Remove unreachable code in ILAstBuilder. Closes #134. Closes #151. Closes #171.

ICSharpCode.Decompiler/ILAst/ILAstBuilder.cs

@@ -426,13 +426,12 @@ namespace ICSharpCode.Decompiler.ILAst
 				}
 			}
 			
-			// Occasionally the compiler generates unreachable code - it can be usually just ignored
+			// Occasionally the compilers or obfuscators generate unreachable code (which migt be intentonally invalid)
-			var reachableBody   = body.Where(b => b.StackBefore != null);
+			// I belive it is safe to just remove it
-			var unreachableBody = body.Where(b => b.StackBefore == null);
+			body.RemoveAll(b => b.StackBefore == null);
 			
 			// Genertate temporary variables to replace stack
-			// Unrachable code does not need temporary variables - the values are never pushed on the stack for consuption
+			foreach(ByteCode byteCode in body) {
-			foreach(ByteCode byteCode in reachableBody) {
 				int argIdx = 0;
 				int popCount = byteCode.PopCount ?? byteCode.StackBefore.Count;
 				for (int i = byteCode.StackBefore.Count - popCount; i < byteCode.StackBefore.Count; i++) {
@@ -450,19 +449,18 @@ namespace ICSharpCode.Decompiler.ILAst
 			
 			// Try to use single temporary variable insted of several if possilbe (especially useful for dup)
 			// This has to be done after all temporary variables are assigned so we know about all loads
-			// Unrachable code will not have any StoreTo
+			foreach(ByteCode byteCode in body) {
-			foreach(ByteCode byteCode in reachableBody) {
 				if (byteCode.StoreTo != null && byteCode.StoreTo.Count > 1) {
 					var locVars = byteCode.StoreTo;
 					// For each of the variables, find the location where it is loaded - there should be preciesly one
-					var loadedBy = locVars.Select(locVar => reachableBody.SelectMany(bc => bc.StackBefore).Single(s => s.LoadFrom == locVar)).ToList();
+					var loadedBy = locVars.Select(locVar => body.SelectMany(bc => bc.StackBefore).Single(s => s.LoadFrom == locVar)).ToList();
 					// We now know that all the variables have a single load,
 					// Let's make sure that they have also a single store - us
 					if (loadedBy.All(slot => slot.PushedBy.Length == 1 && slot.PushedBy[0] == byteCode)) {
 						// Great - we can reduce everything into single variable
 						ILVariable tmpVar = new ILVariable() { Name = string.Format("expr_{0:X2}", byteCode.Offset), IsGenerated = true };
 						byteCode.StoreTo = new List<ILVariable>() { tmpVar };
-						foreach(ByteCode bc in reachableBody) {
+						foreach(ByteCode bc in body) {
 							for (int i = 0; i < bc.StackBefore.Count; i++) {
 								// Is it one of the variable to be merged?
 								if (locVars.Contains(bc.StackBefore[i].LoadFrom)) {
@@ -658,12 +656,14 @@ namespace ICSharpCode.Decompiler.ILAst
 				// Find the first and widest scope
 				int tryStart = ehs.Min(eh => eh.TryStart.Offset);
 				int tryEnd   = ehs.Where(eh => eh.TryStart.Offset == tryStart).Max(eh => eh.TryEnd.Offset);
-				var handlers = ehs.Where(eh => eh.TryStart.Offset == tryStart && eh.TryEnd.Offset == tryEnd).ToList();
+				var handlers = ehs.Where(eh => eh.TryStart.Offset == tryStart && eh.TryEnd.Offset == tryEnd).OrderBy(eh => eh.TryStart.Offset).ToList();
+				
+				// Remember that any part of the body migt have been removed due to unreachability
 				
 				// Cut all instructions up to the try block
 				{
-					int tryStartIdx;
+					int tryStartIdx = 0;
-					for (tryStartIdx = 0; body[tryStartIdx].Offset != tryStart; tryStartIdx++);
+					while (tryStartIdx < body.Count && body[tryStartIdx].Offset < tryStart) tryStartIdx++;
 					ast.AddRange(ConvertToAst(body.CutRange(0, tryStartIdx)));
 				}
 				
@@ -671,24 +671,22 @@ namespace ICSharpCode.Decompiler.ILAst
 				{
 					HashSet<ExceptionHandler> nestedEHs = new HashSet<ExceptionHandler>(ehs.Where(eh => (tryStart <= eh.TryStart.Offset && eh.TryEnd.Offset < tryEnd) || (tryStart < eh.TryStart.Offset && eh.TryEnd.Offset <= tryEnd)));
 					ehs.ExceptWith(nestedEHs);
-					int tryEndIdx;
+					int tryEndIdx = 0;
-					for (tryEndIdx = 0; tryEndIdx < body.Count && body[tryEndIdx].Offset != tryEnd; tryEndIdx++);
+					while (tryEndIdx < body.Count && body[tryEndIdx].Offset < tryEnd) tryEndIdx++;
 					tryCatchBlock.TryBlock = new ILBlock(ConvertToAst(body.CutRange(0, tryEndIdx), nestedEHs));
 				}
 				
 				// Cut all handlers
 				tryCatchBlock.CatchBlocks = new List<ILTryCatchBlock.CatchBlock>();
 				foreach(ExceptionHandler eh in handlers) {
-					int startIndex;
+					int handlerEndOffset = eh.HandlerEnd == null ? methodDef.Body.CodeSize : eh.HandlerEnd.Offset;
-					for (startIndex = 0; body[startIndex].Offset != eh.HandlerStart.Offset; startIndex++);
+					int startIdx = 0;
-					int endInclusiveIndex;
+					while (startIdx < body.Count && body[startIdx].Offset < eh.HandlerStart.Offset) startIdx++;
-					if (eh.HandlerEnd == null) endInclusiveIndex = body.Count - 1;
+					int endIdx = 0;
-					// Note that the end(exclusive) instruction may not necessarly be in our body
+					while (endIdx < body.Count && body[endIdx].Offset < handlerEndOffset) endIdx++;
-					else for (endInclusiveIndex = 0; body[endInclusiveIndex].Next.Offset != eh.HandlerEnd.Offset; endInclusiveIndex++);
+					HashSet<ExceptionHandler> nestedEHs = new HashSet<ExceptionHandler>(ehs.Where(e => (eh.HandlerStart.Offset <= e.TryStart.Offset && e.TryEnd.Offset < handlerEndOffset) || (eh.HandlerStart.Offset < e.TryStart.Offset && e.TryEnd.Offset <= handlerEndOffset)));
-					int count = 1 + endInclusiveIndex - startIndex;
-					HashSet<ExceptionHandler> nestedEHs = new HashSet<ExceptionHandler>(ehs.Where(e => (eh.HandlerStart.Offset <= e.TryStart.Offset && e.TryEnd.Offset < eh.HandlerEnd.Offset) || (eh.HandlerStart.Offset < e.TryStart.Offset && e.TryEnd.Offset <= eh.HandlerEnd.Offset)));
 					ehs.ExceptWith(nestedEHs);
-					List<ILNode> handlerAst = ConvertToAst(body.CutRange(startIndex, count), nestedEHs);
+					List<ILNode> handlerAst = ConvertToAst(body.CutRange(startIdx, endIdx - startIdx), nestedEHs);
 					if (eh.HandlerType == ExceptionHandlerType.Catch) {
 						ILTryCatchBlock.CatchBlock catchBlock = new ILTryCatchBlock.CatchBlock() {
 							ExceptionType = eh.CatchType,