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/*
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 <http://www.gnu.org/licenses/>.
*/
/** @file GasMeter.cpp
* @author Christian <c@ethdev.com>
* @date 2015
*/
#include "GasMeter.h"
#include <libevmasm/KnownState.h>
using namespace std;
using namespace dev;
using namespace dev::eth;
GasMeter::GasConsumption& GasMeter::GasConsumption::operator+=(GasConsumption const& _other)
{
if (_other.isInfinite && !isInfinite)
*this = infinite();
if (isInfinite)
return *this;
bigint v = bigint(value) + _other.value;
if (v > numeric_limits<u256>::max())
*this = infinite();
else
value = u256(v);
return *this;
}
GasMeter::GasConsumption GasMeter::estimateMax(AssemblyItem const& _item, bool _includeExternalCosts)
{
GasConsumption gas;
switch (_item.type())
{
case Push:
case PushTag:
case PushData:
case PushString:
case PushSub:
case PushSubSize:
case PushProgramSize:
case PushLibraryAddress:
gas = runGas(Instruction::PUSH1);
break;
case Tag:
gas = runGas(Instruction::JUMPDEST);
break;
case Operation:
{
ExpressionClasses& classes = m_state->expressionClasses();
gas = runGas(_item.instruction());
switch (_item.instruction())
{
case Instruction::SSTORE:
{
ExpressionClasses::Id slot = m_state->relativeStackElement(0);
ExpressionClasses::Id value = m_state->relativeStackElement(-1);
if (classes.knownZero(value) || (
m_state->storageContent().count(slot) &&
classes.knownNonZero(m_state->storageContent().at(slot))
))
gas += GasCosts::sstoreResetGas; //@todo take refunds into account
else
gas += GasCosts::sstoreSetGas;
break;
}
case Instruction::SLOAD:
gas += GasCosts::sloadGas;
break;
case Instruction::RETURN:
gas += memoryGas(0, -1);
break;
case Instruction::MLOAD:
case Instruction::MSTORE:
gas += memoryGas(classes.find(Instruction::ADD, {
m_state->relativeStackElement(0),
classes.find(AssemblyItem(32))
}));
break;
case Instruction::MSTORE8:
gas += memoryGas(classes.find(Instruction::ADD, {
m_state->relativeStackElement(0),
classes.find(AssemblyItem(1))
}));
break;
case Instruction::SHA3:
gas = GasCosts::sha3Gas;
gas += wordGas(GasCosts::sha3WordGas, m_state->relativeStackElement(-1));
gas += memoryGas(0, -1);
break;
case Instruction::CALLDATACOPY:
case Instruction::CODECOPY:
gas += memoryGas(0, -2);
gas += wordGas(GasCosts::copyGas, m_state->relativeStackElement(-2));
break;
case Instruction::EXTCODECOPY:
gas += memoryGas(-1, -3);
gas += wordGas(GasCosts::copyGas, m_state->relativeStackElement(-3));
break;
case Instruction::LOG0:
case Instruction::LOG1:
case Instruction::LOG2:
case Instruction::LOG3:
case Instruction::LOG4:
{
unsigned n = unsigned(_item.instruction()) - unsigned(Instruction::LOG0);
gas = GasCosts::logGas + GasCosts::logTopicGas * n;
gas += memoryGas(0, -1);
if (u256 const* value = classes.knownConstant(m_state->relativeStackElement(-1)))
gas += GasCosts::logDataGas * (*value);
else
gas = GasConsumption::infinite();
break;
}
case Instruction::CALL:
case Instruction::CALLCODE:
case Instruction::DELEGATECALL:
{
if (_includeExternalCosts)
// We assume that we do not know the target contract and thus, the consumption is infinite.
gas = GasConsumption::infinite();
else
{
gas = GasCosts::callGas;
if (u256 const* value = classes.knownConstant(m_state->relativeStackElement(0)))
gas += (*value);
else
gas = GasConsumption::infinite();
if (_item.instruction() == Instruction::CALL)
gas += GasCosts::callNewAccountGas; // We very rarely know whether the address exists.
int valueSize = _item.instruction() == Instruction::DELEGATECALL ? 0 : 1;
if (!classes.knownZero(m_state->relativeStackElement(-1 - valueSize)))
gas += GasCosts::callValueTransferGas;
gas += memoryGas(-2 - valueSize, -3 - valueSize);
gas += memoryGas(-4 - valueSize, -5 - valueSize);
}
break;
}
case Instruction::CREATE:
if (_includeExternalCosts)
// We assume that we do not know the target contract and thus, the consumption is infinite.
gas = GasConsumption::infinite();
else
{
gas = GasCosts::createGas;
gas += memoryGas(-1, -2);
}
break;
case Instruction::EXP:
gas = GasCosts::expGas;
if (u256 const* value = classes.knownConstant(m_state->relativeStackElement(-1)))
gas += GasCosts::expByteGas * (32 - (h256(*value).firstBitSet() / 8));
else
gas += GasCosts::expByteGas * 32;
break;
default:
break;
}
break;
}
default:
gas = GasConsumption::infinite();
break;
}
m_state->feedItem(_item);
return gas;
}
GasMeter::GasConsumption GasMeter::wordGas(u256 const& _multiplier, ExpressionClasses::Id _position)
{
u256 const* value = m_state->expressionClasses().knownConstant(_position);
if (!value)
return GasConsumption::infinite();
return GasConsumption(_multiplier * ((*value + 31) / 32));
}
GasMeter::GasConsumption GasMeter::memoryGas(ExpressionClasses::Id _position)
{
u256 const* value = m_state->expressionClasses().knownConstant(_position);
if (!value)
return GasConsumption::infinite();
if (*value < m_largestMemoryAccess)
return GasConsumption(u256(0));
u256 previous = m_largestMemoryAccess;
m_largestMemoryAccess = *value;
auto memGas = [=](u256 const& pos) -> u256
{
u256 size = (pos + 31) / 32;
return GasCosts::memoryGas * size + size * size / GasCosts::quadCoeffDiv;
};
return memGas(*value) - memGas(previous);
}
GasMeter::GasConsumption GasMeter::memoryGas(int _stackPosOffset, int _stackPosSize)
{
ExpressionClasses& classes = m_state->expressionClasses();
if (classes.knownZero(m_state->relativeStackElement(_stackPosSize)))
return GasConsumption(0);
else
return memoryGas(classes.find(Instruction::ADD, {
m_state->relativeStackElement(_stackPosOffset),
m_state->relativeStackElement(_stackPosSize)
}));
}
unsigned GasMeter::runGas(Instruction _instruction)
{
if (_instruction == Instruction::JUMPDEST)
return 1;
switch (instructionInfo(_instruction).gasPriceTier)
{
case 0: return GasCosts::tier0Gas;
case 1: return GasCosts::tier1Gas;
case 2: return GasCosts::tier2Gas;
case 3: return GasCosts::tier3Gas;
case 4: return GasCosts::tier4Gas;
case 5: return GasCosts::tier5Gas;
case 6: return GasCosts::tier6Gas;
case 7: return GasCosts::tier7Gas;
default: break;
}
assertThrow(false, OptimizerException, "Invalid gas tier.");
return 0;
}
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