solidity/libyul/SideEffects.h

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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/>.
*/
#pragma once
#include <set>
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namespace solidity::yul
{
/**
* Side effects of code.
*
* The default-constructed value applies to the "empty code".
*/
struct SideEffects
{
/// If true, expressions in this code can be freely moved and copied without altering the
/// semantics.
/// At statement level, it means that functions containing this code can be
/// called multiple times, their calls can be rearranged and calls can also be
/// deleted without changing the semantics.
/// This means it cannot depend on storage or memory, cannot have any side-effects,
/// but it can depend on state that is constant across an EVM-call.
bool movable = true;
/// If true, the code can be removed without changing the semantics.
bool sideEffectFree = true;
/// If true, the code can be removed without changing the semantics as long as
/// the whole program does not contain the msize instruction.
bool sideEffectFreeIfNoMSize = true;
/// If false, storage is guaranteed to be unchanged by the code under all
/// circumstances.
bool invalidatesStorage = false;
/// If false, memory is guaranteed to be unchanged by the code under all
/// circumstances.
bool invalidatesMemory = false;
/// @returns the worst-case side effects.
static SideEffects worst()
{
return SideEffects{false, false, false, true, true};
}
/// @returns the combined side effects of two pieces of code.
SideEffects operator+(SideEffects const& _other)
{
return SideEffects{
movable && _other.movable,
sideEffectFree && _other.sideEffectFree,
sideEffectFreeIfNoMSize && _other.sideEffectFreeIfNoMSize,
invalidatesStorage || _other.invalidatesStorage,
invalidatesMemory || _other.invalidatesMemory
};
}
/// Adds the side effects of another piece of code to this side effect.
SideEffects& operator+=(SideEffects const& _other)
{
*this = *this + _other;
return *this;
}
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bool operator==(SideEffects const& _other) const
{
return
movable == _other.movable &&
sideEffectFree == _other.sideEffectFree &&
sideEffectFreeIfNoMSize == _other.sideEffectFreeIfNoMSize &&
invalidatesStorage == _other.invalidatesStorage &&
invalidatesMemory == _other.invalidatesMemory;
}
};
}