Check the CancellationToken a bit more frequently.

ICSharpCode.Decompiler/FlowAnalysis/DefiniteAssignmentVisitor.cs

@@ -19,6 +19,7 @@
 using System.Diagnostics;
 using ICSharpCode.Decompiler.IL;
 using ICSharpCode.Decompiler.Util;
+using System.Threading;
 
 namespace ICSharpCode.Decompiler.FlowAnalysis
 {
@@ -100,12 +101,15 @@ namespace ICSharpCode.Decompiler.FlowAnalysis
 				return bits[variableIndex];
 			}
 		}
-		
+
+		readonly CancellationToken cancellationToken;
 		readonly ILFunction scope;
 		readonly BitSet variablesWithUninitializedUsage;
 		
-		public DefiniteAssignmentVisitor(ILFunction scope)
+		public DefiniteAssignmentVisitor(ILFunction scope, CancellationToken cancellationToken)
 		{
+			cancellationToken.ThrowIfCancellationRequested();
+			this.cancellationToken = cancellationToken;
 			this.scope = scope;
 			this.variablesWithUninitializedUsage = new BitSet(scope.Variables.Count);
 			base.flagsRequiringManualImpl |= InstructionFlags.MayReadLocals | InstructionFlags.MayWriteLocals;
@@ -120,6 +124,7 @@ namespace ICSharpCode.Decompiler.FlowAnalysis
 		
 		void HandleStore(ILVariable v)
 		{
+			cancellationToken.ThrowIfCancellationRequested();
 			if (v.Function == scope) {
 				// Mark the variable as initialized:
 				state.MarkVariableInitialized(v.IndexInFunction);

ICSharpCode.Decompiler/FlowAnalysis/ReachingDefinitionsVisitor.cs

@@ -22,6 +22,7 @@ using System.Diagnostics;
 using System.Linq;
 using ICSharpCode.Decompiler.IL;
 using ICSharpCode.Decompiler.Util;
+using System.Threading;
 
 namespace ICSharpCode.Decompiler.FlowAnalysis
 {
@@ -188,8 +189,10 @@ namespace ICSharpCode.Decompiler.FlowAnalysis
 		/// </summary>
 		const int FirstStoreIndex = 1;
 		#endregion
-		
+
 		#region Documentation + member fields
+		protected readonly CancellationToken cancellationToken;
+
 		/// <summary>
 		/// The function being analyzed.
 		/// </summary>
@@ -234,9 +237,10 @@ namespace ICSharpCode.Decompiler.FlowAnalysis
 		/// The analysis will track all variables in the scope for which the predicate returns true
 		/// ("analyzed variables").
 		/// </summary>
-		public ReachingDefinitionsVisitor(ILFunction scope, Predicate<ILVariable> pred)
-			: this(scope, GetActiveVariableBitSet(scope, pred))
+		public ReachingDefinitionsVisitor(ILFunction scope, Predicate<ILVariable> pred, CancellationToken cancellationToken)
+			: this(scope, GetActiveVariableBitSet(scope, pred), cancellationToken)
 		{
+			this.cancellationToken = cancellationToken;
 		}
 
 		static BitSet GetActiveVariableBitSet(ILFunction scope, Predicate<ILVariable> pred)
@@ -255,7 +259,7 @@ namespace ICSharpCode.Decompiler.FlowAnalysis
 		/// 
 		/// The analysis will track all variables in the scope for which <c>analyzedVariables[v.IndexInScope]</c> is true.
 		/// </summary>
-		public ReachingDefinitionsVisitor(ILFunction scope, BitSet analyzedVariables)
+		public ReachingDefinitionsVisitor(ILFunction scope, BitSet analyzedVariables, CancellationToken cancellationToken)
 		{
 			if (scope == null)
 				throw new ArgumentNullException(nameof(scope));
@@ -266,11 +270,12 @@ namespace ICSharpCode.Decompiler.FlowAnalysis
 			base.flagsRequiringManualImpl |= InstructionFlags.MayWriteLocals;
 			
 			// Fill `allStores` and `storeIndexMap` and `firstStoreIndexForVariable`.
-			var storesByVar = FindAllStoresByVariable(scope, analyzedVariables);
+			var storesByVar = FindAllStoresByVariable(scope, analyzedVariables, cancellationToken);
 			allStores = new ILInstruction[FirstStoreIndex + storesByVar.Sum(l => l != null ? l.Count : 0)];
 			firstStoreIndexForVariable = new int[scope.Variables.Count + 1];
 			int si = FirstStoreIndex;
 			for (int vi = 0; vi < storesByVar.Length; vi++) {
+				cancellationToken.ThrowIfCancellationRequested();
 				firstStoreIndexForVariable[vi] = si;
 				var stores = storesByVar[vi];
 				if (stores != null) {
@@ -300,7 +305,7 @@ namespace ICSharpCode.Decompiler.FlowAnalysis
 		/// <summary>
 		/// Fill <c>allStores</c> and <c>storeIndexMap</c>.
 		/// </summary>
-		static List<ILInstruction>[] FindAllStoresByVariable(ILFunction scope, BitSet activeVariables)
+		static List<ILInstruction>[] FindAllStoresByVariable(ILFunction scope, BitSet activeVariables, CancellationToken cancellationToken)
 		{
 			// For each variable, find the list of ILInstructions storing to that variable
 			List<ILInstruction>[] storesByVar = new List<ILInstruction>[scope.Variables.Count];
@@ -310,6 +315,7 @@ namespace ICSharpCode.Decompiler.FlowAnalysis
 			}
 			foreach (var inst in scope.Descendants) {
 				if (inst.HasDirectFlag(InstructionFlags.MayWriteLocals)) {
+					cancellationToken.ThrowIfCancellationRequested();
 					ILVariable v = ((IInstructionWithVariableOperand)inst).Variable;
 					if (v.Function == scope && activeVariables[v.IndexInFunction]) {
 						storesByVar[v.IndexInFunction].Add(inst);
@@ -339,6 +345,7 @@ namespace ICSharpCode.Decompiler.FlowAnalysis
 		#region Analysis
 		void HandleStore(ILInstruction inst, ILVariable v)
 		{
+			cancellationToken.ThrowIfCancellationRequested();
 			if (v.Function == scope && analyzedVariables[v.IndexInFunction] && state.IsReachable) {
 				// Clear the set of stores for this variable:
 				state.KillStores(firstStoreIndexForVariable[v.IndexInFunction], firstStoreIndexForVariable[v.IndexInFunction + 1]);

ICSharpCode.Decompiler/IL/ControlFlow/ControlFlowSimplification.cs

@@ -39,6 +39,8 @@ namespace ICSharpCode.Decompiler.IL.ControlFlow
 		public void Run(ILFunction function, ILTransformContext context)
 		{
 			foreach (var block in function.Descendants.OfType<Block>()) {
+				context.CancellationToken.ThrowIfCancellationRequested();
+
 				// Remove 'nop' instructions
 				block.Instructions.RemoveAll(inst => inst.OpCode == OpCode.Nop);
 				

ICSharpCode.Decompiler/IL/ControlFlow/DetectPinnedRegions.cs

@@ -56,6 +56,7 @@ namespace ICSharpCode.Decompiler.IL.ControlFlow
 		public void Run(ILFunction function, ILTransformContext context)
 		{
 			foreach (var container in function.Descendants.OfType<BlockContainer>()) {
+				context.CancellationToken.ThrowIfCancellationRequested();
 				SplitBlocksAtWritesToPinnedLocals(container);
 				DetectNullSafeArrayToPointer(container);
 				foreach (var block in container.Blocks)
@@ -64,6 +65,7 @@ namespace ICSharpCode.Decompiler.IL.ControlFlow
 			}
 			// Sometimes there's leftover writes to the original pinned locals
 			foreach (var block in function.Descendants.OfType<Block>()) {
+				context.CancellationToken.ThrowIfCancellationRequested();
 				for (int i = 0; i < block.Instructions.Count; i++) {
 					var stloc = block.Instructions[i] as StLoc;
 					if (stloc != null && stloc.Variable.Kind == VariableKind.PinnedLocal && stloc.Variable.LoadCount == 0 && stloc.Variable.AddressCount == 0) {

ICSharpCode.Decompiler/IL/ControlFlow/ExitPoints.cs

@@ -19,6 +19,7 @@
 using System;
 using System.Diagnostics;
 using ICSharpCode.Decompiler.IL.Transforms;
+using System.Threading;
 
 namespace ICSharpCode.Decompiler.IL.ControlFlow
 {
@@ -100,6 +101,7 @@ namespace ICSharpCode.Decompiler.IL.ControlFlow
 			}
 		}
 
+		CancellationToken cancellationToken;
 		BlockContainer currentContainer;
 
 		/// <summary>
@@ -112,6 +114,7 @@ namespace ICSharpCode.Decompiler.IL.ControlFlow
 
 		public void Run(ILFunction function, ILTransformContext context)
 		{
+			cancellationToken = context.CancellationToken;
 			currentExit = NoExit;
 			function.AcceptVisitor(this);
 		}
@@ -149,6 +152,7 @@ namespace ICSharpCode.Decompiler.IL.ControlFlow
 
 		protected internal override void VisitBlock(Block block)
 		{
+			cancellationToken.ThrowIfCancellationRequested();
 			// Don't use foreach loop, because the children might add to the block
 			for (int i = 0; i < block.Instructions.Count; i++) {
 				block.Instructions[i].AcceptVisitor(this);

ICSharpCode.Decompiler/IL/ControlFlow/StateRangeAnalysis.cs

@@ -23,6 +23,7 @@ using System.Collections.Generic;
 using System.Diagnostics;
 using System.Linq;
 using System.Text;
+using System.Threading;
 using System.Threading.Tasks;
 
 namespace ICSharpCode.Decompiler.IL.ControlFlow
@@ -49,6 +50,7 @@ namespace ICSharpCode.Decompiler.IL.ControlFlow
 	/// </remarks>
 	class StateRangeAnalysis
 	{
+		public CancellationToken CancellationToken;
 		readonly StateRangeAnalysisMode mode;
 		readonly IField stateField;
 		readonly SymbolicEvaluationContext evalContext;
@@ -80,6 +82,7 @@ namespace ICSharpCode.Decompiler.IL.ControlFlow
 		/// </returns>
 		public LongSet AssignStateRanges(ILInstruction inst, LongSet stateRange)
 		{
+			CancellationToken.ThrowIfCancellationRequested();
 			switch (inst) {
 				case BlockContainer blockContainer:
 					AddStateRange(blockContainer.EntryPoint, stateRange);

ICSharpCode.Decompiler/IL/ControlFlow/SwitchDetection.cs

@@ -41,6 +41,7 @@ namespace ICSharpCode.Decompiler.IL.ControlFlow
 			foreach (var container in function.Descendants.OfType<BlockContainer>()) {
 				bool blockContainerNeedsCleanup = false;
 				foreach (var block in container.Blocks) {
+					context.CancellationToken.ThrowIfCancellationRequested();
 					ProcessBlock(block, ref blockContainerNeedsCleanup);
 				}
 				if (blockContainerNeedsCleanup) {

ICSharpCode.Decompiler/IL/ControlFlow/YieldReturnDecompiler.cs

@@ -443,6 +443,7 @@ namespace ICSharpCode.Decompiler.IL.ControlFlow
 			// So for reconstructing the control flow, we only consider the blocks directly within body.
 
 			var rangeAnalysis = new StateRangeAnalysis(StateRangeAnalysisMode.IteratorMoveNext, stateField);
+			rangeAnalysis.CancellationToken = context.CancellationToken;
 			rangeAnalysis.AssignStateRanges(body, LongSet.Universe);
 
 			var newBody = ConvertBody(body, rangeAnalysis.GetBlockStateSetMapping(body));
@@ -517,6 +518,7 @@ namespace ICSharpCode.Decompiler.IL.ControlFlow
 				var oldBlock = oldBody.Blocks[i];
 				var newBlock = newBody.Blocks[i];
 				foreach (var oldInst in oldBlock.Instructions) {
+					context.CancellationToken.ThrowIfCancellationRequested();
 					if (oldInst.MatchStFld(out var target, out var field, out var value) && target.MatchLdThis()) {
 						if (field.MemberDefinition.Equals(stateField)) {
 							if (value.MatchLdcI4(out int newState)) {
@@ -723,6 +725,7 @@ namespace ICSharpCode.Decompiler.IL.ControlFlow
 			stateToContainer.Add(-1, newBody);
 			// First, analyse the newBody: for each block, determine the active state number.
 			foreach (var block in newBody.Blocks) {
+				context.CancellationToken.ThrowIfCancellationRequested();
 				int oldState = blockState[block.ChildIndex];
 				BlockContainer container; // new container for the block
 				if (GetNewState(block) is int newState) {

ICSharpCode.Decompiler/IL/Transforms/DelegateConstruction.cs

@@ -39,6 +39,7 @@ namespace ICSharpCode.Decompiler.IL.Transforms
 			var targetsToReplace = new List<IInstructionWithVariableOperand>();
 			foreach (var block in function.Descendants.OfType<Block>()) {
 				for (int i = block.Instructions.Count - 1; i >= 0; i--) {
+					context.CancellationToken.ThrowIfCancellationRequested();
 					foreach (var call in block.Instructions[i].Descendants.OfType<NewObj>()) {
 						ILInstruction target;
 						ILFunction f = TransformDelegateConstruction(call, out target);
@@ -67,9 +68,8 @@ namespace ICSharpCode.Decompiler.IL.Transforms
 				function.AcceptVisitor(new TransformDisplayClassUsages(target, target.Variable.CaptureScope, orphanedVariableInits));
 			}
 			foreach (var store in orphanedVariableInits) {
-				ILInstruction containingBlock = store.Parent as Block;
-				if (containingBlock != null)
-					((Block)containingBlock).Instructions.Remove(store);
+				if (store.Parent is Block containingBlock)
+					containingBlock.Instructions.Remove(store);
 			}
 		}
 

ICSharpCode.Decompiler/IL/Transforms/RemoveDeadVariableInit.cs

@@ -30,7 +30,7 @@ namespace ICSharpCode.Decompiler.IL.Transforms
 	{
 		public void Run(ILFunction function, ILTransformContext context)
 		{
-			var visitor = new DefiniteAssignmentVisitor(function);
+			var visitor = new DefiniteAssignmentVisitor(function, context.CancellationToken);
 			function.Body.AcceptVisitor(visitor);
 			foreach (var v in function.Variables) {
 				if (v.Kind != VariableKind.Parameter && !visitor.IsPotentiallyUsedUninitialized(v)) {

ICSharpCode.Decompiler/IL/Transforms/SplitVariables.cs

@@ -20,6 +20,7 @@ using System.Collections.Generic;
 using System.Linq;
 using ICSharpCode.Decompiler.FlowAnalysis;
 using ICSharpCode.Decompiler.Util;
+using System.Threading;
 
 namespace ICSharpCode.Decompiler.IL.Transforms
 {
@@ -30,7 +31,7 @@ namespace ICSharpCode.Decompiler.IL.Transforms
 	{
 		public void Run(ILFunction function, ILTransformContext context)
 		{
-			var groupStores = new GroupStores(function);
+			var groupStores = new GroupStores(function, context.CancellationToken);
 			function.Body.AcceptVisitor(groupStores);
 			var newVariables = new Dictionary<ILInstruction, ILVariable>();
 			// Replace analyzed variables with their split versions:
@@ -67,7 +68,7 @@ namespace ICSharpCode.Decompiler.IL.Transforms
 			readonly UnionFind<IInstructionWithVariableOperand> unionFind = new UnionFind<IInstructionWithVariableOperand>();
 			readonly HashSet<IInstructionWithVariableOperand> uninitVariableUsage = new HashSet<IInstructionWithVariableOperand>();
 			
-			public GroupStores(ILFunction scope) : base(scope, IsCandidateVariable)
+			public GroupStores(ILFunction scope, CancellationToken cancellationToken) : base(scope, IsCandidateVariable, cancellationToken)
 			{
 			}