libyul/optimiser/ExpressionSimplifier.cpp


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

/*
    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/>.
*/
/**
 * Optimiser component that uses the simplification rules to simplify expressions.
 */

#include <libyul/optimiser/ExpressionSimplifier.h>

#include <libyul/optimiser/SimplificationRules.h>
#include <libyul/optimiser/Semantics.h>
#include <libyul/optimiser/SSAValueTracker.h>
#include <libyul/AsmData.h>

#include <libdevcore/CommonData.h>

using namespace std;
using namespace dev;
using namespace dev::yul;
using namespace dev::solidity;


void ExpressionSimplifier::visit(Expression& _expression)
{
    ASTModifier::visit(_expression);
    while (auto match = SimplificationRules::findFirstMatch(_expression, m_ssaValues))
    {
        // Do not apply the rule if it removes non-constant parts of the expression.
        // TODO: The check could actually be less strict than "movable".
        // We only require "Does not cause side-effects".
        // Note: References to variables that are only assigned once are always movable,
        // so if the value of the variable is not movable, the expression that references
        // the variable still is.

        if (match->removesNonConstants && !MovableChecker(_expression).movable())
            return;
        _expression = match->action().toExpression(locationOf(_expression));
    }
}

void ExpressionSimplifier::run(Block& _ast)
{
    SSAValueTracker ssaValues;
    ssaValues(_ast);
    ExpressionSimplifier{ssaValues.values()}(_ast);
}