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78 lines
3.1 KiB
78 lines
3.1 KiB
// Copyright (c) 2019 Siegfried Pammer |
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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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namespace ICSharpCode.Decompiler.IL.Transforms |
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{ |
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class CombineExitsTransform : IILTransform |
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{ |
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public void Run(ILFunction function, ILTransformContext context) |
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{ |
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if (!(function.Body is BlockContainer container && container.Blocks.Count == 1)) |
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return; |
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var combinedExit = CombineExits(container.EntryPoint); |
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if (combinedExit == null) |
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return; |
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ExpressionTransforms.RunOnSingleStatement(combinedExit, context); |
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} |
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static Leave CombineExits(Block block) |
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{ |
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if (!(block.Instructions.SecondToLastOrDefault() is IfInstruction ifInst && block.Instructions.LastOrDefault() is Leave leaveElse)) |
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return null; |
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if (!ifInst.FalseInst.MatchNop()) |
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return null; |
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// try to unwrap true branch to single instruction: |
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var trueInstruction = Block.Unwrap(ifInst.TrueInst); |
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// if the true branch is a block with multiple instructions: |
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// try to apply the combine exits transform to the nested block |
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// and then continue on that transformed block. |
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// Example: |
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// if (cond) { |
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// if (cond2) { |
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// leave (value) |
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// } |
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// leave (value2) |
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// } |
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// leave (value3) |
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// => |
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// leave (if (cond) value else if (cond2) value2 else value3) |
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if (trueInstruction is Block nestedBlock && nestedBlock.Instructions.Count == 2) |
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trueInstruction = CombineExits(nestedBlock); |
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if (!(trueInstruction is Leave leave)) |
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return null; |
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if (!(leave.IsLeavingFunction && leaveElse.IsLeavingFunction)) |
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return null; |
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if (leave.Value.MatchNop() || leaveElse.Value.MatchNop()) |
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return null; |
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// if (cond) { |
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// leave (value) |
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// } |
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// leave (elseValue) |
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// => |
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// leave (if (cond) value else elseValue) |
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IfInstruction value = new IfInstruction(ifInst.Condition, leave.Value, leaveElse.Value); |
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value.AddILRange(ifInst); |
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Leave combinedLeave = new Leave(leave.TargetContainer, value); |
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combinedLeave.AddILRange(leaveElse); |
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combinedLeave.AddILRange(leave); |
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ifInst.ReplaceWith(combinedLeave); |
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block.Instructions.RemoveAt(combinedLeave.ChildIndex + 1); |
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return combinedLeave; |
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} |
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} |
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}
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