mirror of
https://github.com/ethereum/solidity
synced 2023-10-03 13:03:40 +00:00
106 lines
3.3 KiB
C++
106 lines
3.3 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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* Optimiser component that uses the simplification rules to simplify expressions.
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*/
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#pragma once
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#include <libyul/AsmDataForward.h>
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#include <libyul/optimiser/DataFlowAnalyzer.h>
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#include <libdevcore/Common.h>
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namespace yul
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{
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struct Dialect;
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struct ValueConstraint
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{
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static ValueConstraint constant(dev::u256 const& _value);
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static ValueConstraint boolean();
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/// @returns a constraint that does not restrict the bits between
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/// (inclusive) _highest and _lowest bit but forces all other
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/// bits to zero.
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static ValueConstraint bitRange(size_t _highest, size_t _lowest);
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/// Fill the minValue and maxValue fields from the minBits and maxBits fields.
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static ValueConstraint valueFromBits(dev::u256 _minBits, dev::u256 _maxBits);
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/// Fill the minBits and maxBits fields from the minValue and maxValue fields.
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static ValueConstraint bitsFromValue(dev::u256 _minValue, dev::u256 _maxValue);
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ValueConstraint operator&(ValueConstraint const& _other);
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ValueConstraint operator|(ValueConstraint const& _other);
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ValueConstraint operator~();
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ValueConstraint operator+(ValueConstraint const& _other);
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ValueConstraint operator-(ValueConstraint const& _other);
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ValueConstraint operator<(ValueConstraint const& _other);
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ValueConstraint operator==(ValueConstraint const& _other);
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ValueConstraint operator<<(ValueConstraint const& _other);
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ValueConstraint operator>>(ValueConstraint const& _other);
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boost::optional<dev::u256> isConstant() const;
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dev::u256 minValue = 0;
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dev::u256 maxValue = dev::u256(-1);
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dev::u256 minBits = 0; ///< For each 1-bit here, the value's bit is also 1
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dev::u256 maxBits = dev::u256(-1); ///< For each 0-bit here, the value's bit is also 0
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};
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/**
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* Performs simplifications that take value and bit constraints
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* of variables and expressions into account.
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*
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* Example:
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*
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* let x := and(callvalue(), 0xff)
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* if lt(x, 0x100) { ... }
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*
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* is reduced to
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*
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* let x := and(callvalue(), 0xff)
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* if 1 { ... }
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*
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* because ``x`` is known to be at most 0xff.
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*
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* Most effective if run on code in SSA form.
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*
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* Prerequisite: Disambiguator.
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*/
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class ValueConstraintBasedSimplifier: public DataFlowAnalyzer
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{
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public:
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using ASTModifier::operator();
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void visit(Expression& _expression) override;
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static void run(Dialect const& _dialect, Block& _ast);
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protected:
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void handleAssignment(std::set<YulString> const& _names, Expression* _value) override;
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void valuesCleared(std::set<YulString> const& _names) override;
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explicit ValueConstraintBasedSimplifier(Dialect const& _dialect): DataFlowAnalyzer(_dialect) {}
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std::map<YulString, ValueConstraint> m_variableConstraints;
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ValueConstraint m_currentConstraint;
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};
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}
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