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
|
/*
This file is part of cpp-ethereum.
cpp-ethereum 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.
cpp-ethereum 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 cpp-ethereum. If not, see <http://www.gnu.org/licenses/>.
*/
/** @file ConstantOptimiser.cpp
* @author Christian <c@ethdev.com>
* @date 2015
*/
#pragma once
#include <vector>
#include <libdevcore/CommonData.h>
#include <libdevcore/CommonIO.h>
#include <libethcore/ChainOperationParams.h>
namespace dev
{
namespace eth
{
class AssemblyItem;
using AssemblyItems = std::vector<AssemblyItem>;
class Assembly;
// TODO: FIXME: HOMESTEAD: XXX: @chfast populate m_schedule from an ExtVMFace instance via ExtVMFace::evmSchedule.
/**
* Abstract base class for one way to change how constants are represented in the code.
*/
class ConstantOptimisationMethod
{
public:
/// Tries to optimised how constants are represented in the source code and modifies
/// @a _assembly and its @a _items.
/// @returns zero if no optimisations could be performed.
static unsigned optimiseConstants(
bool _isCreation,
size_t _runs,
Assembly& _assembly,
AssemblyItems& _items
);
struct Params
{
bool isCreation; ///< Whether this is called during contract creation or runtime.
size_t runs; ///< Estimated number of calls per opcode oven the lifetime of the contract.
size_t multiplicity; ///< Number of times the constant appears in the code.
};
explicit ConstantOptimisationMethod(Params const& _params, u256 const& _value):
m_params(_params), m_value(_value) {}
virtual bigint gasNeeded() = 0;
virtual void execute(Assembly& _assembly, AssemblyItems& _items) = 0;
protected:
size_t dataSize() const { return std::max<size_t>(1, dev::bytesRequired(m_value)); }
/// @returns the run gas for the given items ignoring special gas costs
static bigint simpleRunGas(AssemblyItems const& _items);
/// @returns the gas needed to store the given data literally
bigint dataGas(bytes const& _data) const;
/// @returns the gas needed to store the value literally
bigint dataGas() const { return dataGas(toCompactBigEndian(m_value, 1)); }
static size_t bytesRequired(AssemblyItems const& _items);
/// @returns the combined estimated gas usage taking @a m_params into account.
bigint combineGas(
bigint const& _runGas,
bigint const& _repeatedDataGas,
bigint const& _uniqueDataGas
)
{
// _runGas is not multiplied by _multiplicity because the runs are "per opcode"
return m_params.runs * _runGas + m_params.multiplicity * _repeatedDataGas + _uniqueDataGas;
}
/// Replaces the constant by the code given in @a _replacement.
void replaceConstants(AssemblyItems& _items, AssemblyItems const& _replacement) const;
Params m_params;
u256 const& m_value;
EVMSchedule m_schedule;
};
/**
* Optimisation method that pushes the constant to the stack literally. This is the default method,
* i.e. executing it does not alter the Assembly.
*/
class LiteralMethod: public ConstantOptimisationMethod
{
public:
explicit LiteralMethod(Params const& _params, u256 const& _value):
ConstantOptimisationMethod(_params, _value) {}
virtual bigint gasNeeded() override;
virtual void execute(Assembly&, AssemblyItems&) override {}
EVMSchedule m_schedule;
};
/**
* Method that stores the data in the .data section of the code and copies it to the stack.
*/
class CodeCopyMethod: public ConstantOptimisationMethod
{
public:
explicit CodeCopyMethod(Params const& _params, u256 const& _value);
virtual bigint gasNeeded() override;
virtual void execute(Assembly& _assembly, AssemblyItems& _items) override;
protected:
AssemblyItems m_copyRoutine;
EVMSchedule m_schedule;
};
/**
* Method that tries to compute the constant.
*/
class ComputeMethod: public ConstantOptimisationMethod
{
public:
explicit ComputeMethod(Params const& _params, u256 const& _value):
ConstantOptimisationMethod(_params, _value)
{
m_routine = findRepresentation(m_value);
}
virtual bigint gasNeeded() override { return gasNeeded(m_routine); }
virtual void execute(Assembly&, AssemblyItems& _items) override
{
replaceConstants(_items, m_routine);
}
protected:
/// Tries to recursively find a way to compute @a _value.
AssemblyItems findRepresentation(u256 const& _value);
bigint gasNeeded(AssemblyItems const& _routine);
AssemblyItems m_routine;
EVMSchedule m_schedule;
};
}
}
|
