Eliminate the dedicated logic.not instruction, and treat it as syntax sugar similar to logic.and/logic.or.

'logic.not(arg)' is now represented using 'comp(arg == ldc.i4 0)'.

ICSharpCode.Decompiler.Tests/PrettyTestRunner.cs

@@ -118,7 +118,11 @@ namespace ICSharpCode.Decompiler.Tests
 		[Test, Ignore("Not implemented")]
 		public void LiftedOperators([ValueSource("defaultOptions")] CompilerOptions cscOptions)
 		{
-			Run(cscOptions: cscOptions);
+			try {
+				Run(cscOptions: cscOptions);
+			} catch (AssertionException) {
+				Assert.Ignore("Not implemented");
+			}
 		}
 
 		[Test, Ignore("Bad variable names; some if-else misdetected")]

ICSharpCode.Decompiler.Tests/TestCases/Pretty/QueryExpressions.cs

@@ -143,8 +143,7 @@ namespace ICSharpCode.Decompiler.Tests.TestCases.Pretty
 			return from c in this.customers
 				   join o in this.orders on c.CustomerID equals o.CustomerID into co
 				   let n = co.Count()
-				   // should be n >= 10
-				   where !(n < 10)
+				   where n >= 10
 				   select new {
 					   Name = c.Name,
 					   OrderCount = n

ICSharpCode.Decompiler/CSharp/ExpressionBuilder.cs

@@ -342,11 +342,6 @@ namespace ICSharpCode.Decompiler.CSharp
 				.WithRR(new TypeOfResolveResult(compilation.FindType(new TopLevelTypeName("System", "RuntimeTypeHandle")), inst.Type));
 		}
 		
-		protected internal override TranslatedExpression VisitLogicNot(LogicNot inst, TranslationContext context)
-		{
-			return TranslateCondition(inst.Argument, negate: true).WithILInstruction(inst);
-		}
-		
 		protected internal override TranslatedExpression VisitBitNot(BitNot inst, TranslationContext context)
 		{
 			var argument = Translate(inst.Argument);

ICSharpCode.Decompiler/CSharp/StatementBuilder.cs

@@ -381,9 +381,9 @@ namespace ICSharpCode.Decompiler.CSharp
 			ILInstruction condition = null;
 			foreach (var c in conditions) {
 				if (condition == null)
-					condition = new LogicNot(c);
+					condition = Comp.LogicNot(c);
 				else
-					condition = IfInstruction.LogicAnd(new LogicNot(c), condition);
+					condition = IfInstruction.LogicAnd(Comp.LogicNot(c), condition);
 			}
 			return condition;
 		}

ICSharpCode.Decompiler/IL/ControlFlow/AsyncAwaitDecompiler.cs

@@ -865,7 +865,7 @@ namespace ICSharpCode.Decompiler.IL.ControlFlow
 			foreach (var tryFinally in function.Descendants.OfType<TryFinally>()) {
 				entryPoint = GetBodyEntryPoint(tryFinally.FinallyBlock as BlockContainer);
 				if (entryPoint?.Instructions[0] is IfInstruction ifInst) {
-					if (ifInst.Condition is LogicNot logicNot && logicNot.Argument.MatchLdLoc(doFinallyBodies)) {
+					if (ifInst.Condition.MatchLogicNot(out var logicNotArg) && logicNotArg.MatchLdLoc(doFinallyBodies)) {
 						context.Step("Remove if(doFinallyBodies) from try-finally", tryFinally);
 						// condition will always be false now that we're using 'await' instructions
 						entryPoint.Instructions.RemoveAt(0);

ICSharpCode.Decompiler/IL/ControlFlow/ConditionDetection.cs

@@ -98,7 +98,7 @@ namespace ICSharpCode.Decompiler.IL.ControlFlow
 				block.Instructions[block.Instructions.Count - 1] = ifInst.TrueInst;
 				ifInst.TrueInst = exitInst;
 				exitInst = block.Instructions.Last();
-				ifInst.Condition = new LogicNot(ifInst.Condition);
+				ifInst.Condition = Comp.LogicNot(ifInst.Condition);
 			}
 
 			ILInstruction trueExitInst;
@@ -119,7 +119,7 @@ namespace ICSharpCode.Decompiler.IL.ControlFlow
 						// "if (...) { if (nestedCondition) goto exitPoint; ... } goto exitPoint;"
 						// -> "if (... && !nestedCondition) { ... } goto exitPoint;"
 						context.Step("Combine 'if (cond1 && !cond2)' in then-branch", ifInst);
-						ifInst.Condition = IfInstruction.LogicAnd(ifInst.Condition, new LogicNot(nestedCondition));
+						ifInst.Condition = IfInstruction.LogicAnd(ifInst.Condition, Comp.LogicNot(nestedCondition));
 						targetBlock.Instructions.RemoveAt(0);
 						// Update targetBlock label now that we've removed the first instruction
 						if (targetBlock.Instructions.FirstOrDefault()?.ILRange.IsEmpty == false) {
@@ -137,7 +137,7 @@ namespace ICSharpCode.Decompiler.IL.ControlFlow
 						// (only if end-point of 'falseInst...' is unreachable)
 						context.Step("Invert nested condition to reduce number of gotos", ifInst);
 						var nestedIfInst = (IfInstruction)targetBlock.Instructions[0];
-						nestedIfInst.Condition = new LogicNot(nestedCondition);
+						nestedIfInst.Condition = Comp.LogicNot(nestedCondition);
 						nestedTrueBlock.Instructions.RemoveAt(nestedTrueBlock.Instructions.Count - 1); // remove nested goto exitPoint;
 						// remove falseInsts from outer block
 						var falseInsts = targetBlock.Instructions.Skip(1).ToArray();
@@ -197,7 +197,7 @@ namespace ICSharpCode.Decompiler.IL.ControlFlow
 				var oldTrue = ifInst.TrueInst;
 				ifInst.TrueInst = ifInst.FalseInst;
 				ifInst.FalseInst = new Nop { ILRange = oldTrue.ILRange };
-				ifInst.Condition = new LogicNot(ifInst.Condition);
+				ifInst.Condition = Comp.LogicNot(ifInst.Condition);
 
 				// After swapping, it's possible that we can introduce a short-circuit operator:
 				Block trueBlock = ifInst.TrueInst as Block;
@@ -218,7 +218,7 @@ namespace ICSharpCode.Decompiler.IL.ControlFlow
 				var oldTrue = ifInst.TrueInst;
 				ifInst.TrueInst = ifInst.FalseInst;
 				ifInst.FalseInst = oldTrue;
-				ifInst.Condition = new LogicNot(ifInst.Condition);
+				ifInst.Condition = Comp.LogicNot(ifInst.Condition);
 			}
 		}
 

ICSharpCode.Decompiler/IL/ControlFlow/SymbolicExecution.cs

@@ -142,18 +142,23 @@ namespace ICSharpCode.Decompiler.IL.ControlFlow
 			} else if (inst is Comp comp) {
 				var left = Eval(comp.Left);
 				var right = Eval(comp.Right);
-				if (left.Type != SymbolicValueType.State || right.Type != SymbolicValueType.IntegerConstant)
-					return Failed;
-				// bool: (state + left.Constant == right.Constant)
-				LongSet trueSums = SwitchAnalysis.MakeSetWhereComparisonIsTrue(comp.Kind, right.Constant, comp.Sign);
-				// symbolic value is true iff trueSums.Contains(state + left.Constant)
-				LongSet trueStates = trueSums.AddOffset(unchecked(-left.Constant));
-				// symbolic value is true iff trueStates.Contains(state)
-				return new SymbolicValue(SymbolicValueType.StateInSet, trueStates);
-			} else if (inst is LogicNot logicNot) {
-				SymbolicValue val = Eval(logicNot.Argument).AsBool();
-				if (val.Type == SymbolicValueType.StateInSet) {
-					return new SymbolicValue(SymbolicValueType.StateInSet, val.ValueSet.Invert());
+				if (left.Type == SymbolicValueType.State && right.Type == SymbolicValueType.IntegerConstant) {
+					// bool: (state + left.Constant == right.Constant)
+					LongSet trueSums = SwitchAnalysis.MakeSetWhereComparisonIsTrue(comp.Kind, right.Constant, comp.Sign);
+					// symbolic value is true iff trueSums.Contains(state + left.Constant)
+					LongSet trueStates = trueSums.AddOffset(unchecked(-left.Constant));
+					// symbolic value is true iff trueStates.Contains(state)
+					return new SymbolicValue(SymbolicValueType.StateInSet, trueStates);
+				} else if (left.Type == SymbolicValueType.StateInSet && right.Type == SymbolicValueType.IntegerConstant) {
+					if (comp.Kind == ComparisonKind.Equality && right.Constant == 0) {
+						// comp((x in set) == 0) ==> x not in set
+						return new SymbolicValue(SymbolicValueType.StateInSet, left.ValueSet.Invert());
+					} else if (comp.Kind == ComparisonKind.Inequality && right.Constant != 0) {
+						// comp((x in set) != 0) => x in set
+						return new SymbolicValue(SymbolicValueType.StateInSet, left.ValueSet);
+					} else {
+						return Failed;
+					}
 				} else {
 					return Failed;
 				}

ICSharpCode.Decompiler/IL/ControlFlow/YieldReturnDecompiler.cs

@@ -995,7 +995,7 @@ namespace ICSharpCode.Decompiler.IL.ControlFlow
 			foreach (var tryFinally in function.Descendants.OfType<TryFinally>()) {
 				entryPoint = AsyncAwaitDecompiler.GetBodyEntryPoint(tryFinally.FinallyBlock as BlockContainer);
 				if (entryPoint?.Instructions[0] is IfInstruction ifInst) {
-					if (ifInst.Condition is LogicNot logicNot && logicNot.Argument.MatchLdLoc(skipFinallyBodies)) {
+					if (ifInst.Condition.MatchLogicNot(out var logicNotArg) && logicNotArg.MatchLdLoc(skipFinallyBodies)) {
 						context.Step("Remove if (skipFinallyBodies) from try-finally", tryFinally);
 						// condition will always be true now that we're using 'yield' instructions
 						entryPoint.Instructions[0] = ifInst.TrueInst;

ICSharpCode.Decompiler/IL/ILReader.cs

@@ -1133,7 +1133,7 @@ namespace ICSharpCode.Decompiler.IL
 			if (left.ResultType == StackType.F && right.ResultType == StackType.F) {
 				if (un) {
 					// for floats, 'un' means 'unordered'
-					return new LogicNot(new Comp(kind.Negate(), Sign.None, left, right));
+					return Comp.LogicNot(new Comp(kind.Negate(), Sign.None, left, right));
 				} else {
 					return new Comp(kind, Sign.None, left, right);
 				}
@@ -1189,7 +1189,7 @@ namespace ICSharpCode.Decompiler.IL
 					break;
 				default:
 					if (negate) {
-						condition = new LogicNot(condition);
+						condition = Comp.LogicNot(condition);
 					}
 					break;
 			}

ICSharpCode.Decompiler/IL/Instructions.cs

@@ -43,8 +43,6 @@ namespace ICSharpCode.Decompiler.IL
 		Block,
 		/// <summary>A region where a pinned variable is used (initial representation of future fixed statement).</summary>
 		PinnedRegion,
-		/// <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>
-		LogicNot,
 		/// <summary>Common instruction for add, sub, mul, div, rem, bit.and, bit.or, bit.xor, shl and shr.</summary>
 		BinaryNumericInstruction,
 		/// <summary>Common instruction for compound assignments.</summary>
@@ -833,34 +831,6 @@ namespace ICSharpCode.Decompiler.IL
 	}
 }
 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
-	{
-		public LogicNot(ILInstruction argument) : base(OpCode.LogicNot, argument)
-		{
-		}
-		public override StackType ResultType { get { return StackType.I4; } }
-		public override void AcceptVisitor(ILVisitor visitor)
-		{
-			visitor.VisitLogicNot(this);
-		}
-		public override T AcceptVisitor<T>(ILVisitor<T> visitor)
-		{
-			return visitor.VisitLogicNot(this);
-		}
-		public override T AcceptVisitor<C, T>(ILVisitor<C, T> visitor, C context)
-		{
-			return visitor.VisitLogicNot(this, context);
-		}
-		protected internal override bool PerformMatch(ILInstruction other, ref Patterns.Match match)
-		{
-			var o = other as LogicNot;
-			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
@@ -4223,10 +4193,6 @@ namespace ICSharpCode.Decompiler.IL
 		{
 			Default(inst);
 		}
-		protected internal virtual void VisitLogicNot(LogicNot inst)
-		{
-			Default(inst);
-		}
 		protected internal virtual void VisitBinaryNumericInstruction(BinaryNumericInstruction inst)
 		{
 			Default(inst);
@@ -4501,10 +4467,6 @@ namespace ICSharpCode.Decompiler.IL
 		{
 			return Default(inst);
 		}
-		protected internal virtual T VisitLogicNot(LogicNot inst)
-		{
-			return Default(inst);
-		}
 		protected internal virtual T VisitBinaryNumericInstruction(BinaryNumericInstruction inst)
 		{
 			return Default(inst);
@@ -4779,10 +4741,6 @@ namespace ICSharpCode.Decompiler.IL
 		{
 			return Default(inst, context);
 		}
-		protected internal virtual T VisitLogicNot(LogicNot inst, C context)
-		{
-			return Default(inst, context);
-		}
 		protected internal virtual T VisitBinaryNumericInstruction(BinaryNumericInstruction inst, C context)
 		{
 			return Default(inst, context);
@@ -5031,7 +4989,6 @@ namespace ICSharpCode.Decompiler.IL
 			"BlockContainer",
 			"Block",
 			"PinnedRegion",
-			"logic.not",
 			"binary",
 			"compound",
 			"bit.not",
@@ -5135,16 +5092,6 @@ namespace ICSharpCode.Decompiler.IL
 			body = default(ILInstruction);
 			return false;
 		}
-		public bool MatchLogicNot(out ILInstruction argument)
-		{
-			var inst = this as LogicNot;
-			if (inst != null) {
-				argument = inst.Argument;
-				return true;
-			}
-			argument = default(ILInstruction);
-			return false;
-		}
 		public bool MatchBitNot(out ILInstruction argument)
 		{
 			var inst = this as BitNot;

ICSharpCode.Decompiler/IL/Instructions.tt

@@ -63,8 +63,6 @@
 				new ChildInfo("init") { CanInlineInto = true },
 				new ChildInfo("body")
 			})),
-		new OpCode("logic.not", "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).",
-			ResultType("I4"), Unary),
 		new OpCode("binary", "Common instruction for add, sub, mul, div, rem, bit.and, bit.or, bit.xor, shl and shr.",
 			CustomClassName("BinaryNumericInstruction"), Binary, CustomWriteTo, CustomConstructor, CustomComputeFlags,
 			MatchCondition("CheckForOverflow == o.CheckForOverflow && Sign == o.Sign && Operator == o.Operator && IsLifted == o.IsLifted")),

ICSharpCode.Decompiler/IL/Instructions/Comp.cs

@@ -20,6 +20,8 @@ using System;
 using System.Diagnostics;
 using ICSharpCode.Decompiler.CSharp.Syntax;
 using ICSharpCode.Decompiler.TypeSystem;
+using ICSharpCode.Decompiler.Util;
+
 namespace ICSharpCode.Decompiler.IL
 {
 	public enum ComparisonKind : byte
@@ -132,7 +134,7 @@ namespace ICSharpCode.Decompiler.IL
 		/// For lifted comparisons, this is the underlying input type.
 		/// </summary>
 		public StackType InputType;
-		
+
 		/// <summary>
 		/// If this is an integer comparison, specifies the sign used to interpret the integers.
 		/// </summary>
@@ -198,6 +200,16 @@ namespace ICSharpCode.Decompiler.IL
 			Right.WriteTo(output);
 			output.Write(')');
 		}
+
+		public static Comp LogicNot(ILInstruction arg)
+		{
+			return new Comp(ComparisonKind.Equality, Sign.None, arg, new LdcI4(0));
+		}
+
+		public static Comp LogicNot(ILInstruction arg, Interval ilrange)
+		{
+			return new Comp(ComparisonKind.Equality, Sign.None, arg, new LdcI4(0)) { ILRange = ilrange };
+		}
 	}
 }
 

ICSharpCode.Decompiler/IL/Instructions/PatternMatching.cs

@@ -257,6 +257,22 @@ namespace ICSharpCode.Decompiler.IL
 			return false;
 		}
 
+		/// <summary>
+		/// Matches an logical negation.
+		/// </summary>
+		public bool MatchLogicNot(out ILInstruction arg)
+		{
+			if (this is Comp comp && comp.Kind == ComparisonKind.Equality
+				&& comp.LiftingKind == ComparisonLiftingKind.None
+				&& comp.Right.MatchLdcI4(0))
+			{
+				arg = comp.Left;
+				return true;
+			}
+			arg = null;
+			return false;
+		}
+
 		public bool MatchTryCatchHandler(out ILVariable variable)
 		{
 			var inst = this as TryCatchHandler;
@@ -273,23 +289,19 @@ namespace ICSharpCode.Decompiler.IL
 		/// </summary>
 		public bool MatchCompEquals(out ILInstruction left, out ILInstruction right)
 		{
-			ComparisonKind op;
-			Comp comp;
-			if (this is LogicNot logicNot) {
-				op = ComparisonKind.Inequality;
-				comp = logicNot.Argument as Comp;
-			} else {
-				op = ComparisonKind.Equality;
-				comp = this as Comp;
-			}
-			if (comp != null && comp.Kind == op) {
+			if (this.MatchLogicNot(out var arg) && arg is Comp nestedComp && nestedComp.Kind == ComparisonKind.Inequality && !nestedComp.IsLifted) {
+				left = nestedComp.Left;
+				right = nestedComp.Right;
+				return true;
+			} else if (this is Comp comp && comp.Kind == ComparisonKind.Equality && !comp.IsLifted) {
 				left = comp.Left;
 				right = comp.Right;
 				return true;
+			} else {
+				left = null;
+				right = null;
+				return false;
 			}
-			left = null;
-			right = null;
-			return false;
 		}
 
 		/// <summary>
@@ -297,23 +309,19 @@ namespace ICSharpCode.Decompiler.IL
 		/// </summary>
 		public bool MatchCompNotEquals(out ILInstruction left, out ILInstruction right)
 		{
-			ComparisonKind op;
-			Comp comp;
-			if (this is LogicNot logicNot) {
-				op = ComparisonKind.Equality;
-				comp = logicNot.Argument as Comp;
-			} else {
-				op = ComparisonKind.Inequality;
-				comp = this as Comp;
-			}
-			if (comp != null && comp.Kind == op) {
+			if (this.MatchLogicNot(out var arg) && arg is Comp nestedComp && nestedComp.Kind == ComparisonKind.Equality && !nestedComp.IsLifted) {
+				left = nestedComp.Left;
+				right = nestedComp.Right;
+				return true;
+			} else if (this is Comp comp && comp.Kind == ComparisonKind.Inequality && !comp.IsLifted) {
 				left = comp.Left;
 				right = comp.Right;
 				return true;
+			} else {
+				left = null;
+				right = null;
+				return false;
 			}
-			left = null;
-			right = null;
-			return false;
 		}
 
 		public bool MatchLdsFld(IField field)

ICSharpCode.Decompiler/IL/Transforms/ExpressionTransforms.cs

@@ -52,8 +52,36 @@ namespace ICSharpCode.Decompiler.IL.Transforms
 			// we know those were already handled previously.
 		}
 
+		static bool IsInConditionSlot(ILInstruction inst)
+		{
+			var slot = inst.SlotInfo;
+			if (slot == IfInstruction.ConditionSlot)
+				return true;
+			if (slot == IfInstruction.TrueInstSlot || slot == IfInstruction.FalseInstSlot || slot == NullCoalescingInstruction.FallbackInstSlot)
+				return IsInConditionSlot(inst.Parent);
+			if (inst.Parent.MatchLogicNot(out _))
+				return true;
+			return false;
+		}
+
 		protected internal override void VisitComp(Comp inst)
 		{
+			// "logic.not(arg)" is sugar for "comp(arg != ldc.i4 0)"
+			if (inst.MatchLogicNot(out var arg)) {
+				VisitLogicNot(inst, arg);
+				return;
+			} else if (inst.Kind == ComparisonKind.Inequality && inst.LiftingKind == ComparisonLiftingKind.None
+				&& inst.Right.MatchLdcI4(0) && (IsInConditionSlot(inst) || inst.Left is Comp)
+			) {
+				// if (comp(x != 0)) ==> if (x)
+				// comp(comp(...) != 0) => comp(...)
+				context.Step("Remove redundant comp(... != 0)", inst);
+				inst.Left.AddILRange(inst.ILRange);
+				inst.ReplaceWith(inst.Left);
+				inst.Left.AcceptVisitor(this);
+				return;
+			}
+
 			base.VisitComp(inst);
 			if (inst.IsLifted) {
 				return;
@@ -94,9 +122,13 @@ namespace ICSharpCode.Decompiler.IL.Transforms
 				if (inst.Kind == ComparisonKind.GreaterThan) {
 					context.Step("comp.unsigned(left > ldc.i4 0) => comp(left != ldc.i4 0)", inst);
 					inst.Kind = ComparisonKind.Inequality;
+					VisitComp(inst);
+					return;
 				} else if (inst.Kind == ComparisonKind.LessThanOrEqual) {
 					context.Step("comp.unsigned(left <= ldc.i4 0) => comp(left == ldc.i4 0)", inst);
 					inst.Kind = ComparisonKind.Equality;
+					VisitComp(inst);
+					return;
 				}
 			}
 		}
@@ -137,17 +169,10 @@ namespace ICSharpCode.Decompiler.IL.Transforms
 			}
 		}
 
-		protected internal override void VisitLogicNot(LogicNot inst)
+		void VisitLogicNot(Comp inst, ILInstruction arg)
 		{
-			ILInstruction arg, lhs, rhs;
-			if (inst.Argument.MatchLogicNot(out arg)) {
-				context.Step("logic.not(logic.not(arg)) => arg", inst);
-				Debug.Assert(arg.ResultType == StackType.I4);
-				arg.AddILRange(inst.ILRange);
-				arg.AddILRange(inst.Argument.ILRange);
-				inst.ReplaceWith(arg);
-				arg.AcceptVisitor(this);
-			} else if (inst.Argument is Comp comp) {
+			ILInstruction lhs, rhs;
+			if (arg is Comp comp) {
 				if ((comp.InputType != StackType.F && !comp.IsLifted) || comp.Kind.IsEqualityOrInequality()) {
 					context.Step("push negation into comparison", inst);
 					comp.Kind = comp.Kind.Negate();
@@ -155,32 +180,32 @@ namespace ICSharpCode.Decompiler.IL.Transforms
 					inst.ReplaceWith(comp);
 				}
 				comp.AcceptVisitor(this);
-			} else if (inst.Argument.MatchLogicAnd(out lhs, out rhs)) {
+			} else if (arg.MatchLogicAnd(out lhs, out rhs)) {
 				// logic.not(if (lhs) rhs else ldc.i4 0)
 				// ==> if (logic.not(lhs)) ldc.i4 1 else logic.not(rhs)
 				context.Step("push negation into logic.and", inst);
-				IfInstruction ifInst = (IfInstruction)inst.Argument;
+				IfInstruction ifInst = (IfInstruction)arg;
 				var ldc0 = ifInst.FalseInst;
 				Debug.Assert(ldc0.MatchLdcI4(0));
-				ifInst.Condition = new LogicNot(lhs) { ILRange = inst.ILRange };
+				ifInst.Condition = Comp.LogicNot(lhs, inst.ILRange);
 				ifInst.TrueInst = new LdcI4(1) { ILRange = ldc0.ILRange };
-				ifInst.FalseInst = new LogicNot(rhs) { ILRange = inst.ILRange };
+				ifInst.FalseInst = Comp.LogicNot(rhs, inst.ILRange);
 				inst.ReplaceWith(ifInst);
 				ifInst.AcceptVisitor(this);
-			} else if (inst.Argument.MatchLogicOr(out lhs, out rhs)) {
+			} else if (arg.MatchLogicOr(out lhs, out rhs)) {
 				// logic.not(if (lhs) ldc.i4 1 else rhs)
 				// ==> if (logic.not(lhs)) logic.not(rhs) else ldc.i4 0)
 				context.Step("push negation into logic.or", inst);
-				IfInstruction ifInst = (IfInstruction)inst.Argument;
+				IfInstruction ifInst = (IfInstruction)arg;
 				var ldc1 = ifInst.TrueInst;
 				Debug.Assert(ldc1.MatchLdcI4(1));
-				ifInst.Condition = new LogicNot(lhs) { ILRange = inst.ILRange };
-				ifInst.TrueInst = new LogicNot(rhs) { ILRange = inst.ILRange };
+				ifInst.Condition = Comp.LogicNot(lhs, inst.ILRange);
+				ifInst.TrueInst = Comp.LogicNot(rhs, inst.ILRange);
 				ifInst.FalseInst = new LdcI4(0) { ILRange = ldc1.ILRange };
 				inst.ReplaceWith(ifInst);
 				ifInst.AcceptVisitor(this);
 			} else {
-				inst.Argument.AcceptVisitor(this);
+				arg.AcceptVisitor(this);
 			}
 		}
 		
@@ -286,7 +311,7 @@ namespace ICSharpCode.Decompiler.IL.Transforms
 				var t = inst.TrueInst;
 				inst.TrueInst = inst.FalseInst;
 				inst.FalseInst = t;
-				inst.Condition = new LogicNot(inst.Condition);
+				inst.Condition = Comp.LogicNot(inst.Condition);
 			}
 
 			base.VisitIfInstruction(inst);
@@ -309,7 +334,7 @@ namespace ICSharpCode.Decompiler.IL.Transforms
 			ILInstruction value1, value2;
 			if (trueInst.Instructions[0].MatchStLoc(out v, out value1) && falseInst.Instructions[0].MatchStLoc(v, out value2)) {
 				context.Step("conditional operator", inst);
-				var newIf = new IfInstruction(new LogicNot(inst.Condition), value2, value1);
+				var newIf = new IfInstruction(Comp.LogicNot(inst.Condition), value2, value1);
 				newIf.ILRange = inst.ILRange;
 				inst.ReplaceWith(new StLoc(v, newIf));
 				return newIf;

ICSharpCode.Decompiler/IL/Transforms/ILInlining.cs

@@ -287,7 +287,7 @@ namespace ICSharpCode.Decompiler.IL.Transforms
 				case OpCode.Leave:
 					return parent == next;
 				case OpCode.IfInstruction:
-					while (parent.OpCode == OpCode.LogicNot) {
+					while (parent.MatchLogicNot(out _)) {
 						parent = parent.Parent;
 					}
 					return parent == next;