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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/>.
*/
/**
* @author Christian <c@ethdev.com>
* @date 2015
* Gas consumption estimator working alongside the AST.
*/
#include "GasEstimator.h"
#include <map>
#include <functional>
#include <memory>
#include <libdevcore/SHA3.h>
#include <libevmasm/ControlFlowGraph.h>
#include <libevmasm/KnownState.h>
#include <libevmasm/PathGasMeter.h>
#include <libsolidity/ast/AST.h>
#include <libsolidity/ast/ASTVisitor.h>
#include <libsolidity/codegen/CompilerUtils.h>
using namespace std;
using namespace dev;
using namespace dev::eth;
using namespace dev::solidity;
GasEstimator::ASTGasConsumptionSelfAccumulated GasEstimator::structuralEstimation(
AssemblyItems const& _items,
vector<ASTNode const*> const& _ast
) const
{
solAssert(std::count(_ast.begin(), _ast.end(), nullptr) == 0, "");
map<SourceLocation, GasConsumption> particularCosts;
ControlFlowGraph cfg(_items);
for (BasicBlock const& block: cfg.optimisedBlocks())
{
solAssert(!!block.startState, "");
GasMeter meter(block.startState->copy(), m_evmVersion);
auto const end = _items.begin() + block.end;
for (auto iter = _items.begin() + block.begin; iter != end; ++iter)
particularCosts[iter->location()] += meter.estimateMax(*iter);
}
set<ASTNode const*> finestNodes = finestNodesAtLocation(_ast);
ASTGasConsumptionSelfAccumulated gasCosts;
auto onNode = [&](ASTNode const& _node)
{
if (!finestNodes.count(&_node))
return true;
gasCosts[&_node][0] = gasCosts[&_node][1] = particularCosts[_node.location()];
return true;
};
auto onEdge = [&](ASTNode const& _parent, ASTNode const& _child)
{
gasCosts[&_parent][1] += gasCosts[&_child][1];
};
ASTReduce folder(onNode, onEdge);
for (ASTNode const* ast: _ast)
ast->accept(folder);
return gasCosts;
}
map<ASTNode const*, GasMeter::GasConsumption> GasEstimator::breakToStatementLevel(
ASTGasConsumptionSelfAccumulated const& _gasCosts,
vector<ASTNode const*> const& _roots
)
{
solAssert(std::count(_roots.begin(), _roots.end(), nullptr) == 0, "");
// first pass: statementDepth[node] is the distance from the deepend statement to node
// in direction of the tree root (or undefined if not possible)
map<ASTNode const*, int> statementDepth;
auto onNodeFirstPass = [&](ASTNode const& _node)
{
if (dynamic_cast<Statement const*>(&_node))
statementDepth[&_node] = 0;
return true;
};
auto onEdgeFirstPass = [&](ASTNode const& _parent, ASTNode const& _child)
{
if (statementDepth.count(&_child))
statementDepth[&_parent] = max(statementDepth[&_parent], statementDepth[&_child] + 1);
};
ASTReduce firstPass(onNodeFirstPass, onEdgeFirstPass);
for (ASTNode const* node: _roots)
node->accept(firstPass);
// we use the location of a node if
// - its statement depth is 0 or
// - its statement depth is undefined but the parent's statement depth is at least 1
map<ASTNode const*, GasConsumption> gasCosts;
auto onNodeSecondPass = [&](ASTNode const& _node)
{
return statementDepth.count(&_node);
};
auto onEdgeSecondPass = [&](ASTNode const& _parent, ASTNode const& _child)
{
bool useNode = false;
if (statementDepth.count(&_child))
useNode = statementDepth[&_child] == 0;
else
useNode = statementDepth.count(&_parent) && statementDepth.at(&_parent) > 0;
if (useNode)
gasCosts[&_child] = _gasCosts.at(&_child)[1];
};
ASTReduce secondPass(onNodeSecondPass, onEdgeSecondPass);
for (ASTNode const* node: _roots)
node->accept(secondPass);
// gasCosts should only contain non-overlapping locations
return gasCosts;
}
GasEstimator::GasConsumption GasEstimator::functionalEstimation(
AssemblyItems const& _items,
string const& _signature
) const
{
auto state = make_shared<KnownState>();
if (!_signature.empty())
{
ExpressionClasses& classes = state->expressionClasses();
using Id = ExpressionClasses::Id;
using Ids = vector<Id>;
// div(calldataload(0), 1 << 224) equals to hashValue
Id hashValue = classes.find(u256(FixedHash<4>::Arith(FixedHash<4>(dev::keccak256(_signature)))));
Id calldata = classes.find(Instruction::CALLDATALOAD, Ids{classes.find(u256(0))});
classes.forceEqual(hashValue, Instruction::DIV, Ids{
calldata,
classes.find(u256(1) << 224)
});
// lt(calldatasize(), 4) equals to 0 (ignore the shortcut for fallback functions)
classes.forceEqual(
classes.find(u256(0)),
Instruction::LT,
Ids{classes.find(Instruction::CALLDATASIZE), classes.find(u256(4))}
);
}
PathGasMeter meter(_items, m_evmVersion);
return meter.estimateMax(0, state);
}
GasEstimator::GasConsumption GasEstimator::functionalEstimation(
AssemblyItems const& _items,
size_t const& _offset,
FunctionDefinition const& _function
) const
{
auto state = make_shared<KnownState>();
unsigned parametersSize = CompilerUtils::sizeOnStack(_function.parameters());
if (parametersSize > 16)
return GasConsumption::infinite();
// Store an invalid return value on the stack, so that the path estimator breaks upon reaching
// the return jump.
AssemblyItem invalidTag(PushTag, u256(-0x10));
state->feedItem(invalidTag, true);
if (parametersSize > 0)
state->feedItem(swapInstruction(parametersSize));
return PathGasMeter(_items, m_evmVersion).estimateMax(_offset, state);
}
set<ASTNode const*> GasEstimator::finestNodesAtLocation(
vector<ASTNode const*> const& _roots
)
{
map<SourceLocation, ASTNode const*> locations;
set<ASTNode const*> nodes;
SimpleASTVisitor visitor(function<bool(ASTNode const&)>(), [&](ASTNode const& _n)
{
if (!locations.count(_n.location()))
{
locations[_n.location()] = &_n;
nodes.insert(&_n);
}
});
for (ASTNode const* root: _roots)
root->accept(visitor);
return nodes;
}
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