mirror of
https://github.com/ethereum/solidity
synced 2023-10-03 13:03:40 +00:00
109 lines
3.5 KiB
C++
109 lines
3.5 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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// SPDX-License-Identifier: GPL-3.0
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/**
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* Base class for both UnusedAssignEliminator and UnusedStoreEliminator.
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*/
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#pragma once
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#include <libyul/optimiser/ASTWalker.h>
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#include <libyul/AST.h>
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#include <range/v3/action/remove_if.hpp>
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#include <variant>
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namespace solidity::yul
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{
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struct Dialect;
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/**
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* Base class for both UnusedAssignEliminator and UnusedStoreEliminator.
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*
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* The class tracks the state of abstract "stores" (assignments or mstore/sstore
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* statements) across the control-flow. It is the job of the derived class to create
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* the stores and track references, but the base class adjusts their "used state" at
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* control-flow splits and joins.
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*
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* Prerequisite: Disambiguator, ForLoopInitRewriter.
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*/
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class UnusedStoreBase: public ASTWalker
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{
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public:
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explicit UnusedStoreBase(Dialect const& _dialect): m_dialect(_dialect) {}
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using ASTWalker::operator();
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void operator()(If const& _if) override;
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void operator()(Switch const& _switch) override;
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void operator()(FunctionDefinition const&) override;
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void operator()(ForLoop const&) override;
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void operator()(Break const&) override;
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void operator()(Continue const&) override;
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protected:
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class State
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{
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public:
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enum Value { Unused, Undecided, Used };
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State(Value _value = Undecided): m_value(_value) {}
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inline bool operator==(State _other) const { return m_value == _other.m_value; }
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inline bool operator!=(State _other) const { return !operator==(_other); }
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static inline void join(State& _a, State const& _b)
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{
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// Using "max" works here because of the order of the values in the enum.
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_a.m_value = Value(std::max(int(_a.m_value), int(_b.m_value)));
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}
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private:
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Value m_value = Undecided;
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};
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using TrackedStores = std::map<YulString, std::map<Statement const*, State>>;
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/// This function is called for a loop that is nested too deep to avoid
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/// horrible runtime and should just resolve the situation in a pragmatic
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/// and correct manner.
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virtual void shortcutNestedLoop(TrackedStores const& _beforeLoop) = 0;
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/// This function is called right before the scoped restore of the function definition.
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virtual void finalizeFunctionDefinition(FunctionDefinition const& /*_functionDefinition*/) {}
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/// Joins the assignment mapping of @a _source into @a _target according to the rules laid out
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/// above.
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/// Will destroy @a _source.
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static void merge(TrackedStores& _target, TrackedStores&& _source);
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static void merge(TrackedStores& _target, std::vector<TrackedStores>&& _source);
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Dialect const& m_dialect;
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std::set<Statement const*> m_pendingRemovals;
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TrackedStores m_stores;
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/// Working data for traversing for-loops.
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struct ForLoopInfo
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{
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/// Tracked assignment states for each break statement.
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std::vector<TrackedStores> pendingBreakStmts;
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/// Tracked assignment states for each continue statement.
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std::vector<TrackedStores> pendingContinueStmts;
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};
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ForLoopInfo m_forLoopInfo;
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size_t m_forLoopNestingDepth = 0;
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};
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}
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