35,12 +35,12 @@ namespace Decompiler.ControlFlow
 			Node mergedNode = new T();
 			
 			// Add the merged node
-			if (Options.ReduceGraph-- <= 0) return mergedNode;
+			Options.NotifyReducingGraph();
 			int headIndex = this.Childs.IndexOf(nodes[0]);
 			this.Childs.Insert(headIndex, mergedNode);
 			
 			foreach(Node node in nodes) {
-				if (Options.ReduceGraph-- <= 0) return mergedNode;
+				Options.NotifyReducingGraph();
 				node.MoveTo(mergedNode);
 			}
 			
@@ -52,7 +52,7 @@ namespace Decompiler.ControlFlow
 		Reset:
 			foreach(Node child in this.Childs) {
 				if (child is AcyclicGraph) {
-					if (Options.ReduceGraph-- <= 0) return;
+					Options.NotifyReducingGraph();
 					child.Childs.MoveTo(this, child.Index);
 					child.Remove();
 					goto Reset;

src/Options.cs

@@ -12,5 +12,24 @@ namespace Decompiler
 		public static bool ReduceAstJumps = true;
 		public static bool ReduceAstLoops = true;
 		public static bool ReduceAstOther = true;
+		
+		public static void NotifyCollapsingExpression()
+		{
+			if (CollapseExpression-- <= 0) {
+				throw new StopOptimizations();
+			}
+		}
+		
+		public static void NotifyReducingGraph()
+		{
+			if (ReduceGraph-- <= 0) {
+				throw new StopOptimizations();
+			}
+		}
+	}
+	
+	class StopOptimizations: Exception
+	{
+		
 	}
 }

src/StackExpressionCollection.cs

@@ -27,7 +27,7 @@ namespace Decompiler
 				    !expr.IsBranchTarget &&
 				    prevExpr.IsClosed)
 				{
-					if (Options.CollapseExpression-- <= 0) return;
+					Options.NotifyCollapsingExpression();
 					this.RemoveAt(i - 1); i--;
 					expr.LastArguments.Insert(0, prevExpr);
 					i--;