mirror of
https://github.com/ethereum/solidity
synced 2023-10-03 13:03:40 +00:00
127 lines
4.5 KiB
C++
127 lines
4.5 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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* @file ExpressionClasses.h
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* @author Christian <c@ethdev.com>
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* @date 2015
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* Container for equivalence classes of expressions for use in common subexpression elimination.
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*/
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#pragma once
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#include <libdevcore/Common.h>
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#include <libevmasm/AssemblyItem.h>
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#include <vector>
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#include <map>
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#include <memory>
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#include <set>
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namespace dev
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{
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namespace eth
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{
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class Pattern;
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struct ExpressionTemplate;
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/**
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* Collection of classes of equivalent expressions that can also determine the class of an expression.
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* Identifiers are contiguously assigned to new classes starting from zero.
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*/
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class ExpressionClasses
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{
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public:
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using Id = unsigned;
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using Ids = std::vector<Id>;
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struct Expression
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{
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Id id;
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AssemblyItem const* item = nullptr;
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Ids arguments;
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/// Storage modification sequence, only used for storage and memory operations.
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unsigned sequenceNumber = 0;
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/// Behaves as if this was a tuple of (item->type(), item->data(), arguments, sequenceNumber).
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bool operator<(Expression const& _other) const;
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};
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/// Retrieves the id of the expression equivalence class resulting from the given item applied to the
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/// given classes, might also create a new one.
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/// @param _copyItem if true, copies the assembly item to an internal storage instead of just
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/// keeping a pointer.
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/// The @a _sequenceNumber indicates the current storage or memory access sequence.
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Id find(
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AssemblyItem const& _item,
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Ids const& _arguments = {},
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bool _copyItem = true,
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unsigned _sequenceNumber = 0
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);
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/// @returns the canonical representative of an expression class.
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Expression const& representative(Id _id) const { return m_representatives.at(_id); }
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/// @returns the number of classes.
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Id size() const { return m_representatives.size(); }
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/// Forces the given @a _item with @a _arguments to the class @a _id. This can be used to
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/// add prior knowledge e.g. about CALLDATA, but has to be used with caution. Will not work as
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/// expected if @a _item applied to @a _arguments already exists.
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void forceEqual(Id _id, AssemblyItem const& _item, Ids const& _arguments, bool _copyItem = true);
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/// @returns the id of a new class which is different to all other classes.
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Id newClass(SourceLocation const& _location);
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/// @returns true if the values of the given classes are known to be different (on every input).
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/// @note that this function might still return false for some different inputs.
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bool knownToBeDifferent(Id _a, Id _b);
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/// Similar to @a knownToBeDifferent but require that abs(_a - b) >= 32.
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bool knownToBeDifferentBy32(Id _a, Id _b);
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/// @returns true if the value of the given class is known to be zero.
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/// @note that this is not the negation of knownNonZero
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bool knownZero(Id _c);
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/// @returns true if the value of the given class is known to be nonzero.
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/// @note that this is not the negation of knownZero
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bool knownNonZero(Id _c);
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/// @returns a pointer to the value if the given class is known to be a constant,
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/// and a nullptr otherwise.
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u256 const* knownConstant(Id _c);
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/// Stores a copy of the given AssemblyItem and returns a pointer to the copy that is valid for
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/// the lifetime of the ExpressionClasses object.
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AssemblyItem const* storeItem(AssemblyItem const& _item);
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std::string fullDAGToString(Id _id) const;
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private:
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/// Tries to simplify the given expression.
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/// @returns its class if it possible or Id(-1) otherwise.
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Id tryToSimplify(Expression const& _expr);
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/// Rebuilds an expression from a (matched) pattern.
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Id rebuildExpression(ExpressionTemplate const& _template);
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std::vector<std::pair<Pattern, std::function<Pattern()>>> createRules() const;
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/// Expression equivalence class representatives - we only store one item of an equivalence.
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std::vector<Expression> m_representatives;
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/// All expression ever encountered.
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std::set<Expression> m_expressions;
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std::vector<std::shared_ptr<AssemblyItem>> m_spareAssemblyItems;
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};
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}
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}
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