/*
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 .
*/
// SPDX-License-Identifier: GPL-3.0
/**
* Optimiser component that uses the simplification rules to simplify expressions.
*/
#include
#include
#include
#include
#include
#include
#include
using namespace std;
using namespace solidity;
using namespace solidity::yul;
void ExpressionSimplifier::run(OptimiserStepContext& _context, Block& _ast)
{
ExpressionSimplifier{_context.dialect}(_ast);
}
void ExpressionSimplifier::visit(Expression& _expression)
{
ASTModifier::visit(_expression);
while (auto const* match = SimplificationRules::findFirstMatch(
_expression,
m_dialect,
[this](YulString _var) { return variableValue(_var); }
))
_expression = match->action().toExpression(debugDataOf(_expression), evmVersionFromDialect(m_dialect));
if (auto* functionCall = get_if(&_expression))
if (optional instruction = toEVMInstruction(m_dialect, functionCall->functionName.name))
for (auto op: evmasm::SemanticInformation::readWriteOperations(*instruction))
if (op.startParameter && op.lengthParameter)
{
Expression& startArgument = functionCall->arguments.at(*op.startParameter);
Expression const& lengthArgument = functionCall->arguments.at(*op.lengthParameter);
if (
knownToBeZero(lengthArgument) &&
!knownToBeZero(startArgument) &&
!holds_alternative(startArgument)
)
startArgument = Literal{debugDataOf(startArgument), LiteralKind::Number, "0"_yulstring, {}};
}
}
bool ExpressionSimplifier::knownToBeZero(Expression const& _expression) const
{
if (auto const* literal = get_if(&_expression))
return valueOfLiteral(*literal) == 0;
else if (auto const* identifier = get_if(&_expression))
return valueOfIdentifier(identifier->name) == 0;
else
return false;
}