path: root/libevmasm/SimplificationRules.cpp

/*
    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 <functional>
#include <boost/range/adaptor/reversed.hpp>
#include <boost/noncopyable.hpp>
#include <libevmasm/Assembly.h>
#include <libevmasm/CommonSubexpressionEliminator.h>
#include <libevmasm/SimplificationRules.h>

#include <libevmasm/RuleList.h>

using namespace std;
using namespace dev;
using namespace dev::eth;


SimplificationRule<Pattern> const* Rules::findFirstMatch(
    Expression const& _expr,
    ExpressionClasses const& _classes
)
{
    resetMatchGroups();

    assertThrow(_expr.item, OptimizerException, "");
    for (auto const& rule: m_rules[byte(_expr.item->instruction())])
    {
        if (rule.pattern.matches(_expr, _classes))
            return &rule;
        resetMatchGroups();
    }
    return nullptr;
}

void Rules::addRules(std::vector<SimplificationRule<Pattern>> const& _rules)
{
    for (auto const& r: _rules)
        addRule(r);
}

void Rules::addRule(SimplificationRule<Pattern> const& _rule)
{
    m_rules[byte(_rule.pattern.instruction())].push_back(_rule);
}

Rules::Rules()
{
    // Multiple occurences of one of these inside one rule must match the same equivalence class.
    // Constants.
    Pattern A(Push);
    Pattern B(Push);
    Pattern C(Push);
    // Anything.
    Pattern X;
    Pattern Y;
    A.setMatchGroup(1, m_matchGroups);
    B.setMatchGroup(2, m_matchGroups);
    C.setMatchGroup(3, m_matchGroups);
    X.setMatchGroup(4, m_matchGroups);
    Y.setMatchGroup(5, m_matchGroups);

    addRules(simplificationRuleList(A, B, C, X, Y));
}

Pattern::Pattern(Instruction _instruction, std::vector<Pattern> const& _arguments):
    m_type(Operation),
    m_instruction(_instruction),
    m_arguments(_arguments)
{
}

void Pattern::setMatchGroup(unsigned _group, map<unsigned, Expression const*>& _matchGroups)
{
    m_matchGroup = _group;
    m_matchGroups = &_matchGroups;
}

bool Pattern::matches(Expression const& _expr, ExpressionClasses const& _classes) const
{
    if (!matchesBaseItem(_expr.item))
        return false;
    if (m_matchGroup)
    {
        if (!m_matchGroups->count(m_matchGroup))
            (*m_matchGroups)[m_matchGroup] = &_expr;
        else if ((*m_matchGroups)[m_matchGroup]->id != _expr.id)
            return false;
    }
    assertThrow(m_arguments.size() == 0 || _expr.arguments.size() == m_arguments.size(), OptimizerException, "");
    for (size_t i = 0; i < m_arguments.size(); ++i)
        if (!m_arguments[i].matches(_classes.representative(_expr.arguments[i]), _classes))
            return false;
    return true;
}

AssemblyItem Pattern::toAssemblyItem(SourceLocation const& _location) const
{
    if (m_type == Operation)
        return AssemblyItem(m_instruction, _location);
    else
        return AssemblyItem(m_type, data(), _location);
}

string Pattern::toString() const
{
    stringstream s;
    switch (m_type)
    {
    case Operation:
        s << instructionInfo(m_instruction).name;
        break;
    case Push:
        if (m_data)
            s << "PUSH " << hex << data();
        else
            s << "PUSH ";
        break;
    case UndefinedItem:
        s << "ANY";
        break;
    default:
        if (m_data)
            s << "t=" << dec << m_type << " d=" << hex << data();
        else
            s << "t=" << dec << m_type << " d: nullptr";
        break;
    }
    if (!m_requireDataMatch)
        s << " ~";
    if (m_matchGroup)
        s << "[" << dec << m_matchGroup << "]";
    s << "(";
    for (Pattern const& p: m_arguments)
        s << p.toString() << ", ";
    s << ")";
    return s.str();
}

bool Pattern::matchesBaseItem(AssemblyItem const* _item) const
{
    if (m_type == UndefinedItem)
        return true;
    if (!_item)
        return false;
    if (m_type != _item->type())
        return false;
    else if (m_type == Operation)
        return m_instruction == _item->instruction();
    else if (m_requireDataMatch)
        return data() == _item->data();
    return true;
}

Pattern::Expression const& Pattern::matchGroupValue() const
{
    assertThrow(m_matchGroup > 0, OptimizerException, "");
    assertThrow(!!m_matchGroups, OptimizerException, "");
    assertThrow((*m_matchGroups)[m_matchGroup], OptimizerException, "");
    return *(*m_matchGroups)[m_matchGroup];
}

u256 const& Pattern::data() const
{
    assertThrow(m_data, OptimizerException, "");
    return *m_data;
}

ExpressionTemplate::ExpressionTemplate(Pattern const& _pattern, SourceLocation const& _location)
{
    if (_pattern.matchGroup())
    {
        hasId = true;
        id = _pattern.id();
    }
    else
    {
        hasId = false;
        item = _pattern.toAssemblyItem(_location);
    }
    for (auto const& arg: _pattern.arguments())
        arguments.push_back(ExpressionTemplate(arg, _location));
}

string ExpressionTemplate::toString() const
{
    stringstream s;
    if (hasId)
        s << id;
    else
        s << item;
    s << "(";
    for (auto const& arg: arguments)
        s << arg.toString();
    s << ")";
    return s.str();
}