mirror of
https://github.com/ethereum/solidity
synced 2023-10-03 13:03:40 +00:00
92 lines
3.1 KiB
C++
92 lines
3.1 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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/**
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* Class that can answer questions about values of variables and their relations.
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*/
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#include <libyul/optimiser/KnowledgeBase.h>
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#include <libyul/AsmData.h>
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#include <libyul/Utilities.h>
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#include <libyul/optimiser/SimplificationRules.h>
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#include <libyul/optimiser/Semantics.h>
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#include <libdevcore/CommonData.h>
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#include <variant>
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using namespace std;
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using namespace yul;
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using namespace dev;
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bool KnowledgeBase::knownToBeDifferent(YulString _a, YulString _b)
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{
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// Try to use the simplification rules together with the
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// current values to turn `sub(_a, _b)` into a nonzero constant.
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// If that fails, try `eq(_a, _b)`.
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Expression expr1 = simplify(FunctionCall{{}, {{}, "sub"_yulstring}, make_vector<Expression>(Identifier{{}, _a}, Identifier{{}, _b})});
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if (holds_alternative<Literal>(expr1))
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return valueOfLiteral(std::get<Literal>(expr1)) != 0;
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Expression expr2 = simplify(FunctionCall{{}, {{}, "eq"_yulstring}, make_vector<Expression>(Identifier{{}, _a}, Identifier{{}, _b})});
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if (holds_alternative<Literal>(expr2))
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return valueOfLiteral(std::get<Literal>(expr2)) == 0;
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return false;
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}
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bool KnowledgeBase::knownToBeDifferentByAtLeast32(YulString _a, YulString _b)
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{
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// Try to use the simplification rules together with the
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// current values to turn `sub(_a, _b)` into a constant whose absolute value is at least 32.
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Expression expr1 = simplify(FunctionCall{{}, {{}, "sub"_yulstring}, make_vector<Expression>(Identifier{{}, _a}, Identifier{{}, _b})});
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if (holds_alternative<Literal>(expr1))
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{
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u256 val = valueOfLiteral(std::get<Literal>(expr1));
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return val >= 32 && val <= u256(0) - 32;
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}
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return false;
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}
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Expression KnowledgeBase::simplify(Expression _expression)
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{
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bool startedRecursion = (m_recursionCounter == 0);
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dev::ScopeGuard{[&] { if (startedRecursion) m_recursionCounter = 0; }};
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if (startedRecursion)
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m_recursionCounter = 100;
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else if (m_recursionCounter == 1)
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return _expression;
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else
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--m_recursionCounter;
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if (holds_alternative<FunctionCall>(_expression))
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for (Expression& arg: std::get<FunctionCall>(_expression).arguments)
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arg = simplify(arg);
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else if (holds_alternative<FunctionalInstruction>(_expression))
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for (Expression& arg: std::get<FunctionalInstruction>(_expression).arguments)
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arg = simplify(arg);
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if (auto match = SimplificationRules::findFirstMatch(_expression, m_dialect, m_variableValues))
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return simplify(match->action().toExpression(locationOf(_expression)));
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return _expression;
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}
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