solidity/libyul/optimiser/Semantics.cpp
2019-12-03 21:38:20 +01:00

230 lines
6.7 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/>.
*/
/**
* Specific AST walkers that collect semantical facts.
*/
#include <libyul/optimiser/Semantics.h>
#include <libyul/Exceptions.h>
#include <libyul/AsmData.h>
#include <libyul/Dialect.h>
#include <libyul/backends/evm/EVMDialect.h>
#include <libevmasm/SemanticInformation.h>
#include <libdevcore/CommonData.h>
#include <libdevcore/Algorithms.h>
using namespace std;
using namespace dev;
using namespace yul;
SideEffectsCollector::SideEffectsCollector(
Dialect const& _dialect,
Expression const& _expression,
map<YulString, SideEffects> const* _functionSideEffects
):
SideEffectsCollector(_dialect, _functionSideEffects)
{
visit(_expression);
}
SideEffectsCollector::SideEffectsCollector(Dialect const& _dialect, Statement const& _statement):
SideEffectsCollector(_dialect)
{
visit(_statement);
}
SideEffectsCollector::SideEffectsCollector(
Dialect const& _dialect,
Block const& _ast,
map<YulString, SideEffects> const* _functionSideEffects
):
SideEffectsCollector(_dialect, _functionSideEffects)
{
operator()(_ast);
}
void SideEffectsCollector::operator()(FunctionalInstruction const& _instr)
{
ASTWalker::operator()(_instr);
m_sideEffects += EVMDialect::sideEffectsOfInstruction(_instr.instruction);
}
void SideEffectsCollector::operator()(FunctionCall const& _functionCall)
{
ASTWalker::operator()(_functionCall);
YulString functionName = _functionCall.functionName.name;
if (BuiltinFunction const* f = m_dialect.builtin(functionName))
m_sideEffects += f->sideEffects;
else if (m_functionSideEffects && m_functionSideEffects->count(functionName))
m_sideEffects += m_functionSideEffects->at(functionName);
else
m_sideEffects += SideEffects::worst();
}
bool MSizeFinder::containsMSize(Dialect const& _dialect, Block const& _ast)
{
MSizeFinder finder(_dialect);
finder(_ast);
return finder.m_msizeFound;
}
void MSizeFinder::operator()(FunctionalInstruction const& _instr)
{
ASTWalker::operator()(_instr);
if (_instr.instruction == eth::Instruction::MSIZE)
m_msizeFound = true;
}
void MSizeFinder::operator()(FunctionCall const& _functionCall)
{
ASTWalker::operator()(_functionCall);
if (BuiltinFunction const* f = m_dialect.builtin(_functionCall.functionName.name))
if (f->isMSize)
m_msizeFound = true;
}
map<YulString, SideEffects> SideEffectsPropagator::sideEffects(
Dialect const& _dialect,
CallGraph const& _directCallGraph
)
{
// Any loop currently makes a function non-movable, because
// it could be a non-terminating loop.
// The same is true for any function part of a call cycle.
// In the future, we should refine that, because the property
// is actually a bit different from "not movable".
map<YulString, SideEffects> ret;
for (auto const& function: _directCallGraph.functionsWithLoops)
{
ret[function].movable = false;
ret[function].sideEffectFree = false;
ret[function].sideEffectFreeIfNoMSize = false;
}
// Detect recursive functions.
for (auto const& call: _directCallGraph.functionCalls)
{
// TODO we could shortcut the search as soon as we find a
// function that has as bad side-effects as we can
// ever achieve via recursion.
auto search = [&](YulString const& _functionName, CycleDetector<YulString>& _cycleDetector, size_t) {
for (auto const& callee: _directCallGraph.functionCalls.at(_functionName))
if (!_dialect.builtin(callee))
if (_cycleDetector.run(callee))
return;
};
if (CycleDetector<YulString>(search).run(call.first))
{
ret[call.first].movable = false;
ret[call.first].sideEffectFree = false;
ret[call.first].sideEffectFreeIfNoMSize = false;
}
}
for (auto const& call: _directCallGraph.functionCalls)
{
YulString funName = call.first;
SideEffects sideEffects;
BreadthFirstSearch<YulString>{call.second, {funName}}.run(
[&](YulString _function, auto&& _addChild) {
if (sideEffects == SideEffects::worst())
return;
if (BuiltinFunction const* f = _dialect.builtin(_function))
sideEffects += f->sideEffects;
else
{
if (ret.count(_function))
sideEffects += ret[_function];
for (YulString callee: _directCallGraph.functionCalls.at(_function))
_addChild(callee);
}
}
);
ret[funName] += sideEffects;
}
return ret;
}
MovableChecker::MovableChecker(Dialect const& _dialect, Expression const& _expression):
MovableChecker(_dialect)
{
visit(_expression);
}
void MovableChecker::operator()(Identifier const& _identifier)
{
SideEffectsCollector::operator()(_identifier);
m_variableReferences.emplace(_identifier.name);
}
void MovableChecker::visit(Statement const&)
{
assertThrow(false, OptimizerException, "Movability for statement requested.");
}
pair<TerminationFinder::ControlFlow, size_t> TerminationFinder::firstUnconditionalControlFlowChange(
vector<Statement> const& _statements
)
{
for (size_t i = 0; i < _statements.size(); ++i)
{
ControlFlow controlFlow = controlFlowKind(_statements[i]);
if (controlFlow != ControlFlow::FlowOut)
return {controlFlow, i};
}
return {ControlFlow::FlowOut, size_t(-1)};
}
TerminationFinder::ControlFlow TerminationFinder::controlFlowKind(Statement const& _statement)
{
if (
holds_alternative<ExpressionStatement>(_statement) &&
isTerminatingBuiltin(std::get<ExpressionStatement>(_statement))
)
return ControlFlow::Terminate;
else if (holds_alternative<Break>(_statement))
return ControlFlow::Break;
else if (holds_alternative<Continue>(_statement))
return ControlFlow::Continue;
else
return ControlFlow::FlowOut;
}
bool TerminationFinder::isTerminatingBuiltin(ExpressionStatement const& _exprStmnt)
{
if (holds_alternative<FunctionalInstruction>(_exprStmnt.expression))
return eth::SemanticInformation::terminatesControlFlow(
std::get<FunctionalInstruction>(_exprStmnt.expression).instruction
);
else if (holds_alternative<FunctionCall>(_exprStmnt.expression))
if (auto const* dialect = dynamic_cast<EVMDialect const*>(&m_dialect))
if (auto const* builtin = dialect->builtin(std::get<FunctionCall>(_exprStmnt.expression).functionName.name))
if (builtin->instruction)
return eth::SemanticInformation::terminatesControlFlow(*builtin->instruction);
return false;
}