solidity/libyul/optimiser/Semantics.cpp

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/*
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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/>.
*/
/**
* Specific AST walkers that collect semantical facts.
*/
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#include <libyul/optimiser/Semantics.h>
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#include <libyul/Exceptions.h>
#include <libyul/AsmData.h>
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#include <libyul/Dialect.h>
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#include <libyul/backends/evm/EVMDialect.h>
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#include <libevmasm/SemanticInformation.h>
#include <libsolutil/CommonData.h>
#include <libsolutil/Algorithms.h>
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using namespace std;
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using namespace solidity;
using namespace solidity::yul;
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SideEffectsCollector::SideEffectsCollector(
Dialect const& _dialect,
Expression const& _expression,
map<YulString, SideEffects> const* _functionSideEffects
):
SideEffectsCollector(_dialect, _functionSideEffects)
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{
visit(_expression);
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}
SideEffectsCollector::SideEffectsCollector(Dialect const& _dialect, Statement const& _statement):
SideEffectsCollector(_dialect)
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{
visit(_statement);
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}
SideEffectsCollector::SideEffectsCollector(
Dialect const& _dialect,
Block const& _ast,
map<YulString, SideEffects> const* _functionSideEffects
):
SideEffectsCollector(_dialect, _functionSideEffects)
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{
operator()(_ast);
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}
void SideEffectsCollector::operator()(FunctionCall const& _functionCall)
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{
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();
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}
bool MSizeFinder::containsMSize(Dialect const& _dialect, Block const& _ast)
{
MSizeFinder finder(_dialect);
finder(_ast);
return finder.m_msizeFound;
}
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;
}
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map<YulString, SideEffects> SideEffectsPropagator::sideEffects(
Dialect const& _dialect,
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CallGraph const& _directCallGraph
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)
{
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// 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".
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map<YulString, SideEffects> ret;
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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.
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auto search = [&](YulString const& _functionName, util::CycleDetector<YulString>& _cycleDetector, size_t) {
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for (auto const& callee: _directCallGraph.functionCalls.at(_functionName))
if (!_dialect.builtin(callee))
if (_cycleDetector.run(callee))
return;
};
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if (util::CycleDetector<YulString>(search).run(call.first))
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{
ret[call.first].movable = false;
ret[call.first].sideEffectFree = false;
ret[call.first].sideEffectFreeIfNoMSize = false;
}
}
for (auto const& call: _directCallGraph.functionCalls)
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{
YulString funName = call.first;
SideEffects sideEffects;
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util::BreadthFirstSearch<YulString>{call.second, {funName}}.run(
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[&](YulString _function, auto&& _addChild) {
if (sideEffects == SideEffects::worst())
return;
if (BuiltinFunction const* f = _dialect.builtin(_function))
sideEffects += f->sideEffects;
else
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{
if (ret.count(_function))
sideEffects += ret[_function];
for (YulString callee: _directCallGraph.functionCalls.at(_function))
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_addChild(callee);
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}
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}
);
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ret[funName] += sideEffects;
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}
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);
}
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void MovableChecker::visit(Statement const&)
{
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assertThrow(false, OptimizerException, "Movability for statement requested.");
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}
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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, numeric_limits<size_t>::max()};
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}
TerminationFinder::ControlFlow TerminationFinder::controlFlowKind(Statement const& _statement)
{
if (
holds_alternative<ExpressionStatement>(_statement) &&
isTerminatingBuiltin(std::get<ExpressionStatement>(_statement))
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)
return ControlFlow::Terminate;
else if (holds_alternative<Break>(_statement))
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return ControlFlow::Break;
else if (holds_alternative<Continue>(_statement))
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return ControlFlow::Continue;
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else if (holds_alternative<Leave>(_statement))
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return ControlFlow::Leave;
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else
return ControlFlow::FlowOut;
}
bool TerminationFinder::isTerminatingBuiltin(ExpressionStatement const& _exprStmnt)
{
if (holds_alternative<FunctionCall>(_exprStmnt.expression))
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if (auto const* dialect = dynamic_cast<EVMDialect const*>(&m_dialect))
if (auto const* builtin = dialect->builtin(std::get<FunctionCall>(_exprStmnt.expression).functionName.name))
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if (builtin->instruction)
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return evmasm::SemanticInformation::terminatesControlFlow(*builtin->instruction);
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return false;
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}