solidity/libyul/optimiser/ForLoopConditionIntoBody.h
2020-01-07 15:51:50 +01:00

58 lines
1.8 KiB
C++

/*
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/>.
*/
#pragma once
#include <libyul/optimiser/ASTWalker.h>
#include <libyul/Dialect.h>
namespace solidity::yul
{
struct OptimiserStepContext;
/**
* Rewrites ForLoop by moving iteration condition into the ForLoop body.
* For example, `for {} lt(a, b) {} { mstore(1, 2) }` will become
* `for {} 1 {} { if iszero(lt(a, b)) { break } mstore(1, 2) }`
*
* By moving the iteration check part into the ForLoop body, we can apply expression splitter
* to the condition expression.
*
* This rewriter will skip loops that already have literal constant as iteration condition.
*
* Requirements:
* - The Disambiguator must be run upfront.
* - To avoid unnecessary rewrite, it is recommended to run this rewriter after StructuralSimplifier.
* - Only works for dialects with a builtin boolean negation function.
*/
class ForLoopConditionIntoBody: public ASTModifier
{
public:
static constexpr char const* name{"ForLoopConditionIntoBody"};
static void run(OptimiserStepContext&, Block& _ast);
using ASTModifier::operator();
void operator()(ForLoop& _forLoop) override;
private:
ForLoopConditionIntoBody(Dialect const& _dialect): m_dialect(_dialect) {}
Dialect const& m_dialect;
};
}