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675 lines
29 KiB
675 lines
29 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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|
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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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bool changed = false; |
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for (int i = block.Instructions.Count - 1; i >= 0; i--) { |
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if (SimplifyCascadingIfStatements(block.Instructions, ref i)) { |
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changed = true; |
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continue; |
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} |
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if (MatchLegacySwitchOnStringWithHashtable(block.Instructions, ref i)) { |
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changed = true; |
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continue; |
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} |
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if (MatchLegacySwitchOnStringWithDict(block.Instructions, ref i)) { |
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changed = true; |
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continue; |
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} |
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if (MatchRoslynSwitchOnString(block.Instructions, ref i)) { |
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changed = true; |
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continue; |
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} |
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} |
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if (!changed) continue; |
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SwitchDetection.SimplifySwitchInstruction(block); |
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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 SimplifyCascadingIfStatements(InstructionCollection<ILInstruction> instructions, ref int i) |
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{ |
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if (i < 1) return false; |
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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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List<(string, Block)> values = new List<(string, Block)>(); |
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ILInstruction switchValue = null; |
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// match call to operator ==(string, string) |
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if (!MatchStringEqualityComparison(condition, out var switchValueVar, out string firstBlockValue)) |
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return false; |
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values.Add((firstBlockValue, firstBlock)); |
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bool extraLoad = false; |
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if (instructions[i - 1].MatchStLoc(switchValueVar, out switchValue)) { |
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// stloc switchValueVar(switchValue) |
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// if (call op_Equality(ldloc switchValueVar, ldstr value)) br firstBlock |
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} else if (instructions[i - 1] is StLoc stloc && stloc.Value.MatchLdLoc(switchValueVar)) { |
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// in case of optimized legacy code there are two stlocs: |
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// stloc otherSwitchValueVar(ldloc switchValue) |
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// stloc switchValueVar(ldloc otherSwitchValueVar) |
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// if (call op_Equality(ldloc otherSwitchValueVar, ldstr value)) br firstBlock |
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var otherSwitchValueVar = switchValueVar; |
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switchValueVar = stloc.Variable; |
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if (i >= 2 && instructions[i - 2].MatchStLoc(otherSwitchValueVar, out switchValue) |
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&& otherSwitchValueVar.IsSingleDefinition && otherSwitchValueVar.LoadCount == 2) |
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{ |
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extraLoad = true; |
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} else { |
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switchValue = new LdLoc(otherSwitchValueVar); |
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} |
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} else { |
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switchValue = new LdLoc(switchValueVar); |
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} |
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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, 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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// We didn't find enough cases, exit |
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if (values.Count < 3) |
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return false; |
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// if the switchValueVar is used in other places as well, do not eliminate the store. |
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bool keepAssignmentBefore = false; |
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if (switchValueVar.LoadCount > values.Count) { |
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keepAssignmentBefore = true; |
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switchValue = new LdLoc(switchValueVar); |
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} |
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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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sections.Add(new SwitchSection { Labels = new LongSet(new LongInterval(0, sections.Count)).Invert(), Body = new Branch(currentCaseBlock) }); |
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var stringToInt = new StringToInt(switchValue, values.SelectArray(item => item.Item1)); |
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var inst = new SwitchInstruction(stringToInt); |
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inst.Sections.AddRange(sections); |
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if (extraLoad) { |
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instructions[i - 2].ReplaceWith(inst); |
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instructions.RemoveRange(i - 1, 3); |
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i -= 2; |
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} else { |
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if (keepAssignmentBefore) { |
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instructions[i].ReplaceWith(inst); |
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instructions.RemoveAt(i + 1); |
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} else { |
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instructions[i - 1].ReplaceWith(inst); |
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instructions.RemoveRange(i, 2); |
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i--; |
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} |
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} |
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return true; |
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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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/// -or- |
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/// if (comp(ldloc switchValueVar == ldnull)) br nextBlock |
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/// br caseBlock |
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/// 2. block is caseBlock |
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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, 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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if (!MatchStringEqualityComparison(condition, switchVariable, out value)) { |
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return null; |
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} |
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return nextBlock; |
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} |
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/// <summary> |
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/// Matches the C# 2.0 switch-on-string pattern, which uses Dictionary<string, int>. |
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/// </summary> |
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bool MatchLegacySwitchOnStringWithDict(InstructionCollection<ILInstruction> instructions, ref int i) |
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{ |
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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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// stloc switchValueVar(switchValue) |
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// if (comp(ldloc switchValueVar == ldnull)) br nullCase |
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// br nextBlock |
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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 (!switchValueVar.IsSingleDefinition) |
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return false; |
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// either br nullCase or leave container |
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if (!exitBlockJump.MatchBranch(out var nullValueCaseBlock) && !exitBlockJump.MatchLeave((BlockContainer)instructions[i].Parent.Parent)) |
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return false; |
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if (!(condition.MatchCompEquals(out var left, out var right) && right.MatchLdNull() |
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&& ((SemanticHelper.IsPure(switchValue.Flags) && 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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// if (comp(volatile.ldobj System.Collections.Generic.Dictionary`2[[System.String],[System.Int32]](ldsflda $$method0x600000c-1) != ldnull)) br caseNullBlock |
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// br dictInitBlock |
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var nextBlock = nextBlockJump.TargetBlock; |
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if (nextBlock.Instructions.Count != 2 || !nextBlock.Instructions[0].MatchIfInstruction(out condition, out var tryGetValueBlockJump)) |
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return false; |
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if (!tryGetValueBlockJump.MatchBranch(out var tryGetValueBlock)) |
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return false; |
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if (!nextBlock.Instructions[1].MatchBranch(out var dictInitBlock) || dictInitBlock.IncomingEdgeCount != 1) |
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return false; |
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if (!(condition.MatchCompNotEquals(out left, out right) && right.MatchLdNull() && |
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MatchDictionaryFieldLoad(left, IsStringToIntDictionary, out var dictField, out var dictionaryType))) |
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return false; |
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// match third block: initialization of compiler-generated Dictionary<string, int> |
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// stloc dict(newobj Dictionary..ctor(ldc.i4 valuesLength)) |
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// call Add(ldloc dict, ldstr value, ldc.i4 index) |
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// ... more calls to Add ... |
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// volatile.stobj System.Collections.Generic.Dictionary`2[[System.String],[System.Int32]](ldsflda $$method0x600003f-1, ldloc dict) |
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// br switchHeadBlock |
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if (dictInitBlock.IncomingEdgeCount != 1 || dictInitBlock.Instructions.Count < 3) |
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return false; |
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if (!ExtractStringValuesFromInitBlock(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 (logic.not(call TryGetValue(volatile.ldobj System.Collections.Generic.Dictionary`2[[System.String],[System.Int32]](ldsflda $$method0x600000c-1), ldloc switchValueVar, ldloca switchIndexVar))) br defaultBlock |
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// br switchBlock |
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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) && !defaultBlockJump.MatchLeave((BlockContainer)tryGetValueBlock.Parent)) |
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return false; |
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if (!(condition.MatchLogicNot(out var arg) && arg is CallInstruction c && c.Method.Name == "TryGetValue" && |
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MatchDictionaryFieldLoad(c.Arguments[0], IsStringToIntDictionary, 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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// switch (ldloc switchVariable) { |
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// case [0..1): br caseBlock1 |
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// ... more cases ... |
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// case [long.MinValue..0),[13..long.MaxValue]: br defaultBlock |
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// } |
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// mcs has a bug: when there is only one case it still generates the full-blown Dictionary<string, int> pattern, |
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// but uses only a simple if statement instead of the switch instruction. |
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if (switchBlock.IncomingEdgeCount != 1 || switchBlock.Instructions.Count == 0) |
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return false; |
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var sections = new List<SwitchSection>(); |
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switch (switchBlock.Instructions[0]) { |
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case SwitchInstruction switchInst: |
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if (switchBlock.Instructions.Count != 1) |
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return false; |
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if (!switchInst.Value.MatchLdLoc(switchIndexVar)) |
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return false; |
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sections.AddRange(switchInst.Sections); |
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break; |
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case IfInstruction ifInst: |
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if (switchBlock.Instructions.Count != 2) |
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return false; |
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if (!ifInst.Condition.MatchCompEquals(out left, out right)) |
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return false; |
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if (!left.MatchLdLoc(switchIndexVar)) |
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return false; |
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if (!right.MatchLdcI4(0)) |
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return false; |
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sections.Add(new SwitchSection() { Body = ifInst.TrueInst, Labels = new LongSet(0), ILRange = ifInst.ILRange }); |
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sections.Add(new SwitchSection() { Body = switchBlock.Instructions[1], Labels = new LongSet(0).Invert(), ILRange = switchBlock.Instructions[1].ILRange }); |
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break; |
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} |
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// mcs: map sections without a value to the default section, if possible |
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if (!FixCasesWithoutValue(sections, stringValues)) |
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return false; |
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// switch contains case null: |
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if (nullValueCaseBlock != defaultBlock) { |
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if (!AddNullSection(sections, stringValues, nullValueCaseBlock)) { |
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return false; |
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} |
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} |
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bool keepAssignmentBefore = false; |
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if (switchValueVar.LoadCount > 2) { |
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switchValue = new LdLoc(switchValueVar); |
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keepAssignmentBefore = true; |
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} |
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var stringToInt = new StringToInt(switchValue, stringValues); |
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var inst = new SwitchInstruction(stringToInt); |
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inst.Sections.AddRange(sections); |
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instructions[i + 1].ReplaceWith(inst); |
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if (keepAssignmentBefore) { |
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// delete if (comp(ldloc switchValueVar == ldnull)) |
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instructions.RemoveAt(i); |
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i--; |
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} else { |
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// delete both the if and the assignment before |
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instructions.RemoveRange(i - 1, 2); |
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i -= 2; |
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} |
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return true; |
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} |
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bool FixCasesWithoutValue(List<SwitchSection> sections, List<(string, int)> stringValues) |
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{ |
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bool HasLabel(SwitchSection section) |
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{ |
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return section.Labels.Values.Any(i => stringValues.Any(value => i == value.Item2)); |
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} |
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// Pick the section with the most labels as default section. |
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// And collect all sections that have no value mapped to them. |
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SwitchSection defaultSection = sections.First(); |
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List<SwitchSection> sectionsWithoutLabels = new List<SwitchSection>(); |
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foreach (var section in sections) { |
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if (section == defaultSection) continue; |
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if (section.Labels.Count() > defaultSection.Labels.Count()) { |
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if (!HasLabel(defaultSection)) |
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sectionsWithoutLabels.Add(defaultSection); |
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defaultSection = section; |
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continue; |
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} |
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if (!HasLabel(section)) |
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sectionsWithoutLabels.Add(section); |
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} |
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foreach (var section in sectionsWithoutLabels) { |
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if (!section.Body.Match(defaultSection.Body).Success) |
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return false; |
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defaultSection.Labels = defaultSection.Labels.UnionWith(section.Labels); |
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if (section.HasNullLabel) |
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defaultSection.HasNullLabel = true; |
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sections.Remove(section); |
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} |
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return true; |
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} |
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bool AddNullSection(List<SwitchSection> sections, List<(string, int)> stringValues, Block nullValueCaseBlock) |
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{ |
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var label = new LongSet(sections.Count); |
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var possibleConflicts = sections.Where(sec => sec.Labels.Overlaps(label)).ToArray(); |
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if (possibleConflicts.Length > 1) |
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return false; |
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else if (possibleConflicts.Length == 1) { |
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if (possibleConflicts[0].Labels.Count() == 1) |
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return false; // cannot remove only label |
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possibleConflicts[0].Labels = possibleConflicts[0].Labels.ExceptWith(label); |
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} |
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stringValues.Add((null, (int)label.Values.First())); |
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sections.Add(new SwitchSection() { Labels = label, Body = new Branch(nullValueCaseBlock) }); |
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return true; |
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} |
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/// <summary> |
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/// Matches 'volatile.ldobj dictionaryType(ldsflda dictField)' |
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/// </summary> |
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bool MatchDictionaryFieldLoad(ILInstruction inst, Func<IType, bool> typeMatcher, 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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typeMatcher(dictionaryType) && |
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dictionaryFieldLoad.MatchLdsFlda(out dictField) && |
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(dictField.IsCompilerGeneratedOrIsInCompilerGeneratedClass() || dictField.Name.StartsWith("$$method", StringComparison.Ordinal)); |
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} |
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/// <summary> |
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/// Matches and extracts values from Add-call sequences. |
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/// </summary> |
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bool ExtractStringValuesFromInitBlock(Block block, out List<(string, int)> values, Block targetBlock, IType dictionaryType, IField dictionaryField) |
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{ |
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values = null; |
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// stloc dictVar(newobj Dictionary..ctor(ldc.i4 valuesLength)) |
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// -or- |
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// stloc dictVar(newobj Hashtable..ctor(ldc.i4 capacity, ldc.f4 loadFactor)) |
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if (!(block.Instructions[0].MatchStLoc(out var dictVar, out var newObjDict) && newObjDict is NewObj newObj)) |
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return false; |
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if (!newObj.Method.DeclaringType.Equals(dictionaryType)) |
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return false; |
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int valuesLength = 0; |
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if (newObj.Arguments.Count == 2) { |
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if (!newObj.Arguments[0].MatchLdcI4(out valuesLength)) |
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return false; |
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if (!newObj.Arguments[1].MatchLdcF4(0.5f)) |
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return false; |
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} else if (newObj.Arguments.Count == 1) { |
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if (!newObj.Arguments[0].MatchLdcI4(out valuesLength)) |
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return false; |
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} |
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values = new List<(string, int)>(valuesLength); |
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int i = 0; |
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while (MatchAddCall(dictionaryType, block.Instructions[i + 1], dictVar, out var index, out var value)) { |
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values.Add((value, index)); |
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i++; |
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} |
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// final store to compiler-generated variable: |
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// volatile.stobj dictionaryType(ldsflda dictionaryField, ldloc dictVar) |
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if (!(block.Instructions[i + 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[i + 2].MatchBranch(targetBlock); |
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} |
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|
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/// <summary> |
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/// call Add(ldloc dictVar, ldstr value, ldc.i4 index) |
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/// -or- |
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/// call Add(ldloc dictVar, ldstr value, box System.Int32(ldc.i4 index)) |
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/// </summary> |
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bool MatchAddCall(IType dictionaryType, ILInstruction inst, ILVariable dictVar, out int index, out string value) |
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{ |
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value = null; |
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index = -1; |
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if (!(inst is CallInstruction c && c.Method.Name == "Add" && c.Arguments.Count == 3)) |
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return false; |
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if (!(c.Arguments[0].MatchLdLoc(dictVar) && c.Arguments[1].MatchLdStr(out value))) |
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return false; |
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if (!(c.Method.DeclaringType.Equals(dictionaryType) && !c.Method.IsStatic)) |
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return false; |
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return (c.Arguments[2].MatchLdcI4(out index) || (c.Arguments[2].MatchBox(out var arg, out _) && arg.MatchLdcI4(out index))); |
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} |
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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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|
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bool IsNonGenericHashtable(IType dictionaryType) |
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{ |
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if (dictionaryType.FullName != "System.Collections.Hashtable") |
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return false; |
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if (dictionaryType.TypeArguments.Count != 0) |
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return false; |
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return true; |
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} |
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|
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bool MatchLegacySwitchOnStringWithHashtable(InstructionCollection<ILInstruction> instructions, ref int i) |
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{ |
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// match first block: checking compiler-generated Hashtable for null |
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// if (comp(volatile.ldobj System.Collections.Hashtable(ldsflda $$method0x600003f-1) != ldnull)) br switchHeadBlock |
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// br tableInitBlock |
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if (!(instructions[i].MatchIfInstruction(out var condition, out var branchToSwitchHead) && i + 1 < instructions.Count)) |
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return false; |
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if (!instructions[i + 1].MatchBranch(out var tableInitBlock) || tableInitBlock.IncomingEdgeCount != 1) |
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return false; |
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if (!(condition.MatchCompNotEquals(out var left, out var right) && right.MatchLdNull() && |
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MatchDictionaryFieldLoad(left, IsNonGenericHashtable, out var dictField, out var dictionaryType))) |
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return false; |
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if (!branchToSwitchHead.MatchBranch(out var switchHead)) |
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return false; |
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// match second block: initialization of compiler-generated Hashtable |
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// stloc table(newobj Hashtable..ctor(ldc.i4 capacity, ldc.f loadFactor)) |
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// call Add(ldloc table, ldstr value, box System.Int32(ldc.i4 index)) |
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// ... more calls to Add ... |
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// volatile.stobj System.Collections.Hashtable(ldsflda $$method0x600003f - 1, ldloc table) |
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// br switchHeadBlock |
|
if (tableInitBlock.IncomingEdgeCount != 1 || tableInitBlock.Instructions.Count < 3) |
|
return false; |
|
if (!ExtractStringValuesFromInitBlock(tableInitBlock, out var stringValues, switchHead, dictionaryType, dictField)) |
|
return false; |
|
// match third block: checking switch-value for null |
|
// stloc tmp(ldloc switch-value) |
|
// stloc switchVariable(ldloc tmp) |
|
// if (comp(ldloc tmp == ldnull)) br nullCaseBlock |
|
// br getItemBlock |
|
if (switchHead.Instructions.Count != 4 || switchHead.IncomingEdgeCount != 2) |
|
return false; |
|
if (!switchHead.Instructions[0].MatchStLoc(out var tmp, out var switchValue)) |
|
return false; |
|
if (!switchHead.Instructions[1].MatchStLoc(out var switchVariable, out var tmpLoad) || !tmpLoad.MatchLdLoc(tmp)) |
|
return false; |
|
if (!switchHead.Instructions[2].MatchIfInstruction(out condition, out var nullCaseBlockBranch)) |
|
return false; |
|
if (!switchHead.Instructions[3].MatchBranch(out var getItemBlock) || !nullCaseBlockBranch.MatchBranch(out var nullCaseBlock)) |
|
return false; |
|
if (!(condition.MatchCompEquals(out left, out right) && right.MatchLdNull() && left.MatchLdLoc(tmp))) |
|
return false; |
|
// match fourth block: get_Item on compiler-generated Hashtable |
|
// stloc tmp2(call get_Item(volatile.ldobj System.Collections.Hashtable(ldsflda $$method0x600003f - 1), ldloc switchVariable)) |
|
// stloc switchVariable(ldloc tmp2) |
|
// if (comp(ldloc tmp2 == ldnull)) br defaultCaseBlock |
|
// br switchBlock |
|
if (getItemBlock.IncomingEdgeCount != 1 || getItemBlock.Instructions.Count != 4) |
|
return false; |
|
if (!(getItemBlock.Instructions[0].MatchStLoc(out var tmp2, out var getItem) && getItem is Call getItemCall && getItemCall.Method.Name == "get_Item")) |
|
return false; |
|
if (!getItemBlock.Instructions[1].MatchStLoc(out var switchVariable2, out var tmp2Load) || !tmp2Load.MatchLdLoc(tmp2)) |
|
return false; |
|
if (!ILVariableEqualityComparer.Instance.Equals(switchVariable, switchVariable2)) |
|
return false; |
|
if (!getItemBlock.Instructions[2].MatchIfInstruction(out condition, out var defaultBlockBranch)) |
|
return false; |
|
if (!getItemBlock.Instructions[3].MatchBranch(out var switchBlock) || !defaultBlockBranch.MatchBranch(out var defaultBlock)) |
|
return false; |
|
if (!(condition.MatchCompEquals(out left, out right) && right.MatchLdNull() && left.MatchLdLoc(tmp2))) |
|
return false; |
|
if (!(getItemCall.Arguments.Count == 2 && MatchDictionaryFieldLoad(getItemCall.Arguments[0], IsStringToIntDictionary, out var dictField2, out _) && dictField2.Equals(dictField)) && |
|
getItemCall.Arguments[1].MatchLdLoc(switchVariable2)) |
|
return false; |
|
// match fifth block: switch-instruction block |
|
// switch (ldobj System.Int32(unbox System.Int32(ldloc switchVariable))) { |
|
// case [0..1): br caseBlock1 |
|
// ... more cases ... |
|
// case [long.MinValue..0),[13..long.MaxValue]: br defaultBlock |
|
// } |
|
if (switchBlock.IncomingEdgeCount != 1 || switchBlock.Instructions.Count != 1) |
|
return false; |
|
if (!(switchBlock.Instructions[0] is SwitchInstruction switchInst && switchInst.Value.MatchLdObj(out var target, out var ldobjType) && |
|
target.MatchUnbox(out var arg, out var unboxType) && arg.MatchLdLoc(switchVariable2) && ldobjType.IsKnownType(KnownTypeCode.Int32) && unboxType.Equals(ldobjType))) |
|
return false; |
|
var sections = new List<SwitchSection>(switchInst.Sections); |
|
// switch contains case null: |
|
if (nullCaseBlock != defaultBlock) { |
|
if (!AddNullSection(sections, stringValues, nullCaseBlock)) { |
|
return false; |
|
} |
|
} |
|
var stringToInt = new StringToInt(switchValue, stringValues); |
|
var inst = new SwitchInstruction(stringToInt); |
|
inst.Sections.AddRange(sections); |
|
instructions[i + 1].ReplaceWith(inst); |
|
instructions.RemoveAt(i); |
|
return true; |
|
} |
|
|
|
bool MatchRoslynSwitchOnString(InstructionCollection<ILInstruction> instructions, ref int i) |
|
{ |
|
if (i < 1) return false; |
|
// stloc switchValueVar(call ComputeStringHash(switchValue)) |
|
// switch (ldloc switchValueVar) { |
|
// case [211455823..211455824): br caseBlock1 |
|
// ... more cases ... |
|
// case [long.MinValue..-365098645),...,[1697255802..long.MaxValue]: br defaultBlock |
|
// } |
|
if (!(instructions[i] is SwitchInstruction switchInst && switchInst.Value.MatchLdLoc(out var switchValueVar) && |
|
MatchComputeStringHashCall(instructions[i - 1], switchValueVar, out LdLoc switchValueLoad))) |
|
return false; |
|
|
|
var stringValues = new List<(int, string, Block)>(); |
|
int index = 0; |
|
SwitchSection defaultSection = switchInst.Sections.MaxBy(s => s.Labels.Count()); |
|
foreach (var section in switchInst.Sections) { |
|
if (section == defaultSection) continue; |
|
// extract target block |
|
if (!section.Body.MatchBranch(out Block target)) |
|
return false; |
|
if (!MatchRoslynCaseBlockHead(target, switchValueLoad.Variable, out Block body, out string stringValue)) |
|
return false; |
|
stringValues.Add((index++, stringValue, body)); |
|
} |
|
ILInstruction switchValueInst = switchValueLoad; |
|
// stloc switchValueLoadVariable(switchValue) |
|
// stloc switchValueVar(call ComputeStringHash(ldloc switchValueLoadVariable)) |
|
// switch (ldloc switchValueVar) { |
|
bool keepAssignmentBefore; |
|
// if the switchValueLoad.Variable is only used in the compiler generated case equality checks, we can remove it. |
|
if (i > 1 && instructions[i - 2].MatchStLoc(switchValueLoad.Variable, out var switchValueTmp) && |
|
switchValueLoad.Variable.IsSingleDefinition && switchValueLoad.Variable.LoadCount == switchInst.Sections.Count) |
|
{ |
|
switchValueInst = switchValueTmp; |
|
keepAssignmentBefore = false; |
|
} else { |
|
keepAssignmentBefore = true; |
|
} |
|
var defaultLabel = new LongSet(new LongInterval(0, index)).Invert(); |
|
var newSwitch = new SwitchInstruction(new StringToInt(switchValueInst, stringValues.Select(item => item.Item2).ToArray())); |
|
newSwitch.Sections.AddRange(stringValues.Select(section => new SwitchSection { Labels = new Util.LongSet(section.Item1), Body = new Branch(section.Item3) })); |
|
newSwitch.Sections.Add(new SwitchSection { Labels = defaultLabel, Body = defaultSection.Body }); |
|
instructions[i].ReplaceWith(newSwitch); |
|
if (keepAssignmentBefore) { |
|
instructions.RemoveAt(i - 1); |
|
i--; |
|
} else { |
|
instructions.RemoveRange(i - 2, 2); |
|
i -= 2; |
|
} |
|
return true; |
|
} |
|
|
|
/// <summary> |
|
/// Matches and the negated version: |
|
/// if (call op_Equality(ldloc V_0, ldstr "Fifth case")) br body |
|
/// br exit |
|
/// </summary> |
|
bool MatchRoslynCaseBlockHead(Block target, ILVariable switchValueVar, out Block body, out string stringValue) |
|
{ |
|
body = null; |
|
stringValue = null; |
|
if (target.Instructions.Count != 2) |
|
return false; |
|
if (!target.Instructions[0].MatchIfInstruction(out var condition, out var bodyBranch)) |
|
return false; |
|
if (!bodyBranch.MatchBranch(out body)) |
|
return false; |
|
if (MatchStringEqualityComparison(condition, switchValueVar, out stringValue)) { |
|
return body != null; |
|
} else if (condition.MatchLogicNot(out condition) && MatchStringEqualityComparison(condition, switchValueVar, out stringValue)) { |
|
if (!target.Instructions[1].MatchBranch(out Block exit)) |
|
return false; |
|
body = exit; |
|
return true; |
|
} else { |
|
return false; |
|
} |
|
} |
|
|
|
/// <summary> |
|
/// Matches 'stloc(targetVar, call ComputeStringHash(ldloc switchValue))' |
|
/// </summary> |
|
bool MatchComputeStringHashCall(ILInstruction inst, ILVariable targetVar, out LdLoc switchValue) |
|
{ |
|
switchValue = null; |
|
if (!inst.MatchStLoc(targetVar, out var value)) |
|
return false; |
|
if (!(value is Call c && c.Arguments.Count == 1 && c.Method.Name == "ComputeStringHash" && c.Method.IsCompilerGeneratedOrIsInCompilerGeneratedClass())) |
|
return false; |
|
if (!(c.Arguments[0] is LdLoc)) |
|
return false; |
|
switchValue = (LdLoc)c.Arguments[0]; |
|
return true; |
|
} |
|
|
|
/// <summary> |
|
/// Matches 'call string.op_Equality(ldloc(variable), ldstr(stringValue))' |
|
/// or 'comp(ldloc(variable) == ldnull)' |
|
/// </summary> |
|
bool MatchStringEqualityComparison(ILInstruction condition, ILVariable variable, out string stringValue) |
|
{ |
|
return MatchStringEqualityComparison(condition, out var v, out stringValue) && v == variable; |
|
} |
|
|
|
/// <summary> |
|
/// Matches 'call string.op_Equality(ldloc(variable), ldstr(stringValue))' |
|
/// or 'comp(ldloc(variable) == ldnull)' |
|
/// </summary> |
|
bool MatchStringEqualityComparison(ILInstruction condition, out ILVariable variable, out string stringValue) |
|
{ |
|
stringValue = null; |
|
variable = null; |
|
ILInstruction left, right; |
|
if (condition is Call c && c.Method.IsOperator && c.Method.Name == "op_Equality" |
|
&& c.Method.DeclaringType.IsKnownType(KnownTypeCode.String) && c.Arguments.Count == 2) |
|
{ |
|
left = c.Arguments[0]; |
|
right = c.Arguments[1]; |
|
return left.MatchLdLoc(out variable) && right.MatchLdStr(out stringValue); |
|
} else if (condition.MatchCompEqualsNull(out var arg)) { |
|
stringValue = null; |
|
return arg.MatchLdLoc(out variable); |
|
} else { |
|
return false; |
|
} |
|
} |
|
} |
|
}
|
|
|