diff --git a/Assembly.cpp b/Assembly.cpp index a9ee96199..8642824f6 100644 --- a/Assembly.cpp +++ b/Assembly.cpp @@ -22,9 +22,12 @@ #include "Assembly.h" #include #include +#include #include #include #include +#include +#include #include using namespace std; using namespace dev; @@ -302,7 +305,7 @@ inline bool matches(AssemblyItemsConstRef _a, AssemblyItemsConstRef _b) struct OptimiserChannel: public LogChannel { static const char* name() { return "OPT"; } static const int verbosity = 12; }; #define copt dev::LogOutputStream() -Assembly& Assembly::optimise(bool _enable) +Assembly& Assembly::optimise(bool _enable, bool _isCreation, size_t _runs) { if (!_enable) return *this; @@ -364,10 +367,17 @@ Assembly& Assembly::optimise(bool _enable) } } + total += ConstantOptimisationMethod::optimiseConstants( + _isCreation, + _isCreation ? 1 : _runs, + *this, + m_items + ); + copt << total << " optimisations done."; for (auto& sub: m_subs) - sub.optimise(true); + sub.optimise(true, false, _runs); return *this; } diff --git a/Assembly.h b/Assembly.h index 3c82125a1..1457173bc 100644 --- a/Assembly.h +++ b/Assembly.h @@ -49,6 +49,7 @@ public: AssemblyItem newPushTag() { return AssemblyItem(PushTag, m_usedTags++); } AssemblyItem newData(bytes const& _data) { h256 h = (u256)std::hash()(asString(_data)); m_data[h] = _data; return AssemblyItem(PushData, h); } AssemblyItem newSub(Assembly const& _sub) { m_subs.push_back(_sub); return AssemblyItem(PushSub, m_subs.size() - 1); } + Assembly const& getSub(size_t _sub) const { return m_subs.at(_sub); } AssemblyItem newPushString(std::string const& _data) { h256 h = (u256)std::hash()(_data); m_strings[h] = _data; return AssemblyItem(PushString, h); } AssemblyItem newPushSubSize(u256 const& _subId) { return AssemblyItem(PushSubSize, _subId); } @@ -92,7 +93,13 @@ public: void setSourceLocation(SourceLocation const& _location) { m_currentSourceLocation = _location; } bytes assemble() const; - Assembly& optimise(bool _enable); + bytes const& data(h256 const& _i) const { return m_data[_i]; } + + /// Modify (if @a _enable is set) and return the current assembly such that creation and + /// execution gas usage is optimised. @a _isCreation should be true for the top-level assembly. + /// @a _runs specifes an estimate on how often each opcode in this assembly will be executed, + /// i.e. use a small value to optimise for size and a large value to optimise for runtime. + Assembly& optimise(bool _enable, bool _isCreation = true, size_t _runs = 200); Json::Value stream( std::ostream& _out, std::string const& _prefix = "", diff --git a/ConstantOptimiser.cpp b/ConstantOptimiser.cpp new file mode 100644 index 000000000..77d1bdfaa --- /dev/null +++ b/ConstantOptimiser.cpp @@ -0,0 +1,225 @@ +/* + This file is part of cpp-ethereum. + + cpp-ethereum is free software: you can redistribute it and/or modify + it under the terms of the GNU General Public License as published by + the Free Software Foundation, either version 3 of the License, or + (at your option) any later version. + + cpp-ethereum is distributed in the hope that it will be useful, + but WITHOUT ANY WARRANTY; without even the implied warranty of + MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + GNU General Public License for more details. + + You should have received a copy of the GNU General Public License + along with cpp-ethereum. If not, see . +*/ +/** @file ConstantOptimiser.cpp + * @author Christian + * @date 2015 + */ + +#include "libevmasm/ConstantOptimiser.h" +#include +#include +#include +using namespace std; +using namespace dev; +using namespace dev::eth; + +unsigned ConstantOptimisationMethod::optimiseConstants( + bool _isCreation, + size_t _runs, + Assembly& _assembly, + AssemblyItems& _items +) +{ + unsigned optimisations = 0; + map pushes; + for (AssemblyItem const& item: _items) + if (item.type() == Push) + pushes[item]++; + for (auto it: pushes) + { + AssemblyItem const& item = it.first; + if (item.data() < 0x100) + continue; + Params params; + params.multiplicity = it.second; + params.isCreation = _isCreation; + params.runs = _runs; + LiteralMethod lit(params, item.data()); + bigint literalGas = lit.gasNeeded(); + CodeCopyMethod copy(params, item.data()); + bigint copyGas = copy.gasNeeded(); + ComputeMethod compute(params, item.data()); + bigint computeGas = compute.gasNeeded(); + if (copyGas < literalGas && copyGas < computeGas) + { + copy.execute(_assembly, _items); + optimisations++; + } + else if (computeGas < literalGas && computeGas < copyGas) + { + compute.execute(_assembly, _items); + optimisations++; + } + } + return optimisations; +} + +bigint ConstantOptimisationMethod::simpleRunGas(AssemblyItems const& _items) +{ + bigint gas = 0; + for (AssemblyItem const& item: _items) + if (item.type() == Push) + gas += GasMeter::runGas(eth::Instruction::PUSH1); + else if (item.type() == Operation) + gas += GasMeter::runGas(item.instruction()); + return gas; +} + +bigint ConstantOptimisationMethod::dataGas(bytes const& _data) const +{ + if (m_params.isCreation) + { + bigint gas; + for (auto b: _data) + gas += b ? c_txDataNonZeroGas : c_txDataZeroGas; + return gas; + } + else + return c_createDataGas * dataSize(); +} + +size_t ConstantOptimisationMethod::bytesRequired(AssemblyItems const& _items) +{ + size_t size = 0; + for (AssemblyItem const& item: _items) + size += item.bytesRequired(3); // assume 3 byte addresses + return size; +} + +void ConstantOptimisationMethod::replaceConstants( + AssemblyItems& _items, + AssemblyItems const& _replacement +) const +{ + assertThrow(_items.size() > 0, OptimizerException, ""); + for (size_t i = 0; i < _items.size(); ++i) + { + if (_items.at(i) != AssemblyItem(m_value)) + continue; + _items[i] = _replacement[0]; + _items.insert(_items.begin() + i + 1, _replacement.begin() + 1, _replacement.end()); + i += _replacement.size() - 1; + } +} + +bigint LiteralMethod::gasNeeded() +{ + return combineGas( + simpleRunGas({eth::Instruction::PUSH1}), + // PUSHX plus data + (m_params.isCreation ? c_txDataNonZeroGas : c_createDataGas) + dataGas(), + 0 + ); +} + +CodeCopyMethod::CodeCopyMethod(Params const& _params, u256 const& _value): + ConstantOptimisationMethod(_params, _value), + m_copyRoutine{ + u256(0), + eth::Instruction::DUP1, + eth::Instruction::MLOAD, // back up memory + u256(32), + AssemblyItem(PushData, u256(1) << 16), // has to be replaced + eth::Instruction::DUP4, + eth::Instruction::CODECOPY, + eth::Instruction::DUP2, + eth::Instruction::MLOAD, + eth::Instruction::SWAP2, + eth::Instruction::MSTORE + } +{ +} + +bigint CodeCopyMethod::gasNeeded() +{ + return combineGas( + // Run gas: we ignore memory increase costs + simpleRunGas(m_copyRoutine) + c_copyGas, + // Data gas for copy routines: Some bytes are zero, but we ignore them. + bytesRequired(m_copyRoutine) * (m_params.isCreation ? c_txDataNonZeroGas : c_createDataGas), + // Data gas for data itself + dataGas(toBigEndian(m_value)) + ); +} + +void CodeCopyMethod::execute(Assembly& _assembly, AssemblyItems& _items) +{ + bytes data = toBigEndian(m_value); + m_copyRoutine[4] = _assembly.newData(data); + replaceConstants(_items, m_copyRoutine); +} + +AssemblyItems ComputeMethod::findRepresentation(u256 const& _value) +{ + if (_value < 0x10000) + // Very small value, not worth computing + return AssemblyItems{_value}; + else if (dev::bytesRequired(~_value) < dev::bytesRequired(_value)) + // Negated is shorter to represent + return findRepresentation(~_value) + AssemblyItems{Instruction::NOT}; + else + { + // Decompose value into a * 2**k + b where abs(b) << 2**k + // Is not always better, try literal and decomposition method. + AssemblyItems routine{u256(_value)}; + bigint bestGas = gasNeeded(routine); + for (unsigned bits = 255; bits > 8; --bits) + { + unsigned gapDetector = unsigned(_value >> (bits - 8)) & 0x1ff; + if (gapDetector != 0xff && gapDetector != 0x100) + continue; + + u256 powerOfTwo = u256(1) << bits; + u256 upperPart = _value >> bits; + bigint lowerPart = _value & (powerOfTwo - 1); + if (abs(powerOfTwo - lowerPart) < lowerPart) + lowerPart = lowerPart - powerOfTwo; // make it negative + if (abs(lowerPart) >= (powerOfTwo >> 8)) + continue; + + AssemblyItems newRoutine; + if (lowerPart != 0) + newRoutine += findRepresentation(u256(abs(lowerPart))); + newRoutine += AssemblyItems{u256(bits), u256(2), Instruction::EXP}; + if (upperPart != 1 && upperPart != 0) + newRoutine += findRepresentation(upperPart) + AssemblyItems{Instruction::MUL}; + if (lowerPart > 0) + newRoutine += AssemblyItems{Instruction::ADD}; + else if (lowerPart < 0) + newRoutine.push_back(eth::Instruction::SUB); + + bigint newGas = gasNeeded(newRoutine); + if (newGas < bestGas) + { + bestGas = move(newGas); + routine = move(newRoutine); + } + } + return routine; + } +} + +bigint ComputeMethod::gasNeeded(AssemblyItems const& _routine) +{ + size_t numExps = count(_routine.begin(), _routine.end(), eth::Instruction::EXP); + return combineGas( + simpleRunGas(_routine) + numExps * (c_expGas + c_expByteGas), + // Data gas for routine: Some bytes are zero, but we ignore them. + bytesRequired(_routine) * (m_params.isCreation ? c_txDataNonZeroGas : c_createDataGas), + 0 + ); +} diff --git a/ConstantOptimiser.h b/ConstantOptimiser.h new file mode 100644 index 000000000..e75eff380 --- /dev/null +++ b/ConstantOptimiser.h @@ -0,0 +1,147 @@ +/* + This file is part of cpp-ethereum. + + cpp-ethereum is free software: you can redistribute it and/or modify + it under the terms of the GNU General Public License as published by + the Free Software Foundation, either version 3 of the License, or + (at your option) any later version. + + cpp-ethereum is distributed in the hope that it will be useful, + but WITHOUT ANY WARRANTY; without even the implied warranty of + MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + GNU General Public License for more details. + + You should have received a copy of the GNU General Public License + along with cpp-ethereum. If not, see . +*/ +/** @file ConstantOptimiser.cpp + * @author Christian + * @date 2015 + */ + +#pragma once + +#include +#include +#include + +namespace dev +{ +namespace eth +{ + +class AssemblyItem; +using AssemblyItems = std::vector; +class Assembly; + +/** + * Abstract base class for one way to change how constants are represented in the code. + */ +class ConstantOptimisationMethod +{ +public: + /// Tries to optimised how constants are represented in the source code and modifies + /// @a _assembly and its @a _items. + /// @returns zero if no optimisations could be performed. + static unsigned optimiseConstants( + bool _isCreation, + size_t _runs, + Assembly& _assembly, + AssemblyItems& _items + ); + + struct Params + { + bool isCreation; ///< Whether this is called during contract creation or runtime. + size_t runs; ///< Estimated number of calls per opcode oven the lifetime of the contract. + size_t multiplicity; ///< Number of times the constant appears in the code. + }; + + explicit ConstantOptimisationMethod(Params const& _params, u256 const& _value): + m_params(_params), m_value(_value) {} + virtual bigint gasNeeded() = 0; + virtual void execute(Assembly& _assembly, AssemblyItems& _items) = 0; + +protected: + size_t dataSize() const { return std::max(1, dev::bytesRequired(m_value)); } + + /// @returns the run gas for the given items ignoring special gas costs + static bigint simpleRunGas(AssemblyItems const& _items); + /// @returns the gas needed to store the given data literally + bigint dataGas(bytes const& _data) const; + /// @returns the gas needed to store the value literally + bigint dataGas() const { return dataGas(toCompactBigEndian(m_value, 1)); } + static size_t bytesRequired(AssemblyItems const& _items); + /// @returns the combined estimated gas usage taking @a m_params into account. + bigint combineGas( + bigint const& _runGas, + bigint const& _repeatedDataGas, + bigint const& _uniqueDataGas + ) + { + // _runGas is not multiplied by _multiplicity because the runs are "per opcode" + return m_params.runs * _runGas + m_params.multiplicity * _repeatedDataGas + _uniqueDataGas; + } + + /// Replaces the constant by the code given in @a _replacement. + void replaceConstants(AssemblyItems& _items, AssemblyItems const& _replacement) const; + + Params m_params; + u256 const& m_value; +}; + +/** + * Optimisation method that pushes the constant to the stack literally. This is the default method, + * i.e. executing it does not alter the Assembly. + */ +class LiteralMethod: public ConstantOptimisationMethod +{ +public: + explicit LiteralMethod(Params const& _params, u256 const& _value): + ConstantOptimisationMethod(_params, _value) {} + virtual bigint gasNeeded() override; + virtual void execute(Assembly&, AssemblyItems&) override {} +}; + +/** + * Method that stores the data in the .data section of the code and copies it to the stack. + */ +class CodeCopyMethod: public ConstantOptimisationMethod +{ +public: + explicit CodeCopyMethod(Params const& _params, u256 const& _value); + virtual bigint gasNeeded() override; + virtual void execute(Assembly& _assembly, AssemblyItems& _items) override; + +protected: + AssemblyItems m_copyRoutine; +}; + +/** + * Method that tries to compute the constant. + */ +class ComputeMethod: public ConstantOptimisationMethod +{ +public: + explicit ComputeMethod(Params const& _params, u256 const& _value): + ConstantOptimisationMethod(_params, _value) + { + m_routine = findRepresentation(m_value); + } + + virtual bigint gasNeeded() override { return gasNeeded(m_routine); } + virtual void execute(Assembly&, AssemblyItems& _items) override + { + replaceConstants(_items, m_routine); + } + +protected: + /// Tries to recursively find a way to compute @a _value. + AssemblyItems findRepresentation(u256 const& _value); + bigint gasNeeded(AssemblyItems const& _routine); + + AssemblyItems m_routine; +}; + +} +} diff --git a/GasMeter.cpp b/GasMeter.cpp index 4e5289e38..42a5bed2e 100644 --- a/GasMeter.cpp +++ b/GasMeter.cpp @@ -201,13 +201,14 @@ GasMeter::GasConsumption GasMeter::memoryGas(int _stackPosOffset, int _stackPosS })); } -GasMeter::GasConsumption GasMeter::runGas(Instruction _instruction) +u256 GasMeter::runGas(Instruction _instruction) { if (_instruction == Instruction::JUMPDEST) - return GasConsumption(1); + return 1; int tier = instructionInfo(_instruction).gasPriceTier; - return tier == InvalidTier ? GasConsumption::infinite() : c_tierStepGas[tier]; + assertThrow(tier != InvalidTier, OptimizerException, "Invalid gas tier."); + return c_tierStepGas[tier]; } diff --git a/GasMeter.h b/GasMeter.h index 6949c193e..90f151fc4 100644 --- a/GasMeter.h +++ b/GasMeter.h @@ -66,6 +66,8 @@ public: u256 const& largestMemoryAccess() const { return m_largestMemoryAccess; } + static u256 runGas(Instruction _instruction); + private: /// @returns _multiplier * (_value + 31) / 32, if _value is a known constant and infinite otherwise. GasConsumption wordGas(u256 const& _multiplier, ExpressionClasses::Id _value); @@ -76,8 +78,6 @@ private: /// given as values on the stack at the given relative positions. GasConsumption memoryGas(int _stackPosOffset, int _stackPosSize); - static GasConsumption runGas(Instruction _instruction); - std::shared_ptr m_state; /// Largest point where memory was accessed since the creation of this object. u256 m_largestMemoryAccess;