Cache and read storage variables from the stack can save gas

[code423n4]

Handle

WatchPug

Vulnerability details

For the storage variables that will be accessed multiple times, cache and read from the stack can save ~100 gas from each extra read (SLOAD after Berlin).

For example:

https://github.com/code-423n4/2021-11-nested/blob/f646002b692ca5fa3631acfff87dda897541cf41/contracts/FeeSplitter.sol#L152-L162

function sendFeesWithRoyalties(
    address _royaltiesTarget,
    IERC20 _token,
    uint256 _amount
) external nonReentrant {
    require(_royaltiesTarget != address(0), "FeeSplitter: INVALID_ROYALTIES_TARGET_ADDRESS");

    _sendFees(_token, _amount, totalWeights);
    _addShares(_royaltiesTarget, _computeShareCount(_amount, royaltiesWeight, totalWeights), address(_token));
}

Recommendation

Change to:

function sendFeesWithRoyalties(
    address _royaltiesTarget,
    IERC20 _token,
    uint256 _amount
) external nonReentrant {
    require(_royaltiesTarget != address(0), "FeeSplitter: INVALID_ROYALTIES_TARGET_ADDRESS");

    uint256 _totalWeights = totalWeights;

    _sendFees(_token, _amount, _totalWeights);
    _addShares(_royaltiesTarget, _computeShareCount(_amount, royaltiesWeight, _totalWeights), address(_token));
}

[adrien-supizet]

✅
Before:
| Contract · Method · Min · Max · Avg · # calls · usd (avg) │
| FeeSplitter · sendFeesWithRoyalties · 74018 · 159518 · 121043 · 4 · - │

After:
| FeeSplitter · sendFeesWithRoyalties · 73923 · 159423 · 120948 · 4 · - │