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404 lines
18 KiB
404 lines
18 KiB
// Copyright (c) 2017 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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using System; |
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using System.Collections.Generic; |
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using System.Linq; |
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using ICSharpCode.Decompiler.IL.ControlFlow; |
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using ICSharpCode.Decompiler.TypeSystem; |
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using ICSharpCode.Decompiler.Util; |
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namespace ICSharpCode.Decompiler.IL.Transforms |
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{ |
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/// <summary> |
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/// Detects switch-on-string patterns employed by the C# compiler and transforms them to an ILAst-switch-instruction. |
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/// </summary> |
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class SwitchOnStringTransform : 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 (!context.Settings.SwitchStatementOnString) |
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return; |
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HashSet<BlockContainer> changedContainers = new HashSet<BlockContainer>(); |
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foreach (var block in function.Descendants.OfType<Block>()) { |
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for (int i = block.Instructions.Count - 1; i >= 0; i--) { |
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SwitchInstruction newSwitch; |
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Block blockAfterSwitch = null; |
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bool removeExtraStore = false; // the Roslyn switch pattern uses an extra store for hash calculation. |
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if (!MatchCascadingIfStatements(block.Instructions, i, out newSwitch, out blockAfterSwitch)) |
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if (!MatchLegacySwitchOnString(block.Instructions, i, out newSwitch, out blockAfterSwitch)) |
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if (MatchRoslynSwitchOnString(block.Instructions, i, out newSwitch)) |
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removeExtraStore = true; |
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else |
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continue; |
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if (i + 1 < block.Instructions.Count && block.Instructions[i + 1] is Branch b && blockAfterSwitch != null) { |
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block.Instructions[i + 1].ReplaceWith(new Branch(blockAfterSwitch)); |
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} |
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block.Instructions[i].ReplaceWith(newSwitch); |
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if (removeExtraStore) { |
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block.Instructions.RemoveAt(i - 1); |
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i--; |
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} |
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// Combine cases with the same branch target: |
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SwitchDetection.SimplifySwitchInstruction(block); |
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// This happens in some cases: |
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// Use correct index after transformation. |
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if (i >= block.Instructions.Count) |
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i = block.Instructions.Count; |
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} |
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if (block.Parent is BlockContainer container) |
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changedContainers.Add(container); |
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} |
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foreach (var container in changedContainers) |
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container.SortBlocks(deleteUnreachableBlocks: true); |
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} |
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bool MatchCascadingIfStatements(InstructionCollection<ILInstruction> instructions, int i, out SwitchInstruction inst, out Block blockAfterSwitch) |
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{ |
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inst = null; |
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blockAfterSwitch = null; |
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// match first block: checking switch-value for null or first value (Roslyn) |
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// if (call op_Equality(ldloc switchValueVar, ldstr value)) br firstBlock |
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// -or- |
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// if (comp(ldloc switchValueVar == ldnull)) br defaultBlock |
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if (!(instructions[i].MatchIfInstruction(out var condition, out var firstBlockJump))) |
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return false; |
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if (!firstBlockJump.MatchBranch(out var firstBlock)) |
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return false; |
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bool isLegacy; |
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Block defaultBlock; |
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List<(string, Block)> values = new List<(string, Block)>(); |
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// match null check: this is used by the old C# compiler. |
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if (condition.MatchCompEquals(out var left, out var right) && right.MatchLdNull() && left.MatchLdLoc(out var switchValueVar)) { |
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isLegacy = true; |
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defaultBlock = firstBlock; |
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// Roslyn: match call to operator ==(string, string) |
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} else if (MatchStringEqualityComparison(condition, out switchValueVar, out string value)) { |
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isLegacy = false; |
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defaultBlock = null; |
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values.Add((value, firstBlock)); |
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} else return false; |
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// switchValueVar must be assigned only once. |
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if (!switchValueVar.IsSingleDefinition) |
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return false; |
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// if instruction must be followed by a branch to the next case |
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if (!(instructions.ElementAtOrDefault(i + 1) is Branch nextCaseJump)) |
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return false; |
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// extract all cases and add them to the values list. |
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Block currentCaseBlock = nextCaseJump.TargetBlock; |
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Block nextCaseBlock; |
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while ((nextCaseBlock = MatchCaseBlock(currentCaseBlock, ref switchValueVar, out string value, out Block block)) != null) { |
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values.Add((value, block)); |
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currentCaseBlock = nextCaseBlock; |
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} |
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// the last instruction of the last case/default block must be either |
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// a branch to the a block after the switch statement or a leave instruction. |
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var container = BlockContainer.FindClosestContainer(firstBlock); |
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if (!ExtractLastJumpFromBlock(currentCaseBlock, out var exitBlock) && !ExtractLastLeaveFromBlock(currentCaseBlock, container)) |
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return false; |
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// We didn't find any cases, exit |
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if (values.Count == 0) |
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return false; |
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// All case blocks must either leave the current block container or branch to the same block after the switch statement. |
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if (exitBlock == null) { |
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if (!values.All(b => ExtractLastLeaveFromBlock(b.Item2, container))) |
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return false; |
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} else { |
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// Compare blocks by label as duplicated blocks should have the same label. |
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if (!(values.All(b => ExtractLastJumpFromBlock(b.Item2, out var nextExitBlock) && nextExitBlock.Label == exitBlock.Label))) |
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return false; |
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} |
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// if the block after the switch has the correct number of branches, generate the switch statement |
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// and return it and the block. |
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if (currentCaseBlock.IncomingEdgeCount == (isLegacy ? 2 : 1)) { |
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var sections = new List<SwitchSection>(values.SelectWithIndex((index, b) => new SwitchSection { Labels = new LongSet(index), Body = new Branch(b.Item2) })); |
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var stringToInt = new StringToInt(new LdLoc(switchValueVar), values.SelectArray(item => item.Item1)); |
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inst = new SwitchInstruction(stringToInt); |
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inst.Sections.AddRange(sections); |
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blockAfterSwitch = currentCaseBlock; |
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return true; |
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} |
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return false; |
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} |
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bool ExtractLastJumpFromBlock(Block block, out Block exitBlock) |
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{ |
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exitBlock = null; |
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var lastInst = block.Instructions.LastOrDefault(); |
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if (lastInst == null || !lastInst.MatchBranch(out exitBlock)) |
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return false; |
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return true; |
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} |
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bool ExtractLastLeaveFromBlock(Block block, BlockContainer container) |
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{ |
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var lastInst = block.Instructions.LastOrDefault(); |
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if (lastInst == null || !lastInst.MatchLeave(out var b, out _)) |
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return false; |
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return b == container; |
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} |
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/// <summary> |
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/// Each case consists of two blocks: |
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/// 1. block: |
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/// if (call op_Equality(ldloc switchVariable, ldstr value)) br caseBlock |
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/// br nextBlock |
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/// This method matches the above pattern or its inverted form: |
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/// the call to ==(string, string) is wrapped in logic.not and the branch targets are reversed. |
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/// Returns the next block that follows in the block-chain. |
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/// The <paramref name="switchVariable"/> is updated if the value gets copied to a different variable. |
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/// See comments below for more info. |
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/// </summary> |
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Block MatchCaseBlock(Block currentBlock, ref ILVariable switchVariable, out string value, out Block caseBlock) |
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{ |
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value = null; |
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caseBlock = null; |
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if (currentBlock.IncomingEdgeCount != 1 || currentBlock.Instructions.Count != 2) |
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return null; |
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if (!currentBlock.Instructions[0].MatchIfInstruction(out var condition, out var caseBlockBranch)) |
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return null; |
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if (!caseBlockBranch.MatchBranch(out caseBlock)) |
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return null; |
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Block nextBlock; |
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if (condition.MatchLogicNot(out var inner)) { |
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condition = inner; |
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nextBlock = caseBlock; |
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if (!currentBlock.Instructions[1].MatchBranch(out caseBlock)) |
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return null; |
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} else { |
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if (!currentBlock.Instructions[1].MatchBranch(out nextBlock)) |
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return null; |
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} |
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// Sometimes the switch pattern uses one variable at the beginning for null checks |
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// and another variable for the if-else-if-else-pattern. |
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// both variables must be only assigned once and be of the type: System.String. |
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if (!MatchStringEqualityComparison(condition, out var newSwitchVariable, out value)) |
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return null; |
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if (!newSwitchVariable.IsSingleDefinition) |
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return null; |
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// if the used variable differs and both variables are not related, return null: |
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if (switchVariable != newSwitchVariable && !(IsInitializedBy(switchVariable, newSwitchVariable) || IsInitializedBy(newSwitchVariable, switchVariable))) |
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return null; |
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if (!newSwitchVariable.Type.IsKnownType(KnownTypeCode.String)) |
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return null; |
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switchVariable = newSwitchVariable; |
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return nextBlock; |
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} |
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/// <summary> |
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/// Returns true if <paramref name="left"/> is only assigned once and the initialization is done by copying <paramref name="right"/>. |
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/// </summary> |
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bool IsInitializedBy(ILVariable left, ILVariable right) |
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{ |
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if (!left.IsSingleDefinition) |
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return false; |
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var storeInst = left.StoreInstructions.OfType<StLoc>().SingleOrDefault(); |
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if (storeInst == null) |
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return false; |
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return storeInst.Value.MatchLdLoc(right); |
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} |
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bool MatchLegacySwitchOnString(InstructionCollection<ILInstruction> instructions, int i, out SwitchInstruction inst, out Block blockAfterSwitch) |
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{ |
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inst = null; |
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blockAfterSwitch = null; |
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if (i < 1) return false; |
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// match first block: checking switch-value for null |
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if (!(instructions[i].MatchIfInstruction(out var condition, out var exitBlockJump) && |
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instructions[i - 1].MatchStLoc(out var switchValueVar, out var switchValue) && switchValueVar.Type.IsKnownType(KnownTypeCode.String))) |
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return false; |
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if (!exitBlockJump.MatchBranch(out var exitBlock)) |
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return false; |
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if (!(condition.MatchCompEquals(out var left, out var right) && right.MatchLdNull() && (left.Match(switchValue).Success || left.MatchLdLoc(switchValueVar)))) |
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return false; |
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var nextBlockJump = instructions.ElementAtOrDefault(i + 1) as Branch; |
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if (nextBlockJump == null || nextBlockJump.TargetBlock.IncomingEdgeCount != 1) |
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return false; |
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// match second block: checking compiler-generated Dictionary<string, int> for null |
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var nextBlock = nextBlockJump.TargetBlock; |
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if (nextBlock.Instructions.Count != 2 || !nextBlock.Instructions[0].MatchIfInstruction(out condition, out var tryGetValueBlockJump)) |
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return false; |
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if (!tryGetValueBlockJump.MatchBranch(out var tryGetValueBlock)) |
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return false; |
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if (!nextBlock.Instructions[1].MatchBranch(out var dictInitBlock) || dictInitBlock.IncomingEdgeCount != 1) |
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return false; |
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if (!(condition.MatchCompNotEquals(out left, out right) && right.MatchLdNull() && |
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MatchDictionaryFieldLoad(left, out var dictField, out var dictionaryType))) |
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return false; |
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// match third block: initialization of compiler-generated Dictionary<string, int> |
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if (dictInitBlock.IncomingEdgeCount != 1 || dictInitBlock.Instructions.Count < 3) |
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return false; |
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if (!ExtractStringValuesFromDictionaryInitBlock(dictInitBlock, out var stringValues, tryGetValueBlock, dictionaryType, dictField)) |
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return false; |
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// match fourth block: TryGetValue on compiler-generated Dictionary<string, int> |
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if (tryGetValueBlock.IncomingEdgeCount != 2 || tryGetValueBlock.Instructions.Count != 2) |
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return false; |
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if (!tryGetValueBlock.Instructions[0].MatchIfInstruction(out condition, out var defaultBlockJump)) |
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return false; |
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if (!defaultBlockJump.MatchBranch(out var defaultBlock)) |
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return false; |
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if (!(condition.MatchLogicNot(out var arg) && arg is Call c && c.Method.Name == "TryGetValue" && |
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MatchDictionaryFieldLoad(c.Arguments[0], out var dictField2, out _) && dictField2.Equals(dictField))) |
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return false; |
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if (!c.Arguments[1].MatchLdLoc(switchValueVar) || !c.Arguments[2].MatchLdLoca(out var switchIndexVar)) |
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return false; |
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if (!tryGetValueBlock.Instructions[1].MatchBranch(out var switchBlock)) |
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return false; |
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// match fifth block: switch-instruction block |
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if (switchBlock.IncomingEdgeCount != 1 || switchBlock.Instructions.Count != 2) |
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return false; |
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if (!(switchBlock.Instructions[0] is SwitchInstruction switchInst && switchInst.Value.MatchLdLoc(switchIndexVar))) |
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return false; |
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if (!switchBlock.Instructions[1].MatchBranch(defaultBlock)) |
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return false; |
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// switch contains case null: |
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var sections = new List<SwitchSection>(switchInst.Sections); |
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if (exitBlock != defaultBlock) { |
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stringValues.Add(null); |
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sections.Add(new SwitchSection() { Labels = new Util.LongSet(stringValues.Count - 1), Body = new Branch(exitBlock) }); |
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} |
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var stringToInt = new StringToInt(new LdLoc(switchValueVar), stringValues.ToArray()); |
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inst = new SwitchInstruction(stringToInt); |
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inst.DefaultBody = switchInst.DefaultBody; |
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inst.Sections.AddRange(sections); |
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blockAfterSwitch = defaultBlock; |
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return true; |
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} |
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bool MatchDictionaryFieldLoad(ILInstruction inst, out IField dictField, out IType dictionaryType) |
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{ |
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dictField = null; |
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dictionaryType = null; |
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return inst.MatchLdObj(out var dictionaryFieldLoad, out dictionaryType) && |
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IsStringToIntDictionary(dictionaryType) && |
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dictionaryFieldLoad.MatchLdsFlda(out dictField) && |
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dictField.IsCompilerGeneratedOrIsInCompilerGeneratedClass(); |
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} |
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bool ExtractStringValuesFromDictionaryInitBlock(Block block, out List<string> values, Block targetBlock, IType dictionaryType, IField dictionaryField) |
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{ |
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values = null; |
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if (!(block.Instructions[0].MatchStLoc(out var dictVar, out var newObjDict) && |
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newObjDict is NewObj newObj && newObj.Arguments.Count == 1 && newObj.Arguments[0].MatchLdcI4(out var valuesLength))) |
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return false; |
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if (block.Instructions.Count != valuesLength + 3) |
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return false; |
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values = new List<string>(valuesLength); |
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for (int i = 0; i < valuesLength; i++) { |
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if (!(block.Instructions[i + 1] is Call c && c.Method.Name == "Add" && c.Arguments.Count == 3 && |
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c.Arguments[0].MatchLdLoc(dictVar) && c.Arguments[1].MatchLdStr(out var value) && c.Arguments[2].MatchLdcI4(i))) |
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return false; |
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values.Add(value); |
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} |
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if (!(block.Instructions[valuesLength + 1].MatchStObj(out var loadField, out var dictVarLoad, out var dictType) && |
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dictType.Equals(dictionaryType) && loadField.MatchLdsFlda(out var dictField) && dictField.Equals(dictionaryField)) && |
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dictVarLoad.MatchLdLoc(dictVar)) |
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return false; |
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return block.Instructions[valuesLength + 2].MatchBranch(targetBlock); |
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} |
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bool IsStringToIntDictionary(IType dictionaryType) |
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{ |
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if (dictionaryType.FullName != "System.Collections.Generic.Dictionary") |
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return false; |
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if (dictionaryType.TypeArguments.Count != 2) |
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return false; |
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return dictionaryType.TypeArguments[0].IsKnownType(KnownTypeCode.String) && |
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dictionaryType.TypeArguments[1].IsKnownType(KnownTypeCode.Int32); |
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} |
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bool MatchRoslynSwitchOnString(InstructionCollection<ILInstruction> instructions, int i, out SwitchInstruction inst) |
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{ |
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inst = null; |
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if (i < 1) return false; |
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if (!(instructions[i] is SwitchInstruction switchInst && switchInst.Value.MatchLdLoc(out var targetVar) && |
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MatchComputeStringHashCall(instructions[i - 1], targetVar, out var switchValue))) |
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return false; |
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var stringValues = new List<(int, string, Block)>(); |
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int index = 0; |
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foreach (var section in switchInst.Sections) { |
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if (!section.Body.MatchBranch(out Block target)) |
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return false; |
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if (target.IncomingEdgeCount != 1 || target.Instructions.Count != 2) |
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return false; |
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if (!target.Instructions[0].MatchIfInstruction(out var condition, out var bodyBranch)) |
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return false; |
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if (!bodyBranch.MatchBranch(out Block body)) |
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return false; |
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if (!MatchStringEqualityComparison(condition, switchValue.Variable, out string stringValue)) { |
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if (condition.MatchLogicNot(out condition) && MatchStringEqualityComparison(condition, switchValue.Variable, out stringValue)) { |
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if (!target.Instructions[1].MatchBranch(out Block exit)) |
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return false; |
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body = exit; |
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} else |
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return false; |
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} |
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stringValues.Add((index++, stringValue, body)); |
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} |
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var value = new StringToInt(switchValue.Clone(), stringValues.Select(item => item.Item2).ToArray()); |
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inst = new SwitchInstruction(value); |
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inst.Sections.AddRange(stringValues.Select(section => new SwitchSection { Labels = new Util.LongSet(section.Item1), Body = new Branch(section.Item3) })); |
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return true; |
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} |
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bool MatchComputeStringHashCall(ILInstruction inst, ILVariable targetVar, out LdLoc switchValue) |
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{ |
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switchValue = null; |
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if (!inst.MatchStLoc(targetVar, out var value)) |
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return false; |
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if (!(value is Call c && c.Arguments.Count == 1 && c.Method.Name == "ComputeStringHash" && c.Method.IsCompilerGeneratedOrIsInCompilerGeneratedClass())) |
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return false; |
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if (!(c.Arguments[0] is LdLoc)) |
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return false; |
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switchValue = (LdLoc)c.Arguments[0]; |
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return true; |
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} |
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bool MatchStringEqualityComparison(ILInstruction condition, ILVariable variable, out string stringValue) |
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{ |
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return MatchStringEqualityComparison(condition, out var v, out stringValue) && v == variable; |
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} |
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bool MatchStringEqualityComparison(ILInstruction condition, out ILVariable variable, out string stringValue) |
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{ |
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stringValue = null; |
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variable = null; |
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ILInstruction left, right; |
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if (condition is Call c && c.Method.IsOperator && c.Method.Name == "op_Equality" && c.Arguments.Count == 2) { |
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left = c.Arguments[0]; |
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right = c.Arguments[1]; |
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if (!right.MatchLdStr(out stringValue)) |
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return false; |
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} else if (condition.MatchCompEquals(out left, out right) && right.MatchLdNull()) { |
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} else return false; |
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return left.MatchLdLoc(out variable); |
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} |
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} |
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}
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