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@ -215,6 +215,7 @@ namespace ICSharpCode.Decompiler.IL.ControlFlow
@@ -215,6 +215,7 @@ namespace ICSharpCode.Decompiler.IL.ControlFlow
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if (exitPoint != null) { |
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// Either we are in case 1 and just picked an exit that maximizes the amount of code
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// outside the loop, or we are in case 2 and found an exit point via post-dominance.
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// Note that if exitPoint == NoExitPoint, we end up adding all dominated blocks to the loop.
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var ep = exitPoint; |
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foreach (var node in TreeTraversal.PreOrder(loopHead, n => (n != ep) ? n.DominatorTreeChildren : null)) { |
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if (node != exitPoint && !node.Visited) { |
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@ -228,10 +229,21 @@ namespace ICSharpCode.Decompiler.IL.ControlFlow
@@ -228,10 +229,21 @@ namespace ICSharpCode.Decompiler.IL.ControlFlow
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ExtendLoopHeuristic(loopHead, loop, loopHead); |
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} |
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} |
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/// <summary>
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/// Special control flow node (not part of any graph) that signifies that we want to construct a loop
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/// without any exit point.
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/// </summary>
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static readonly ControlFlowNode NoExitPoint = new ControlFlowNode(); |
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/// <summary>
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/// Finds a suitable single exit point for the specified loop.
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/// </summary>
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/// <returns>
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/// 1) If a suitable exit point was found: the control flow block that should be reached when breaking from the loop
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/// 2) If the loop should not have any exit point (extend by all dominated blocks): NoExitPoint
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/// 3) otherwise (exit point unknown, heuristically extend loop): null
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/// </returns>
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/// <remarks>This method must not write to the Visited flags on the CFG.</remarks>
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ControlFlowNode FindExitPoint(ControlFlowNode loopHead, IReadOnlyList<ControlFlowNode> naturalLoop, bool treatBackEdgesAsExits) |
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{ |
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@ -245,6 +257,16 @@ namespace ICSharpCode.Decompiler.IL.ControlFlow
@@ -245,6 +257,16 @@ namespace ICSharpCode.Decompiler.IL.ControlFlow
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// Case 1:
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// There are no nodes n so that loopHead dominates a predecessor of n but not n itself
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// -> we could build a loop with zero exit points.
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if (IsPossibleForeachLoop((Block)loopHead.UserData, out var exitBranch)) { |
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if (exitBranch != null) { |
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// let's see if the target of the exit branch is a suitable exit point
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var cfgNode = loopHead.Successors.FirstOrDefault(n => n.UserData == exitBranch.TargetBlock); |
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if (cfgNode != null && loopHead.Dominates(cfgNode) && !context.ControlFlowGraph.HasReachableExit(cfgNode)) { |
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return cfgNode; |
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} |
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} |
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return NoExitPoint; |
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} |
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ControlFlowNode exitPoint = null; |
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int exitPointILOffset = -1; |
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foreach (var node in loopHead.DominatorTreeChildren) { |
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@ -388,8 +410,38 @@ namespace ICSharpCode.Decompiler.IL.ControlFlow
@@ -388,8 +410,38 @@ namespace ICSharpCode.Decompiler.IL.ControlFlow
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Dominance.ComputeDominance(exitNode, context.CancellationToken); |
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return rev; |
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} |
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static bool IsPossibleForeachLoop(Block loopHead, out Branch exitBranch) |
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{ |
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exitBranch = null; |
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var container = (BlockContainer)loopHead.Parent; |
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if (!(container.SlotInfo == TryInstruction.TryBlockSlot && container.Parent is TryFinally)) |
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return false; |
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if (loopHead.Instructions.Count != 2) |
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return false; |
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if (!loopHead.Instructions[0].MatchIfInstruction(out var condition, out var trueInst)) |
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return false; |
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var falseInst = loopHead.Instructions[1]; |
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while (condition.MatchLogicNot(out var arg)) { |
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condition = arg; |
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ExtensionMethods.Swap(ref trueInst, ref falseInst); |
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} |
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if (!(condition is CallInstruction call && call.Method.Name == "MoveNext")) |
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return false; |
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if (!(call.Arguments.Count == 1 && call.Arguments[0].MatchLdLocRef(out var enumeratorVar))) |
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return false; |
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exitBranch = falseInst as Branch; |
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// Check that loopHead is entry-point of try-block:
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Block entryPoint = container.EntryPoint; |
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while (entryPoint.IncomingEdgeCount == 1 && entryPoint.Instructions.Count == 1 && entryPoint.Instructions[0].MatchBranch(out var targetBlock)) { |
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// skip blocks that only branch to another block
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entryPoint = targetBlock; |
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} |
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return entryPoint == loopHead; |
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} |
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#endregion
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#region ExtendLoop (fall-back heuristic)
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/// <summary>
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/// This function implements a heuristic algorithm that tries to reduce the number of exit
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Daniel Grunwald
8 years ago