247 lines
6.5 KiB
C#
247 lines
6.5 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;
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using System.Collections.Generic;
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using dnlib.DotNet;
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using dnlib.DotNet.Emit;
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using de4dot.blocks;
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namespace de4dot.blocks.cflow {
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// Very simple constants folder which is all that's needed at the moment
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class ConstantsFolder : BlockDeobfuscator {
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InstructionEmulator instructionEmulator = new InstructionEmulator();
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IList<Parameter> args;
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public bool DisableNewCode { get; set; }
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protected override void Initialize(List<Block> allBlocks) {
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base.Initialize(allBlocks);
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args = blocks.Method.Parameters;
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}
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protected override bool Deobfuscate(Block block) {
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bool modified = false;
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instructionEmulator.Initialize(blocks, allBlocks[0] == block);
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var instrs = block.Instructions;
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for (int i = 0; i < instrs.Count; i++) {
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var instr = instrs[i];
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switch (instr.OpCode.Code) {
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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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modified |= FixLoadInstruction(block, i, instructionEmulator.GetArg(instr.Instruction.GetParameter(args)));
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break;
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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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modified |= FixLoadInstruction(block, i, instructionEmulator.GetLocal(instr.Instruction.GetLocal(blocks.Locals)));
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break;
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case Code.Ldarga:
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case Code.Ldarga_S:
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instructionEmulator.MakeArgUnknown((Parameter)instr.Operand);
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break;
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case Code.Ldloca:
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case Code.Ldloca_S:
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instructionEmulator.MakeLocalUnknown((Local)instr.Operand);
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break;
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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.Ceq:
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case Code.Cgt:
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case Code.Cgt_Un:
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case Code.Clt:
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case Code.Clt_Un:
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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_I_Un:
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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_U:
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case Code.Conv_Ovf_U_Un:
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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_R_Un:
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case Code.Conv_R4:
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case Code.Conv_R8:
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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.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.Not:
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case Code.Or:
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case Code.Rem:
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case Code.Rem_Un:
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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.Sub:
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case Code.Sub_Ovf:
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case Code.Sub_Ovf_Un:
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case Code.Xor:
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if (DisableNewCode)
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break;
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if (i + 1 < instrs.Count && instrs[i + 1].OpCode.Code == Code.Pop)
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break;
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if (!VerifyValidArgs(instr.Instruction))
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break;
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instructionEmulator.Emulate(instr.Instruction);
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var tos = instructionEmulator.Peek();
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Instruction newInstr = null;
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if (tos.IsInt32()) {
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var val = (Int32Value)tos;
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if (val.AllBitsValid())
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newInstr = Instruction.CreateLdcI4(val.Value);
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}
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else if (tos.IsInt64()) {
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var val = (Int64Value)tos;
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if (val.AllBitsValid())
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newInstr = OpCodes.Ldc_I8.ToInstruction(val.Value);
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}
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else if (tos.IsReal8()) {
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var val = (Real8Value)tos;
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if (val.IsValid)
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newInstr = GetLoadRealInstruction(val.Value);
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}
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if (newInstr != null) {
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block.Insert(i + 1, Instruction.Create(OpCodes.Pop));
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block.Insert(i + 2, newInstr);
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i += 2;
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modified = true;
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}
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continue;
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}
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try {
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instructionEmulator.Emulate(instr.Instruction);
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}
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catch (NullReferenceException) {
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// Here if eg. invalid metadata token in a call instruction (operand is null)
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break;
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}
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}
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return modified;
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}
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bool VerifyValidArgs(Instruction instr) {
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int pushes, pops;
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instr.CalculateStackUsage(out pushes, out pops);
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if (pops < 0)
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return false;
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bool retVal;
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Value val2, val1;
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switch (pops) {
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case 0:
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return true;
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case 1:
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val1 = instructionEmulator.Pop();
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retVal = VerifyValidArg(val1);
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instructionEmulator.Push(val1);
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return retVal;
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case 2:
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val2 = instructionEmulator.Pop();
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val1 = instructionEmulator.Pop();
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retVal = VerifyValidArg(val2) && VerifyValidArg(val1);
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instructionEmulator.Push(val1);
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instructionEmulator.Push(val2);
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return retVal;
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}
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return false;
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}
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static bool VerifyValidArg(Value value) {
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if (value.IsInt32())
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return ((Int32Value)value).AllBitsValid();
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if (value.IsInt64())
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return ((Int64Value)value).AllBitsValid();
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if (value.IsReal8())
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return ((Real8Value)value).IsValid;
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return false;
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}
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static Instruction GetLoadRealInstruction(double value) {
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var floatVal = (float)value;
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if (floatVal == value || double.IsNaN(value))
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return OpCodes.Ldc_R4.ToInstruction(floatVal);
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return OpCodes.Ldc_R8.ToInstruction(value);
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}
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bool FixLoadInstruction(Block block, int index, Value value) {
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if (value.IsInt32()) {
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var intValue = (Int32Value)value;
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if (!intValue.AllBitsValid())
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return false;
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block.Instructions[index] = new Instr(Instruction.CreateLdcI4(intValue.Value));
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return true;
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}
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else if (value.IsInt64()) {
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var intValue = (Int64Value)value;
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if (!intValue.AllBitsValid())
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return false;
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block.Instructions[index] = new Instr(OpCodes.Ldc_I8.ToInstruction(intValue.Value));
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return true;
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}
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return false;
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}
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}
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}
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