solidity/libevmasm/SemanticInformation.cpp

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/*
This file is part of solidity.
solidity 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.
solidity 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 solidity. If not, see <http://www.gnu.org/licenses/>.
*/
// SPDX-License-Identifier: GPL-3.0
/**
* @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;
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using namespace solidity;
using namespace solidity::evmasm;
bool SemanticInformation::breaksCSEAnalysisBlock(AssemblyItem const& _item, bool _msizeImportant)
{
switch (_item.type())
{
default:
case UndefinedItem:
case Tag:
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case PushDeployTimeAddress:
case AssignImmutable:
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case VerbatimBytecode:
return true;
case Push:
case PushTag:
case PushSub:
case PushSubSize:
case PushProgramSize:
case PushData:
case PushLibraryAddress:
case PushImmutable:
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;
if (!_msizeImportant && (
_item.instruction() == Instruction::MLOAD ||
_item.instruction() == Instruction::KECCAK256
))
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;
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return evmasm::isDupInstruction(_item.instruction());
}
bool SemanticInformation::isSwapInstruction(AssemblyItem const& _item)
{
if (_item.type() != Operation)
return false;
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return evmasm::isSwapInstruction(_item.instruction());
}
bool SemanticInformation::isJumpInstruction(AssemblyItem const& _item)
{
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return _item == Instruction::JUMP || _item == 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
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// continue on the next instruction
case Instruction::JUMP:
case Instruction::JUMPI:
case Instruction::RETURN:
case Instruction::SELFDESTRUCT:
case Instruction::STOP:
case Instruction::INVALID:
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case Instruction::REVERT:
return true;
default:
return false;
}
}
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bool SemanticInformation::terminatesControlFlow(Instruction _instruction)
{
switch (_instruction)
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{
case Instruction::RETURN:
case Instruction::SELFDESTRUCT:
case Instruction::STOP:
case Instruction::INVALID:
case Instruction::REVERT:
return true;
default:
return false;
}
}
bool SemanticInformation::reverts(Instruction _instruction)
{
switch (_instruction)
{
case Instruction::INVALID:
case Instruction::REVERT:
return true;
default:
return false;
}
}
bool SemanticInformation::isDeterministic(AssemblyItem const& _item)
{
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assertThrow(_item.type() != VerbatimBytecode, AssemblyException, "");
if (_item.type() != Operation)
return true;
switch (_item.instruction())
{
case Instruction::CALL:
case Instruction::CALLCODE:
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case Instruction::DELEGATECALL:
case Instruction::STATICCALL:
case Instruction::CREATE:
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case Instruction::CREATE2:
case Instruction::GAS:
case Instruction::PC:
case Instruction::MSIZE: // depends on previous writes and reads, not only on content
case Instruction::BALANCE: // depends on previous calls
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case Instruction::SELFBALANCE: // depends on previous calls
case Instruction::EXTCODESIZE:
case Instruction::EXTCODEHASH:
case Instruction::RETURNDATACOPY: // depends on previous calls
case Instruction::RETURNDATASIZE:
return false;
default:
return true;
}
}
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bool SemanticInformation::movable(Instruction _instruction)
{
// These are not really functional.
if (isDupInstruction(_instruction) || isSwapInstruction(_instruction))
return false;
InstructionInfo info = instructionInfo(_instruction);
if (info.sideEffects)
return false;
switch (_instruction)
{
case Instruction::KECCAK256:
case Instruction::BALANCE:
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case Instruction::SELFBALANCE:
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case Instruction::EXTCODESIZE:
case Instruction::EXTCODEHASH:
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case Instruction::RETURNDATASIZE:
case Instruction::SLOAD:
case Instruction::PC:
case Instruction::MSIZE:
case Instruction::GAS:
return false;
default:
return true;
}
return true;
}
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bool SemanticInformation::canBeRemoved(Instruction _instruction)
{
// These are not really functional.
assertThrow(!isDupInstruction(_instruction) && !isSwapInstruction(_instruction), AssemblyException, "");
return !instructionInfo(_instruction).sideEffects;
}
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bool SemanticInformation::canBeRemovedIfNoMSize(Instruction _instruction)
{
if (_instruction == Instruction::KECCAK256 || _instruction == Instruction::MLOAD)
return true;
else
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return canBeRemoved(_instruction);
}
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SemanticInformation::Effect SemanticInformation::memory(Instruction _instruction)
{
switch (_instruction)
{
case Instruction::CALLDATACOPY:
case Instruction::CODECOPY:
case Instruction::EXTCODECOPY:
case Instruction::RETURNDATACOPY:
case Instruction::MSTORE:
case Instruction::MSTORE8:
case Instruction::CALL:
case Instruction::CALLCODE:
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case Instruction::DELEGATECALL:
case Instruction::STATICCALL:
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return SemanticInformation::Write;
case Instruction::CREATE:
case Instruction::CREATE2:
case Instruction::KECCAK256:
case Instruction::MLOAD:
case Instruction::MSIZE:
case Instruction::RETURN:
case Instruction::REVERT:
case Instruction::LOG0:
case Instruction::LOG1:
case Instruction::LOG2:
case Instruction::LOG3:
case Instruction::LOG4:
return SemanticInformation::Read;
default:
return SemanticInformation::None;
}
}
bool SemanticInformation::movableApartFromEffects(Instruction _instruction)
{
switch (_instruction)
{
case Instruction::EXTCODEHASH:
case Instruction::EXTCODESIZE:
case Instruction::RETURNDATASIZE:
case Instruction::BALANCE:
case Instruction::SELFBALANCE:
case Instruction::SLOAD:
case Instruction::KECCAK256:
case Instruction::MLOAD:
return true;
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default:
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return movable(_instruction);
}
}
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SemanticInformation::Effect SemanticInformation::storage(Instruction _instruction)
{
switch (_instruction)
{
case Instruction::CALL:
case Instruction::CALLCODE:
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case Instruction::DELEGATECALL:
case Instruction::CREATE:
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case Instruction::CREATE2:
case Instruction::SSTORE:
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return SemanticInformation::Write;
case Instruction::SLOAD:
case Instruction::STATICCALL:
return SemanticInformation::Read;
default:
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return SemanticInformation::None;
}
}
SemanticInformation::Effect SemanticInformation::otherState(Instruction _instruction)
{
switch (_instruction)
{
case Instruction::CALL:
case Instruction::CALLCODE:
case Instruction::DELEGATECALL:
case Instruction::CREATE:
case Instruction::CREATE2:
case Instruction::SELFDESTRUCT:
case Instruction::STATICCALL: // because it can affect returndatasize
// Strictly speaking, log0, .., log4 writes to the state, but the EVM cannot read it, so they
// are just marked as having 'other side effects.'
return SemanticInformation::Write;
case Instruction::EXTCODESIZE:
case Instruction::EXTCODEHASH:
case Instruction::RETURNDATASIZE:
case Instruction::BALANCE:
case Instruction::SELFBALANCE:
case Instruction::RETURNDATACOPY:
case Instruction::EXTCODECOPY:
// PC and GAS are specifically excluded here. Instructions such as CALLER, CALLVALUE,
// ADDRESS are excluded because they cannot change during execution.
return SemanticInformation::Read;
default:
return SemanticInformation::None;
}
}
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bool SemanticInformation::invalidInPureFunctions(Instruction _instruction)
{
switch (_instruction)
{
case Instruction::ADDRESS:
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case Instruction::SELFBALANCE:
case Instruction::BALANCE:
case Instruction::ORIGIN:
case Instruction::CALLER:
case Instruction::CALLVALUE:
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case Instruction::CHAINID:
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case Instruction::BASEFEE:
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case Instruction::GAS:
case Instruction::GASPRICE:
case Instruction::EXTCODESIZE:
case Instruction::EXTCODECOPY:
case Instruction::EXTCODEHASH:
case Instruction::BLOCKHASH:
case Instruction::COINBASE:
case Instruction::TIMESTAMP:
case Instruction::NUMBER:
case Instruction::DIFFICULTY:
case Instruction::GASLIMIT:
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case Instruction::STATICCALL:
case Instruction::SLOAD:
return true;
default:
break;
}
return invalidInViewFunctions(_instruction);
}
bool SemanticInformation::invalidInViewFunctions(Instruction _instruction)
{
switch (_instruction)
{
case Instruction::SSTORE:
case Instruction::JUMP:
case Instruction::JUMPI:
case Instruction::LOG0:
case Instruction::LOG1:
case Instruction::LOG2:
case Instruction::LOG3:
case Instruction::LOG4:
case Instruction::CREATE:
case Instruction::CALL:
case Instruction::CALLCODE:
case Instruction::DELEGATECALL:
case Instruction::CREATE2:
case Instruction::SELFDESTRUCT:
return true;
default:
break;
}
return false;
}