Gas Optimizations

[code423n4]

Add unchecked to save gas

In Solidity 0.8.4 and above there is a default underflow/overflow checks on unsigned integers. it is possible to avoid this check by using unchecked. If the expression does not cause overflow/underflow, it can be unchecked to save some gas.

Proof of concept

https://github.com/code-423n4/2022-08-rigor/blob/b17b2a11d04289f9e927c71703b42771dd7b86a4/contracts/Community.sol#L794

        require(_lentAndInterest >= _repayAmount, "Community::!Liquid");
        _interest = 0;
        _lentAmount = _lentAndInterest - _repayAmount;


L785    if (_repayAmount > _interest) {
            ...
        } else {
            _interest -= _repayAmount;
        }

https://github.com/code-423n4/2022-08-rigor/blob/b17b2a11d04289f9e927c71703b42771dd7b86a4/contracts/Project.sol#L425

        if (_newCost < _taskCost) {
            // Find the difference between old - new.
            uint256 _withdrawDifference = _taskCost - _newCost;

https://github.com/code-423n4/2022-08-rigor/blob/b17b2a11d04289f9e927c71703b42771dd7b86a4/contracts/Project.sol#L614

        if (_costToAllocate >= _taskCost) {
            // Reduce task cost from _costToAllocate
            _costToAllocate -= _taskCost;

https://github.com/code-423n4/2022-08-rigor/blob/b17b2a11d04289f9e927c71703b42771dd7b86a4/contracts/Project.sol#L661

        if (_costToAllocate >= _taskCost) {
            // Reduce task cost from _costToAllocate
            _costToAllocate -= _taskCost;

> 0 is less efficient than != 0 for unsigned integers

!= 0 costs less gas compared to > 0 for unsigned integers in require statements with the optimizer enabled (6 gas)

Proof of concept

https://github.com/code-423n4/2022-08-rigor/blob/b17b2a11d04289f9e927c71703b42771dd7b86a4/contracts/Project.sol#L195

    require(_cost > 0, "Project::!value>0"); 

Pre-increment(++i) costs less than post-increment(i++)

Pre-increment saves a small amount of gas than postfix increment because it doesnt have to store the previous value. This can be more significant in loops where this operation is done multiple times.

Proof of concept

https://github.com/code-423n4/2022-08-rigor/blob/b17b2a11d04289f9e927c71703b42771dd7b86a4/contracts/HomeFiProxy.sol#L87

    for (uint256 i = 0; i < _length; i++)

https://github.com/code-423n4/2022-08-rigor/blob/b17b2a11d04289f9e927c71703b42771dd7b86a4/contracts/HomeFiProxy.sol#L136

    for (uint256 i = 0; i < _length; i++) 

https://github.com/code-423n4/2022-08-rigor/blob/b17b2a11d04289f9e927c71703b42771dd7b86a4/contracts/Project.sol#L248

        for (uint256 i = 0; i < _length; i++)

https://github.com/code-423n4/2022-08-rigor/blob/b17b2a11d04289f9e927c71703b42771dd7b86a4/contracts/Project.sol#L311

        for (uint256 i = 0; i < _length; i++)

https://github.com/code-423n4/2022-08-rigor/blob/b17b2a11d04289f9e927c71703b42771dd7b86a4/contracts/Project.sol#L322

        for (uint256 i = 0; i < _length; i++)

https://github.com/code-423n4/2022-08-rigor/blob/b17b2a11d04289f9e927c71703b42771dd7b86a4/contracts/Project.sol#L368

        for (uint256 _taskID = 1; _taskID <= _length; _taskID++) 

https://github.com/code-423n4/2022-08-rigor/blob/b17b2a11d04289f9e927c71703b42771dd7b86a4/contracts/Project.sol#L650

        for (++j; j <= taskCount; j++) {

https://github.com/code-423n4/2022-08-rigor/blob/b17b2a11d04289f9e927c71703b42771dd7b86a4/contracts/Project.sol#L710

        for (uint256 _taskID = 1; _taskID <= _length; _taskID++) { 

https://github.com/code-423n4/2022-08-rigor/blob/b17b2a11d04289f9e927c71703b42771dd7b86a4/contracts/libraries/Tasks.sol#L181

        for (uint256 i = 0; i < _length; i++) _alerts[i] = _self.alerts[i];

https://github.com/code-423n4/2022-08-rigor/blob/b17b2a11d04289f9e927c71703b42771dd7b86a4/contracts/Community.sol#L624

        for (uint256 i = 0; i < _communities[_communityID].memberCount; i++)

external call value can be cached and reused

The return value of external functions that are called multiple times can be cached and reused to save gas

Proof of concept

https://github.com/code-423n4/2022-08-rigor/blob/b17b2a11d04289f9e927c71703b42771dd7b86a4/contracts/Project.sol#L323

        tasks[_taskList[i]].acceptInvitation(_msgSender());

Function calls can be replaced with cached value in _sender

https://github.com/code-423n4/2022-08-rigor/blob/b17b2a11d04289f9e927c71703b42771dd7b86a4/contracts/Community.sol#L446

L380    address _sender = _msgSender();

        _currency.safeTransferFrom(_msgSender(), homeFi.treasury(), _lenderFee);

        // Transfer _amountToProject to _project from lender account
        _currency.safeTransferFrom(_msgSender(), _project, _amountToProject);

https://github.com/code-423n4/2022-08-rigor/blob/b17b2a11d04289f9e927c71703b42771dd7b86a4/contracts/Community.sol#L505

        emit ApproveHash(_hash, _msgSender());

Split require statement that use && and save gas

require statements that use && operator to check multiple condition can be split into multiple statements of one condition to save gas

Proof of concept

https://github.com/code-423n4/2022-08-rigor/blob/b17b2a11d04289f9e927c71703b42771dd7b86a4/contracts/Disputes.sol#L61

       require(
            _disputeID < disputeCount &&
                disputes[_disputeID].status == Status.Active,
            "Disputes::!Resolvable"
        ); 

https://github.com/code-423n4/2022-08-rigor/blob/b17b2a11d04289f9e927c71703b42771dd7b86a4/contracts/Disputes.sol#L106

        require(
            _actionType > 0 && _actionType <= uint8(ActionType.TaskPay),
            "Disputes::!ActionType"
        ); 

Cache storage variable and save gas

Storage variables that are read more than once can be cached in a temporary variable to save a SLOAD(100 gas) operation and save gas

Proof of concept

projectCount in

https://github.com/code-423n4/2022-08-rigor/blob/b17b2a11d04289f9e927c71703b42771dd7b86a4/contracts/HomeFi.sol#L231

        projects[projectCount] = _project;
        projectTokenId[_project] = projectCount;

        emit ProjectAdded(projectCount, _project, _sender, _currency, _hash); 

https://github.com/code-423n4/2022-08-rigor/blob/b17b2a11d04289f9e927c71703b42771dd7b86a4/contracts/HomeFi.sol#L295

        projectCount += 1;

        // Mints NFT and set token URI
        _mint(_to, projectCount);   
        _setTokenURI(projectCount, _tokenURI);

        emit NftCreated(projectCount, _to); 

https://github.com/code-423n4/2022-08-rigor/blob/b17b2a11d04289f9e927c71703b42771dd7b86a4/contracts/ProjectFactory.sol#L90

        Project(_clone).initialize(_currency, _sender, homeFi);

https://github.com/code-423n4/2022-08-rigor/blob/b17b2a11d04289f9e927c71703b42771dd7b86a4/contracts/Project.sol#L144

        emit ContractorInvited(contractor);

Array length can be cached in a variable and reused

https://github.com/code-423n4/2022-08-rigor/blob/b17b2a11d04289f9e927c71703b42771dd7b86a4/contracts/Project.sol#L603

L603        for (; i < _changeOrderedTask.length; i++)

L635        if (i == _changeOrderedTask.length) {

taskCount in

https://github.com/code-423n4/2022-08-rigor/blob/b17b2a11d04289f9e927c71703b42771dd7b86a4/contracts/Project.sol#L650

L650    for (++j; j <= taskCount; j++) {    

L681    if (j > taskCount) {
                lastAllocatedTask = taskCount;
            }

https://github.com/code-423n4/2022-08-rigor/blob/b17b2a11d04289f9e927c71703b42771dd7b86a4/contracts/Community.sol#L150

        emit CommunityAdded(communityCount, _sender, _currency, _hash);

_communities[_communityID].memberCount in

https://github.com/code-423n4/2022-08-rigor/blob/b17b2a11d04289f9e927c71703b42771dd7b86a4/contracts/Community.sol#L624

        for (uint256 i = 0; i < _communities[_communityID].memberCount; i++) 

Use custom errors than require statements

As the code is already using a compiler version >= 0.8.4, there is a more convenient and gas-efficient way to handle revert strings: custom errors.
Custom errors decrease both deploy and runtime gas costs.
Source: https://blog.soliditylang.org/2021/04/21/custom-errors/

Proof of concept

https://github.com/code-423n4/2022-08-rigor/blob/b17b2a11d04289f9e927c71703b42771dd7b86a4/contracts/HomeFiProxy.sol

    require(_address != address(0), "Proxy::0 address");

    require(_length == _implementations.length, "Proxy::Lengths !match");

    require(
        contractAddress[_contractName] == address(0),
        "Proxy::Name !OK"
    );
    require(_length == _contractAddresses.length, "Proxy::Lengths !match"); 

https://github.com/code-423n4/2022-08-rigor/blob/b17b2a11d04289f9e927c71703b42771dd7b86a4/contracts/Project.sol

    require(!contractorConfirmed, "Project::GC accepted");
    require(_projectAddress == address(this), "Project::!projectAddress");
    require(_contractor != address(0), "Project::0 address");
    require(_msgSender() == builder, "Project::!B");
    require(contractor != address(0), "Project::0 address");
    require(_nonce == hashChangeNonce, "Project::!Nonce");
    require(
        _sender == builder || _sender == homeFi.communityContract(),
        "Project::!Builder&&!Community"
    );
    require(_cost > 0, "Project::!value>0"); 
    require(
        projectCost() >= uint256(_newTotalLent),
        "Project::value>required"
    );
    require(_taskCount == taskCount, "Project::!taskCount");
    require(_projectAddress == address(this), "Project::!projectAddress");
    require(_length == _taskCosts.length, "Project::Lengths !match");
    require(_nonce == hashChangeNonce, "Project::!Nonce");
    require(
        _msgSender() == builder || _msgSender() == contractor,
        "Project::!Builder||!GC"
    );
    require(_length == _scList.length, "Project::Lengths !match");
    require(_projectAddress == address(this), "Project::!Project");
            require(tasks[_taskID].getState() == 3, "Project::!Complete");
    require(_project == address(this), "Project::!projectAddress");
    require(_project == address(this), "Project::!projectAddress");
    require(
        signer == builder || signer == contractor,
        "Project::!(GC||Builder)"
    );
                require(
        signer == builder ||
            signer == contractor ||
            signer == tasks[_task].subcontractor,
        "Project::!(GC||Builder||SC)"
    );
    require(getAlerts(_task)[2], "Project::!SCConfirmed");
    require(_sc != address(0), "Project::0 address");
    require(
        _recoveredSignature == _address || approvedHashes[_address][_hash],
        "Project::invalid signature"
    );
            require(
        ((_amount / 1000) * 1000) == _amount,
        "Project::Precision>=1000"
    );

https://github.com/code-423n4/2022-08-rigor/blob/b17b2a11d04289f9e927c71703b42771dd7b86a4/contracts/HomeFi.sol

    require(admin == _msgSender(), "HomeFi::!Admin");
    require(_address != address(0), "HomeFi::0 address");
    require(_oldAddress != _newAddress, "HomeFi::!Change");
    require(!addrSet, "HomeFi::Set");
    require(lenderFee != _newLenderFee, "HomeFi::!Change");
    require(
        _currency == tokenCurrency1 ||
            _currency == tokenCurrency2 ||
            _currency == tokenCurrency3,
        "HomeFi::!Currency"
    );

https://github.com/code-423n4/2022-08-rigor/blob/b17b2a11d04289f9e927c71703b42771dd7b86a4/contracts/Disputes.sol

        require(_address != address(0), "Disputes::0 address");
        require(homeFi.admin() == _msgSender(), "Disputes::!Admin");
        require(homeFi.isProjectExist(_msgSender()), "Disputes::!Project");
        require(
            _disputeID < disputeCount &&
                disputes[_disputeID].status == Status.Active,
            "Disputes::!Resolvable"
        ); 
                require(
            _actionType > 0 && _actionType <= uint8(ActionType.TaskPay),
            "Disputes::!ActionType"
        );
        require(_result, "Disputes::!Member");

https://github.com/code-423n4/2022-08-rigor/blob/b17b2a11d04289f9e927c71703b42771dd7b86a4/contracts/ProjectFactory.sol

    require(_address != address(0), "PF::0 address");
    require(
        _msgSender() == IHomeFi(homeFi).admin(),
        "ProjectFactory::!Owner"
    );
    require(_msgSender() == homeFi, "PF::!HomeFiContract");

https://github.com/code-423n4/2022-08-rigor/blob/b17b2a11d04289f9e927c71703b42771dd7b86a4/contracts/DebtToken.sol

    require(
        communityContract == _msgSender(),
        "DebtToken::!CommunityContract"
    );
    require(_communityContract != address(0), "DebtToken::0 address");

    revert("DebtToken::blocked");

https://github.com/code-423n4/2022-08-rigor/blob/b17b2a11d04289f9e927c71703b42771dd7b86a4/contracts/libraries/Tasks.sol

        require(_self.subcontractor == _sc, "Task::!SC");

Using bool incurs storage overhead

Use uint256(0) & uint256(1) for false and true instead of the boolean variable

Proof of concept

https://github.com/code-423n4/2022-08-rigor/blob/b17b2a11d04289f9e927c71703b42771dd7b86a4/contracts/HomeFiProxy.sol#L30

    mapping(address => bool) internal contractsActive;

https://github.com/OpenZeppelin/openzeppelin-contracts/blob/58f635312aa21f947cae5f8578638a85aa2519f5/contracts/security/ReentrancyGuard.sol#L23-L27

    // Booleans are more expensive than uint256 or any type that takes up a full
    // word because each write operation emits an extra SLOAD to first read the
    // slot's contents, replace the bits taken up by the boolean, and then write
    // back. This is the compiler's defense against contract upgrades and
    // pointer aliasing, and it cannot be disabled.