Try to detect while conditions, do-while-loops and for-loops

ICSharpCode.Decompiler/CSharp/StatementBuilder.cs

@@ -24,6 +24,7 @@ using ICSharpCode.Decompiler.CSharp.Syntax;
 using ICSharpCode.Decompiler.Semantics;
 using ICSharpCode.Decompiler.TypeSystem;
 using ICSharpCode.Decompiler.Util;
+using ICSharpCode.Decompiler.IL.Patterns;
 
 namespace ICSharpCode.Decompiler.CSharp
 {
@@ -267,25 +268,87 @@ namespace ICSharpCode.Decompiler.CSharp
 			}
 		}
 		
-		WhileStatement ConvertLoop(BlockContainer container)
+		Statement ConvertLoop(BlockContainer container)
 		{
 			continueTarget = container.EntryPoint;
 			continueCount = 0;
 			breakTarget = container;
-			var blockStatement = ConvertBlockContainer(container, true);
-			Debug.Assert(continueCount < container.EntryPoint.IncomingEdgeCount);
-			Debug.Assert(blockStatement.Statements.First() is LabelStatement);
-			if (container.EntryPoint.IncomingEdgeCount == continueCount + 1) {
-				// Remove the entrypoint label if all jumps to the label were replaced with 'continue;' statements
-				blockStatement.Statements.First().Remove();
+			Expression conditionExpr = new PrimitiveExpression(true);
+			BlockStatement blockStatement;
+			if (container.EntryPoint.Instructions.Count == 2
+			    && container.EntryPoint.Instructions[0].MatchIfInstruction(out var conditionInst, out var trueInst)
+			    && container.EntryPoint.Instructions[1].MatchLeave(container)) {
+				// detected while(condition)-loop or for-loop
+				conditionExpr = exprBuilder.TranslateCondition(conditionInst);
+				if (container.EntryPoint.IncomingEdgeCount == 2) {
+					var incrementBlock = container.Blocks.SingleOrDefault(b => b.Instructions.Last().MatchBranch(container.EntryPoint));
+					if (incrementBlock != null) {
+						// for-loop
+						continueTarget = incrementBlock;
+						var forStmt = new ForStatement() {
+							Condition = conditionExpr,
+							EmbeddedStatement = ConvertBlockContainer(ConvertAsBlock(trueInst), container, container.Blocks.Skip(1).Where(b => b != incrementBlock), true)
+						};
+						for (int i = 0; i < incrementBlock.Instructions.Count - 1; i++) {
+							forStmt.Iterators.Add(Convert(incrementBlock.Instructions[i]));
+						}
+						return forStmt;
+					}
+				}
+				blockStatement = ConvertBlockContainer(ConvertAsBlock(trueInst), container, container.Blocks.Skip(1), true);
+			} else {
+				// do-while or while(true)-loop
+				if (container.EntryPoint.IncomingEdgeCount == 2) {
+					Block conditionBlock = FindDoWhileConditionBlock(container, out var condition);
+					if (conditionBlock != null) {
+						continueTarget = conditionBlock;
+						return new DoWhileStatement {
+							EmbeddedStatement = ConvertBlockContainer(new BlockStatement(), container, container.Blocks.Where(b => b != conditionBlock), true),
+							Condition = exprBuilder.TranslateCondition(condition)
+						};
+					}
+				}
+				blockStatement = ConvertBlockContainer(container, true);
+				Debug.Assert(continueCount < container.EntryPoint.IncomingEdgeCount);
+				Debug.Assert(blockStatement.Statements.First() is LabelStatement);
+				if (container.EntryPoint.IncomingEdgeCount == continueCount + 1) {
+					// Remove the entrypoint label if all jumps to the label were replaced with 'continue;' statements
+					blockStatement.Statements.First().Remove();
+				}
 			}
-			return new WhileStatement(new PrimitiveExpression(true), blockStatement);
+			if (blockStatement.LastOrDefault() is ContinueStatement stmt)
+				stmt.Remove();
+			return new WhileStatement(conditionExpr, blockStatement);
 		}
-		
+
+		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)
+				}
+			};
+			foreach (var b in container.Blocks) {
+				var match = conditionBlockPattern.Match(b);
+				if (match.Success) {
+					condition = match.Get(conditionGroup).Single();
+					return b;
+				}
+			}
+			condition = null;
+			return null;
+		}
+
 		BlockStatement ConvertBlockContainer(BlockContainer container, bool isLoop)
 		{
-			BlockStatement blockStatement = new BlockStatement();
-			foreach (var block in container.Blocks) {
+			return ConvertBlockContainer(new BlockStatement(), container, container.Blocks, isLoop);
+		}
+
+		BlockStatement ConvertBlockContainer(BlockStatement blockStatement, BlockContainer container, IEnumerable<Block> blocks, bool isLoop)
+		{
+			foreach (var block in blocks) {
 				if (block.IncomingEdgeCount > 1 || block != container.EntryPoint) {
 					// If there are any incoming branches to this block, add a label:
 					blockStatement.Add(new LabelStatement { Label = block.Label });

ICSharpCode.Decompiler/CSharp/Transforms/DeclareVariables.cs

@@ -33,6 +33,10 @@ namespace ICSharpCode.Decompiler.CSharp.Transforms
 	/// </summary>
 	public class DeclareVariables : IAstTransform
 	{
+		/// <summary>
+		/// Represents a position immediately before nextNode.
+		/// nextNode is either an ExpressionStatement in a BlockStatement, or an initializer in a for-loop.
+		/// </summary>
 		struct InsertionPoint
 		{
 			internal int level;
@@ -212,6 +216,8 @@ namespace ICSharpCode.Decompiler.CSharp.Transforms
 				// guarantee that it finds only blocks.
 				// Fix that up now.
 				while (!(v.InsertionPoint.nextNode.Parent is BlockStatement)) {
+					if (v.InsertionPoint.nextNode.Parent is ForStatement f && v.InsertionPoint.nextNode == f.Initializers.FirstOrDefault())
+						break;
 					v.InsertionPoint = v.InsertionPoint.Up();
 				}
 				
@@ -254,22 +260,22 @@ namespace ICSharpCode.Decompiler.CSharp.Transforms
 				if (v.RemovedDueToCollision)
 					continue;
 				
-				var boe = (v.InsertionPoint.nextNode as ExpressionStatement)?.Expression as AssignmentExpression;
+				var assignment = (v.InsertionPoint.nextNode as ExpressionStatement)?.Expression as AssignmentExpression;
 				Expression expectedExpr = new IdentifierExpression(v.Name);
 				if (v.Type.Kind == TypeKind.ByReference) {
 					expectedExpr = new DirectionExpression(FieldDirection.Ref, expectedExpr);
 				}
-				if (boe != null && boe.Left.IsMatch(expectedExpr)) {
+				if (assignment != null && assignment.Left.IsMatch(expectedExpr)) {
 					AstType type;
 					if (v.Type.ContainsAnonymousType()) {
 						type = new SimpleType("var");
 					} else {
 						type = context.TypeSystemAstBuilder.ConvertType(v.Type);
 					}
-					var vds = new VariableDeclarationStatement(type, v.Name, boe.Right.Detach());
+					var vds = new VariableDeclarationStatement(type, v.Name, assignment.Right.Detach());
 					var init = vds.Variables.Single();
-					init.AddAnnotation(boe.Left.GetResolveResult());
-					foreach (object annotation in boe.Left.Annotations.Concat(boe.Annotations)) {
+					init.AddAnnotation(assignment.Left.GetResolveResult());
+					foreach (object annotation in assignment.Left.Annotations.Concat(assignment.Annotations)) {
 						if (!(annotation is ResolveResult)) {
 							init.AddAnnotation(annotation);
 						}

ICSharpCode.Decompiler/ICSharpCode.Decompiler.csproj

@@ -275,6 +275,7 @@
     <Compile Include="Documentation\IdStringMemberReference.cs" />
     <Compile Include="Documentation\IdStringProvider.cs" />
     <Compile Include="Documentation\XmlDocumentationProvider.cs" />
+    <Compile Include="IL\Patterns\AnyNode.cs" />
     <Compile Include="Util\UnicodeNewline.cs" />
     <Compile Include="FlowAnalysis\ControlFlowNode.cs" />
     <Compile Include="FlowAnalysis\DataFlowVisitor.cs" />

ICSharpCode.Decompiler/IL/Instructions.cs

@@ -17,6 +17,7 @@
 // DEALINGS IN THE SOFTWARE.
 
 using System;
+using System.Collections.Generic;
 using System.Diagnostics;
 using System.Linq;
 using ICSharpCode.Decompiler.TypeSystem;
@@ -155,8 +156,13 @@ namespace ICSharpCode.Decompiler.IL
 		RefAnyType,
 		/// <summary>Push the address stored in a typed reference.</summary>
 		RefAnyValue,
+		/// <summary>Matches any node</summary>
+		AnyNode,
 	}
+}
 
+namespace ICSharpCode.Decompiler.IL
+{
 	/// <summary>Instruction without any arguments</summary>
 	public abstract partial class SimpleInstruction : ILInstruction
 	{
@@ -203,7 +209,9 @@ namespace ICSharpCode.Decompiler.IL
 			}
 		}
 	}
-
+}
+namespace ICSharpCode.Decompiler.IL
+{
 	/// <summary>Instruction with a single argument</summary>
 	public abstract partial class UnaryInstruction : ILInstruction
 	{
@@ -275,7 +283,9 @@ namespace ICSharpCode.Decompiler.IL
 			output.Write(')');
 		}
 	}
-
+}
+namespace ICSharpCode.Decompiler.IL
+{
 	/// <summary>Instruction with two arguments: Left and Right</summary>
 	public abstract partial class BinaryInstruction : ILInstruction
 	{
@@ -367,7 +377,9 @@ namespace ICSharpCode.Decompiler.IL
 			output.Write(')');
 		}
 	}
-
+}
+namespace ICSharpCode.Decompiler.IL
+{
 	/// <summary>Instruction with a list of arguments.</summary>
 	public abstract partial class CallInstruction : ILInstruction
 	{
@@ -421,7 +433,20 @@ namespace ICSharpCode.Decompiler.IL
 			}
 		}
 	}
-
+}
+namespace ICSharpCode.Decompiler.IL.Patterns
+{
+	/// <summary>Base class for pattern matching in ILAst.</summary>
+	public abstract partial class PatternInstruction : ILInstruction
+	{
+		protected PatternInstruction(OpCode opCode) : base(opCode)
+		{
+		}
+		public override StackType ResultType { get { return StackType.Unknown; } }
+	}
+}
+namespace ICSharpCode.Decompiler.IL
+{
 	/// <summary>Represents invalid IL. Semantically, this instruction is considered to throw some kind of exception.</summary>
 	public sealed partial class InvalidInstruction : SimpleInstruction
 	{
@@ -456,7 +481,9 @@ namespace ICSharpCode.Decompiler.IL
 			return o != null;
 		}
 	}
-
+}
+namespace ICSharpCode.Decompiler.IL
+{
 	/// <summary>No operation. Takes 0 arguments and returns void.</summary>
 	public sealed partial class Nop : SimpleInstruction
 	{
@@ -482,7 +509,9 @@ namespace ICSharpCode.Decompiler.IL
 			return o != null;
 		}
 	}
-
+}
+namespace ICSharpCode.Decompiler.IL
+{
 	/// <summary>A container of IL blocks.</summary>
 	public sealed partial class ILFunction : ILVariableScope
 	{
@@ -553,7 +582,9 @@ namespace ICSharpCode.Decompiler.IL
 			return o != null && this.body.PerformMatch(o.body, ref match);
 		}
 	}
-
+}
+namespace ICSharpCode.Decompiler.IL
+{
 	/// <summary>A container of IL blocks.</summary>
 	public sealed partial class BlockContainer : ILInstruction
 	{
@@ -576,7 +607,9 @@ namespace ICSharpCode.Decompiler.IL
 			return o != null && Patterns.ListMatch.DoMatch(this.Blocks, o.Blocks, ref match);
 		}
 	}
-
+}
+namespace ICSharpCode.Decompiler.IL
+{
 	/// <summary>A block of IL instructions.</summary>
 	public sealed partial class Block : ILInstruction
 	{
@@ -599,7 +632,9 @@ namespace ICSharpCode.Decompiler.IL
 			return o != null && this.Type == o.Type && Patterns.ListMatch.DoMatch(this.Instructions, o.Instructions, ref match) && this.FinalInstruction.PerformMatch(o.FinalInstruction, ref match);
 		}
 	}
-
+}
+namespace ICSharpCode.Decompiler.IL
+{
 	/// <summary>A region where a pinned variable is used (initial representation of future fixed statement).</summary>
 	public sealed partial class PinnedRegion : ILInstruction, IInstructionWithVariableOperand
 	{
@@ -742,7 +777,9 @@ namespace ICSharpCode.Decompiler.IL
 			return o != null && variable == o.variable && this.init.PerformMatch(o.init, ref match) && this.body.PerformMatch(o.body, ref match);
 		}
 	}
-
+}
+namespace ICSharpCode.Decompiler.IL
+{
 	/// <summary>Unary operator that expects an input of type I4. Returns 1 (of type I4) if the input value is 0. Otherwise, returns 0 (of type I4).</summary>
 	public sealed partial class LogicNot : UnaryInstruction
 	{
@@ -768,7 +805,9 @@ namespace ICSharpCode.Decompiler.IL
 			return o != null && this.Argument.PerformMatch(o.Argument, ref match);
 		}
 	}
-
+}
+namespace ICSharpCode.Decompiler.IL
+{
 	/// <summary>Common instruction for add, sub, mul, div, rem, bit.and, bit.or, bit.xor, shl and shr.</summary>
 	public sealed partial class BinaryNumericInstruction : BinaryInstruction
 	{
@@ -791,7 +830,9 @@ namespace ICSharpCode.Decompiler.IL
 			return o != null && this.Left.PerformMatch(o.Left, ref match) && this.Right.PerformMatch(o.Right, ref match) && CheckForOverflow == o.CheckForOverflow && Sign == o.Sign && Operator == o.Operator;
 		}
 	}
-
+}
+namespace ICSharpCode.Decompiler.IL
+{
 	/// <summary>Common instruction for compound assignments.</summary>
 	public sealed partial class CompoundAssignmentInstruction : ILInstruction
 	{
@@ -881,7 +922,9 @@ namespace ICSharpCode.Decompiler.IL
 			return o != null && this.target.PerformMatch(o.target, ref match) && this.value.PerformMatch(o.value, ref match) && type.Equals(o.type) && CheckForOverflow == o.CheckForOverflow && Sign == o.Sign && Operator == o.Operator;
 		}
 	}
-
+}
+namespace ICSharpCode.Decompiler.IL
+{
 	/// <summary>Bitwise NOT</summary>
 	public sealed partial class BitNot : UnaryInstruction
 	{
@@ -907,7 +950,9 @@ namespace ICSharpCode.Decompiler.IL
 			return o != null && this.Argument.PerformMatch(o.Argument, ref match);
 		}
 	}
-
+}
+namespace ICSharpCode.Decompiler.IL
+{
 	/// <summary>Retrieves the RuntimeArgumentHandle.</summary>
 	public sealed partial class Arglist : SimpleInstruction
 	{
@@ -933,7 +978,9 @@ namespace ICSharpCode.Decompiler.IL
 			return o != null;
 		}
 	}
-
+}
+namespace ICSharpCode.Decompiler.IL
+{
 	/// <summary>Unconditional branch. <c>goto target;</c></summary>
 	public sealed partial class Branch : SimpleInstruction
 	{
@@ -956,7 +1003,9 @@ namespace ICSharpCode.Decompiler.IL
 			return o != null && this.TargetBlock == o.TargetBlock;
 		}
 	}
-
+}
+namespace ICSharpCode.Decompiler.IL
+{
 	/// <summary>Unconditional branch to end of block container. <c>goto container_end;</c>, often <c>break;</c></summary>
 	public sealed partial class Leave : SimpleInstruction
 	{
@@ -979,7 +1028,9 @@ namespace ICSharpCode.Decompiler.IL
 			return o != null && this.TargetContainer == o.TargetContainer;
 		}
 	}
-
+}
+namespace ICSharpCode.Decompiler.IL
+{
 	/// <summary>If statement / conditional expression. <c>if (condition) trueExpr else falseExpr</c></summary>
 	public sealed partial class IfInstruction : ILInstruction
 	{
@@ -1082,7 +1133,9 @@ namespace ICSharpCode.Decompiler.IL
 			return o != null && this.condition.PerformMatch(o.condition, ref match) && this.trueInst.PerformMatch(o.trueInst, ref match) && this.falseInst.PerformMatch(o.falseInst, ref match);
 		}
 	}
-
+}
+namespace ICSharpCode.Decompiler.IL
+{
 	/// <summary>Switch statement</summary>
 	public sealed partial class SwitchInstruction : ILInstruction
 	{
@@ -1105,7 +1158,9 @@ namespace ICSharpCode.Decompiler.IL
 			return o != null && Value.PerformMatch(o.Value, ref match) && DefaultBody.PerformMatch(o.DefaultBody, ref match) && Patterns.ListMatch.DoMatch(this.Sections, o.Sections, ref match);
 		}
 	}
-
+}
+namespace ICSharpCode.Decompiler.IL
+{
 	/// <summary>Switch section within a switch statement</summary>
 	public sealed partial class SwitchSection : ILInstruction
 	{
@@ -1175,7 +1230,9 @@ namespace ICSharpCode.Decompiler.IL
 			return o != null && this.body.PerformMatch(o.body, ref match) && this.Labels.Intervals.SequenceEqual(o.Labels.Intervals);
 		}
 	}
-
+}
+namespace ICSharpCode.Decompiler.IL
+{
 	/// <summary>Try-catch statement.</summary>
 	public sealed partial class TryCatch : TryInstruction
 	{
@@ -1198,7 +1255,9 @@ namespace ICSharpCode.Decompiler.IL
 			return o != null && TryBlock.PerformMatch(o.TryBlock, ref match) && Patterns.ListMatch.DoMatch(Handlers, o.Handlers, ref match);
 		}
 	}
-
+}
+namespace ICSharpCode.Decompiler.IL
+{
 	/// <summary>Catch handler within a try-catch statement.</summary>
 	public sealed partial class TryCatchHandler : ILInstruction, IInstructionWithVariableOperand
 	{
@@ -1315,7 +1374,9 @@ namespace ICSharpCode.Decompiler.IL
 			return o != null && this.filter.PerformMatch(o.filter, ref match) && this.body.PerformMatch(o.body, ref match) && variable == o.variable;
 		}
 	}
-
+}
+namespace ICSharpCode.Decompiler.IL
+{
 	/// <summary>Try-finally statement</summary>
 	public sealed partial class TryFinally : TryInstruction
 	{
@@ -1338,7 +1399,9 @@ namespace ICSharpCode.Decompiler.IL
 			return o != null && TryBlock.PerformMatch(o.TryBlock, ref match) && finallyBlock.PerformMatch(o.finallyBlock, ref match);
 		}
 	}
-
+}
+namespace ICSharpCode.Decompiler.IL
+{
 	/// <summary>Try-fault statement</summary>
 	public sealed partial class TryFault : TryInstruction
 	{
@@ -1361,7 +1424,9 @@ namespace ICSharpCode.Decompiler.IL
 			return o != null && TryBlock.PerformMatch(o.TryBlock, ref match) && faultBlock.PerformMatch(o.faultBlock, ref match);
 		}
 	}
-
+}
+namespace ICSharpCode.Decompiler.IL
+{
 	/// <summary>Breakpoint instruction</summary>
 	public sealed partial class DebugBreak : SimpleInstruction
 	{
@@ -1396,7 +1461,9 @@ namespace ICSharpCode.Decompiler.IL
 			return o != null;
 		}
 	}
-
+}
+namespace ICSharpCode.Decompiler.IL
+{
 	/// <summary>Comparison. The inputs must be both integers; or both floats; or both object references. Object references can only be compared for equality or inequality. Floating-point comparisons evaluate to 0 (false) when an input is NaN, except for 'NaN != NaN' which evaluates to 1 (true).</summary>
 	public sealed partial class Comp : BinaryInstruction
 	{
@@ -1419,7 +1486,9 @@ namespace ICSharpCode.Decompiler.IL
 			return o != null && this.Left.PerformMatch(o.Left, ref match) && this.Right.PerformMatch(o.Right, ref match) && this.Kind == o.Kind && this.Sign == o.Sign;
 		}
 	}
-
+}
+namespace ICSharpCode.Decompiler.IL
+{
 	/// <summary>Non-virtual method call.</summary>
 	public sealed partial class Call : CallInstruction
 	{
@@ -1440,7 +1509,9 @@ namespace ICSharpCode.Decompiler.IL
 			return visitor.VisitCall(this, context);
 		}
 	}
-
+}
+namespace ICSharpCode.Decompiler.IL
+{
 	/// <summary>Virtual method call.</summary>
 	public sealed partial class CallVirt : CallInstruction
 	{
@@ -1461,7 +1532,9 @@ namespace ICSharpCode.Decompiler.IL
 			return visitor.VisitCallVirt(this, context);
 		}
 	}
-
+}
+namespace ICSharpCode.Decompiler.IL
+{
 	/// <summary>Checks that the input float is not NaN or infinite.</summary>
 	public sealed partial class Ckfinite : UnaryInstruction
 	{
@@ -1496,7 +1569,9 @@ namespace ICSharpCode.Decompiler.IL
 			return o != null && this.Argument.PerformMatch(o.Argument, ref match);
 		}
 	}
-
+}
+namespace ICSharpCode.Decompiler.IL
+{
 	/// <summary>Numeric cast.</summary>
 	public sealed partial class Conv : UnaryInstruction
 	{
@@ -1519,7 +1594,9 @@ namespace ICSharpCode.Decompiler.IL
 			return o != null && this.Argument.PerformMatch(o.Argument, ref match) && CheckForOverflow == o.CheckForOverflow && Kind == o.Kind && InputSign == o.InputSign && TargetType == o.TargetType;
 		}
 	}
-
+}
+namespace ICSharpCode.Decompiler.IL
+{
 	/// <summary>Loads the value of a local variable. (ldarg/ldloc)</summary>
 	public sealed partial class LdLoc : SimpleInstruction, IInstructionWithVariableOperand
 	{
@@ -1591,7 +1668,9 @@ namespace ICSharpCode.Decompiler.IL
 			return o != null && variable == o.variable;
 		}
 	}
-
+}
+namespace ICSharpCode.Decompiler.IL
+{
 	/// <summary>Loads the address of a local variable. (ldarga/ldloca)</summary>
 	public sealed partial class LdLoca : SimpleInstruction, IInstructionWithVariableOperand
 	{
@@ -1654,7 +1733,9 @@ namespace ICSharpCode.Decompiler.IL
 			return o != null && variable == o.variable;
 		}
 	}
-
+}
+namespace ICSharpCode.Decompiler.IL
+{
 	/// <summary>Stores a value into a local variable. (starg/stloc)</summary>
 	public sealed partial class StLoc : ILInstruction, IInstructionWithVariableOperand
 	{
@@ -1777,7 +1858,9 @@ namespace ICSharpCode.Decompiler.IL
 			return o != null && variable == o.variable && this.value.PerformMatch(o.value, ref match);
 		}
 	}
-
+}
+namespace ICSharpCode.Decompiler.IL
+{
 	/// <summary>Stores the value into an anonymous temporary variable, and returns the address of that variable.</summary>
 	public sealed partial class AddressOf : ILInstruction
 	{
@@ -1867,7 +1950,9 @@ namespace ICSharpCode.Decompiler.IL
 			return o != null && this.value.PerformMatch(o.value, ref match);
 		}
 	}
-
+}
+namespace ICSharpCode.Decompiler.IL
+{
 	/// <summary>Loads a constant string.</summary>
 	public sealed partial class LdStr : SimpleInstruction
 	{
@@ -1901,7 +1986,9 @@ namespace ICSharpCode.Decompiler.IL
 			return o != null && this.Value == o.Value;
 		}
 	}
-
+}
+namespace ICSharpCode.Decompiler.IL
+{
 	/// <summary>Loads a constant 32-bit integer.</summary>
 	public sealed partial class LdcI4 : SimpleInstruction
 	{
@@ -1935,7 +2022,9 @@ namespace ICSharpCode.Decompiler.IL
 			return o != null && this.Value == o.Value;
 		}
 	}
-
+}
+namespace ICSharpCode.Decompiler.IL
+{
 	/// <summary>Loads a constant 64-bit integer.</summary>
 	public sealed partial class LdcI8 : SimpleInstruction
 	{
@@ -1969,7 +2058,9 @@ namespace ICSharpCode.Decompiler.IL
 			return o != null && this.Value == o.Value;
 		}
 	}
-
+}
+namespace ICSharpCode.Decompiler.IL
+{
 	/// <summary>Loads a constant floating-point number.</summary>
 	public sealed partial class LdcF : SimpleInstruction
 	{
@@ -2003,7 +2094,9 @@ namespace ICSharpCode.Decompiler.IL
 			return o != null && this.Value == o.Value;
 		}
 	}
-
+}
+namespace ICSharpCode.Decompiler.IL
+{
 	/// <summary>Loads a constant decimal.</summary>
 	public sealed partial class LdcDecimal : SimpleInstruction
 	{
@@ -2037,7 +2130,9 @@ namespace ICSharpCode.Decompiler.IL
 			return o != null && this.Value == o.Value;
 		}
 	}
-
+}
+namespace ICSharpCode.Decompiler.IL
+{
 	/// <summary>Loads the null reference.</summary>
 	public sealed partial class LdNull : SimpleInstruction
 	{
@@ -2063,7 +2158,9 @@ namespace ICSharpCode.Decompiler.IL
 			return o != null;
 		}
 	}
-
+}
+namespace ICSharpCode.Decompiler.IL
+{
 	/// <summary>Load method pointer</summary>
 	public sealed partial class LdFtn : SimpleInstruction, IInstructionWithMethodOperand
 	{
@@ -2099,7 +2196,9 @@ namespace ICSharpCode.Decompiler.IL
 			return o != null && method.Equals(o.method);
 		}
 	}
-
+}
+namespace ICSharpCode.Decompiler.IL
+{
 	/// <summary>Load method pointer</summary>
 	public sealed partial class LdVirtFtn : UnaryInstruction, IInstructionWithMethodOperand
 	{
@@ -2147,7 +2246,9 @@ namespace ICSharpCode.Decompiler.IL
 			return o != null && this.Argument.PerformMatch(o.Argument, ref match) && method.Equals(o.method);
 		}
 	}
-
+}
+namespace ICSharpCode.Decompiler.IL
+{
 	/// <summary>Loads runtime representation of metadata token</summary>
 	public sealed partial class LdTypeToken : SimpleInstruction
 	{
@@ -2183,7 +2284,9 @@ namespace ICSharpCode.Decompiler.IL
 			return o != null && type.Equals(o.type);
 		}
 	}
-
+}
+namespace ICSharpCode.Decompiler.IL
+{
 	/// <summary>Loads runtime representation of metadata token</summary>
 	public sealed partial class LdMemberToken : SimpleInstruction
 	{
@@ -2219,7 +2322,9 @@ namespace ICSharpCode.Decompiler.IL
 			return o != null && member.Equals(o.member);
 		}
 	}
-
+}
+namespace ICSharpCode.Decompiler.IL
+{
 	/// <summary>Allocates space in the stack frame</summary>
 	public sealed partial class LocAlloc : UnaryInstruction
 	{
@@ -2254,7 +2359,9 @@ namespace ICSharpCode.Decompiler.IL
 			return o != null && this.Argument.PerformMatch(o.Argument, ref match);
 		}
 	}
-
+}
+namespace ICSharpCode.Decompiler.IL
+{
 	/// <summary>Returns from the current method or lambda.</summary>
 	public sealed partial class Return : ILInstruction
 	{
@@ -2277,7 +2384,9 @@ namespace ICSharpCode.Decompiler.IL
 			return o != null && this.hasArgument == o.hasArgument && (!hasArgument || this.ReturnValue.PerformMatch(o.ReturnValue, ref match));
 		}
 	}
-
+}
+namespace ICSharpCode.Decompiler.IL
+{
 	/// <summary>Load address of instance field</summary>
 	public sealed partial class LdFlda : ILInstruction, IInstructionWithFieldOperand
 	{
@@ -2374,7 +2483,9 @@ namespace ICSharpCode.Decompiler.IL
 			return o != null && this.target.PerformMatch(o.target, ref match) && field.Equals(o.field);
 		}
 	}
-
+}
+namespace ICSharpCode.Decompiler.IL
+{
 	/// <summary>Load static field address</summary>
 	public sealed partial class LdsFlda : SimpleInstruction, IInstructionWithFieldOperand
 	{
@@ -2410,7 +2521,9 @@ namespace ICSharpCode.Decompiler.IL
 			return o != null && field.Equals(o.field);
 		}
 	}
-
+}
+namespace ICSharpCode.Decompiler.IL
+{
 	/// <summary>Casts an object to a class.</summary>
 	public sealed partial class CastClass : UnaryInstruction
 	{
@@ -2458,7 +2571,9 @@ namespace ICSharpCode.Decompiler.IL
 			return o != null && this.Argument.PerformMatch(o.Argument, ref match) && type.Equals(o.type);
 		}
 	}
-
+}
+namespace ICSharpCode.Decompiler.IL
+{
 	/// <summary>Test if object is instance of class or interface.</summary>
 	public sealed partial class IsInst : UnaryInstruction
 	{
@@ -2497,7 +2612,9 @@ namespace ICSharpCode.Decompiler.IL
 			return o != null && this.Argument.PerformMatch(o.Argument, ref match) && type.Equals(o.type);
 		}
 	}
-
+}
+namespace ICSharpCode.Decompiler.IL
+{
 	/// <summary>Indirect load (ref/pointer dereference).</summary>
 	public sealed partial class LdObj : ILInstruction, ISupportsVolatilePrefix, ISupportsUnalignedPrefix
 	{
@@ -2601,7 +2718,9 @@ namespace ICSharpCode.Decompiler.IL
 			return o != null && this.target.PerformMatch(o.target, ref match) && type.Equals(o.type) && IsVolatile == o.IsVolatile && UnalignedPrefix == o.UnalignedPrefix;
 		}
 	}
-
+}
+namespace ICSharpCode.Decompiler.IL
+{
 	/// <summary>Indirect store (store to ref/pointer).</summary>
 	public sealed partial class StObj : ILInstruction, ISupportsVolatilePrefix, ISupportsUnalignedPrefix
 	{
@@ -2725,7 +2844,9 @@ namespace ICSharpCode.Decompiler.IL
 			return o != null && this.target.PerformMatch(o.target, ref match) && this.value.PerformMatch(o.value, ref match) && type.Equals(o.type) && IsVolatile == o.IsVolatile && UnalignedPrefix == o.UnalignedPrefix;
 		}
 	}
-
+}
+namespace ICSharpCode.Decompiler.IL
+{
 	/// <summary>Boxes a value.</summary>
 	public sealed partial class Box : UnaryInstruction
 	{
@@ -2773,7 +2894,9 @@ namespace ICSharpCode.Decompiler.IL
 			return o != null && this.Argument.PerformMatch(o.Argument, ref match) && type.Equals(o.type);
 		}
 	}
-
+}
+namespace ICSharpCode.Decompiler.IL
+{
 	/// <summary>Compute address inside box.</summary>
 	public sealed partial class Unbox : UnaryInstruction
 	{
@@ -2821,7 +2944,9 @@ namespace ICSharpCode.Decompiler.IL
 			return o != null && this.Argument.PerformMatch(o.Argument, ref match) && type.Equals(o.type);
 		}
 	}
-
+}
+namespace ICSharpCode.Decompiler.IL
+{
 	/// <summary>Unbox a value.</summary>
 	public sealed partial class UnboxAny : UnaryInstruction
 	{
@@ -2869,7 +2994,9 @@ namespace ICSharpCode.Decompiler.IL
 			return o != null && this.Argument.PerformMatch(o.Argument, ref match) && type.Equals(o.type);
 		}
 	}
-
+}
+namespace ICSharpCode.Decompiler.IL
+{
 	/// <summary>Creates an object instance and calls the constructor.</summary>
 	public sealed partial class NewObj : CallInstruction
 	{
@@ -2890,7 +3017,9 @@ namespace ICSharpCode.Decompiler.IL
 			return visitor.VisitNewObj(this, context);
 		}
 	}
-
+}
+namespace ICSharpCode.Decompiler.IL
+{
 	/// <summary>Creates an array instance.</summary>
 	public sealed partial class NewArr : ILInstruction
 	{
@@ -2979,7 +3108,9 @@ namespace ICSharpCode.Decompiler.IL
 			return o != null && type.Equals(o.type) && Patterns.ListMatch.DoMatch(this.Indices, o.Indices, ref match);
 		}
 	}
-
+}
+namespace ICSharpCode.Decompiler.IL
+{
 	/// <summary>Returns the default value for a type.</summary>
 	public sealed partial class DefaultValue : SimpleInstruction
 	{
@@ -3015,7 +3146,9 @@ namespace ICSharpCode.Decompiler.IL
 			return o != null && type.Equals(o.type);
 		}
 	}
-
+}
+namespace ICSharpCode.Decompiler.IL
+{
 	/// <summary>Throws an exception.</summary>
 	public sealed partial class Throw : UnaryInstruction
 	{
@@ -3050,7 +3183,9 @@ namespace ICSharpCode.Decompiler.IL
 			return o != null && this.Argument.PerformMatch(o.Argument, ref match);
 		}
 	}
-
+}
+namespace ICSharpCode.Decompiler.IL
+{
 	/// <summary>Rethrows the current exception.</summary>
 	public sealed partial class Rethrow : SimpleInstruction
 	{
@@ -3085,7 +3220,9 @@ namespace ICSharpCode.Decompiler.IL
 			return o != null;
 		}
 	}
-
+}
+namespace ICSharpCode.Decompiler.IL
+{
 	/// <summary>Gets the size of a type in bytes.</summary>
 	public sealed partial class SizeOf : SimpleInstruction
 	{
@@ -3121,7 +3258,9 @@ namespace ICSharpCode.Decompiler.IL
 			return o != null && type.Equals(o.type);
 		}
 	}
-
+}
+namespace ICSharpCode.Decompiler.IL
+{
 	/// <summary>Returns the length of an array as 'native unsigned int'.</summary>
 	public sealed partial class LdLen : ILInstruction
 	{
@@ -3199,7 +3338,9 @@ namespace ICSharpCode.Decompiler.IL
 			return o != null && this.array.PerformMatch(o.array, ref match);
 		}
 	}
-
+}
+namespace ICSharpCode.Decompiler.IL
+{
 	/// <summary>Load address of array element.</summary>
 	public sealed partial class LdElema : ILInstruction
 	{
@@ -3311,7 +3452,9 @@ namespace ICSharpCode.Decompiler.IL
 			return o != null && type.Equals(o.type) && this.array.PerformMatch(o.array, ref match) && Patterns.ListMatch.DoMatch(this.Indices, o.Indices, ref match) && IsReadOnly == o.IsReadOnly;
 		}
 	}
-
+}
+namespace ICSharpCode.Decompiler.IL
+{
 	/// <summary>Converts an array pointer (O) to a reference to the first element, or to a null reference if the array is null or empty.
 	/// Also used to convert a string to a reference to the first character.</summary>
 	public sealed partial class ArrayToPointer : ILInstruction
@@ -3402,7 +3545,9 @@ namespace ICSharpCode.Decompiler.IL
 			return o != null && this.array.PerformMatch(o.array, ref match);
 		}
 	}
-
+}
+namespace ICSharpCode.Decompiler.IL
+{
 	/// <summary>Push a typed reference of type class onto the stack.</summary>
 	public sealed partial class MakeRefAny : UnaryInstruction
 	{
@@ -3441,7 +3586,9 @@ namespace ICSharpCode.Decompiler.IL
 			return o != null && this.Argument.PerformMatch(o.Argument, ref match) && type.Equals(o.type);
 		}
 	}
-
+}
+namespace ICSharpCode.Decompiler.IL
+{
 	/// <summary>Push the type token stored in a typed reference.</summary>
 	public sealed partial class RefAnyType : UnaryInstruction
 	{
@@ -3467,7 +3614,9 @@ namespace ICSharpCode.Decompiler.IL
 			return o != null && this.Argument.PerformMatch(o.Argument, ref match);
 		}
 	}
-
+}
+namespace ICSharpCode.Decompiler.IL
+{
 	/// <summary>Push the address stored in a typed reference.</summary>
 	public sealed partial class RefAnyValue : UnaryInstruction
 	{
@@ -3515,8 +3664,53 @@ namespace ICSharpCode.Decompiler.IL
 			return o != null && this.Argument.PerformMatch(o.Argument, ref match) && type.Equals(o.type);
 		}
 	}
+}
+namespace ICSharpCode.Decompiler.IL.Patterns
+{
+	/// <summary>Matches any node</summary>
+	public sealed partial class AnyNode : PatternInstruction
+	{
+		protected sealed override int GetChildCount()
+		{
+			return 0;
+		}
+		protected sealed override ILInstruction GetChild(int index)
+		{
+			switch (index) {
+				default:
+					throw new IndexOutOfRangeException();
+			}
+		}
+		protected sealed override void SetChild(int index, ILInstruction value)
+		{
+			switch (index) {
+				default:
+					throw new IndexOutOfRangeException();
+			}
+		}
+		protected sealed override SlotInfo GetChildSlot(int index)
+		{
+			switch (index) {
+				default:
+					throw new IndexOutOfRangeException();
+			}
+		}
+		public sealed override ILInstruction Clone()
+		{
+			var clone = (AnyNode)ShallowClone();
+			return clone;
+		}
+		public override void WriteTo(ITextOutput output)
+		{
+			output.Write(OpCode);
+			output.Write('(');
+			output.Write(')');
+		}
+	}
+}
 
-
+namespace ICSharpCode.Decompiler.IL
+{
 	/// <summary>
 	/// Base class for visitor pattern.
 	/// </summary>
@@ -4369,6 +4563,7 @@ namespace ICSharpCode.Decompiler.IL
 			"mkrefany",
 			"refanytype",
 			"refanyval",
+			"AnyNode",
 		};
 	}
 	

ICSharpCode.Decompiler/IL/Instructions.tt

@@ -33,6 +33,7 @@
 		new OpCode("CallInstruction", "Instruction with a list of arguments.",
 			AbstractBaseClass, CustomChildren(new []{ new ArgumentInfo("arguments") { IsCollection = true }}),
 			CustomWriteTo, MayThrow, SideEffect),
+		new OpCode("PatternInstruction", "Base class for pattern matching in ILAst.", AbstractBaseClass, ResultType("Unknown")) { Namespace = "ICSharpCode.Decompiler.IL.Patterns" }
 	};
 	
 	OpCode[] opCodes = {
@@ -209,6 +210,9 @@
 			CustomClassName("RefAnyType"), Unary, ResultType("O")),
 		new OpCode("refanyval", "Push the address stored in a typed reference.",
 			CustomClassName("RefAnyValue"), Unary, HasTypeOperand, MayThrow, ResultType("Ref")),
+
+		// patterns
+		new OpCode("AnyNode", "Matches any node", Pattern, CustomArguments(), CustomConstructor),
 	};
 #>
 using System;
@@ -229,8 +233,11 @@ namespace ICSharpCode.Decompiler.IL
 		<#=opCode.Name#>,
 <#  } #>
 	}
+}
 
 <#	foreach (OpCode opCode in baseClasses.Concat(opCodes)) { #>
+namespace <#=opCode.Namespace#>
+{
 	/// <summary><#=opCode.Description.Replace("\n", "\n\t/// ")#></summary>
 	<#=opCode.ClassModifiers#> partial class <#=opCode.Name#> : <#=string.Join(", ", new[]{opCode.BaseClass}.Concat(opCode.Interfaces))#>
 	{
@@ -278,9 +285,11 @@ namespace ICSharpCode.Decompiler.IL
 		}
 <#		} #>
 	}
-
+}
 <#	} #>
 
+namespace ICSharpCode.Decompiler.IL
+{
 	/// <summary>
 	/// Base class for visitor pattern.
 	/// </summary>
@@ -289,7 +298,7 @@ namespace ICSharpCode.Decompiler.IL
 		/// <summary>Called by Visit*() methods that were not overridden</summary>
 		protected abstract void Default(ILInstruction inst);
 		
-<#	foreach (OpCode opCode in opCodes) { #>
+<#	foreach (OpCode opCode in opCodes.Where(o => o.GenerateAcceptVisitor)) { #>
 		protected internal virtual void Visit<#=opCode.Name#>(<#=opCode.Name#> <#=opCode.VariableName#>)
 		{
 			Default(<#=opCode.VariableName#>);
@@ -305,7 +314,7 @@ namespace ICSharpCode.Decompiler.IL
 		/// <summary>Called by Visit*() methods that were not overridden</summary>
 		protected abstract T Default(ILInstruction inst);
 		
-<#	foreach (OpCode opCode in opCodes) { #>
+<#	foreach (OpCode opCode in opCodes.Where(o => o.GenerateAcceptVisitor)) { #>
 		protected internal virtual T Visit<#=opCode.Name#>(<#=opCode.Name#> <#=opCode.VariableName#>)
 		{
 			return Default(<#=opCode.VariableName#>);
@@ -321,7 +330,7 @@ namespace ICSharpCode.Decompiler.IL
 		/// <summary>Called by Visit*() methods that were not overridden</summary>
 		protected abstract T Default(ILInstruction inst, C context);
 		
-<#	foreach (OpCode opCode in opCodes) { #>
+<#	foreach (OpCode opCode in opCodes.Where(o => o.GenerateAcceptVisitor)) { #>
 		protected internal virtual T Visit<#=opCode.Name#>(<#=opCode.Name#> <#=opCode.VariableName#>, C context)
 		{
 			return Default(<#=opCode.VariableName#>, context);
@@ -395,6 +404,7 @@ namespace ICSharpCode.Decompiler.IL
 	{
 		public readonly string OriginalName;
 		public string Name;
+		public string Namespace = "ICSharpCode.Decompiler.IL";
 		public readonly string Description;
 		public string VariableName = "inst";
 
@@ -944,4 +954,12 @@ protected override void Disconnected()
 		opCode.WriteOpCodePrefix.Add("if (IsReadOnly)" + Environment.NewLine + "\toutput.Write(\"readonly.\");");
 		opCode.PerformMatchConditions.Add("IsReadOnly == o.IsReadOnly");
 	};
+
+	static Action<OpCode> Pattern = opCode => {
+		BaseClass("PatternInstruction")(opCode);
+		opCode.Namespace = "ICSharpCode.Decompiler.IL.Patterns";
+		opCode.GenerateAcceptVisitor = false;
+		opCode.GenerateMatch = false;
+		opCode.GeneratePerformMatch = false;
+	};
 #>

ICSharpCode.Decompiler/IL/Patterns/AnyNode.cs

@@ -0,0 +1,57 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+
+namespace ICSharpCode.Decompiler.IL.Patterns
+{
+	partial class PatternInstruction : ILInstruction
+	{
+		public override void AcceptVisitor(ILVisitor visitor)
+		{
+			throw new NotSupportedException();
+		}
+		
+		public override T AcceptVisitor<C, T>(ILVisitor<C, T> visitor, C context)
+		{
+			throw new NotSupportedException();
+		}
+		
+		public override T AcceptVisitor<T>(ILVisitor<T> visitor)
+		{
+			throw new NotSupportedException();
+		}
+
+		protected override InstructionFlags ComputeFlags()
+		{
+			throw new NotSupportedException();
+		}
+
+		public override InstructionFlags DirectFlags
+		{
+			get {
+				throw new NotSupportedException();
+			}
+		}
+	}
+
+	partial class AnyNode : PatternInstruction
+	{
+		CaptureGroup group;
+
+		public AnyNode(CaptureGroup group = null)
+			: base(OpCode.AnyNode)
+		{
+			this.group = group;
+		}
+
+		protected internal override bool PerformMatch(ILInstruction other, ref Match match)
+		{
+			if (other == null)
+				return false;
+			match.Add(group, other);
+			return true;
+		}
+	}
+}