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908 lines
40 KiB
908 lines
40 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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using HashtableInitializer = Dictionary<IField, (List<(string, int)> Labels, IfInstruction JumpToNext, Block ContainingBlock, Block Previous, Block Next, bool Transformed)>; |
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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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BlockContainer body = (BlockContainer)function.Body; |
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var hashtableInitializers = ScanHashtableInitializerBlocks(body.EntryPoint); |
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HashSet<BlockContainer> changedContainers = new HashSet<BlockContainer>(); |
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|
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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 (SimplifyCSharp1CascadingIfStatements(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, hashtableInitializers, 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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var omittedBlocks = new Dictionary<Block, Block>(); |
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|
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// Remove all transformed hashtable initializers from the entrypoint. |
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foreach (var item in hashtableInitializers) { |
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var (labels, jumpToNext, containingBlock, previous, next, transformed) = item.Value; |
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if (!transformed) continue; |
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if (!omittedBlocks.TryGetValue(previous, out var actual)) |
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actual = previous; |
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if (jumpToNext != null) { |
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actual.Instructions.SecondToLastOrDefault().ReplaceWith(jumpToNext); |
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} |
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actual.Instructions.LastOrDefault().ReplaceWith(new Branch(next)); |
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omittedBlocks.Add(containingBlock, previous); |
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changedContainers.Add(body); |
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} |
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// If all initializer where removed, remove the initial null check as well. |
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if (hashtableInitializers.Count > 0 && omittedBlocks.Count == hashtableInitializers.Count && body.EntryPoint.Instructions.Count == 2) { |
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if (body.EntryPoint.Instructions[0] is IfInstruction ifInst |
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&& ifInst.TrueInst.MatchBranch(out var beginOfMethod) && body.EntryPoint.Instructions[1].MatchBranch(beginOfMethod)) { |
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body.EntryPoint.Instructions.RemoveAt(0); |
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} |
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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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HashtableInitializer ScanHashtableInitializerBlocks(Block entryPoint) |
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{ |
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var hashtables = new HashtableInitializer(); |
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if (entryPoint.Instructions.Count != 2) |
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return hashtables; |
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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 $$method0x600003f-1) != ldnull)) br switchHeadBlock |
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// br tableInitBlock |
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if (!(entryPoint.Instructions[0].MatchIfInstruction(out var condition, out var branchToSwitchHead))) |
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return hashtables; |
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if (!entryPoint.Instructions[1].MatchBranch(out var tableInitBlock)) |
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return hashtables; |
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if (!(condition.MatchCompNotEquals(out var left, out var right) && right.MatchLdNull() && |
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MatchDictionaryFieldLoad(left, IsNonGenericHashtable, out var dictField, out var dictionaryType))) |
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return hashtables; |
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if (!branchToSwitchHead.MatchBranch(out var switchHead)) |
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return hashtables; |
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// match second block: initialization of compiler-generated Hashtable |
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// stloc table(newobj Hashtable..ctor(ldc.i4 capacity, ldc.f loadFactor)) |
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// call Add(ldloc table, ldstr value, box System.Int32(ldc.i4 index)) |
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// ... more calls to Add ... |
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// volatile.stobj System.Collections.Hashtable(ldsflda $$method0x600003f - 1, ldloc table) |
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// br switchHeadBlock |
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if (tableInitBlock.IncomingEdgeCount != 1 || tableInitBlock.Instructions.Count < 3) |
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return hashtables; |
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Block previousBlock = entryPoint; |
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while (tableInitBlock != null) { |
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if (!ExtractStringValuesFromInitBlock(tableInitBlock, out var stringValues, out var blockAfterThisInitBlock, dictionaryType, dictField, true)) |
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break; |
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var nextHashtableInitHead = tableInitBlock.Instructions.SecondToLastOrDefault() as IfInstruction; |
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hashtables.Add(dictField, (stringValues, nextHashtableInitHead, tableInitBlock, previousBlock, blockAfterThisInitBlock, false)); |
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previousBlock = tableInitBlock; |
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// if there is another IfInstruction before the end of the block, it might be a jump to the next hashtable init block. |
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// if (comp(volatile.ldobj System.Collections.Hashtable(ldsflda $$method0x600003f-2) != ldnull)) br switchHeadBlock |
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if (nextHashtableInitHead != null) { |
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if (!(nextHashtableInitHead.Condition.MatchCompNotEquals(out left, out right) && right.MatchLdNull() && |
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MatchDictionaryFieldLoad(left, IsNonGenericHashtable, out var nextDictField, out _))) |
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break; |
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if (!nextHashtableInitHead.TrueInst.MatchBranch(switchHead)) |
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break; |
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tableInitBlock = blockAfterThisInitBlock; |
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dictField = nextDictField; |
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} else { |
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break; |
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} |
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} |
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return hashtables; |
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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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bool keepAssignmentBefore = 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) { |
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if (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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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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// Variable before the start of the switch is not related to the switch. |
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keepAssignmentBefore = true; |
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switchValue = new LdLoc(switchValueVar); |
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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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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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inst.AddILRange(instructions[i - 2]); |
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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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inst.AddILRange(instructions[i]); |
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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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inst.AddILRange(instructions[i - 1]); |
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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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bool SimplifyCSharp1CascadingIfStatements(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: |
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// stloc switchValueVar(ldloc temp) |
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// if (comp(ldloc temp == ldnull)) br defaultBlock |
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// br isInternedBlock |
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if (!(instructions[i].MatchIfInstruction(out var condition, out var defaultBlockJump))) |
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return false; |
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if (!instructions[i + 1].MatchBranch(out var isInternedBlock)) |
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return false; |
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if (!defaultBlockJump.MatchBranch(out var defaultOrNullBlock)) |
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return false; |
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if (!(condition.MatchCompEqualsNull(out var tempLoad) && tempLoad.MatchLdLoc(out var temp))) |
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return false; |
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if (!(temp.Kind == VariableKind.StackSlot && temp.LoadCount == 2)) |
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return false; |
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if (!(instructions[i - 1].MatchStLoc(out var switchValueVar, out var switchValue) && switchValue.MatchLdLoc(temp))) |
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return false; |
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// match isInternedBlock: |
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// stloc switchValueVarCopy(call IsInterned(ldloc switchValueVar)) |
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// if (comp(ldloc switchValueVarCopy == ldstr "case1")) br caseBlock1 |
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// br caseHeader2 |
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if (isInternedBlock.IncomingEdgeCount != 1 || isInternedBlock.Instructions.Count != 3) |
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return false; |
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if (!(isInternedBlock.Instructions[0].MatchStLoc(out var switchValueVarCopy, out var arg) && IsIsInternedCall(arg as Call, out arg) && arg.MatchLdLoc(switchValueVar))) |
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return false; |
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switchValueVar = switchValueVarCopy; |
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int conditionOffset = 1; |
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Block currentCaseBlock = isInternedBlock; |
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var values = new List<(string, ILInstruction)>(); |
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if (!switchValueVarCopy.IsSingleDefinition) |
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return false; |
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// each case starts with: |
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// if (comp(ldloc switchValueVar == ldstr "case label")) br caseBlock |
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// br currentCaseBlock |
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while (currentCaseBlock.Instructions[conditionOffset].MatchIfInstruction(out condition, out var caseBlockJump)) { |
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if (currentCaseBlock.Instructions.Count != conditionOffset + 2) |
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break; |
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if (!condition.MatchCompEquals(out var left, out var right)) |
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break; |
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if (!left.MatchLdLoc(switchValueVar)) |
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break; |
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if (!right.MatchLdStr(out string value)) |
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break; |
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if (!(caseBlockJump.MatchBranch(out var caseBlock) || caseBlockJump.MatchLeave((BlockContainer)currentCaseBlock.Parent))) |
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break; |
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if (!currentCaseBlock.Instructions[conditionOffset + 1].MatchBranch(out currentCaseBlock)) |
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break; |
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conditionOffset = 0; |
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values.Add((value, caseBlockJump.Clone())); |
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} |
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if (values.Count != switchValueVarCopy.LoadCount) |
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return false; |
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// switch contains case null: |
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if (currentCaseBlock != defaultOrNullBlock) { |
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values.Add((null, new Branch(defaultOrNullBlock))); |
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} |
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var sections = new List<SwitchSection>(values.SelectWithIndex((index, b) => new SwitchSection { Labels = new LongSet(index), Body = 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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inst.AddILRange(instructions[i - 1]); |
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instructions[i].ReplaceWith(inst); |
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instructions.RemoveAt(i + 1); |
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instructions.RemoveAt(i - 1); |
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return true; |
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} |
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bool IsIsInternedCall(Call call, out ILInstruction argument) |
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{ |
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if (call != null |
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&& call.Method.DeclaringType.IsKnownType(KnownTypeCode.String) |
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&& call.Method.IsStatic |
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&& call.Method.Name == "IsInterned" |
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&& call.Arguments.Count == 1) { |
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argument = call.Arguments[0]; |
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return true; |
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} |
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argument = null; |
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return false; |
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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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// match first block: checking switch-value for null: |
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// (In some cases, i.e., if switchValueVar is a parameter, the initial store is optional.) |
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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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return false; |
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if (!(condition.MatchCompEquals(out var left, out var right) && right.MatchLdNull())) |
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return false; |
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// The initial store can be omitted in some cases. If there is no initial store or the switch value variable is reused later, |
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// we do not inline the "switch value", but create an extra load later on. |
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if (i > 0 && instructions[i - 1].MatchStLoc(out var switchValueVar, out var switchValue)) { |
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if (!(switchValueVar.IsSingleDefinition && ((SemanticHelper.IsPure(switchValue.Flags) && left.Match(switchValue).Success) || left.MatchLdLoc(switchValueVar)))) |
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return false; |
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} else { |
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if (!left.MatchLdLoc(out switchValueVar)) |
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return false; |
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switchValue = null; |
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} |
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if (!switchValueVar.Type.IsKnownType(KnownTypeCode.String)) |
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return false; |
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// either br nullCase or leave container |
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var leaveContainer = BlockContainer.FindClosestContainer(instructions[i]); |
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if (leaveContainer.Parent is TryInstruction) { |
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leaveContainer = BlockContainer.FindClosestContainer(leaveContainer.Parent); |
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} |
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if (!exitBlockJump.MatchBranch(out var nullValueCaseBlock) && !exitBlockJump.MatchLeave(leaveContainer)) |
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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 $$method0x600003f-1, ldloc dict) |
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// br switchHeadBlock |
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if (dictInitBlock.IncomingEdgeCount != 1 || dictInitBlock.Instructions.Count < 3) |
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return false; |
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if (!ExtractStringValuesFromInitBlock(dictInitBlock, out var stringValues, out var blockAfterInit, dictionaryType, dictField, false)) |
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return false; |
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if (tryGetValueBlock != blockAfterInit) |
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return false; |
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// match fourth block: TryGetValue on compiler-generated Dictionary<string, int> |
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// if (logic.not(call TryGetValue(volatile.ldobj System.Collections.Generic.Dictionary`2[[System.String],[System.Int32]](ldsflda $$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(leaveContainer)) |
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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; |
|
if (!switchInst.Value.MatchLdLoc(switchIndexVar)) |
|
return false; |
|
sections.AddRange(switchInst.Sections); |
|
break; |
|
case IfInstruction ifInst: |
|
if (switchBlock.Instructions.Count != 2) |
|
return false; |
|
if (!ifInst.Condition.MatchCompEquals(out left, out right)) |
|
return false; |
|
if (!left.MatchLdLoc(switchIndexVar)) |
|
return false; |
|
if (!right.MatchLdcI4(0)) |
|
return false; |
|
sections.Add(new SwitchSection() { Body = ifInst.TrueInst, Labels = new LongSet(0) }.WithILRange(ifInst)); |
|
sections.Add(new SwitchSection() { Body = switchBlock.Instructions[1], Labels = new LongSet(0).Invert() }.WithILRange(switchBlock.Instructions[1])); |
|
break; |
|
} |
|
// mcs: map sections without a value to the default section, if possible |
|
if (!FixCasesWithoutValue(sections, stringValues)) |
|
return false; |
|
// switch contains case null: |
|
if (nullValueCaseBlock != defaultBlock) { |
|
if (!AddNullSection(sections, stringValues, nullValueCaseBlock)) { |
|
return false; |
|
} |
|
} |
|
bool keepAssignmentBefore = false; |
|
if (switchValueVar.LoadCount > 2 || switchValue == null) { |
|
switchValue = new LdLoc(switchValueVar); |
|
keepAssignmentBefore = true; |
|
} |
|
var stringToInt = new StringToInt(switchValue, stringValues); |
|
var inst = new SwitchInstruction(stringToInt); |
|
inst.Sections.AddRange(sections); |
|
instructions[i + 1].ReplaceWith(inst); |
|
if (keepAssignmentBefore) { |
|
// delete if (comp(ldloc switchValueVar == ldnull)) |
|
inst.AddILRange(instructions[i]); |
|
instructions.RemoveAt(i); |
|
i--; |
|
} else { |
|
// delete both the if and the assignment before |
|
inst.AddILRange(instructions[i - 1]); |
|
instructions.RemoveRange(i - 1, 2); |
|
i -= 2; |
|
} |
|
return true; |
|
} |
|
|
|
bool FixCasesWithoutValue(List<SwitchSection> sections, List<(string, int)> stringValues) |
|
{ |
|
bool HasLabel(SwitchSection section) |
|
{ |
|
return section.Labels.Values.Any(i => stringValues.Any(value => i == value.Item2)); |
|
} |
|
|
|
// Pick the section with the most labels as default section. |
|
// And collect all sections that have no value mapped to them. |
|
SwitchSection defaultSection = sections.First(); |
|
List<SwitchSection> sectionsWithoutLabels = new List<SwitchSection>(); |
|
foreach (var section in sections) { |
|
if (section == defaultSection) continue; |
|
if (section.Labels.Count() > defaultSection.Labels.Count()) { |
|
if (!HasLabel(defaultSection)) |
|
sectionsWithoutLabels.Add(defaultSection); |
|
defaultSection = section; |
|
continue; |
|
} |
|
if (!HasLabel(section)) |
|
sectionsWithoutLabels.Add(section); |
|
} |
|
|
|
foreach (var section in sectionsWithoutLabels) { |
|
if (!section.Body.Match(defaultSection.Body).Success) |
|
return false; |
|
defaultSection.Labels = defaultSection.Labels.UnionWith(section.Labels); |
|
if (section.HasNullLabel) |
|
defaultSection.HasNullLabel = true; |
|
sections.Remove(section); |
|
} |
|
|
|
return true; |
|
} |
|
|
|
bool AddNullSection(List<SwitchSection> sections, List<(string, int)> stringValues, Block nullValueCaseBlock) |
|
{ |
|
var label = new LongSet(sections.Count); |
|
var possibleConflicts = sections.Where(sec => sec.Labels.Overlaps(label)).ToArray(); |
|
if (possibleConflicts.Length > 1) |
|
return false; |
|
else if (possibleConflicts.Length == 1) { |
|
if (possibleConflicts[0].Labels.Count() == 1) |
|
return false; // cannot remove only label |
|
possibleConflicts[0].Labels = possibleConflicts[0].Labels.ExceptWith(label); |
|
} |
|
stringValues.Add((null, (int)label.Values.First())); |
|
sections.Add(new SwitchSection() { Labels = label, Body = new Branch(nullValueCaseBlock) }); |
|
return true; |
|
} |
|
|
|
/// <summary> |
|
/// Matches 'volatile.ldobj dictionaryType(ldsflda dictField)' |
|
/// </summary> |
|
bool MatchDictionaryFieldLoad(ILInstruction inst, Func<IType, bool> typeMatcher, out IField dictField, out IType dictionaryType) |
|
{ |
|
dictField = null; |
|
dictionaryType = null; |
|
return inst.MatchLdObj(out var dictionaryFieldLoad, out dictionaryType) && |
|
typeMatcher(dictionaryType) && |
|
dictionaryFieldLoad.MatchLdsFlda(out dictField) && |
|
(dictField.IsCompilerGeneratedOrIsInCompilerGeneratedClass() || dictField.Name.StartsWith("$$method", StringComparison.Ordinal)); |
|
} |
|
|
|
/// <summary> |
|
/// Matches and extracts values from Add-call sequences. |
|
/// </summary> |
|
bool ExtractStringValuesFromInitBlock(Block block, out List<(string, int)> values, out Block blockAfterInit, IType dictionaryType, IField dictionaryField, bool isHashtablePattern) |
|
{ |
|
values = null; |
|
blockAfterInit = null; |
|
// stloc dictVar(newobj Dictionary..ctor(ldc.i4 valuesLength)) |
|
// -or- |
|
// stloc dictVar(newobj Hashtable..ctor(ldc.i4 capacity, ldc.f4 loadFactor)) |
|
if (!(block.Instructions[0].MatchStLoc(out var dictVar, out var newObjDict) && newObjDict is NewObj newObj)) |
|
return false; |
|
if (!newObj.Method.DeclaringType.Equals(dictionaryType)) |
|
return false; |
|
int valuesLength = 0; |
|
if (newObj.Arguments.Count == 2) { |
|
if (!newObj.Arguments[0].MatchLdcI4(out valuesLength)) |
|
return false; |
|
if (!newObj.Arguments[1].MatchLdcF4(0.5f)) |
|
return false; |
|
} else if (newObj.Arguments.Count == 1) { |
|
if (!newObj.Arguments[0].MatchLdcI4(out valuesLength)) |
|
return false; |
|
} |
|
values = new List<(string, int)>(valuesLength); |
|
int i = 0; |
|
while (MatchAddCall(dictionaryType, block.Instructions[i + 1], dictVar, out var index, out var value)) { |
|
values.Add((value, index)); |
|
i++; |
|
} |
|
// final store to compiler-generated variable: |
|
// volatile.stobj dictionaryType(ldsflda dictionaryField, ldloc dictVar) |
|
if (!(block.Instructions[i + 1].MatchStObj(out var loadField, out var dictVarLoad, out var dictType) && |
|
dictType.Equals(dictionaryType) && loadField.MatchLdsFlda(out var dictField) && dictField.Equals(dictionaryField) && |
|
dictVarLoad.MatchLdLoc(dictVar))) |
|
return false; |
|
if (isHashtablePattern && block.Instructions[i + 2] is IfInstruction) { |
|
return block.Instructions[i + 3].MatchBranch(out blockAfterInit); |
|
} |
|
return block.Instructions[i + 2].MatchBranch(out blockAfterInit); |
|
} |
|
|
|
/// <summary> |
|
/// call Add(ldloc dictVar, ldstr value, ldc.i4 index) |
|
/// -or- |
|
/// call Add(ldloc dictVar, ldstr value, box System.Int32(ldc.i4 index)) |
|
/// </summary> |
|
bool MatchAddCall(IType dictionaryType, ILInstruction inst, ILVariable dictVar, out int index, out string value) |
|
{ |
|
value = null; |
|
index = -1; |
|
if (!(inst is CallInstruction c && c.Method.Name == "Add" && c.Arguments.Count == 3)) |
|
return false; |
|
if (!(c.Arguments[0].MatchLdLoc(dictVar) && c.Arguments[1].MatchLdStr(out value))) |
|
return false; |
|
if (!(c.Method.DeclaringType.Equals(dictionaryType) && !c.Method.IsStatic)) |
|
return false; |
|
return (c.Arguments[2].MatchLdcI4(out index) || (c.Arguments[2].MatchBox(out var arg, out _) && arg.MatchLdcI4(out index))); |
|
} |
|
|
|
bool IsStringToIntDictionary(IType dictionaryType) |
|
{ |
|
if (dictionaryType.FullName != "System.Collections.Generic.Dictionary") |
|
return false; |
|
if (dictionaryType.TypeArguments.Count != 2) |
|
return false; |
|
return dictionaryType.TypeArguments[0].IsKnownType(KnownTypeCode.String) && |
|
dictionaryType.TypeArguments[1].IsKnownType(KnownTypeCode.Int32); |
|
} |
|
|
|
bool IsNonGenericHashtable(IType dictionaryType) |
|
{ |
|
if (dictionaryType.FullName != "System.Collections.Hashtable") |
|
return false; |
|
if (dictionaryType.TypeArguments.Count != 0) |
|
return false; |
|
return true; |
|
} |
|
|
|
bool MatchLegacySwitchOnStringWithHashtable(Block block, HashtableInitializer hashtableInitializers, ref int i) |
|
{ |
|
// match first block: checking switch-value for null |
|
// stloc tmp(ldloc switch-value) |
|
// stloc switchVariable(ldloc tmp) |
|
// if (comp(ldloc tmp == ldnull)) br nullCaseBlock |
|
// br getItemBloc |
|
if (block.Instructions.Count != i + 4) |
|
return false; |
|
if (!block.Instructions[i].MatchStLoc(out var tmp, out var switchValue)) |
|
return false; |
|
if (!block.Instructions[i + 1].MatchStLoc(out var switchVariable, out var tmpLoad) || !tmpLoad.MatchLdLoc(tmp)) |
|
return false; |
|
if (!block.Instructions[i + 2].MatchIfInstruction(out var condition, out var nullCaseBlockBranch)) |
|
return false; |
|
if (!block.Instructions[i + 3].MatchBranch(out var getItemBlock) || !(nullCaseBlockBranch.MatchBranch(out var nullCaseBlock) || nullCaseBlockBranch is Leave)) |
|
return false; |
|
if (!(condition.MatchCompEquals(out var left, out var right) && right.MatchLdNull() && left.MatchLdLoc(tmp))) |
|
return false; |
|
// match second 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) || defaultBlockBranch is Leave)) |
|
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], IsNonGenericHashtable, out var dictField, out _) && getItemCall.Arguments[1].MatchLdLoc(switchVariable))) |
|
return false; |
|
// Check if there is a hashtable init block at the beginning of the method |
|
if (!hashtableInitializers.TryGetValue(dictField, out var info)) |
|
return false; |
|
var stringValues = info.Labels; |
|
// match third 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 (!(nullCaseBlockBranch is Leave) && nullCaseBlock != defaultBlock) { |
|
if (!AddNullSection(sections, stringValues, nullCaseBlock)) { |
|
return false; |
|
} |
|
} |
|
var stringToInt = new StringToInt(switchValue, stringValues); |
|
var inst = new SwitchInstruction(stringToInt); |
|
inst.Sections.AddRange(sections); |
|
inst.AddILRange(block.Instructions[i]); |
|
block.Instructions[i].ReplaceWith(inst); |
|
block.Instructions.RemoveRange(i + 1, 3); |
|
info.Transformed = true; |
|
hashtableInitializers[dictField] = info; |
|
return true; |
|
} |
|
|
|
bool FindHashtableInitBlock(Block entryPoint, out List<(string, int)> stringValues, out IField dictField, out Block blockAfterThisInitBlock, out ILInstruction thisSwitchInitJumpInst, out ILInstruction nextSwitchInitJumpInst) |
|
{ |
|
stringValues = null; |
|
dictField = null; |
|
blockAfterThisInitBlock = null; |
|
nextSwitchInitJumpInst = null; |
|
thisSwitchInitJumpInst = null; |
|
if (entryPoint.Instructions.Count != 2) |
|
return false; |
|
// match first block: checking compiler-generated Hashtable for null |
|
// if (comp(volatile.ldobj System.Collections.Hashtable(ldsflda $$method0x600003f-1) != ldnull)) br switchHeadBlock |
|
// br tableInitBlock |
|
if (!(entryPoint.Instructions[0].MatchIfInstruction(out var condition, out var branchToSwitchHead))) |
|
return false; |
|
if (!entryPoint.Instructions[1].MatchBranch(out var tableInitBlock)) |
|
return false; |
|
if (!(condition.MatchCompNotEquals(out var left, out var right) && right.MatchLdNull() && |
|
MatchDictionaryFieldLoad(left, IsNonGenericHashtable, out dictField, out var dictionaryType))) |
|
return false; |
|
if (!branchToSwitchHead.MatchBranch(out var switchHead)) |
|
return false; |
|
thisSwitchInitJumpInst = entryPoint.Instructions[0]; |
|
// match second block: initialization of compiler-generated Hashtable |
|
// stloc table(newobj Hashtable..ctor(ldc.i4 capacity, ldc.f loadFactor)) |
|
// call Add(ldloc table, ldstr value, box System.Int32(ldc.i4 index)) |
|
// ... more calls to Add ... |
|
// volatile.stobj System.Collections.Hashtable(ldsflda $$method0x600003f - 1, ldloc table) |
|
// br switchHeadBlock |
|
if (tableInitBlock.IncomingEdgeCount != 1 || tableInitBlock.Instructions.Count < 3) |
|
return false; |
|
if (!ExtractStringValuesFromInitBlock(tableInitBlock, out stringValues, out blockAfterThisInitBlock, dictionaryType, dictField, true)) |
|
return false; |
|
// if there is another IfInstruction before the end of the block, it might be a jump to the next hashtable init block. |
|
// if (comp(volatile.ldobj System.Collections.Hashtable(ldsflda $$method0x600003f-2) != ldnull)) br switchHeadBlock |
|
if (tableInitBlock.Instructions.SecondToLastOrDefault() is IfInstruction nextHashtableInitHead) { |
|
if (!(nextHashtableInitHead.Condition.MatchCompNotEquals(out left, out right) && right.MatchLdNull() && |
|
MatchDictionaryFieldLoad(left, IsNonGenericHashtable, out var nextSwitchInitField, out _))) |
|
return false; |
|
if (!nextHashtableInitHead.TrueInst.MatchBranch(switchHead)) |
|
return false; |
|
nextSwitchInitJumpInst = nextHashtableInitHead; |
|
} |
|
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) { |
|
newSwitch.AddILRange(instructions[i - 1]); |
|
instructions.RemoveAt(i - 1); |
|
i--; |
|
} else { |
|
newSwitch.AddILRange(instructions[i - 2]); |
|
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 (MatchStringEqualityComparison(condition, switchValueVar, out stringValue)) { |
|
var exitBranch = target.Instructions[1]; |
|
if (!(exitBranch.MatchBranch(out _) || exitBranch.MatchLeave(out _))) |
|
return false; |
|
return bodyBranch.MatchBranch(out body) && body != null; |
|
} else if (condition.MatchLogicNot(out condition) && MatchStringEqualityComparison(condition, switchValueVar, out stringValue)) { |
|
if (!(bodyBranch.MatchBranch(out _) || bodyBranch.MatchLeave(out _))) |
|
return false; |
|
return target.Instructions[1].MatchBranch(out body) && body != null; |
|
} else { |
|
return false; |
|
} |
|
} |
|
|
|
/// <summary> |
|
/// Matches 'stloc(targetVar, call ComputeStringHash(ldloc switchValue))' |
|
/// </summary> |
|
internal static 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; |
|
} |
|
} |
|
} |
|
}
|
|
|