1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
|
/*
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>;
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) << (8 * 28))
});
}
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;
}
|
