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unused store

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This commit is contained in:
chriseth 2022-11-28 13:28:21 +01:00
parent ddbcea047b
commit b09a8c62bb
2 changed files with 43 additions and 55 deletions
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79
libyul/optimiser/UnusedStoreEliminator.cpp
View File

@ -50,7 +50,7 @@ static string const one{"@ 1"};
static string const thirtyTwo{"@ 32"};
void UnusedStoreEliminator::run(OptimiserStepContext& /*_context*/, Block& /*_ast*/)
void UnusedStoreEliminator::run(OptimiserStepContext& _context, Block& _ast)
{
map<YulString, SideEffects> functionSideEffects = SideEffectsPropagator::sideEffects(
_context.dialect,
@ -87,9 +87,8 @@ void UnusedStoreEliminator::run(OptimiserStepContext& /*_context*/, Block& /*_as
else
rse.markActiveAsUsed(Location::Memory);
rse.markActiveAsUsed(Location::Storage);
rse.scheduleUnusedForDeletion();
StatementRemover remover(rse.m_pendingRemovals);
StatementRemover remover{rse.m_allStores - rse.m_usedStores};
remover(_ast);
}
@ -192,9 +191,9 @@ void UnusedStoreEliminator::visit(Statement const& _statement)
vector<Operation> operations = operationsFromFunctionCall(*funCall);
yulAssert(operations.size() == 1, "");
if (operations.front().location == Location::Storage)
m_activeStores["s"_yulstring].insert(&_statement);
activeStorageStores().insert(&_statement);
else
m_activeStores["m"_yulstring].insert(&_statement);
activeMemoryStores().insert(&_statement);
m_storeOperations[&_statement] = std::move(operations.front());
}
}
@ -202,7 +201,6 @@ void UnusedStoreEliminator::visit(Statement const& _statement)
void UnusedStoreEliminator::finalizeFunctionDefinition(FunctionDefinition const&)
{
markActiveAsUsed();
scheduleUnusedForDeletion();
}
vector<UnusedStoreEliminator::Operation> UnusedStoreEliminator::operationsFromFunctionCall(
@ -257,31 +255,27 @@ vector<UnusedStoreEliminator::Operation> UnusedStoreEliminator::operationsFromFu
void UnusedStoreEliminator::applyOperation(UnusedStoreEliminator::Operation const& _operation)
{
// TODO only one will be relevant, depending on _operation.location
for (Statement const* statement: m_activeStores["s"_yulstring])
set<Statement const*> toRemove;
set<Statement const*>& active =
_operation.location == Location::Storage ?
activeStorageStores() :
activeMemoryStores();
// TODO this loop could be done more efficiently - removing while iterating.
for (Statement const* statement: active)
{
Operation const& storeOperation = m_storeOperations.at(statement);
if (_operation.effect == Effect::Read && !knownUnrelated(storeOperation, _operation))
// TODO remove from active!
m_usedStores.insert(statement);
else if (_operation.effect == Effect::Write && knownCovered(storeOperation, _operation))
{
// TODO remove from active
// state = State::Unused;
}
}
for (Statement const* statement: m_activeStores["m"_yulstring])
{
Operation const& storeOperation = m_storeOperations.at(statement);
if (_operation.effect == Effect::Read && !knownUnrelated(storeOperation, _operation))
// TODO remove from active!
// This store is read from, mark it as used and remove it from the active set.
m_usedStores.insert(statement);
else if (_operation.effect == Effect::Write && knownCovered(storeOperation, _operation))
{
// TODO remove from active
// state = State::Unused;
toRemove.insert(statement);
}
else if (_operation.effect == Effect::Write && knownCovered(storeOperation, _operation))
// This store is overwritten before being read, remove it from the active set.
toRemove.insert(statement);
}
active -= toRemove;
}
bool UnusedStoreEliminator::knownUnrelated(
@ -403,26 +397,26 @@ bool UnusedStoreEliminator::knownCovered(
}
void UnusedStoreEliminator::markActiveAsUsed(
optional<UnusedStoreEliminator::Location> _onlyLocation)
optional<UnusedStoreEliminator::Location> _onlyLocation
)
{
// TODO it might make sense to use YulString{"m"} and YulString{"s"} for memory and storage.
// BUT: Could be both!
for (Statement const* statement: m_activeStores[YulString{}])
if (_onlyLocation == nullopt || *_onlyLocation == m_storeOperations.at(statement).location)
if (_onlyLocation == nullopt || _onlyLocation == Location::Memory)
for (Statement const* statement: activeMemoryStores())
m_usedStores.insert(statement);
// TODO and remove from active
if (_onlyLocation == nullopt || _onlyLocation == Location::Storage)
for (Statement const* statement: activeStorageStores())
m_usedStores.insert(statement);
clearActive(_onlyLocation);
}
void UnusedStoreEliminator::changeUndecidedTo(
State _newState,
optional<UnusedStoreEliminator::Location> _onlyLocation)
void UnusedStoreEliminator::clearActive(
optional<UnusedStoreEliminator::Location> _onlyLocation
)
{
for (auto& [statement, state]: m_activeStores[YulString{}])
if (
state == State::Undecided &&
(_onlyLocation == nullopt || *_onlyLocation == m_storeOperations.at(statement).location)
)
state = _newState;
if (_onlyLocation == nullopt || _onlyLocation == Location::Memory)
activeMemoryStores() = {};
if (_onlyLocation == nullopt || _onlyLocation == Location::Storage)
activeStorageStores() = {};
}
optional<YulString> UnusedStoreEliminator::identifierNameIfSSA(Expression const& _expression) const
@ -432,10 +426,3 @@ optional<YulString> UnusedStoreEliminator::identifierNameIfSSA(Expression const&
return {identifier->name};
return nullopt;
}
void UnusedStoreEliminator::scheduleUnusedForDeletion()
{
for (auto const& [statement, state]: m_activeStores[YulString{}])
if (state == State::Unused)
m_pendingRemovals.insert(statement);
}

19
libyul/optimiser/UnusedStoreEliminator.h
View File

@ -49,8 +49,7 @@ struct AssignedValue;
* 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.
* The m_store member of UnusedStoreBase uses the key "m" for memory ond "s" for storage stores.
*
* Best run in SSA form.
*
@ -64,12 +63,12 @@ public:
explicit UnusedStoreEliminator(
Dialect const& _dialect,
std::map<YulString, SideEffects> const& ,//_functionSideEffects,
std::map<YulString, ControlFlowSideEffects>,// _controlFlowSideEffects,
std::map<YulString, AssignedValue> const&,// _ssaValues,
bool// _ignoreMemory
std::map<YulString, SideEffects> const& _functionSideEffects,
std::map<YulString, ControlFlowSideEffects> _controlFlowSideEffects,
std::map<YulString, AssignedValue> const& _ssaValues,
bool _ignoreMemory
):
UnusedStoreBase(_dialect)//,
UnusedStoreBase(_dialect),
m_ignoreMemory(_ignoreMemory),
m_functionSideEffects(_functionSideEffects),
m_controlFlowSideEffects(_controlFlowSideEffects),
@ -98,10 +97,13 @@ public:
};
private:
std::set<Statement const*>& activeMemoryStores() { return m_activeStores["m"_yulstring]; }
std::set<Statement const*>& activeStorageStores() { return m_activeStores["m"_yulstring]; }
void shortcutNestedLoop(ActiveStores const&) override
{
// We might only need to do this for newly introduced stores in the loop.
changeUndecidedTo(State::Used);
markActiveAsUsed();
}
void finalizeFunctionDefinition(FunctionDefinition const&) override;
@ -112,7 +114,6 @@ private:
void markActiveAsUsed(std::optional<Location> _onlyLocation = std::nullopt);
void clearActive(std::optional<Location> _onlyLocation = std::nullopt);
void scheduleUnusedForDeletion();
std::optional<YulString> identifierNameIfSSA(Expression const& _expression) const;