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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 SemanticInformation.cpp
* @author Christian <c@ethdev.com>
* @date 2015
* Helper to provide semantic information about assembly items.
*/
#include <libevmasm/SemanticInformation.h>
#include <libevmasm/AssemblyItem.h>
using namespace std;
using namespace dev;
using namespace dev::eth;
bool SemanticInformation::breaksCSEAnalysisBlock(AssemblyItem const& _item)
{
switch (_item.type())
{
default:
case UndefinedItem:
case Tag:
return true;
case Push:
case PushString:
case PushTag:
case PushSub:
case PushSubSize:
case PushProgramSize:
case PushData:
return false;
case Operation:
{
if (isSwapInstruction(_item) || isDupInstruction(_item))
return false;
if (_item.instruction() == Instruction::GAS || _item.instruction() == Instruction::PC)
return true; // GAS and PC assume a specific order of opcodes
if (_item.instruction() == Instruction::MSIZE)
return true; // msize is modified already by memory access, avoid that for now
InstructionInfo info = instructionInfo(_item.instruction());
if (_item.instruction() == Instruction::SSTORE)
return false;
if (_item.instruction() == Instruction::MSTORE)
return false;
//@todo: We do not handle the following memory instructions for now:
// calldatacopy, codecopy, extcodecopy, mstore8,
// msize (note that msize also depends on memory read access)
// the second requirement will be lifted once it is implemented
return info.sideEffects || info.args > 2;
}
}
}
bool SemanticInformation::isCommutativeOperation(AssemblyItem const& _item)
{
if (_item.type() != Operation)
return false;
switch (_item.instruction())
{
case Instruction::ADD:
case Instruction::MUL:
case Instruction::EQ:
case Instruction::AND:
case Instruction::OR:
case Instruction::XOR:
return true;
default:
return false;
}
}
bool SemanticInformation::isDupInstruction(AssemblyItem const& _item)
{
if (_item.type() != Operation)
return false;
return Instruction::DUP1 <= _item.instruction() && _item.instruction() <= Instruction::DUP16;
}
bool SemanticInformation::isSwapInstruction(AssemblyItem const& _item)
{
if (_item.type() != Operation)
return false;
return Instruction::SWAP1 <= _item.instruction() && _item.instruction() <= Instruction::SWAP16;
}
bool SemanticInformation::isJumpInstruction(AssemblyItem const& _item)
{
return _item == AssemblyItem(Instruction::JUMP) || _item == AssemblyItem(Instruction::JUMPI);
}
bool SemanticInformation::altersControlFlow(AssemblyItem const& _item)
{
if (_item.type() != Operation)
return false;
switch (_item.instruction())
{
// note that CALL, CALLCODE and CREATE do not really alter the control flow, because we
// continue on the next instruction (unless an exception happens which can always happen)
case Instruction::JUMP:
case Instruction::JUMPI:
case Instruction::RETURN:
case Instruction::SUICIDE:
case Instruction::STOP:
return true;
default:
return false;
}
}
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