mirror of
https://github.com/ethereum/solidity
synced 2023-10-03 13:03:40 +00:00
135 lines
3.7 KiB
C++
135 lines
3.7 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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#include <libyul/optimiser/StructuralSimplifier.h>
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#include <libyul/AST.h>
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#include <libyul/Utilities.h>
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#include <libsolutil/CommonData.h>
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#include <libsolutil/Visitor.h>
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using namespace std;
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using namespace solidity;
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using namespace solidity::yul;
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using OptionalStatements = std::optional<vector<Statement>>;
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namespace
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{
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OptionalStatements replaceConstArgSwitch(Switch& _switchStmt, u256 const& _constExprVal)
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{
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Block* matchingCaseBlock = nullptr;
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Case* defaultCase = nullptr;
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for (auto& _case: _switchStmt.cases)
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{
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if (_case.value && valueOfLiteral(*_case.value) == _constExprVal)
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{
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matchingCaseBlock = &_case.body;
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break;
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}
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else if (!_case.value)
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defaultCase = &_case;
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}
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if (!matchingCaseBlock && defaultCase)
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matchingCaseBlock = &defaultCase->body;
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if (matchingCaseBlock)
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return util::make_vector<Statement>(std::move(*matchingCaseBlock));
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else
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return optional<vector<Statement>>{vector<Statement>{}};
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}
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optional<u256> hasLiteralValue(Expression const& _expression)
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{
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if (holds_alternative<Literal>(_expression))
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return valueOfLiteral(std::get<Literal>(_expression));
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else
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return std::optional<u256>();
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}
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bool expressionAlwaysTrue(Expression const& _expression)
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{
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if (std::optional<u256> value = hasLiteralValue(_expression))
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return *value != 0;
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else
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return false;
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}
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bool expressionAlwaysFalse(Expression const& _expression)
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{
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if (std::optional<u256> value = hasLiteralValue(_expression))
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return *value == 0;
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else
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return false;
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}
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}
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void StructuralSimplifier::run(OptimiserStepContext&, Block& _ast)
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{
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StructuralSimplifier{}(_ast);
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}
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void StructuralSimplifier::operator()(Block& _block)
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{
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simplify(_block.statements);
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}
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void StructuralSimplifier::simplify(std::vector<yul::Statement>& _statements)
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{
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// Explicit local variables ifLambda, switchLambda, forLoopLambda are created to avoid MSVC C++17 Debug test crash
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// (Run-Time Check Failure #2 - Stack around the variable '....' was corrupted).
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// As soon as the issue is fixed, this workaround can be removed.
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auto ifLambda = [&](If& _ifStmt) -> OptionalStatements
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{
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if (expressionAlwaysTrue(*_ifStmt.condition))
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return {std::move(_ifStmt.body.statements)};
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else if (expressionAlwaysFalse(*_ifStmt.condition))
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return {vector<Statement>{}};
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return {};
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};
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auto switchLambda = [&](Switch& _switchStmt) -> OptionalStatements
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{
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if (std::optional<u256> const constExprVal = hasLiteralValue(*_switchStmt.expression))
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return replaceConstArgSwitch(_switchStmt, constExprVal.value());
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return {};
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};
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auto forLoopLambda = [&](ForLoop& _forLoop) -> OptionalStatements
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{
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if (expressionAlwaysFalse(*_forLoop.condition))
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return {std::move(_forLoop.pre.statements)};
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return {};
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};
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util::GenericVisitor visitor{util::VisitorFallback<OptionalStatements>{}, ifLambda, switchLambda, forLoopLambda};
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util::iterateReplacing(
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_statements,
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[&](Statement& _stmt) -> OptionalStatements
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{
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OptionalStatements result = std::visit(visitor, _stmt);
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if (result)
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simplify(*result);
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else
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visit(_stmt);
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return result;
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}
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);
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}
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