solidity/libyul/optimiser/StackToMemoryMover.cpp

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/*
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/AsmData.h>
#include <libsolutil/CommonData.h>
#include <libsolutil/Visitor.h>
using namespace std;
using namespace solidity;
using namespace solidity::yul;
namespace
{
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vector<Statement> generateMemoryStore(
Dialect const& _dialect,
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langutil::SourceLocation const& _loc,
YulString _mpos,
Expression _value
)
{
BuiltinFunction const* memoryStoreFunction = _dialect.memoryStoreFunction(_dialect.defaultType);
yulAssert(memoryStoreFunction, "");
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vector<Statement> result;
result.emplace_back(ExpressionStatement{_loc, FunctionCall{
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_loc,
Identifier{_loc, memoryStoreFunction->name},
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{
Literal{_loc, LiteralKind::Number, _mpos, {}},
std::move(_value)
}
}});
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return result;
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}
FunctionCall generateMemoryLoad(Dialect const& _dialect, langutil::SourceLocation const& _loc, YulString _mpos)
{
BuiltinFunction const* memoryLoadFunction = _dialect.memoryLoadFunction(_dialect.defaultType);
yulAssert(memoryLoadFunction, "");
return FunctionCall{
_loc,
Identifier{_loc, memoryLoadFunction->name}, {
Literal{
_loc,
LiteralKind::Number,
_mpos,
{}
}
}
};
}
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}
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void StackToMemoryMover::run(
OptimiserStepContext& _context,
u256 _reservedMemory,
map<YulString, uint64_t> const& _memorySlots,
uint64_t _numRequiredSlots,
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Block& _block
)
{
VariableMemoryOffsetTracker memoryOffsetTracker(_reservedMemory, _memorySlots, _numRequiredSlots);
StackToMemoryMover stackToMemoryMover(_context, memoryOffsetTracker);
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stackToMemoryMover(_block);
}
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StackToMemoryMover::StackToMemoryMover(
OptimiserStepContext& _context,
VariableMemoryOffsetTracker const& _memoryOffsetTracker
):
m_context(_context),
m_memoryOffsetTracker(_memoryOffsetTracker),
m_nameDispenser(_context.dispenser)
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{
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);
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}
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);
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});
if (!leftHandSideNeedsMoving)
return {};
langutil::SourceLocation loc = _stmt.location;
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if (_variables.size() == 1)
{
optional<YulString> offset = m_memoryOffsetTracker(_variables.front().name);
yulAssert(offset, "");
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return generateMemoryStore(
m_context.dialect,
loc,
*offset,
_stmt.value ? *std::move(_stmt.value) : Literal{loc, LiteralKind::Number, "0"_yulstring, {}}
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);
}
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VariableDeclaration tempDecl{loc, {}, std::move(_stmt.value)};
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vector<Statement> memoryAssignments;
vector<Statement> variableAssignments;
for (auto& var: _variables)
{
YulString tempVarName = m_nameDispenser.newName(var.name);
tempDecl.variables.emplace_back(TypedName{var.location, tempVarName, {}});
if (optional<YulString> offset = m_memoryOffsetTracker(var.name))
memoryAssignments += generateMemoryStore(
m_context.dialect,
loc,
*offset,
Identifier{loc, tempVarName}
);
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else
variableAssignments.emplace_back(StatementType{
loc, {move(var)},
make_unique<Expression>(Identifier{loc, tempVarName})
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});
}
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)};
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};
util::iterateReplacing(
_block.statements,
[&](Statement& _statement)
{
return std::visit(util::GenericVisitor{
[&](Assignment& _assignment) -> OptionalStatements
{
return rewriteAssignmentOrVariableDeclaration(_assignment, _assignment.variableNames);
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},
[&](VariableDeclaration& _varDecl) -> OptionalStatements
{
return rewriteAssignmentOrVariableDeclaration(_varDecl, _varDecl.variables);
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},
[&](auto& _stmt) -> OptionalStatements { (*this)(_stmt); return {}; }
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}, _statement);
}
);
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}
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->location, *offset);
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}
optional<YulString> StackToMemoryMover::VariableMemoryOffsetTracker::operator()(YulString _variable) const
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{
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;
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}