mirror of https://github.com/icsharpcode/ILSpy.git
Siegfried Pammer
8 years ago
5 changed files with 230 additions and 8 deletions
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// Copyright (c) 2018 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 System.Text; |
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using ICSharpCode.Decompiler.IL.Transforms; |
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namespace ICSharpCode.Decompiler.IL.ControlFlow |
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{ |
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class AwaitInCatchTransform |
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{ |
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public static void Run(ILFunction function, ILTransformContext context) |
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{ |
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HashSet<BlockContainer> changedContainers = new HashSet<BlockContainer>(); |
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// analyze all try-catch statements in the function
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foreach (var tryCatch in function.Descendants.OfType<TryCatch>().ToArray()) { |
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if (!(tryCatch.Parent?.Parent is BlockContainer container)) |
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continue; |
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// Detect all handlers that contain an await expression
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AnalyzeHandlers(tryCatch.Handlers, out var transformableCatchBlocks); |
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var cfg = new ControlFlowGraph(container, context.CancellationToken); |
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if (transformableCatchBlocks.Count > 0) |
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changedContainers.Add(container); |
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foreach (var result in transformableCatchBlocks) { |
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var node = cfg.GetNode(result.RealCatchBlockEntryPoint); |
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context.Step("Inline catch block with await", result.Handler); |
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// Remove the IfInstruction from the jump table and eliminate all branches to the block.
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var jumpTableBlock = (Block)result.JumpTableEntry.Parent; |
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jumpTableBlock.Instructions.RemoveAt(result.JumpTableEntry.ChildIndex); |
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if (result.NextBlock != null) { |
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foreach (var branch in tryCatch.Descendants.OfType<Branch>()) { |
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if (branch.TargetBlock == jumpTableBlock) |
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branch.ReplaceWith(new Branch(result.NextBlock)); |
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} |
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} |
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// Add the real catch block entry-point to the block container
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var catchBlockHead = ((BlockContainer)result.Handler.Body).Blocks.Last(); |
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result.RealCatchBlockEntryPoint.Remove(); |
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((BlockContainer)result.Handler.Body).Blocks.Insert(0, result.RealCatchBlockEntryPoint); |
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// Remove the generated catch block
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catchBlockHead.Remove(); |
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// Inline all blocks that are dominated by the entrypoint of the real catch block
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foreach (var n in cfg.cfg) { |
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if (((Block)n.UserData).Parent == result.Handler.Body) |
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continue; |
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if (node.Dominates(n)) { |
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MoveBlock((Block)n.UserData, (BlockContainer)result.Handler.Body); |
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} |
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} |
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// Remove all assignments to the common object variable that stores the exception object.
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if (result.ObjectVariableStore != null) { |
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foreach (var load in result.ObjectVariableStore.Variable.LoadInstructions.ToArray()) { |
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if (load.Parent is CastClass cc && cc.Type == result.Handler.Variable.Type) |
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cc.ReplaceWith(new LdLoc(result.Handler.Variable)); |
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else |
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load.ReplaceWith(new LdLoc(result.Handler.Variable)); |
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} |
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} |
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} |
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} |
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// clean up all modified containers
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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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static void MoveBlock(Block block, BlockContainer target) |
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{ |
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block.Remove(); |
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target.Blocks.Add(block); |
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} |
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/// <summary>
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/// Analyzes all catch handlers and returns every handler that follows the await catch handler pattern.
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/// </summary>
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static bool AnalyzeHandlers(InstructionCollection<TryCatchHandler> handlers, out List<(int Id, TryCatchHandler Handler, Block RealCatchBlockEntryPoint, Block NextBlock, IfInstruction JumpTableEntry, StLoc ObjectVariableStore)> transformableCatchBlocks) |
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{ |
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transformableCatchBlocks = new List<(int Id, TryCatchHandler Handler, Block RealCatchBlockEntryPoint, Block NextBlock, IfInstruction JumpTableEntry, StLoc ObjectVariableStore)>(); |
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ILVariable catchHandlerIdentifier = null; |
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foreach (var handler in handlers) { |
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if (!MatchAwaitCatchHandler((BlockContainer)handler.Body, out int id, out var identifierVariable, out var realEntryPoint, out var nextBlock, out var jumpTableEntry, out var objectVariableStore)) |
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continue; |
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if (id < 1 || (catchHandlerIdentifier != null && identifierVariable != catchHandlerIdentifier)) |
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continue; |
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catchHandlerIdentifier = identifierVariable; |
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transformableCatchBlocks.Add((id, handler, realEntryPoint, nextBlock, jumpTableEntry, objectVariableStore)); |
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} |
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return transformableCatchBlocks.Count > 0; |
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} |
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/// <summary>
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/// Matches the await catch handler pattern:
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/// stloc V_3(ldloc E_100) - copy exception variable to a temporary
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/// stloc V_6(ldloc V_3) - store exception in 'global' object variable
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/// stloc V_5(ldc.i4 2) - store id of catch block in 'identifierVariable'
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/// br IL_0075 - jump out of catch block to the head of the catch-handler jump table
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/// </summary>
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static bool MatchAwaitCatchHandler(BlockContainer container, out int id, out ILVariable identifierVariable, out Block realEntryPoint, out Block nextBlock, out IfInstruction jumpTableEntry, out StLoc objectVariableStore) |
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{ |
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id = default(int); |
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identifierVariable = null; |
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realEntryPoint = null; |
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jumpTableEntry = null; |
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objectVariableStore = null; |
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nextBlock = null; |
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var catchBlock = container.EntryPoint; |
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if (catchBlock.Instructions.Count < 2 || catchBlock.Instructions.Count > 4) |
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return false; |
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if (!catchBlock.Instructions.Last().MatchBranch(out var jumpTableStartBlock)) |
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return false; |
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if (catchBlock.Instructions.Count > 2) { |
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objectVariableStore = (StLoc)catchBlock.Instructions[catchBlock.Instructions.Count - 3]; |
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} |
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var identifierVariableAssignment = catchBlock.Instructions.SecondToLastOrDefault(); |
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if (!identifierVariableAssignment.MatchStLoc(out identifierVariable, out var value) || !value.MatchLdcI4(out id)) |
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return false; |
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// analyze jump table:
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// [stloc identifierVariableCopy(identifierVariable)]
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// if (comp(identifierVariable == id)) br realEntryPoint
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// br jumpTableEntryBlock
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ILVariable identifierVariableCopy; |
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if (jumpTableStartBlock.Instructions.Count == 3) { |
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if (!jumpTableStartBlock.Instructions[0].MatchStLoc(out identifierVariableCopy, out var identifierVariableLoad) || !identifierVariableLoad.MatchLdLoc(identifierVariable)) |
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return false; |
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} else if (jumpTableStartBlock.Instructions.Count == 2) { |
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identifierVariableCopy = identifierVariable; |
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} else return false; |
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var jumpTableEntryBlock = jumpTableStartBlock; |
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do { |
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if (!(jumpTableEntryBlock.Instructions.SecondToLastOrDefault() is IfInstruction ifInst)) |
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return false; |
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ILInstruction lastInst = jumpTableEntryBlock.Instructions.Last(); |
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if (ifInst.Condition.MatchCompEquals(out var left, out var right)) { |
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if (!ifInst.TrueInst.MatchBranch(out realEntryPoint)) |
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return false; |
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if (!lastInst.MatchBranch(out jumpTableEntryBlock)) { |
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if (!lastInst.MatchLeave((BlockContainer)lastInst.Parent.Parent)) |
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return false; |
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} |
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} else if (ifInst.Condition.MatchCompNotEquals(out left, out right)) { |
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if (!lastInst.MatchBranch(out realEntryPoint)) |
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return false; |
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if (!ifInst.TrueInst.MatchBranch(out jumpTableEntryBlock)) { |
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if (!ifInst.TrueInst.MatchLeave((BlockContainer)lastInst.Parent.Parent)) |
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return false; |
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} |
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} else { |
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return false; |
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} |
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if (!left.MatchLdLoc(identifierVariableCopy)) |
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return false; |
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if (right.MatchLdcI4(id)) { |
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nextBlock = jumpTableEntryBlock; |
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jumpTableEntry = ifInst; |
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return true; |
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} |
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} while (jumpTableEntryBlock?.Instructions.Count == 2); |
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return false; |
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} |
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} |
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} |
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