386 lines
9.4 KiB
C#
386 lines
9.4 KiB
C#
/*
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Copyright (C) 2011-2015 de4dot@gmail.com
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This file is part of de4dot.
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de4dot is free software: you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation, either version 3 of the License, or
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(at your option) any later version.
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de4dot is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with de4dot. If not, see <http://www.gnu.org/licenses/>.
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*/
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using System.Collections.Generic;
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using dnlib.DotNet.Emit;
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namespace de4dot.blocks.cflow {
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// Removes dead code that is the result of one of our optimizations, or created by the
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// obfuscator.
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class DeadCodeRemover : BlockDeobfuscator {
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List<int> allDeadInstructions = new List<int>();
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InstructionExpressionFinder instructionExpressionFinder = new InstructionExpressionFinder();
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protected override bool Deobfuscate(Block block) {
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allDeadInstructions.Clear();
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bool modified = false;
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var instructions = block.Instructions;
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for (int i = 0; i < instructions.Count; i++) {
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var instr = instructions[i];
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switch (instr.OpCode.Code) {
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case Code.Nop:
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// The NOP is recreated if the block is empty so don't remove it if it's
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// the only instruction.
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if (instructions.Count > 1)
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allDeadInstructions.Add(i);
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break;
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case Code.Dup:
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if (i + 1 >= instructions.Count)
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break;
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if (instructions[i + 1].OpCode.Code != Code.Pop)
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break;
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allDeadInstructions.Add(i);
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allDeadInstructions.Add(i + 1);
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i++;
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break;
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case Code.Leave:
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case Code.Leave_S:
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case Code.Endfinally:
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case Code.Pop:
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instructionExpressionFinder.Initialize(block, false);
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if (!instructionExpressionFinder.Find(i))
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continue;
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if (!OkInstructions(block, instructionExpressionFinder.DeadInstructions))
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continue;
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allDeadInstructions.AddRange(instructionExpressionFinder.DeadInstructions);
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break;
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default:
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break;
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}
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}
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if (allDeadInstructions.Count > 0) {
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block.Remove(allDeadInstructions);
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modified = true;
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}
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return modified;
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}
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bool OkInstructions(Block block, IEnumerable<int> indexes) {
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foreach (var index in indexes) {
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var instr = block.Instructions[index];
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switch (instr.OpCode.Code) {
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case Code.Add:
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case Code.Add_Ovf:
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case Code.Add_Ovf_Un:
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case Code.And:
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case Code.Arglist:
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case Code.Beq:
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case Code.Beq_S:
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case Code.Bge:
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case Code.Bge_S:
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case Code.Bge_Un:
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case Code.Bge_Un_S:
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case Code.Bgt:
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case Code.Bgt_S:
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case Code.Bgt_Un:
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case Code.Bgt_Un_S:
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case Code.Ble:
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case Code.Ble_S:
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case Code.Ble_Un:
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case Code.Ble_Un_S:
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case Code.Blt:
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case Code.Blt_S:
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case Code.Blt_Un:
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case Code.Blt_Un_S:
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case Code.Bne_Un:
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case Code.Bne_Un_S:
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case Code.Box:
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case Code.Br:
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case Code.Br_S:
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case Code.Break:
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case Code.Brfalse:
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case Code.Brfalse_S:
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case Code.Brtrue:
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case Code.Brtrue_S:
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case Code.Castclass:
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case Code.Ceq:
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case Code.Cgt:
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case Code.Cgt_Un:
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case Code.Ckfinite:
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case Code.Clt:
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case Code.Clt_Un:
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case Code.Constrained:
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case Code.Conv_I:
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case Code.Conv_I1:
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case Code.Conv_I2:
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case Code.Conv_I4:
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case Code.Conv_I8:
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case Code.Conv_Ovf_I:
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case Code.Conv_Ovf_I1:
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case Code.Conv_Ovf_I1_Un:
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case Code.Conv_Ovf_I2:
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case Code.Conv_Ovf_I2_Un:
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case Code.Conv_Ovf_I4:
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case Code.Conv_Ovf_I4_Un:
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case Code.Conv_Ovf_I8:
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case Code.Conv_Ovf_I8_Un:
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case Code.Conv_Ovf_I_Un:
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case Code.Conv_Ovf_U:
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case Code.Conv_Ovf_U1:
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case Code.Conv_Ovf_U1_Un:
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case Code.Conv_Ovf_U2:
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case Code.Conv_Ovf_U2_Un:
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case Code.Conv_Ovf_U4:
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case Code.Conv_Ovf_U4_Un:
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case Code.Conv_Ovf_U8:
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case Code.Conv_Ovf_U8_Un:
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case Code.Conv_Ovf_U_Un:
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case Code.Conv_R4:
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case Code.Conv_R8:
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case Code.Conv_R_Un:
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case Code.Conv_U:
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case Code.Conv_U1:
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case Code.Conv_U2:
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case Code.Conv_U4:
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case Code.Conv_U8:
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case Code.Div:
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case Code.Div_Un:
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case Code.Dup:
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case Code.Endfilter:
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case Code.Endfinally:
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case Code.Isinst:
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case Code.Jmp:
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case Code.Ldarg:
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case Code.Ldarg_0:
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case Code.Ldarg_1:
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case Code.Ldarg_2:
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case Code.Ldarg_3:
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case Code.Ldarg_S:
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case Code.Ldarga:
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case Code.Ldarga_S:
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case Code.Ldc_I4:
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case Code.Ldc_I4_0:
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case Code.Ldc_I4_1:
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case Code.Ldc_I4_2:
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case Code.Ldc_I4_3:
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case Code.Ldc_I4_4:
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case Code.Ldc_I4_5:
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case Code.Ldc_I4_6:
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case Code.Ldc_I4_7:
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case Code.Ldc_I4_8:
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case Code.Ldc_I4_M1:
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case Code.Ldc_I4_S:
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case Code.Ldc_I8:
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case Code.Ldc_R4:
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case Code.Ldc_R8:
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case Code.Ldelem:
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case Code.Ldelem_I:
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case Code.Ldelem_I1:
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case Code.Ldelem_I2:
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case Code.Ldelem_I4:
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case Code.Ldelem_I8:
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case Code.Ldelem_R4:
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case Code.Ldelem_R8:
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case Code.Ldelem_Ref:
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case Code.Ldelem_U1:
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case Code.Ldelem_U2:
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case Code.Ldelem_U4:
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case Code.Ldelema:
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case Code.Ldfld:
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case Code.Ldflda:
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case Code.Ldftn:
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case Code.Ldind_I:
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case Code.Ldind_I1:
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case Code.Ldind_I2:
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case Code.Ldind_I4:
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case Code.Ldind_I8:
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case Code.Ldind_R4:
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case Code.Ldind_R8:
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case Code.Ldind_Ref:
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case Code.Ldind_U1:
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case Code.Ldind_U2:
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case Code.Ldind_U4:
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case Code.Ldlen:
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case Code.Ldloc:
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case Code.Ldloc_0:
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case Code.Ldloc_1:
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case Code.Ldloc_2:
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case Code.Ldloc_3:
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case Code.Ldloc_S:
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case Code.Ldloca:
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case Code.Ldloca_S:
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case Code.Ldnull:
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case Code.Ldobj:
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case Code.Ldsfld:
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case Code.Ldsflda:
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case Code.Ldstr:
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case Code.Ldtoken:
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case Code.Ldvirtftn:
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case Code.Leave:
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case Code.Leave_S:
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case Code.Localloc:
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case Code.Mkrefany:
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case Code.Mul:
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case Code.Mul_Ovf:
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case Code.Mul_Ovf_Un:
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case Code.Neg:
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case Code.Newarr:
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case Code.Nop:
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case Code.Not:
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case Code.Or:
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case Code.Pop:
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case Code.Readonly:
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case Code.Refanytype:
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case Code.Refanyval:
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case Code.Rem:
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case Code.Rem_Un:
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case Code.Ret:
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case Code.Rethrow:
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case Code.Shl:
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case Code.Shr:
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case Code.Shr_Un:
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case Code.Sizeof:
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case Code.Sub:
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case Code.Sub_Ovf:
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case Code.Sub_Ovf_Un:
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case Code.Switch:
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case Code.Tailcall:
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case Code.Throw:
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case Code.Unaligned:
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case Code.Unbox:
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case Code.Unbox_Any:
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case Code.Volatile:
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case Code.Xor:
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break;
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case Code.Call:
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case Code.Calli:
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case Code.Callvirt:
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case Code.Cpblk:
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case Code.Cpobj:
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case Code.Initblk:
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case Code.Initobj:
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case Code.Newobj:
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case Code.Starg:
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case Code.Starg_S:
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case Code.Stelem:
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case Code.Stelem_I:
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case Code.Stelem_I1:
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case Code.Stelem_I2:
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case Code.Stelem_I4:
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case Code.Stelem_I8:
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case Code.Stelem_R4:
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case Code.Stelem_R8:
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case Code.Stelem_Ref:
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case Code.Stfld:
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case Code.Stind_I:
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case Code.Stind_I1:
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case Code.Stind_I2:
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case Code.Stind_I4:
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case Code.Stind_I8:
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case Code.Stind_R4:
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case Code.Stind_R8:
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case Code.Stind_Ref:
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case Code.Stloc:
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case Code.Stloc_0:
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case Code.Stloc_1:
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case Code.Stloc_2:
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case Code.Stloc_3:
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case Code.Stloc_S:
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case Code.Stobj:
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case Code.Stsfld:
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default:
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return false;
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}
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}
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return true;
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}
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class InstructionExpressionFinder {
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List<int> deadInstructions = new List<int>();
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Block block;
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bool methodHasReturnValue;
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public List<int> DeadInstructions {
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get { return deadInstructions; }
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}
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public void Initialize(Block block, bool methodHasReturnValue) {
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deadInstructions.Clear();
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this.block = block;
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this.methodHasReturnValue = methodHasReturnValue;
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}
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public bool Find(int index) {
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return Find(ref index, true);
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}
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bool Find(ref int index, bool addIt) {
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if (index < 0)
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return false;
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var startInstr = block.Instructions[index];
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int startInstrPushes, startInstrPops;
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CalculateStackUsage(startInstr.Instruction, false, out startInstrPushes, out startInstrPops);
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// Don't add it if it clears the stack (eg. leave)
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if (addIt && startInstrPops >= 0)
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AddIndex(index);
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if (startInstrPops == 0)
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return true;
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while (index > 0) {
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var instr = block.Instructions[index - 1];
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if (startInstrPops == 0 && instr.OpCode.OpCodeType != OpCodeType.Prefix)
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break;
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int pushes, pops;
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CalculateStackUsage(instr.Instruction, methodHasReturnValue, out pushes, out pops);
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if (pops < 0)
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break; // eg. leave
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index--;
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if (pops > 0) { // if instr uses any args
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bool otherExpr = pops > 0 && pushes == 0;
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if (!Find(ref index, addIt && !otherExpr))
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break;
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}
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else if (pushes != 0 || pops != 0) {
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if (addIt)
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AddIndex(index);
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}
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if (pushes > 0 && startInstrPops >= 0) {
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if (pushes > startInstrPops)
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return false;
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startInstrPops -= pushes;
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}
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}
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return startInstrPops <= 0;
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}
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void AddIndex(int index) {
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deadInstructions.Add(index);
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}
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}
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static void CalculateStackUsage(Instruction instr, bool methodHasReturnValue, out int pushes, out int pops) {
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instr.CalculateStackUsage(false, out pushes, out pops);
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}
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}
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}
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