solidity/libyul/ControlFlowSideEffectsCollector.cpp
2022-08-30 11:12:15 +02:00

286 lines
7.9 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/>.
*/
// SPDX-License-Identifier: GPL-3.0
#include <libyul/ControlFlowSideEffectsCollector.h>
#include <libyul/AST.h>
#include <libyul/Dialect.h>
#include <libyul/FunctionReferenceResolver.h>
#include <libsolutil/Common.h>
#include <libsolutil/CommonData.h>
#include <libsolutil/Algorithms.h>
#include <range/v3/view/map.hpp>
#include <range/v3/view/reverse.hpp>
#include <range/v3/algorithm/find_if.hpp>
using namespace std;
using namespace solidity::yul;
ControlFlowBuilder::ControlFlowBuilder(Block const& _ast)
{
m_currentNode = newNode();
(*this)(_ast);
}
void ControlFlowBuilder::operator()(FunctionCall const& _functionCall)
{
walkVector(_functionCall.arguments | ranges::views::reverse);
newConnectedNode();
m_currentNode->functionCall = &_functionCall;
}
void ControlFlowBuilder::operator()(If const& _if)
{
visit(*_if.condition);
ControlFlowNode* node = m_currentNode;
(*this)(_if.body);
newConnectedNode();
node->successors.emplace_back(m_currentNode);
}
void ControlFlowBuilder::operator()(Switch const& _switch)
{
visit(*_switch.expression);
ControlFlowNode* initialNode = m_currentNode;
ControlFlowNode* finalNode = newNode();
if (_switch.cases.back().value)
initialNode->successors.emplace_back(finalNode);
for (Case const& case_: _switch.cases)
{
m_currentNode = initialNode;
(*this)(case_.body);
newConnectedNode();
m_currentNode->successors.emplace_back(finalNode);
}
m_currentNode = finalNode;
}
void ControlFlowBuilder::operator()(FunctionDefinition const& _function)
{
ScopedSaveAndRestore currentNode(m_currentNode, nullptr);
ScopedSaveAndRestore leave(m_leave, nullptr);
ScopedSaveAndRestore _break(m_break, nullptr);
ScopedSaveAndRestore _continue(m_continue, nullptr);
FunctionFlow flow;
flow.exit = newNode();
m_currentNode = newNode();
flow.entry = m_currentNode;
m_leave = flow.exit;
(*this)(_function.body);
m_currentNode->successors.emplace_back(flow.exit);
m_functionFlows[&_function] = std::move(flow);
m_leave = nullptr;
}
void ControlFlowBuilder::operator()(ForLoop const& _for)
{
ScopedSaveAndRestore scopedBreakNode(m_break, nullptr);
ScopedSaveAndRestore scopedContinueNode(m_continue, nullptr);
(*this)(_for.pre);
ControlFlowNode* breakNode = newNode();
m_break = breakNode;
ControlFlowNode* continueNode = newNode();
m_continue = continueNode;
newConnectedNode();
ControlFlowNode* loopNode = m_currentNode;
visit(*_for.condition);
m_currentNode->successors.emplace_back(m_break);
newConnectedNode();
(*this)(_for.body);
m_currentNode->successors.emplace_back(m_continue);
m_currentNode = continueNode;
(*this)(_for.post);
m_currentNode->successors.emplace_back(loopNode);
m_currentNode = breakNode;
}
void ControlFlowBuilder::operator()(Break const&)
{
yulAssert(m_break);
m_currentNode->successors.emplace_back(m_break);
m_currentNode = newNode();
}
void ControlFlowBuilder::operator()(Continue const&)
{
yulAssert(m_continue);
m_currentNode->successors.emplace_back(m_continue);
m_currentNode = newNode();
}
void ControlFlowBuilder::operator()(Leave const&)
{
yulAssert(m_leave);
m_currentNode->successors.emplace_back(m_leave);
m_currentNode = newNode();
}
void ControlFlowBuilder::newConnectedNode()
{
ControlFlowNode* node = newNode();
m_currentNode->successors.emplace_back(node);
m_currentNode = node;
}
ControlFlowNode* ControlFlowBuilder::newNode()
{
m_nodes.emplace_back(make_shared<ControlFlowNode>());
return m_nodes.back().get();
}
ControlFlowSideEffectsCollector::ControlFlowSideEffectsCollector(
Dialect const& _dialect,
Block const& _ast
):
m_dialect(_dialect),
m_cfgBuilder(_ast),
m_functionReferences(FunctionReferenceResolver{_ast}.references())
{
for (auto&& [function, flow]: m_cfgBuilder.functionFlows())
{
yulAssert(!flow.entry->functionCall);
yulAssert(function);
m_processedNodes[function] = {};
m_pendingNodes[function].push_front(flow.entry);
m_functionSideEffects[function] = {false, false, false};
m_functionCalls[function] = {};
}
// Process functions while we have progress. For now, we are only interested
// in `canContinue`.
bool progress = true;
while (progress)
{
progress = false;
for (FunctionDefinition const* function: m_pendingNodes | ranges::views::keys)
if (processFunction(*function))
progress = true;
}
// No progress anymore: All remaining nodes are calls
// to functions that always recurse.
// If we have not set `canContinue` by now, the function's exit
// is not reachable.
// Now it is sufficient to handle the reachable function calls (`m_functionCalls`),
// we do not have to consider the control-flow graph anymore.
for (auto&& [function, calls]: m_functionCalls)
{
yulAssert(function);
ControlFlowSideEffects& functionSideEffects = m_functionSideEffects[function];
auto _visit = [&, visited = std::set<FunctionDefinition const*>{}](FunctionDefinition const& _function, auto&& _recurse) mutable {
// Worst side-effects already, stop searching.
if (functionSideEffects.canTerminate && functionSideEffects.canRevert)
return;
if (!visited.insert(&_function).second)
return;
for (FunctionCall const* call: m_functionCalls.at(&_function))
{
ControlFlowSideEffects const& calledSideEffects = sideEffects(*call);
if (calledSideEffects.canTerminate)
functionSideEffects.canTerminate = true;
if (calledSideEffects.canRevert)
functionSideEffects.canRevert = true;
if (m_functionReferences.count(call))
_recurse(*m_functionReferences.at(call), _recurse);
}
};
_visit(*function, _visit);
}
}
map<YulString, ControlFlowSideEffects> ControlFlowSideEffectsCollector::functionSideEffectsNamed() const
{
map<YulString, ControlFlowSideEffects> result;
for (auto&& [function, sideEffects]: m_functionSideEffects)
yulAssert(result.insert({function->name, sideEffects}).second);
return result;
}
bool ControlFlowSideEffectsCollector::processFunction(FunctionDefinition const& _function)
{
bool progress = false;
while (ControlFlowNode const* node = nextProcessableNode(_function))
{
if (node == m_cfgBuilder.functionFlows().at(&_function).exit)
{
m_functionSideEffects[&_function].canContinue = true;
return true;
}
for (ControlFlowNode const* s: node->successors)
recordReachabilityAndQueue(_function, s);
progress = true;
}
return progress;
}
ControlFlowNode const* ControlFlowSideEffectsCollector::nextProcessableNode(FunctionDefinition const& _function)
{
std::list<ControlFlowNode const*>& nodes = m_pendingNodes[&_function];
auto it = ranges::find_if(nodes, [this](ControlFlowNode const* _node) {
return !_node->functionCall || sideEffects(*_node->functionCall).canContinue;
});
if (it == nodes.end())
return nullptr;
ControlFlowNode const* node = *it;
nodes.erase(it);
return node;
}
ControlFlowSideEffects const& ControlFlowSideEffectsCollector::sideEffects(FunctionCall const& _call) const
{
if (auto const* builtin = m_dialect.builtin(_call.functionName.name))
return builtin->controlFlowSideEffects;
else
return m_functionSideEffects.at(m_functionReferences.at(&_call));
}
void ControlFlowSideEffectsCollector::recordReachabilityAndQueue(
FunctionDefinition const& _function,
ControlFlowNode const* _node
)
{
if (_node->functionCall)
m_functionCalls[&_function].insert(_node->functionCall);
if (m_processedNodes[&_function].insert(_node).second)
m_pendingNodes.at(&_function).push_front(_node);
}