chriseth
10 years ago
6 changed files with 455 additions and 307 deletions
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/*
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This file is part of cpp-ethereum. |
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|
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cpp-ethereum 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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|
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cpp-ethereum 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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|
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You should have received a copy of the GNU General Public License |
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along with cpp-ethereum. If not, see <http://www.gnu.org/licenses/>.
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*/ |
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/**
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* @file KnownState.cpp |
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* @author Christian <c@ethdev.com> |
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* @date 2015 |
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* Contains knowledge about the state of the virtual machine at a specific instruction. |
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*/ |
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#include "KnownState.h" |
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#include <functional> |
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#include <libdevcrypto/SHA3.h> |
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#include <libevmasm/AssemblyItem.h> |
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using namespace std; |
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using namespace dev; |
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using namespace dev::eth; |
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ostream& KnownState::stream( |
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ostream& _out, |
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map<int, Id> _initialStack, |
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map<int, Id> _targetStack |
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) const |
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{ |
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auto streamExpressionClass = [this](ostream& _out, Id _id) |
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{ |
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auto const& expr = m_expressionClasses->representative(_id); |
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_out << " " << dec << _id << ": " << *expr.item; |
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if (expr.sequenceNumber) |
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_out << "@" << dec << expr.sequenceNumber; |
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_out << "("; |
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for (Id arg: expr.arguments) |
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_out << dec << arg << ","; |
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_out << ")" << endl; |
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}; |
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_out << "Optimizer analysis:" << endl; |
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_out << "Final stack height: " << dec << m_stackHeight << endl; |
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_out << "Equivalence classes: " << endl; |
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for (Id eqClass = 0; eqClass < m_expressionClasses->size(); ++eqClass) |
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streamExpressionClass(_out, eqClass); |
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_out << "Initial stack: " << endl; |
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for (auto const& it: _initialStack) |
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{ |
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_out << " " << dec << it.first << ": "; |
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streamExpressionClass(_out, it.second); |
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} |
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_out << "Target stack: " << endl; |
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for (auto const& it: _targetStack) |
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{ |
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_out << " " << dec << it.first << ": "; |
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streamExpressionClass(_out, it.second); |
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} |
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return _out; |
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} |
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KnownState::StoreOperation KnownState::feedItem(AssemblyItem const& _item, bool _copyItem) |
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{ |
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StoreOperation op; |
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if (_item.type() != Operation) |
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{ |
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assertThrow(_item.deposit() == 1, InvalidDeposit, ""); |
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setStackElement(++m_stackHeight, m_expressionClasses->find(_item, {}, _copyItem)); |
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} |
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else |
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{ |
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Instruction instruction = _item.instruction(); |
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InstructionInfo info = instructionInfo(instruction); |
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if (SemanticInformation::isDupInstruction(_item)) |
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setStackElement( |
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m_stackHeight + 1, |
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stackElement( |
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m_stackHeight - int(instruction) + int(Instruction::DUP1), |
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_item.getLocation() |
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) |
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); |
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else if (SemanticInformation::isSwapInstruction(_item)) |
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swapStackElements( |
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m_stackHeight, |
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m_stackHeight - 1 - int(instruction) + int(Instruction::SWAP1), |
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_item.getLocation() |
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); |
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else if (instruction != Instruction::POP) |
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{ |
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vector<Id> arguments(info.args); |
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for (int i = 0; i < info.args; ++i) |
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arguments[i] = stackElement(m_stackHeight - i, _item.getLocation()); |
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if (_item.instruction() == Instruction::SSTORE) |
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op = storeInStorage(arguments[0], arguments[1], _item.getLocation()); |
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else if (_item.instruction() == Instruction::SLOAD) |
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setStackElement( |
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m_stackHeight + _item.deposit(), |
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loadFromStorage(arguments[0], _item.getLocation()) |
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); |
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else if (_item.instruction() == Instruction::MSTORE) |
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op = storeInMemory(arguments[0], arguments[1], _item.getLocation()); |
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else if (_item.instruction() == Instruction::MLOAD) |
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setStackElement( |
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m_stackHeight + _item.deposit(), |
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loadFromMemory(arguments[0], _item.getLocation()) |
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); |
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else if (_item.instruction() == Instruction::SHA3) |
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setStackElement( |
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m_stackHeight + _item.deposit(), |
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applySha3(arguments.at(0), arguments.at(1), _item.getLocation()) |
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); |
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else |
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setStackElement( |
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m_stackHeight + _item.deposit(), |
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m_expressionClasses->find(_item, arguments, _copyItem) |
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); |
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} |
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m_stackHeight += _item.deposit(); |
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} |
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return op; |
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} |
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ExpressionClasses::Id KnownState::stackElement(int _stackHeight, SourceLocation const& _location) |
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{ |
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if (m_stackElements.count(_stackHeight)) |
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return m_stackElements.at(_stackHeight); |
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// Stack element not found (not assigned yet), create new equivalence class.
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return m_stackElements[_stackHeight] = initialStackElement(_stackHeight, _location); |
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} |
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ExpressionClasses::Id KnownState::initialStackElement( |
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int _stackHeight, |
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SourceLocation const& _location |
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) |
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{ |
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assertThrow(_stackHeight <= 0, OptimizerException, "Initial stack element of positive height requested."); |
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assertThrow(_stackHeight > -16, StackTooDeepException, ""); |
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// This is a special assembly item that refers to elements pre-existing on the initial stack.
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return m_expressionClasses->find(AssemblyItem(dupInstruction(1 - _stackHeight), _location)); |
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} |
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void KnownState::setStackElement(int _stackHeight, Id _class) |
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{ |
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m_stackElements[_stackHeight] = _class; |
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} |
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void KnownState::swapStackElements( |
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int _stackHeightA, |
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int _stackHeightB, |
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SourceLocation const& _location |
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) |
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{ |
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assertThrow(_stackHeightA != _stackHeightB, OptimizerException, "Swap on same stack elements."); |
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// ensure they are created
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stackElement(_stackHeightA, _location); |
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stackElement(_stackHeightB, _location); |
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swap(m_stackElements[_stackHeightA], m_stackElements[_stackHeightB]); |
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} |
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KnownState::StoreOperation KnownState::storeInStorage( |
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Id _slot, |
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Id _value, |
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SourceLocation const& _location) |
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{ |
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if (m_storageContent.count(_slot) && m_storageContent[_slot] == _value) |
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// do not execute the storage if we know that the value is already there
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return StoreOperation(); |
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m_sequenceNumber++; |
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decltype(m_storageContent) storageContents; |
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// Copy over all values (i.e. retain knowledge about them) where we know that this store
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// operation will not destroy the knowledge. Specifically, we copy storage locations we know
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// are different from _slot or locations where we know that the stored value is equal to _value.
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for (auto const& storageItem: m_storageContent) |
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if (m_expressionClasses->knownToBeDifferent(storageItem.first, _slot) || storageItem.second == _value) |
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storageContents.insert(storageItem); |
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m_storageContent = move(storageContents); |
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AssemblyItem item(Instruction::SSTORE, _location); |
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Id id = m_expressionClasses->find(item, {_slot, _value}, true, m_sequenceNumber); |
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StoreOperation operation(StoreOperation::Storage, _slot, m_sequenceNumber, id); |
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m_storageContent[_slot] = _value; |
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// increment a second time so that we get unique sequence numbers for writes
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m_sequenceNumber++; |
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return operation; |
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} |
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ExpressionClasses::Id KnownState::loadFromStorage(Id _slot, SourceLocation const& _location) |
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{ |
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if (m_storageContent.count(_slot)) |
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return m_storageContent.at(_slot); |
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AssemblyItem item(Instruction::SLOAD, _location); |
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return m_storageContent[_slot] = m_expressionClasses->find(item, {_slot}, true, m_sequenceNumber); |
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} |
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KnownState::StoreOperation KnownState::storeInMemory(Id _slot, Id _value, SourceLocation const& _location) |
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{ |
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if (m_memoryContent.count(_slot) && m_memoryContent[_slot] == _value) |
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// do not execute the store if we know that the value is already there
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return StoreOperation(); |
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m_sequenceNumber++; |
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decltype(m_memoryContent) memoryContents; |
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// copy over values at points where we know that they are different from _slot by at least 32
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for (auto const& memoryItem: m_memoryContent) |
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if (m_expressionClasses->knownToBeDifferentBy32(memoryItem.first, _slot)) |
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memoryContents.insert(memoryItem); |
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m_memoryContent = move(memoryContents); |
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AssemblyItem item(Instruction::MSTORE, _location); |
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Id id = m_expressionClasses->find(item, {_slot, _value}, true, m_sequenceNumber); |
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StoreOperation operation(StoreOperation(StoreOperation::Memory, _slot, m_sequenceNumber, id)); |
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m_memoryContent[_slot] = _value; |
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// increment a second time so that we get unique sequence numbers for writes
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m_sequenceNumber++; |
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return operation; |
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} |
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ExpressionClasses::Id KnownState::loadFromMemory(Id _slot, SourceLocation const& _location) |
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{ |
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if (m_memoryContent.count(_slot)) |
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return m_memoryContent.at(_slot); |
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AssemblyItem item(Instruction::MLOAD, _location); |
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return m_memoryContent[_slot] = m_expressionClasses->find(item, {_slot}, true, m_sequenceNumber); |
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} |
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KnownState::Id KnownState::applySha3( |
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Id _start, |
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Id _length, |
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SourceLocation const& _location |
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) |
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{ |
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AssemblyItem sha3Item(Instruction::SHA3, _location); |
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// Special logic if length is a short constant, otherwise we cannot tell.
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u256 const* l = m_expressionClasses->knownConstant(_length); |
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// unknown or too large length
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if (!l || *l > 128) |
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return m_expressionClasses->find(sha3Item, {_start, _length}, true, m_sequenceNumber); |
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vector<Id> arguments; |
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for (u256 i = 0; i < *l; i += 32) |
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{ |
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Id slot = m_expressionClasses->find( |
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AssemblyItem(Instruction::ADD, _location), |
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{_start, m_expressionClasses->find(i)} |
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); |
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arguments.push_back(loadFromMemory(slot, _location)); |
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} |
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if (m_knownSha3Hashes.count(arguments)) |
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return m_knownSha3Hashes.at(arguments); |
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Id v; |
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// If all arguments are known constants, compute the sha3 here
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if (all_of(arguments.begin(), arguments.end(), [this](Id _a) { return !!m_expressionClasses->knownConstant(_a); })) |
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{ |
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bytes data; |
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for (Id a: arguments) |
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data += toBigEndian(*m_expressionClasses->knownConstant(a)); |
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data.resize(size_t(*l)); |
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v = m_expressionClasses->find(AssemblyItem(u256(sha3(data)), _location)); |
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} |
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else |
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v = m_expressionClasses->find(sha3Item, {_start, _length}, true, m_sequenceNumber); |
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return m_knownSha3Hashes[arguments] = v; |
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} |
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@ -0,0 +1,149 @@ |
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/*
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This file is part of cpp-ethereum. |
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|
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cpp-ethereum 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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|
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cpp-ethereum 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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|
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You should have received a copy of the GNU General Public License |
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along with cpp-ethereum. If not, see <http://www.gnu.org/licenses/>.
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*/ |
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/**
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* @file KnownState.h |
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* @author Christian <c@ethdev.com> |
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* @date 2015 |
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* Contains knowledge about the state of the virtual machine at a specific instruction. |
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*/ |
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#pragma once |
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#include <vector> |
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#include <map> |
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#include <set> |
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#include <tuple> |
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#include <ostream> |
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#include <libdevcore/CommonIO.h> |
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#include <libdevcore/Exceptions.h> |
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#include <libevmasm/ExpressionClasses.h> |
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#include <libevmasm/SemanticInformation.h> |
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namespace dev |
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{ |
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namespace eth |
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{ |
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class AssemblyItem; |
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using AssemblyItems = std::vector<AssemblyItem>; |
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/**
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* Class to infer and store knowledge about the state of the virtual machine at a specific |
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* instruction. |
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* |
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* The general workings are that for each assembly item that is fed, an equivalence class is |
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* derived from the operation and the equivalence class of its arguments. DUPi, SWAPi and some |
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* arithmetic instructions are used to infer equivalences while these classes are determined. |
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*/ |
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class KnownState |
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{ |
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public: |
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using Id = ExpressionClasses::Id; |
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struct StoreOperation |
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{ |
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enum Target { Invalid, Memory, Storage }; |
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StoreOperation(): target(Invalid), sequenceNumber(-1) {} |
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StoreOperation( |
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Target _target, |
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Id _slot, |
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unsigned _sequenceNumber, |
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Id _expression |
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): target(_target), slot(_slot), sequenceNumber(_sequenceNumber), expression(_expression) {} |
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bool isValid() const { return target != Invalid; } |
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Target target; |
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Id slot; |
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unsigned sequenceNumber; |
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Id expression; |
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}; |
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KnownState(): m_expressionClasses(std::make_shared<ExpressionClasses>()) {} |
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/// Streams debugging information to @a _out.
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std::ostream& stream( |
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std::ostream& _out, |
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std::map<int, Id> _initialStack = std::map<int, Id>(), |
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std::map<int, Id> _targetStack = std::map<int, Id>() |
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) const; |
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/// Feeds the item into the system for analysis.
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/// @returns a possible store operation
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StoreOperation feedItem(AssemblyItem const& _item, bool _copyItem = false); |
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/// Resets any knowledge about storage.
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void resetStorage() { m_storageContent.clear(); } |
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/// Resets any knowledge about storage.
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void resetMemory() { m_memoryContent.clear(); } |
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/// Resets any knowledge about the current stack.
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void resetStack() { m_stackElements.clear(); m_stackHeight = 0; } |
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/// Resets any knowledge.
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void reset() { resetStorage(); resetMemory(); resetStack(); } |
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///@todo the sequence numbers in two copies of this class should never be the same.
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/// might be doable using two-dimensional sequence numbers, where the first value is incremented
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/// for each copy
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/// Retrieves the current equivalence class fo the given stack element (or generates a new
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/// one if it does not exist yet).
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Id stackElement(int _stackHeight, SourceLocation const& _location); |
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/// @returns the equivalence class id of the special initial stack element at the given height
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/// (must not be positive).
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Id initialStackElement(int _stackHeight, SourceLocation const& _location); |
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int stackHeight() const { return m_stackHeight; } |
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std::map<int, Id> const& stackElements() const { return m_stackElements; } |
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ExpressionClasses& expressionClasses() const { return *m_expressionClasses; } |
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private: |
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/// Assigns a new equivalence class to the next sequence number of the given stack element.
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void setStackElement(int _stackHeight, Id _class); |
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/// Swaps the given stack elements in their next sequence number.
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void swapStackElements(int _stackHeightA, int _stackHeightB, SourceLocation const& _location); |
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/// Increments the sequence number, deletes all storage information that might be overwritten
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/// and stores the new value at the given slot.
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/// @returns the store operation, which might be invalid if storage was not modified
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StoreOperation storeInStorage(Id _slot, Id _value, SourceLocation const& _location); |
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/// Retrieves the current value at the given slot in storage or creates a new special sload class.
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Id loadFromStorage(Id _slot, SourceLocation const& _location); |
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/// Increments the sequence number, deletes all memory information that might be overwritten
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/// and stores the new value at the given slot.
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/// @returns the store operation, which might be invalid if memory was not modified
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StoreOperation storeInMemory(Id _slot, Id _value, SourceLocation const& _location); |
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/// Retrieves the current value at the given slot in memory or creates a new special mload class.
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Id loadFromMemory(Id _slot, SourceLocation const& _location); |
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/// Finds or creates a new expression that applies the sha3 hash function to the contents in memory.
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Id applySha3(Id _start, Id _length, SourceLocation const& _location); |
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/// Current stack height, can be negative.
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int m_stackHeight = 0; |
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/// Current stack layout, mapping stack height -> equivalence class
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std::map<int, Id> m_stackElements; |
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/// Current sequence number, this is incremented with each modification to storage or memory.
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unsigned m_sequenceNumber = 1; |
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/// Knowledge about storage content.
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std::map<Id, Id> m_storageContent; |
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/// Knowledge about memory content. Keys are memory addresses, note that the values overlap
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/// and are not contained here if they are not completely known.
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std::map<Id, Id> m_memoryContent; |
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/// Keeps record of all sha3 hashes that are computed.
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std::map<std::vector<Id>, Id> m_knownSha3Hashes; |
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/// Structure containing the classes of equivalent expressions.
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std::shared_ptr<ExpressionClasses> m_expressionClasses; |
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}; |
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} |
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} |
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