path: root/libevmasm/SemanticInformation.h

/*
    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 SemanticInformation.h
 * @author Christian <c@ethdev.com>
 * @date 2015
 * Helper to provide semantic information about assembly items.
 */

#pragma once

#include <libevmasm/Instruction.h>

namespace dev
{
namespace eth
{

class AssemblyItem;

/**
 * Helper functions to provide context-independent information about assembly items.
 */
struct SemanticInformation
{
    /// @returns true if the given items starts a new block for common subexpression analysis.
    /// @param _msizeImportant if false, consider an operation non-breaking if its only side-effect is that it modifies msize.
    static bool breaksCSEAnalysisBlock(AssemblyItem const& _item, bool _msizeImportant);
    /// @returns true if the item is a two-argument operation whose value does not depend on the
    /// order of its arguments.
    static bool isCommutativeOperation(AssemblyItem const& _item);
    static bool isDupInstruction(AssemblyItem const& _item);
    static bool isSwapInstruction(AssemblyItem const& _item);
    static bool isJumpInstruction(AssemblyItem const& _item);
    static bool altersControlFlow(AssemblyItem const& _item);
    /// @returns false if the value put on the stack by _item depends on anything else than
    /// the information in the current block header, memory, storage or stack.
    static bool isDeterministic(AssemblyItem const& _item);
    /// @returns true if the instruction can be moved or copied (together with its arguments)
    /// without altering the semantics. This means it cannot depend on storage or memory,
    /// cannot have any side-effects, but it can depend on a call-constant state of the blockchain.
    static bool movable(solidity::Instruction _instruction);
    /// @returns true if the given instruction modifies memory.
    static bool invalidatesMemory(solidity::Instruction _instruction);
    /// @returns true if the given instruction modifies storage (even indirectly).
    static bool invalidatesStorage(solidity::Instruction _instruction);
    static bool invalidInPureFunctions(solidity::Instruction _instruction);
    static bool invalidInViewFunctions(solidity::Instruction _instruction);
};

}
}