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116 lines
3.6 KiB
116 lines
3.6 KiB
// Copyright (c) 2021 Daniel Grunwald, 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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#nullable enable
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using System.Diagnostics.CodeAnalysis;
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using System.Linq;
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namespace ICSharpCode.Decompiler.IL.Transforms
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{
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/// <summary>
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/// Block IL_0018 (incoming: *) {
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/// stloc s(ldc.i4 1)
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/// br IL_0019
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/// }
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///
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/// Block IL_0019 (incoming: > 1) {
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/// if (logic.not(ldloc s)) br IL_0027
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/// br IL_001d
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/// }
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///
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/// replace br IL_0019 with br IL_0027
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/// </summary>
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class RemoveInfeasiblePathTransform : IILTransform
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{
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void IILTransform.Run(ILFunction function, ILTransformContext context)
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{
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foreach (var container in function.Descendants.OfType<BlockContainer>())
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{
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bool changed = false;
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foreach (var block in container.Blocks)
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{
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changed |= DoTransform(block, context);
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}
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if (changed)
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{
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container.SortBlocks(deleteUnreachableBlocks: true);
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}
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}
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}
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private bool DoTransform(Block block, ILTransformContext context)
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{
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if (!MatchBlock1(block, out var s, out int value, out var br))
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return false;
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if (!MatchBlock2(br.TargetBlock, s, value, out var exitInst))
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return false;
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context.Step("RemoveInfeasiblePath", br);
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br.ReplaceWith(exitInst.Clone());
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s.RemoveIfRedundant = true;
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return true;
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}
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// Block IL_0018 (incoming: *) {
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// stloc s(ldc.i4 1)
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// br IL_0019
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// }
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private bool MatchBlock1(Block block, [NotNullWhen(true)] out ILVariable? variable, out int constantValue, [NotNullWhen(true)] out Branch? branch)
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{
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variable = null;
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constantValue = 0;
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branch = null;
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if (block.Instructions.Count != 2)
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return false;
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if (block.Instructions[0] is not StLoc {
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Variable: { Kind: VariableKind.StackSlot } s,
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Value: LdcI4 { Value: 0 or 1 } valueInst
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})
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{
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return false;
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}
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if (block.Instructions[1] is not Branch br)
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return false;
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variable = s;
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constantValue = valueInst.Value;
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branch = br;
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return true;
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}
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// Block IL_0019 (incoming: > 1) {
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// if (logic.not(ldloc s)) br IL_0027
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// br IL_001d
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// }
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bool MatchBlock2(Block block, ILVariable s, int constantValue, [NotNullWhen(true)] out ILInstruction? exitInst)
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{
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exitInst = null;
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if (block.Instructions.Count != 2)
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return false;
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if (block.IncomingEdgeCount <= 1)
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return false;
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if (!block.MatchIfAtEndOfBlock(out var load, out var trueInst, out var falseInst))
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return false;
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if (!load.MatchLdLoc(s))
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return false;
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exitInst = constantValue != 0 ? trueInst : falseInst;
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return exitInst is Branch or Leave { Value: Nop };
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}
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}
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}
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