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875 lines
38 KiB
875 lines
38 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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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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// 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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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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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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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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List<(string, Block)> values = new List<(string, Block)>();
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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))
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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, caseBlock));
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}
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// switch contains case null:
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if (currentCaseBlock != defaultOrNullBlock) {
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values.Add((null, 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 = 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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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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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 $$method0x600003f-1, ldloc dict)
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// br switchHeadBlock
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if (dictInitBlock.IncomingEdgeCount != 1 || dictInitBlock.Instructions.Count < 3)
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return false;
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if (!ExtractStringValuesFromInitBlock(dictInitBlock, out var stringValues, out var blockAfterInit, dictionaryType, dictField, false))
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return false;
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if (tryGetValueBlock != blockAfterInit)
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return false;
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// match fourth block: TryGetValue on compiler-generated Dictionary<string, int>
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// if (logic.not(call TryGetValue(volatile.ldobj System.Collections.Generic.Dictionary`2[[System.String],[System.Int32]](ldsflda $$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((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;
|
|
if (!c.Arguments[1].MatchLdLoc(switchValueVar) || !c.Arguments[2].MatchLdLoca(out var switchIndexVar))
|
|
return false;
|
|
if (!tryGetValueBlock.Instructions[1].MatchBranch(out var switchBlock))
|
|
return false;
|
|
// match fifth block: switch-instruction block
|
|
// switch (ldloc switchVariable) {
|
|
// case [0..1): br caseBlock1
|
|
// ... more cases ...
|
|
// case [long.MinValue..0),[13..long.MaxValue]: br defaultBlock
|
|
// }
|
|
// mcs has a bug: when there is only one case it still generates the full-blown Dictionary<string, int> pattern,
|
|
// but uses only a simple if statement instead of the switch instruction.
|
|
if (switchBlock.IncomingEdgeCount != 1 || switchBlock.Instructions.Count == 0)
|
|
return false;
|
|
var sections = new List<SwitchSection>();
|
|
switch (switchBlock.Instructions[0]) {
|
|
case SwitchInstruction switchInst:
|
|
if (switchBlock.Instructions.Count != 1)
|
|
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), ILRange = ifInst.ILRange });
|
|
sections.Add(new SwitchSection() { Body = switchBlock.Instructions[1], Labels = new LongSet(0).Invert(), ILRange = switchBlock.Instructions[1].ILRange });
|
|
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 = 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))
|
|
instructions.RemoveAt(i);
|
|
i--;
|
|
} else {
|
|
// delete both the if and the assignment before
|
|
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);
|
|
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) {
|
|
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;
|
|
}
|
|
}
|
|
}
|
|
}
|