mirror of
https://github.com/ethereum/solidity
synced 2023-10-03 13:03:40 +00:00
76 lines
2.6 KiB
C++
76 lines
2.6 KiB
C++
/*
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This file is part of solidity.
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solidity is free software: you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation, either version 3 of the License, or
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(at your option) any later version.
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solidity is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with solidity. If not, see <http://www.gnu.org/licenses/>.
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*/
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// SPDX-License-Identifier: GPL-3.0
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/**
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* Optimiser component that uses the simplification rules to simplify expressions.
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*/
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#include <libyul/optimiser/ExpressionSimplifier.h>
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#include <libyul/optimiser/SimplificationRules.h>
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#include <libyul/optimiser/OptimiserStep.h>
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#include <libyul/optimiser/OptimizerUtilities.h>
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#include <libyul/AST.h>
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#include <libyul/Utilities.h>
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#include <libevmasm/SemanticInformation.h>
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using namespace solidity;
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using namespace solidity::yul;
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void ExpressionSimplifier::run(OptimiserStepContext& _context, Block& _ast)
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{
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ExpressionSimplifier{_context.dialect}(_ast);
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}
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void ExpressionSimplifier::visit(Expression& _expression)
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{
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ASTModifier::visit(_expression);
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while (auto const* match = SimplificationRules::findFirstMatch(
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_expression,
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m_dialect,
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[this](YulString _var) { return variableValue(_var); }
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))
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_expression = match->action().toExpression(debugDataOf(_expression), evmVersionFromDialect(m_dialect));
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if (auto* functionCall = std::get_if<FunctionCall>(&_expression))
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if (std::optional<evmasm::Instruction> instruction = toEVMInstruction(m_dialect, functionCall->functionName.name))
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for (auto op: evmasm::SemanticInformation::readWriteOperations(*instruction))
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if (op.startParameter && op.lengthParameter)
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{
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Expression& startArgument = functionCall->arguments.at(*op.startParameter);
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Expression const& lengthArgument = functionCall->arguments.at(*op.lengthParameter);
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if (
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knownToBeZero(lengthArgument) &&
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!knownToBeZero(startArgument) &&
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!std::holds_alternative<FunctionCall>(startArgument)
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)
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startArgument = Literal{debugDataOf(startArgument), LiteralKind::Number, "0"_yulstring, {}};
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}
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}
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bool ExpressionSimplifier::knownToBeZero(Expression const& _expression) const
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{
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if (auto const* literal = std::get_if<Literal>(&_expression))
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return valueOfLiteral(*literal) == 0;
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else if (auto const* identifier = std::get_if<Identifier>(&_expression))
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return valueOfIdentifier(identifier->name) == 0;
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else
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return false;
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}
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