solidity/libyul/optimiser/StackToMemoryMover.cpp
2021-05-04 16:05:23 +02:00

207 lines
6.2 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/>.
*/
#include <libyul/optimiser/StackToMemoryMover.h>
#include <libyul/optimiser/NameDispenser.h>
#include <libyul/backends/evm/EVMDialect.h>
#include <libyul/AST.h>
#include <libsolutil/CommonData.h>
#include <libsolutil/Visitor.h>
using namespace std;
using namespace solidity;
using namespace solidity::yul;
namespace
{
vector<Statement> generateMemoryStore(
Dialect const& _dialect,
shared_ptr<DebugData const> const& _debugData,
YulString _mpos,
Expression _value
)
{
BuiltinFunction const* memoryStoreFunction = _dialect.memoryStoreFunction(_dialect.defaultType);
yulAssert(memoryStoreFunction, "");
vector<Statement> result;
result.emplace_back(ExpressionStatement{_debugData, FunctionCall{
_debugData,
Identifier{_debugData, memoryStoreFunction->name},
{
Literal{_debugData, LiteralKind::Number, _mpos, {}},
std::move(_value)
}
}});
return result;
}
FunctionCall generateMemoryLoad(Dialect const& _dialect, std::shared_ptr<DebugData const> const& _debugData, YulString _mpos)
{
BuiltinFunction const* memoryLoadFunction = _dialect.memoryLoadFunction(_dialect.defaultType);
yulAssert(memoryLoadFunction, "");
return FunctionCall{
_debugData,
Identifier{_debugData, memoryLoadFunction->name}, {
Literal{
_debugData,
LiteralKind::Number,
_mpos,
{}
}
}
};
}
}
void StackToMemoryMover::run(
OptimiserStepContext& _context,
u256 _reservedMemory,
map<YulString, uint64_t> const& _memorySlots,
uint64_t _numRequiredSlots,
Block& _block
)
{
VariableMemoryOffsetTracker memoryOffsetTracker(_reservedMemory, _memorySlots, _numRequiredSlots);
StackToMemoryMover stackToMemoryMover(_context, memoryOffsetTracker);
stackToMemoryMover(_block);
}
StackToMemoryMover::StackToMemoryMover(
OptimiserStepContext& _context,
VariableMemoryOffsetTracker const& _memoryOffsetTracker
):
m_context(_context),
m_memoryOffsetTracker(_memoryOffsetTracker),
m_nameDispenser(_context.dispenser)
{
auto const* evmDialect = dynamic_cast<EVMDialect const*>(&_context.dialect);
yulAssert(
evmDialect && evmDialect->providesObjectAccess(),
"StackToMemoryMover can only be run on objects using the EVMDialect with object access."
);
}
void StackToMemoryMover::operator()(FunctionDefinition& _functionDefinition)
{
for (TypedName const& param: _functionDefinition.parameters + _functionDefinition.returnVariables)
if (m_memoryOffsetTracker(param.name))
{
// TODO: we cannot handle function parameters yet.
return;
}
ASTModifier::operator()(_functionDefinition);
}
void StackToMemoryMover::operator()(Block& _block)
{
using OptionalStatements = std::optional<vector<Statement>>;
auto rewriteAssignmentOrVariableDeclaration = [&](
auto& _stmt,
auto const& _variables
) -> OptionalStatements {
using StatementType = decay_t<decltype(_stmt)>;
if (_stmt.value)
visit(*_stmt.value);
bool leftHandSideNeedsMoving = util::contains_if(_variables, [&](auto const& var) {
return m_memoryOffsetTracker(var.name);
});
if (!leftHandSideNeedsMoving)
return {};
if (_variables.size() == 1)
{
optional<YulString> offset = m_memoryOffsetTracker(_variables.front().name);
yulAssert(offset, "");
return generateMemoryStore(
m_context.dialect,
_stmt.debugData,
*offset,
_stmt.value ? *std::move(_stmt.value) : Literal{_stmt.debugData, LiteralKind::Number, "0"_yulstring, {}}
);
}
VariableDeclaration tempDecl{_stmt.debugData, {}, std::move(_stmt.value)};
vector<Statement> memoryAssignments;
vector<Statement> variableAssignments;
for (auto& var: _variables)
{
YulString tempVarName = m_nameDispenser.newName(var.name);
tempDecl.variables.emplace_back(TypedName{var.debugData, tempVarName, {}});
if (optional<YulString> offset = m_memoryOffsetTracker(var.name))
memoryAssignments += generateMemoryStore(
m_context.dialect,
_stmt.debugData,
*offset,
Identifier{_stmt.debugData, tempVarName}
);
else
variableAssignments.emplace_back(StatementType{
_stmt.debugData,
{move(var)},
make_unique<Expression>(Identifier{_stmt.debugData, tempVarName})
});
}
std::vector<Statement> result;
result.emplace_back(std::move(tempDecl));
std::reverse(memoryAssignments.begin(), memoryAssignments.end());
result += std::move(memoryAssignments);
std::reverse(variableAssignments.begin(), variableAssignments.end());
result += std::move(variableAssignments);
return OptionalStatements{move(result)};
};
util::iterateReplacing(
_block.statements,
[&](Statement& _statement)
{
return std::visit(util::GenericVisitor{
[&](Assignment& _assignment) -> OptionalStatements
{
return rewriteAssignmentOrVariableDeclaration(_assignment, _assignment.variableNames);
},
[&](VariableDeclaration& _varDecl) -> OptionalStatements
{
return rewriteAssignmentOrVariableDeclaration(_varDecl, _varDecl.variables);
},
[&](auto& _stmt) -> OptionalStatements { (*this)(_stmt); return {}; }
}, _statement);
}
);
}
void StackToMemoryMover::visit(Expression& _expression)
{
ASTModifier::visit(_expression);
if (Identifier* identifier = std::get_if<Identifier>(&_expression))
if (optional<YulString> offset = m_memoryOffsetTracker(identifier->name))
_expression = generateMemoryLoad(m_context.dialect, identifier->debugData, *offset);
}
optional<YulString> StackToMemoryMover::VariableMemoryOffsetTracker::operator()(YulString _variable) const
{
if (m_memorySlots.count(_variable))
{
uint64_t slot = m_memorySlots.at(_variable);
yulAssert(slot < m_numRequiredSlots, "");
return YulString{util::toCompactHexWithPrefix(m_reservedMemory + 32 * (m_numRequiredSlots - slot - 1))};
}
else
return std::nullopt;
}