Gas Optimizations

[code423n4]

Gas Optimizations

	Finding	Instances
[G-01]	Multiple address mappings can be combined into a single mapping of an address to a struct, where appropriate	1
[G-02]	require()/revert() checks used multiples times should be turned into a function or modifier	4
[G-03]	bool is gas inefficient when used in storage	3
[G-04]	Redundant require check	1
[G-05]	Implementing return is redundant if function already has a named returns method implemented	2
[G-06]	array.length should be cached in for loop	2
[G-07]	for loop increments should be unchecked{} if overflow is not possible	6
[G-08]	Using prefix(++i) instead of postfix (i++) saves gas	7
[G-09]	Setting variable to default value is redundant	4
[G-10]	Use custom errors rather than revert()/require() strings to save gas	20

Gas overview per contract

Contract	Instances	Gas Ops
Project.sol	29	7
HomeFi.sol	11	5
DebtToken.sol	6	2
Community.sol	4	4

Gas Optimizations

[G-01] Multiple address mappings can be combined into a single mapping of an address to a struct, where appropriate

Saves a storage slot for the mapping. Depending on the circumstances and sizes of types, can avoid a Gsset (20000 gas) per mapping combined. Reads and subsequent writes can also be cheaper when a function requires both values and they both fit in the same storage slot. Finally, if both fields are accessed in the same function, can save ~42 gas per access due to not having to recalculate the key's keccak256 hash (Gkeccak256 - 30 gas) and that calculation's associated stack operatio
1 instance of this issue has been found:

[G-01] HomeFi.sol#L64-L66

    mapping(address => uint256) public override projectTokenId;
    /// @inheritdoc IHomeFi
    mapping(address => address) public override wrappedToken;

[G-02] require()/revert() checks used multiples times should be turned into a function or modifier

Doing so increases code readability decreases number of instructions for the compiler.
4 instances of this issue have been found:

[G-02] Project.sol#L153-L154

        require(contractor != address(0), "Project::0 address");

[G-02b] Project.sol#L135-L136

        require(_contractor != address(0), "Project::0 address");

[G-02c] DebtToken.sol#L96-L97

        revert("DebtToken::blocked");

[G-02d] DebtToken.sol#L104-L105

        revert("DebtToken::blocked");

[G-03] bool is gas inefficient when used in storage

Instead use uint256 values to represent true/false instead.
Reference
3 instances of this issue have been found:

[G-03] Project.sol#L78-L79

    bool public override contractorDelegated;

[G-03b] Project.sol#L68-L69

    bool public override contractorConfirmed;

[G-03c] HomeFi.sol#L50-L51

    bool public override addrSet;

[G-04] Redundant require check

Modifier noChange can be used instead.
1 instance of this issue has been found:

[G-04] HomeFi.sol#L191-L192

        require(lenderFee != _newLenderFee, "HomeFi::!Change");

[G-05] Implementing return is redundant if function already has a named returns method implemented

Redundant return methods increase gas on deployment and execution.
2 instances of this issue have been found:

[G-05] HomeFi.sol#L318-L321

    returns (bytes calldata)
    {
        // We want to use the _msgData() implementation of ERC2771ContextUpgradeable
        return super._msgData();

[G-05b] HomeFi.sol#L307-L310

        returns (address sender)
    {
        // We want to use the _msgSender() implementation of ERC2771ContextUpgradeable
        return super._msgSender();

[G-06] array.length should be cached in for loop

Caching the length array would save gas on each iteration by not having to read from memory or storage multiple times.
Example:

uint length = array.length;
for (uint i; i < length;){
		uncheck { ++i }
}

2 instances of this issue have been found:

[G-06] Community.sol#L624-L625

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

[G-06b] Project.sol#L603-L604

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

[G-07] for loop increments should be unchecked{} if overflow is not possible

From Solidity 0.8.0 onwards using the unchecked keyword saves 30 to 40 gas per loop.
Example:

uint length = array.length;
for (uint i; i < length;){
		uncheck { ++i }
}

6 instances of this issue have been found:

[G-07] Community.sol#L624-L625

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

[G-07b] Project.sol#L650-L651

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

[G-07c] Project.sol#L322-L323

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

[G-07d] Project.sol#L311-L312

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

[G-07e] Project.sol#L248-L249

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

[G-07f] Project.sol#L603-L604

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

[G-08] Using prefix(++i) instead of postfix (i++) saves gas

It saves 6 gas per iteration.
7 instances of this issue have been found:

[G-08] Community.sol#L624-L625

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

[G-08b] Project.sol#L650-L651

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

[G-08c] Project.sol#L322-L323

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

[G-08d] Project.sol#L311-L312

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

[G-08e] Project.sol#L248-L249

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

[G-08f] Project.sol#L625-L626

                    _loopCount++;

[G-08g] Project.sol#L603-L604

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

[G-09] Setting variable to default value is redundant

Setting variable to default value is redundant.
4 instances of this issue have been found:

[G-09] Community.sol#L624-L625

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

[G-09b] Project.sol#L322-L323

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

[G-09c] Project.sol#L311-L312

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

[G-09d] Project.sol#L248-L249

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

[G-10] Use custom errors rather than revert()/require() strings to save gas

Custom errors save ~50 gas each time they're hit by avoiding having to allocate and store the revert string.
20 instances of this issue have been found:

[G-10] Project.sol#L341-L342

        require(_projectAddress == address(this), "Project::!Project");

[G-10b] Project.sol#L199-L202

        require(
            projectCost() >= uint256(_newTotalLent),
            "Project::value>required"
        );

[G-10c] Project.sol#L195-L196

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

[G-10d] Project.sol#L189-L192

        require(
            _sender == builder || _sender == homeFi.communityContract(),
            "Project::!Builder&&!Community"
        );

[G-10e] Project.sol#L176-L177

        require(_nonce == hashChangeNonce, "Project::!Nonce");

[G-10f] Project.sol#L153-L154

        require(contractor != address(0), "Project::0 address");

[G-10g] Project.sol#L150-L151

        require(_msgSender() == builder, "Project::!B");

[G-10h] Project.sol#L135-L136

        require(_contractor != address(0), "Project::0 address");

[G-10i] Project.sol#L132-L133

        require(_projectAddress == address(this), "Project::!projectAddress");

[G-10j] Project.sol#L123-L124

        require(!contractorConfirmed, "Project::GC accepted");

[G-10k] HomeFi.sol#L255-L260

        require(
            _currency == tokenCurrency1 ||
                _currency == tokenCurrency2 ||
                _currency == tokenCurrency3,
            "HomeFi::!Currency"
        );

[G-10l] HomeFi.sol#L191-L192

        require(lenderFee != _newLenderFee, "HomeFi::!Change");

[G-10m] HomeFi.sol#L142-L143

        require(!addrSet, "HomeFi::Set");

[G-10n] HomeFi.sol#L84-L85

        require(_oldAddress != _newAddress, "HomeFi::!Change");

[G-10o] HomeFi.sol#L78-L79

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

[G-10p] HomeFi.sol#L73-L74

        require(admin == _msgSender(), "HomeFi::!Admin");

[G-10q] DebtToken.sol#L31-L35

        require(
            communityContract == _msgSender(),
            "DebtToken::!CommunityContract"
        );
        _;

[G-10r] DebtToken.sol#L50-L51

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

[G-10s] DebtToken.sol#L96-L97

        revert("DebtToken::blocked");

[G-10t] DebtToken.sol#L104-L105

        revert("DebtToken::blocked");