Remove more dead code and useless stores
This commit is contained in:
parent
9d132bfeaf
commit
2bba9e688a
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@ -40,18 +40,23 @@ namespace de4dot.blocks {
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}
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public IList<BaseBlock> getAllBaseBlocks() {
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return getAllBlocks(new List<BaseBlock>());
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return getTheBlocks(new List<BaseBlock>());
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}
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public IList<Block> getAllBlocks() {
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return getAllBlocks(new List<Block>());
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return getTheBlocks(new List<Block>());
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}
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public IList<Block> getAllBlocks(IList<Block> allBlocks) {
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allBlocks.Clear();
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return getTheBlocks(allBlocks);
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}
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public IList<ScopeBlock> getAllScopeBlocks() {
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return getAllBlocks(new List<ScopeBlock>());
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return getTheBlocks(new List<ScopeBlock>());
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}
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IList<T> getAllBlocks<T>(IList<T> list) where T : BaseBlock {
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public IList<T> getTheBlocks<T>(IList<T> list) where T : BaseBlock {
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addBlocks(list, this);
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return list;
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}
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@ -319,7 +324,7 @@ namespace de4dot.blocks {
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// Get removed blocks and make sure they're not referenced by remaining code
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var removedBlocks = new List<Block>();
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foreach (var handler in tryBlock.TryHandlerBlocks)
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handler.getAllBlocks(removedBlocks);
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handler.getTheBlocks(removedBlocks);
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if (!verifyNoExternalRefs(removedBlocks))
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throw new ApplicationException("Removed blocks are referenced by remaining code");
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@ -38,10 +38,12 @@
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<Compile Include="cflow\BlockCflowDeobfuscator.cs" />
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<Compile Include="cflow\CflowUtils.cs" />
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<Compile Include="cflow\DeadCodeRemover.cs" />
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<Compile Include="cflow\DeadStoreRemover.cs" />
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<Compile Include="cflow\InstructionEmulator.cs" />
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<Compile Include="cflow\Int32Value.cs" />
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<Compile Include="cflow\Int64Value.cs" />
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<Compile Include="cflow\Real8Value.cs" />
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<Compile Include="cflow\StLdlocFixer.cs" />
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<Compile Include="cflow\SwitchCflowDeobfuscator.cs" />
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<Compile Include="cflow\Value.cs" />
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<Compile Include="cflow\ValueStack.cs" />
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@ -39,14 +39,15 @@ namespace de4dot.blocks.cflow {
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var allBlocks = new List<Block>();
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var switchCflowDeobfuscator = new SwitchCflowDeobfuscator();
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var deadCodeRemover = new DeadCodeRemover();
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var deadStoreRemover = new DeadStoreRemover();
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var stLdlocFixer = new StLdlocFixer();
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bool changed;
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do {
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changed = false;
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removeDeadBlocks();
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mergeBlocks();
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allBlocks.Clear();
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allBlocks.AddRange(blocks.MethodBlocks.getAllBlocks());
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blocks.MethodBlocks.getAllBlocks(allBlocks);
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foreach (var block in allBlocks) {
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var lastInstr = block.LastInstr;
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@ -59,8 +60,16 @@ namespace de4dot.blocks.cflow {
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switchCflowDeobfuscator.init(blocks, allBlocks);
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changed |= switchCflowDeobfuscator.deobfuscate();
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deadStoreRemover.init(blocks, allBlocks);
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changed |= deadStoreRemover.remove();
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deadCodeRemover.init(allBlocks);
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changed |= deadCodeRemover.remove();
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if (!changed) {
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stLdlocFixer.init(allBlocks, blocks.Locals);
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changed |= stLdlocFixer.fix();
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}
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} while (changed);
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}
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@ -21,6 +21,8 @@ using System.Collections.Generic;
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using Mono.Cecil.Cil;
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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 {
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List<Block> allBlocks;
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List<int> allDeadInstructions = new List<int>();
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@ -42,6 +44,7 @@ namespace de4dot.blocks.cflow {
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bool remove(Block block) {
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allDeadInstructions.Clear();
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bool changed = 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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@ -79,11 +82,13 @@ namespace de4dot.blocks.cflow {
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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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return false;
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block.remove(allDeadInstructions);
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return true;
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if (allDeadInstructions.Count > 0) {
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block.remove(allDeadInstructions);
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changed = true;
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}
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return changed;
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}
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bool okInstructions(Block block, IEnumerable<int> indexes) {
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152
blocks/cflow/DeadStoreRemover.cs
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152
blocks/cflow/DeadStoreRemover.cs
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@ -0,0 +1,152 @@
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/*
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Copyright (C) 2011 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 Mono.Cecil.Cil;
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namespace de4dot.blocks.cflow {
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// Removes dead stores by replacing the stloc with a pop. Other optimizations will notice it's
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// dead code and remove it.
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// I've only seen Xenocode generate this kind of code, so the code below is a special case of
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// the more general case.
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class DeadStoreRemover {
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Blocks blocks;
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List<Block> allBlocks = new List<Block>();
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List<AccessFlags> localFlags = new List<AccessFlags>();
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List<bool> deadLocals = new List<bool>();
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public void init(Blocks blocks, List<Block> allBlocks) {
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this.blocks = blocks;
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this.allBlocks = allBlocks;
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}
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[Flags]
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enum AccessFlags {
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None = 0,
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Read = 1,
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Write = 2,
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}
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public bool remove() {
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if (blocks.Locals.Count == 0)
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return false;
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localFlags.Clear();
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deadLocals.Clear();
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for (int i = 0; i < blocks.Locals.Count; i++) {
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localFlags.Add(AccessFlags.None);
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deadLocals.Add(false);
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}
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findLoadStores();
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bool deadStores = false;
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for (int i = 0; i < blocks.Locals.Count; i++) {
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var flags = localFlags[i];
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if ((flags & AccessFlags.Read) == AccessFlags.None) {
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deadLocals[i] = true;
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deadStores = true;
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}
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}
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if (!deadStores)
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return false;
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return removeDeadStores();
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}
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void findLoadStores() {
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foreach (var block in allBlocks) {
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foreach (var instr in block.Instructions) {
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VariableDefinition local;
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AccessFlags flags;
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switch (instr.OpCode.Code) {
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case Code.Ldloc:
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case Code.Ldloc_S:
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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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local = Instr.getLocalVar(blocks.Locals, instr);
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flags = AccessFlags.Read;
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break;
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case Code.Stloc:
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case Code.Stloc_S:
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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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local = Instr.getLocalVar(blocks.Locals, instr);
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flags = AccessFlags.Write;
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break;
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case Code.Ldloca_S:
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case Code.Ldloca:
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local = instr.Operand as VariableDefinition;
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flags = AccessFlags.Read | AccessFlags.Write;
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break;
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default:
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local = null;
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flags = AccessFlags.None;
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break;
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}
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if (local == null)
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continue;
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localFlags[local.Index] |= flags;
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}
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}
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}
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bool removeDeadStores() {
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bool changed = false;
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foreach (var block in allBlocks) {
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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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VariableDefinition local;
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switch (instr.OpCode.Code) {
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case Code.Stloc:
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case Code.Stloc_S:
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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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local = Instr.getLocalVar(blocks.Locals, instr);
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break;
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default:
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continue;
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}
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if (local == null)
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continue;
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if (!deadLocals[local.Index])
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continue;
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instructions[i] = new Instr(Instruction.Create(OpCodes.Pop));
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changed = true;
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}
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}
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return changed;
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}
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}
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}
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76
blocks/cflow/StLdlocFixer.cs
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76
blocks/cflow/StLdlocFixer.cs
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@ -0,0 +1,76 @@
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/*
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Copyright (C) 2011 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 Mono.Cecil.Cil;
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namespace de4dot.blocks.cflow {
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// Replace stloc + ldloc with dup + stloc
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class StLdlocFixer {
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IList<VariableDefinition> locals;
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List<Block> allBlocks;
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public void init(List<Block> allBlocks, IList<VariableDefinition> locals) {
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this.allBlocks = allBlocks;
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this.locals = locals;
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}
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public bool fix() {
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bool changed = false;
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foreach (var block in allBlocks)
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changed |= fix(block);
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return changed;
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}
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bool fix(Block block) {
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bool changed = 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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// Xenocode generates stloc + ldloc. Replace it with dup + stloc. It will eventually
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// become dup + pop and be removed.
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case Code.Stloc:
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case Code.Stloc_S:
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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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if (i + 1 >= instructions.Count)
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break;
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if (!instructions[i + 1].isLdloc())
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break;
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if (Instr.getLocalVar(locals, instr) != Instr.getLocalVar(locals, instructions[i + 1]))
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break;
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instructions[i] = new Instr(Instruction.Create(OpCodes.Dup));
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instructions[i + 1] = instr;
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changed = true;
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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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return changed;
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}
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}
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}
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