mirror of https://github.com/icsharpcode/ILSpy.git
Daniel Grunwald
4 years ago
14 changed files with 292 additions and 117 deletions
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@@ -0,0 +1,115 @@
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// Copyright (c) Daniel Grunwald
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//
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// Permission is hereby granted, free of charge, to any person obtaining a copy of this
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// software and associated documentation files (the "Software"), to deal in the Software
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// without restriction, including without limitation the rights to use, copy, modify, merge,
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// publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons
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// to whom the Software is furnished to do so, subject to the following conditions:
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//
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// The above copyright notice and this permission notice shall be included in all copies or
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// substantial portions of the Software.
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//
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// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED,
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// INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR
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// PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE
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// FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR
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// OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
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// DEALINGS IN THE SOFTWARE.
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#nullable enable |
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using System.Linq; |
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using ICSharpCode.Decompiler.IL.Transforms; |
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namespace ICSharpCode.Decompiler.IL.ControlFlow |
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{ |
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/// <summary>
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/// Similar to <see cref="DetectExitPoints"/>, but acts only on <c>leave</c> instructions
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/// leaving the whole function (<c>return</c>/<c>yield break</c>) that can be made implicit
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/// without using goto.
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/// </summary>
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class RemoveRedundantReturn : IILTransform |
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{ |
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public void Run(ILFunction function, ILTransformContext context) |
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{ |
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foreach (var lambda in function.Descendants.OfType<ILFunction>()) |
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{ |
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if (lambda.Body is BlockContainer c && ((lambda.AsyncReturnType ?? lambda.ReturnType).Kind == TypeSystem.TypeKind.Void || lambda.IsIterator)) |
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{ |
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Block lastBlock = c.Blocks.Last(); |
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if (lastBlock.Instructions.Last() is Leave { IsLeavingFunction: true }) |
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{ |
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ConvertReturnToFallthrough(lastBlock.Instructions.SecondToLastOrDefault()); |
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} |
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else |
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{ |
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if (ConvertReturnToFallthrough(lastBlock.Instructions.Last())) |
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{ |
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lastBlock.Instructions.Add(new Leave(c)); |
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} |
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} |
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} |
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} |
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} |
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private static bool ConvertReturnToFallthrough(ILInstruction? inst) |
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{ |
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bool result = false; |
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switch (inst) |
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{ |
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case BlockContainer c when c.Kind == ContainerKind.Normal: |
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// body of try block, or similar: recurse into last instruction in container
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// Note: no need to handle loops/switches here; those already were handled by DetectExitPoints
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Block lastBlock = c.Blocks.Last(); |
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if (lastBlock.Instructions.Last() is Leave { IsLeavingFunction: true, Value: Nop } leave) |
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{ |
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leave.TargetContainer = c; |
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result = true; |
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} |
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else if (ConvertReturnToFallthrough(lastBlock.Instructions.Last())) |
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{ |
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lastBlock.Instructions.Add(new Leave(c)); |
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result = true; |
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} |
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break; |
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case TryCatch tryCatch: |
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result |= ConvertReturnToFallthrough(tryCatch.TryBlock); |
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foreach (var h in tryCatch.Handlers) |
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{ |
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result |= ConvertReturnToFallthrough(h.Body); |
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} |
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break; |
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case TryFinally tryFinally: |
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result |= ConvertReturnToFallthrough(tryFinally.TryBlock); |
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break; |
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case LockInstruction lockInst: |
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result |= ConvertReturnToFallthrough(lockInst.Body); |
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break; |
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case UsingInstruction usingInst: |
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result |= ConvertReturnToFallthrough(usingInst.Body); |
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break; |
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case PinnedRegion pinnedRegion: |
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result |= ConvertReturnToFallthrough(pinnedRegion.Body); |
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break; |
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case IfInstruction ifInstruction: |
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result |= ConvertReturnToFallthrough(ifInstruction.TrueInst); |
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result |= ConvertReturnToFallthrough(ifInstruction.FalseInst); |
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break; |
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case Block block when block.Kind == BlockKind.ControlFlow: |
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{ |
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var lastInst = block.Instructions.LastOrDefault(); |
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if (lastInst is Leave { IsLeavingFunction: true, Value: Nop }) |
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{ |
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block.Instructions.RemoveAt(block.Instructions.Count - 1); |
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result = true; |
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lastInst = block.Instructions.LastOrDefault(); |
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} |
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result |= ConvertReturnToFallthrough(lastInst); |
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break; |
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} |
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} |
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return result; |
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} |
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} |
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} |
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