mirror of https://github.com/icsharpcode/ILSpy.git
Eusebiu Marcu
15 years ago
9 changed files with 658 additions and 475 deletions
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// Copyright (c) AlphaSierraPapa for the SharpDevelop Team (for details please see \doc\copyright.txt)
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// This code is distributed under MIT X11 license (for details please see \doc\license.txt)
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using System; |
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using System.Collections.Generic; |
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using System.Linq; |
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using ICSharpCode.Decompiler.FlowAnalysis; |
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namespace ICSharpCode.Decompiler.ILAst |
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{ |
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/// <summary>
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/// Description of LoopsAndConditions.
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/// </summary>
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public class LoopsAndConditions |
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{ |
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Dictionary<ILLabel, ControlFlowNode> labelToCfNode = new Dictionary<ILLabel, ControlFlowNode>(); |
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DecompilerContext context; |
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uint nextLabelIndex = 0; |
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public LoopsAndConditions(DecompilerContext context) |
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{ |
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this.context = context; |
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} |
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public void FindLoops(ILBlock block) |
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{ |
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ControlFlowGraph graph; |
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graph = BuildGraph(block.Body, (ILLabel)block.EntryGoto.Operand); |
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graph.ComputeDominance(context.CancellationToken); |
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graph.ComputeDominanceFrontier(); |
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block.Body = FindLoops(new HashSet<ControlFlowNode>(graph.Nodes.Skip(3)), graph.EntryPoint, false); |
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} |
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public void FindConditions(ILBlock block) |
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{ |
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ControlFlowGraph graph; |
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graph = BuildGraph(block.Body, (ILLabel)block.EntryGoto.Operand); |
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graph.ComputeDominance(context.CancellationToken); |
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graph.ComputeDominanceFrontier(); |
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block.Body = FindConditions(new HashSet<ControlFlowNode>(graph.Nodes.Skip(3)), graph.EntryPoint); |
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} |
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ControlFlowGraph BuildGraph(List<ILNode> nodes, ILLabel entryLabel) |
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{ |
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int index = 0; |
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List<ControlFlowNode> cfNodes = new List<ControlFlowNode>(); |
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ControlFlowNode entryPoint = new ControlFlowNode(index++, 0, ControlFlowNodeType.EntryPoint); |
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cfNodes.Add(entryPoint); |
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ControlFlowNode regularExit = new ControlFlowNode(index++, -1, ControlFlowNodeType.RegularExit); |
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cfNodes.Add(regularExit); |
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ControlFlowNode exceptionalExit = new ControlFlowNode(index++, -1, ControlFlowNodeType.ExceptionalExit); |
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cfNodes.Add(exceptionalExit); |
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// Create graph nodes
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labelToCfNode = new Dictionary<ILLabel, ControlFlowNode>(); |
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Dictionary<ILNode, ControlFlowNode> astNodeToCfNode = new Dictionary<ILNode, ControlFlowNode>(); |
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foreach(ILNode node in nodes) { |
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ControlFlowNode cfNode = new ControlFlowNode(index++, -1, ControlFlowNodeType.Normal); |
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cfNodes.Add(cfNode); |
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astNodeToCfNode[node] = cfNode; |
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cfNode.UserData = node; |
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// Find all contained labels
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foreach(ILLabel label in node.GetSelfAndChildrenRecursive<ILLabel>()) { |
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labelToCfNode[label] = cfNode; |
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} |
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} |
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// Entry endge
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ControlFlowNode entryNode = labelToCfNode[entryLabel]; |
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ControlFlowEdge entryEdge = new ControlFlowEdge(entryPoint, entryNode, JumpType.Normal); |
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entryPoint.Outgoing.Add(entryEdge); |
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entryNode.Incoming.Add(entryEdge); |
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// Create edges
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foreach(ILNode node in nodes) { |
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ControlFlowNode source = astNodeToCfNode[node]; |
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// Find all branches
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foreach(ILExpression child in node.GetSelfAndChildrenRecursive<ILExpression>()) { |
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IEnumerable<ILLabel> targets = child.GetBranchTargets(); |
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if (targets != null) { |
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foreach(ILLabel target in targets) { |
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ControlFlowNode destination; |
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// Labels which are out of out scope will not be int the collection
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if (labelToCfNode.TryGetValue(target, out destination) && destination != source) { |
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ControlFlowEdge edge = new ControlFlowEdge(source, destination, JumpType.Normal); |
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source.Outgoing.Add(edge); |
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destination.Incoming.Add(edge); |
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} |
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} |
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} |
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} |
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} |
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return new ControlFlowGraph(cfNodes.ToArray()); |
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} |
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List<ILNode> FindLoops(HashSet<ControlFlowNode> scope, ControlFlowNode entryPoint, bool excludeEntryPoint) |
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{ |
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List<ILNode> result = new List<ILNode>(); |
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// Do not modify entry data
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scope = new HashSet<ControlFlowNode>(scope); |
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Queue<ControlFlowNode> agenda = new Queue<ControlFlowNode>(); |
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agenda.Enqueue(entryPoint); |
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while(agenda.Count > 0) { |
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ControlFlowNode node = agenda.Dequeue(); |
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// If the node is a loop header
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if (scope.Contains(node) |
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&& node.DominanceFrontier.Contains(node) |
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&& (node != entryPoint || !excludeEntryPoint)) |
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{ |
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HashSet<ControlFlowNode> loopContents = FindLoopContent(scope, node); |
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// If the first expression is a loop condition
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ILBasicBlock basicBlock = (ILBasicBlock)node.UserData; |
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ILExpression condExpr; |
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ILLabel trueLabel; |
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ILLabel falseLabel; |
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if(basicBlock.Match(ILCode.Brtrue, out trueLabel, out condExpr, out falseLabel)) |
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{ |
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ControlFlowNode trueTarget; |
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labelToCfNode.TryGetValue(trueLabel, out trueTarget); |
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ControlFlowNode falseTarget; |
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labelToCfNode.TryGetValue(falseLabel, out falseTarget); |
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// If one point inside the loop and the other outside
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if ((!loopContents.Contains(trueTarget) && loopContents.Contains(falseTarget)) || |
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(loopContents.Contains(trueTarget) && !loopContents.Contains(falseTarget)) ) |
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{ |
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loopContents.RemoveOrThrow(node); |
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scope.RemoveOrThrow(node); |
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// If false means enter the loop
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if (loopContents.Contains(falseTarget)) |
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{ |
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// Negate the condition
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condExpr = new ILExpression(ILCode.LogicNot, null, condExpr); |
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ILLabel tmp = trueLabel; |
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trueLabel = falseLabel; |
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falseLabel = tmp; |
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} |
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ControlFlowNode postLoopTarget; |
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labelToCfNode.TryGetValue(falseLabel, out postLoopTarget); |
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if (postLoopTarget != null) { |
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// Pull more nodes into the loop
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HashSet<ControlFlowNode> postLoopContents = FindDominatedNodes(scope, postLoopTarget); |
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var pullIn = scope.Except(postLoopContents).Where(n => node.Dominates(n)); |
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loopContents.UnionWith(pullIn); |
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} |
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// Use loop to implement the condition
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result.Add(new ILBasicBlock() { |
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EntryLabel = basicBlock.EntryLabel, |
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Body = new List<ILNode>() { |
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new ILWhileLoop() { |
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Condition = condExpr, |
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BodyBlock = new ILBlock() { |
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EntryGoto = new ILExpression(ILCode.Br, trueLabel), |
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Body = FindLoops(loopContents, node, true) |
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} |
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}, |
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new ILExpression(ILCode.Br, falseLabel) |
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}, |
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FallthoughGoto = null |
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}); |
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} |
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} |
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// Fallback method: while(true)
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if (scope.Contains(node)) { |
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result.Add(new ILBasicBlock() { |
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EntryLabel = new ILLabel() { Name = "Loop_" + (nextLabelIndex++) }, |
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Body = new List<ILNode>() { |
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new ILWhileLoop() { |
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BodyBlock = new ILBlock() { |
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EntryGoto = new ILExpression(ILCode.Br, basicBlock.EntryLabel), |
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Body = FindLoops(loopContents, node, true) |
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} |
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}, |
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}, |
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FallthoughGoto = null |
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}); |
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} |
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// Move the content into loop block
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scope.ExceptWith(loopContents); |
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} |
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// Using the dominator tree should ensure we find the the widest loop first
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foreach(var child in node.DominatorTreeChildren) { |
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agenda.Enqueue(child); |
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} |
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} |
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// Add whatever is left
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foreach(var node in scope) { |
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result.Add((ILNode)node.UserData); |
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} |
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scope.Clear(); |
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return result; |
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} |
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List<ILNode> FindConditions(HashSet<ControlFlowNode> scope, ControlFlowNode entryNode) |
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{ |
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List<ILNode> result = new List<ILNode>(); |
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// Do not modify entry data
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scope = new HashSet<ControlFlowNode>(scope); |
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HashSet<ControlFlowNode> agenda = new HashSet<ControlFlowNode>(); |
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agenda.Add(entryNode); |
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while(agenda.Any()) { |
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ControlFlowNode node = agenda.First(); |
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// Attempt for a good order
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while(agenda.Contains(node.ImmediateDominator)) { |
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node = node.ImmediateDominator; |
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} |
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agenda.Remove(node); |
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// Find a block that represents a simple condition
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if (scope.Contains(node)) { |
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ILBasicBlock block = node.UserData as ILBasicBlock; |
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if (block != null && block.Body.Count == 1) { |
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ILExpression condBranch = block.Body[0] as ILExpression; |
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// Switch
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ILLabel[] caseLabels; |
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List<ILExpression> switchArgs; |
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if (condBranch.Match(ILCode.Switch, out caseLabels, out switchArgs)) { |
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ILSwitch ilSwitch = new ILSwitch() { Condition = switchArgs.Single() }; |
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ILBasicBlock newBB = new ILBasicBlock() { |
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EntryLabel = block.EntryLabel, // Keep the entry label
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Body = { ilSwitch }, |
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FallthoughGoto = block.FallthoughGoto |
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}; |
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result.Add(newBB); |
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// Remove the item so that it is not picked up as content
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scope.RemoveOrThrow(node); |
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// Find the switch offset
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int addValue = 0; |
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List<ILExpression> subArgs; |
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if (ilSwitch.Condition.Match(ILCode.Sub, out subArgs) && subArgs[1].Match(ILCode.Ldc_I4, out addValue)) { |
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ilSwitch.Condition = subArgs[0]; |
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} |
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// Pull in code of cases
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ILLabel fallLabel = (ILLabel)block.FallthoughGoto.Operand; |
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ControlFlowNode fallTarget = null; |
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labelToCfNode.TryGetValue(fallLabel, out fallTarget); |
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HashSet<ControlFlowNode> frontiers = new HashSet<ControlFlowNode>(); |
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if (fallTarget != null) |
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frontiers.UnionWith(fallTarget.DominanceFrontier); |
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foreach(ILLabel condLabel in caseLabels) { |
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ControlFlowNode condTarget = null; |
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labelToCfNode.TryGetValue(condLabel, out condTarget); |
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if (condTarget != null) |
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frontiers.UnionWith(condTarget.DominanceFrontier); |
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} |
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for (int i = 0; i < caseLabels.Length; i++) { |
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ILLabel condLabel = caseLabels[i]; |
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// Find or create new case block
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ILSwitch.CaseBlock caseBlock = ilSwitch.CaseBlocks.Where(b => b.EntryGoto.Operand == condLabel).FirstOrDefault(); |
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if (caseBlock == null) { |
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caseBlock = new ILSwitch.CaseBlock() { |
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Values = new List<int>(), |
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EntryGoto = new ILExpression(ILCode.Br, condLabel) |
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}; |
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ilSwitch.CaseBlocks.Add(caseBlock); |
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ControlFlowNode condTarget = null; |
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labelToCfNode.TryGetValue(condLabel, out condTarget); |
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if (condTarget != null && !frontiers.Contains(condTarget)) { |
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HashSet<ControlFlowNode> content = FindDominatedNodes(scope, condTarget); |
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scope.ExceptWith(content); |
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caseBlock.Body.AddRange(FindConditions(content, condTarget)); |
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// Add explicit break which should not be used by default, but the goto removal might decide to use it
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caseBlock.Body.Add(new ILBasicBlock() { Body = { new ILExpression(ILCode.LoopOrSwitchBreak, null) } }); |
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} |
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} |
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caseBlock.Values.Add(i + addValue); |
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} |
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// Heuristis to determine if we want to use fallthough as default case
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if (fallTarget != null && !frontiers.Contains(fallTarget)) { |
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HashSet<ControlFlowNode> content = FindDominatedNodes(scope, fallTarget); |
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if (content.Any()) { |
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var caseBlock = new ILSwitch.CaseBlock() { EntryGoto = new ILExpression(ILCode.Br, fallLabel) }; |
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ilSwitch.CaseBlocks.Add(caseBlock); |
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newBB.FallthoughGoto = null; |
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scope.ExceptWith(content); |
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caseBlock.Body.AddRange(FindConditions(content, fallTarget)); |
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// Add explicit break which should not be used by default, but the goto removal might decide to use it
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caseBlock.Body.Add(new ILBasicBlock() { Body = { new ILExpression(ILCode.LoopOrSwitchBreak, null) } }); |
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} |
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} |
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} |
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// Two-way branch
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ILExpression condExpr; |
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ILLabel trueLabel; |
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ILLabel falseLabel; |
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if(block.Match(ILCode.Brtrue, out trueLabel, out condExpr, out falseLabel)) { |
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// Swap bodies since that seems to be the usual C# order
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ILLabel temp = trueLabel; |
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trueLabel = falseLabel; |
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falseLabel = temp; |
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condExpr = new ILExpression(ILCode.LogicNot, null, condExpr); |
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// Convert the basic block to ILCondition
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ILCondition ilCond = new ILCondition() { |
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Condition = condExpr, |
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TrueBlock = new ILBlock() { EntryGoto = new ILExpression(ILCode.Br, trueLabel) }, |
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FalseBlock = new ILBlock() { EntryGoto = new ILExpression(ILCode.Br, falseLabel) } |
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}; |
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result.Add(new ILBasicBlock() { |
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EntryLabel = block.EntryLabel, // Keep the entry label
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Body = { ilCond } |
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}); |
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// Remove the item immediately so that it is not picked up as content
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scope.RemoveOrThrow(node); |
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ControlFlowNode trueTarget = null; |
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labelToCfNode.TryGetValue(trueLabel, out trueTarget); |
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ControlFlowNode falseTarget = null; |
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labelToCfNode.TryGetValue(falseLabel, out falseTarget); |
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// Pull in the conditional code
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HashSet<ControlFlowNode> frontiers = new HashSet<ControlFlowNode>(); |
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if (trueTarget != null) |
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frontiers.UnionWith(trueTarget.DominanceFrontier); |
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if (falseTarget != null) |
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frontiers.UnionWith(falseTarget.DominanceFrontier); |
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if (trueTarget != null && !frontiers.Contains(trueTarget)) { |
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HashSet<ControlFlowNode> content = FindDominatedNodes(scope, trueTarget); |
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scope.ExceptWith(content); |
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ilCond.TrueBlock.Body.AddRange(FindConditions(content, trueTarget)); |
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} |
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if (falseTarget != null && !frontiers.Contains(falseTarget)) { |
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HashSet<ControlFlowNode> content = FindDominatedNodes(scope, falseTarget); |
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scope.ExceptWith(content); |
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ilCond.FalseBlock.Body.AddRange(FindConditions(content, falseTarget)); |
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} |
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} |
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} |
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// Add the node now so that we have good ordering
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if (scope.Contains(node)) { |
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result.Add((ILNode)node.UserData); |
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scope.Remove(node); |
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} |
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} |
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// Using the dominator tree should ensure we find the the widest loop first
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foreach(var child in node.DominatorTreeChildren) { |
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agenda.Add(child); |
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} |
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} |
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// Add whatever is left
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foreach(var node in scope) { |
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result.Add((ILNode)node.UserData); |
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} |
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return result; |
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} |
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static HashSet<ControlFlowNode> FindDominatedNodes(HashSet<ControlFlowNode> scope, ControlFlowNode head) |
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{ |
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HashSet<ControlFlowNode> agenda = new HashSet<ControlFlowNode>(); |
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HashSet<ControlFlowNode> result = new HashSet<ControlFlowNode>(); |
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agenda.Add(head); |
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while(agenda.Count > 0) { |
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ControlFlowNode addNode = agenda.First(); |
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agenda.Remove(addNode); |
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if (scope.Contains(addNode) && head.Dominates(addNode) && result.Add(addNode)) { |
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foreach (var successor in addNode.Successors) { |
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agenda.Add(successor); |
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} |
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} |
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} |
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return result; |
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} |
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static HashSet<ControlFlowNode> FindLoopContent(HashSet<ControlFlowNode> scope, ControlFlowNode head) |
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{ |
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var viaBackEdges = head.Predecessors.Where(p => head.Dominates(p)); |
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HashSet<ControlFlowNode> agenda = new HashSet<ControlFlowNode>(viaBackEdges); |
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HashSet<ControlFlowNode> result = new HashSet<ControlFlowNode>(); |
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while(agenda.Count > 0) { |
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ControlFlowNode addNode = agenda.First(); |
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agenda.Remove(addNode); |
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if (scope.Contains(addNode) && head.Dominates(addNode) && result.Add(addNode)) { |
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foreach (var predecessor in addNode.Predecessors) { |
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agenda.Add(predecessor); |
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} |
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} |
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} |
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if (scope.Contains(head)) |
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result.Add(head); |
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return result; |
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} |
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} |
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} |
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