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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/>.
*/
/**
* @file ExpressionClasses.cpp
* @author Christian <c@ethdev.com>
* @date 2015
* Container for equivalence classes of expressions for use in common subexpression elimination.
*/
#include <libevmasm/ExpressionClasses.h>
#include <utility>
#include <tuple>
#include <functional>
#include <boost/range/adaptor/reversed.hpp>
#include <boost/noncopyable.hpp>
#include <libevmasm/Assembly.h>
#include <libevmasm/CommonSubexpressionEliminator.h>
#include <libevmasm/SimplificationRules.h>
using namespace std;
using namespace dev;
using namespace dev::eth;
bool ExpressionClasses::Expression::operator<(ExpressionClasses::Expression const& _other) const
{
assertThrow(!!item && !!_other.item, OptimizerException, "");
auto type = item->type();
auto otherType = _other.item->type();
if (type != otherType)
return type < otherType;
else if (type == Operation)
{
auto instr = item->instruction();
auto otherInstr = _other.item->instruction();
return std::tie(instr, arguments, sequenceNumber) <
std::tie(otherInstr, _other.arguments, _other.sequenceNumber);
}
else
return std::tie(item->data(), arguments, sequenceNumber) <
std::tie(_other.item->data(), _other.arguments, _other.sequenceNumber);
}
ExpressionClasses::Id ExpressionClasses::find(
AssemblyItem const& _item,
Ids const& _arguments,
bool _copyItem,
unsigned _sequenceNumber
)
{
Expression exp;
exp.id = Id(-1);
exp.item = &_item;
exp.arguments = _arguments;
exp.sequenceNumber = _sequenceNumber;
if (SemanticInformation::isCommutativeOperation(_item))
sort(exp.arguments.begin(), exp.arguments.end());
if (SemanticInformation::isDeterministic(_item))
{
auto it = m_expressions.find(exp);
if (it != m_expressions.end())
return it->id;
}
if (_copyItem)
exp.item = storeItem(_item);
ExpressionClasses::Id id = tryToSimplify(exp);
if (id < m_representatives.size())
exp.id = id;
else
{
exp.id = m_representatives.size();
m_representatives.push_back(exp);
}
m_expressions.insert(exp);
return exp.id;
}
void ExpressionClasses::forceEqual(
ExpressionClasses::Id _id,
AssemblyItem const& _item,
ExpressionClasses::Ids const& _arguments,
bool _copyItem
)
{
Expression exp;
exp.id = _id;
exp.item = &_item;
exp.arguments = _arguments;
if (SemanticInformation::isCommutativeOperation(_item))
sort(exp.arguments.begin(), exp.arguments.end());
if (_copyItem)
exp.item = storeItem(_item);
m_expressions.insert(exp);
}
ExpressionClasses::Id ExpressionClasses::newClass(SourceLocation const& _location)
{
Expression exp;
exp.id = m_representatives.size();
exp.item = storeItem(AssemblyItem(UndefinedItem, (u256(1) << 255) + exp.id, _location));
m_representatives.push_back(exp);
m_expressions.insert(exp);
return exp.id;
}
bool ExpressionClasses::knownToBeDifferent(ExpressionClasses::Id _a, ExpressionClasses::Id _b)
{
// Try to simplify "_a - _b" and return true iff the value is a non-zero constant.
return knownNonZero(find(Instruction::SUB, {_a, _b}));
}
bool ExpressionClasses::knownToBeDifferentBy32(ExpressionClasses::Id _a, ExpressionClasses::Id _b)
{
// Try to simplify "_a - _b" and return true iff the value is at least 32 away from zero.
u256 const* v = knownConstant(find(Instruction::SUB, {_a, _b}));
// forbidden interval is ["-31", 31]
return v && *v + 31 > u256(62);
}
bool ExpressionClasses::knownZero(Id _c)
{
return Pattern(u256(0)).matches(representative(_c), *this);
}
bool ExpressionClasses::knownNonZero(Id _c)
{
return Pattern(u256(0)).matches(representative(find(Instruction::ISZERO, {_c})), *this);
}
u256 const* ExpressionClasses::knownConstant(Id _c)
{
map<unsigned, Expression const*> matchGroups;
Pattern constant(Push);
constant.setMatchGroup(1, matchGroups);
if (!constant.matches(representative(_c), *this))
return nullptr;
return &constant.d();
}
AssemblyItem const* ExpressionClasses::storeItem(AssemblyItem const& _item)
{
m_spareAssemblyItems.push_back(make_shared<AssemblyItem>(_item));
return m_spareAssemblyItems.back().get();
}
string ExpressionClasses::fullDAGToString(ExpressionClasses::Id _id) const
{
Expression const& expr = representative(_id);
stringstream str;
str << dec << expr.id << ":";
if (expr.item)
{
str << *expr.item << "(";
for (Id arg: expr.arguments)
str << fullDAGToString(arg) << ",";
str << ")";
}
else
str << " UNIQUE";
return str.str();
}
ExpressionClasses::Id ExpressionClasses::tryToSimplify(Expression const& _expr, bool _secondRun)
{
static Rules rules;
if (
!_expr.item ||
_expr.item->type() != Operation ||
!SemanticInformation::isDeterministic(*_expr.item)
)
return -1;
if (auto match = rules.findFirstMatch(_expr, *this))
{
// Debug info
//cout << "Simplifying " << *_expr.item << "(";
//for (Id arg: _expr.arguments)
// cout << fullDAGToString(arg) << ", ";
//cout << ")" << endl;
//cout << "with rule " << match->first.toString() << endl;
//ExpressionTemplate t(match->second());
//cout << "to " << match->second().toString() << endl;
return rebuildExpression(ExpressionTemplate(match->second(), _expr.item->location()));
}
if (!_secondRun && _expr.arguments.size() == 2 && SemanticInformation::isCommutativeOperation(*_expr.item))
{
Expression expr = _expr;
swap(expr.arguments[0], expr.arguments[1]);
return tryToSimplify(expr, true);
}
return -1;
}
ExpressionClasses::Id ExpressionClasses::rebuildExpression(ExpressionTemplate const& _template)
{
if (_template.hasId)
return _template.id;
Ids arguments;
for (ExpressionTemplate const& t: _template.arguments)
arguments.push_back(rebuildExpression(t));
return find(_template.item, arguments);
}
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