/*(
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 .
*/
/**
* Optimisation stage that replaces variables by their most recently assigned expressions.
*/
#include
#include
#include
#include
#include
#include
#include
using namespace solidity;
using namespace solidity::yul;
void Rematerialiser::run(Dialect const& _dialect, Block& _ast, std::set _varsToAlwaysRematerialize, bool _onlySelectedVariables)
{
Rematerialiser{_dialect, _ast, std::move(_varsToAlwaysRematerialize), _onlySelectedVariables}(_ast);
}
Rematerialiser::Rematerialiser(
Dialect const& _dialect,
Block& _ast,
std::set _varsToAlwaysRematerialize,
bool _onlySelectedVariables
):
DataFlowAnalyzer(_dialect, MemoryAndStorage::Ignore),
m_referenceCounts(VariableReferencesCounter::countReferences(_ast)),
m_varsToAlwaysRematerialize(std::move(_varsToAlwaysRematerialize)),
m_onlySelectedVariables(_onlySelectedVariables)
{
}
void Rematerialiser::visit(Expression& _e)
{
if (std::holds_alternative(_e))
{
Identifier& identifier = std::get(_e);
YulString name = identifier.name;
if (AssignedValue const* value = variableValue(name))
{
assertThrow(value->value, OptimizerException, "");
size_t refs = m_referenceCounts[name];
size_t cost = CodeCost::codeCost(m_dialect, *value->value);
if (
(
!m_onlySelectedVariables && (
(refs <= 1 && value->loopDepth == m_loopDepth) ||
cost == 0 ||
(refs <= 5 && cost <= 1 && m_loopDepth == 0)
)
) || m_varsToAlwaysRematerialize.count(name)
)
{
assertThrow(m_referenceCounts[name] > 0, OptimizerException, "");
auto variableReferences = references(name);
if (!variableReferences || ranges::all_of(*variableReferences, [&](auto const& ref) { return inScope(ref); }))
{
// update reference counts
m_referenceCounts[name]--;
for (auto const& ref: VariableReferencesCounter::countReferences(
*value->value
))
m_referenceCounts[ref.first] += ref.second;
_e = (ASTCopier{}).translate(*value->value);
}
}
}
}
DataFlowAnalyzer::visit(_e);
}
void LiteralRematerialiser::visit(Expression& _e)
{
if (std::holds_alternative(_e))
{
Identifier& identifier = std::get(_e);
YulString name = identifier.name;
if (AssignedValue const* value = variableValue(name))
{
assertThrow(value->value, OptimizerException, "");
if (std::holds_alternative(*value->value))
_e = *value->value;
}
}
DataFlowAnalyzer::visit(_e);
}