mirror of
https://github.com/ethereum/solidity
synced 2023-10-03 13:03:40 +00:00
124 lines
4.4 KiB
C++
124 lines
4.4 KiB
C++
/*
|
|
This file is part of solidity.
|
|
|
|
solidity is free software: you can redistribute it and/or modify
|
|
it under the terms of the GNU General Public License as published by
|
|
the Free Software Foundation, either version 3 of the License, or
|
|
(at your option) any later version.
|
|
|
|
solidity is distributed in the hope that it will be useful,
|
|
but WITHOUT ANY WARRANTY; without even the implied warranty of
|
|
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
|
|
GNU General Public License for more details.
|
|
|
|
You should have received a copy of the GNU General Public License
|
|
along with solidity. If not, see <http://www.gnu.org/licenses/>.
|
|
*/
|
|
// SPDX-License-Identifier: GPL-3.0
|
|
/**
|
|
* Optimiser component that removes stores to memory and storage slots that are not used
|
|
* or overwritten later on.
|
|
*/
|
|
|
|
#pragma once
|
|
|
|
#include <libyul/ASTForward.h>
|
|
#include <libyul/optimiser/ASTWalker.h>
|
|
#include <libyul/optimiser/OptimiserStep.h>
|
|
#include <libyul/optimiser/Semantics.h>
|
|
#include <libyul/optimiser/UnusedStoreBase.h>
|
|
#include <libyul/optimiser/KnowledgeBase.h>
|
|
|
|
#include <libevmasm/SemanticInformation.h>
|
|
|
|
#include <map>
|
|
#include <vector>
|
|
|
|
namespace solidity::yul
|
|
{
|
|
struct Dialect;
|
|
struct AssignedValue;
|
|
|
|
/**
|
|
* Optimizer component that removes sstore and memory store statements if conditions are met for their removal.
|
|
* In case of an sstore, if all outgoing code paths revert (due to an explicit revert(), invalid(),
|
|
* or infinite recursion) or lead to another ``sstore`` for which the optimizer can tell that it will overwrite the first store,
|
|
* the statement will be removed.
|
|
*
|
|
* For memory store operations, things are generally simpler, at least in the outermost yul block as all such statements
|
|
* will be removed if they are never read from in any code path. At function analysis level however, the approach is similar
|
|
* to sstore, as we don't know whether the memory location will be read once we leave the function's scope,
|
|
* so the statement will be removed only if all code code paths lead to a memory overwrite.
|
|
*
|
|
* The m_store member of UnusedStoreBase is only used with the empty yul string
|
|
* as key in the first dimension.
|
|
*
|
|
* Best run in SSA form.
|
|
*
|
|
* Prerequisite: Disambiguator, ForLoopInitRewriter.
|
|
*/
|
|
class UnusedStoreEliminator: public UnusedStoreBase
|
|
{
|
|
public:
|
|
static constexpr char const* name{"UnusedStoreEliminator"};
|
|
static void run(OptimiserStepContext& _context, Block& _ast);
|
|
|
|
explicit UnusedStoreEliminator(
|
|
Dialect const& _dialect,
|
|
std::map<YulString, SideEffects> const& _functionSideEffects,
|
|
std::map<YulString, ControlFlowSideEffects> _controlFlowSideEffects,
|
|
std::map<YulString, AssignedValue> const& _ssaValues,
|
|
bool _ignoreMemory
|
|
);
|
|
|
|
using UnusedStoreBase::operator();
|
|
void operator()(FunctionCall const& _functionCall) override;
|
|
void operator()(FunctionDefinition const&) override;
|
|
void operator()(Leave const&) override;
|
|
|
|
using UnusedStoreBase::visit;
|
|
void visit(Statement const& _statement) override;
|
|
|
|
using Location = evmasm::SemanticInformation::Location;
|
|
using Effect = evmasm::SemanticInformation::Effect;
|
|
struct Operation
|
|
{
|
|
Location location;
|
|
Effect effect;
|
|
/// Start of affected area. Unknown if not provided.
|
|
std::optional<YulString> start;
|
|
/// Length of affected area, unknown if not provided.
|
|
/// Unused for storage.
|
|
std::optional<YulString> length;
|
|
};
|
|
|
|
private:
|
|
void shortcutNestedLoop(TrackedStores const&) override
|
|
{
|
|
// We might only need to do this for newly introduced stores in the loop.
|
|
changeUndecidedTo(State::Used);
|
|
}
|
|
void finalizeFunctionDefinition(FunctionDefinition const&) override;
|
|
|
|
std::vector<Operation> operationsFromFunctionCall(FunctionCall const& _functionCall) const;
|
|
void applyOperation(Operation const& _operation);
|
|
bool knownUnrelated(Operation const& _op1, Operation const& _op2) const;
|
|
bool knownCovered(Operation const& _covered, Operation const& _covering) const;
|
|
|
|
void changeUndecidedTo(State _newState, std::optional<Location> _onlyLocation = std::nullopt);
|
|
void scheduleUnusedForDeletion();
|
|
|
|
std::optional<YulString> identifierNameIfSSA(Expression const& _expression) const;
|
|
|
|
bool const m_ignoreMemory;
|
|
std::map<YulString, SideEffects> const& m_functionSideEffects;
|
|
std::map<YulString, ControlFlowSideEffects> m_controlFlowSideEffects;
|
|
std::map<YulString, AssignedValue> const& m_ssaValues;
|
|
|
|
std::map<Statement const*, Operation> m_storeOperations;
|
|
|
|
KnowledgeBase mutable m_knowledgeBase;
|
|
};
|
|
|
|
}
|