LI.FI contest - rfa's results

Gas opt #1 Using == true cost more gas https://github.com/code-423n4/2022-03-lifinance/blob/main/src/Facets/Swapper.sol#L16 Using == true to validate bool variable is unnecessary:

require(ls.dexWhitelist[_swapData[i].approveTo]);

#2 Using && in require() can cost more execution gas fee https://github.com/code-423n4/2022-03-lifinance/blob/main/src/Facets/Swapper.sol#L15-L18 Using multiple require() can save execution gas:

require(
                ls.dexWhitelist[_swapData[i].approveTo] == true ,
                "Contract call not allowed!"
            );
require(
                ls.dexWhitelist[_swapData[i].callTo] == true,
                "Contract call not allowed!"
            );

#3 Using unchecked and prefix increment for loop increment https://github.com/code-423n4/2022-03-lifinance/blob/main/src/Facets/Swapper.sol#L14 Using unchecked can save gas:

for (uint8 i; i < _swapData.length) {
            require(
                ls.dexWhitelist[_swapData[i].approveTo] == true && ls.dexWhitelist[_swapData[i].callTo] == true,
                "Contract call not allowed!"
            );
Unchecked{++i}

#4 Relocate the toAmount var declaration location https://github.com/code-423n4/2022-03-lifinance/blob/main/src/Libraries/LibSwap.sol#L31 Declare the var at L48, then put the value LibAsset.getOwnBalance(_swapData.receivingAssetId) replacing toAmount. Remove L31

uint toAmount = LibAsset.getOwnBalance(_swapData.receivingAssetId) - LibAsset.getOwnBalance(_swapData.receivingAssetId);

#5 Using parameter to emit event https://github.com/code-423n4/2022-03-lifinance/blob/main/src/Facets/CBridgeFacet.sol#L47 Instead of reading from storage to get s.cBridge and s.cBridgeChainId value, using _cBridge and _chainId to emit can save gas

#6 Unnecessary _sendingAssetIdBalance var declaration https://github.com/code-423n4/2022-03-lifinance/blob/main/src/Facets/NXTPFacet.sol#L54-L57 _sendingAssetIdBalance was only called once in the contract. Caching LibAsset.getOwnBalance(sendingAssetId) into memory is consuming gas. I recommend just put it directly at L57

require(
                LibAsset.getOwnBalance(sendingAssetId) - LibAsset.getOwnBalance(sendingAssetId) ==  _nxtpData.amount,
                "ERR_INVALID_AMOUNT"
            );

Same case at: https://github.com/code-423n4/2022-03-lifinance/blob/main/src/Facets/NXTPFacet.sol#L91

#7 Using calldata on struct parameter https://github.com/code-423n4/2022-03-lifinance/blob/main/src/Facets/Swapper.sol#L12 https://github.com/code-423n4/2022-03-lifinance/blob/main/src/Facets/AnyswapFacet.sol#L35 https://github.com/code-423n4/2022-03-lifinance/blob/main/src/Facets/AnyswapFacet.sol#L75 Using calldata to store struct data type (LifiData) can save gas

#8 != more effective than < https://github.com/code-423n4/2022-03-lifinance/blob/main/src/Facets/AnyswapFacet.sol#L92 https://github.com/code-423n4/2022-03-lifinance/blob/main/src/Facets/AnyswapFacet.sol#L105 Using != to validate than value is not 0 is gas saving

#9 Using unchecked on calculating finalBalance https://github.com/code-423n4/2022-03-lifinance/blob/main/src/Facets/NXTPFacet.sol#L166 The calculation of finalBalance won't underflow because of the if condition at L165. Using unchecked will save gas:

Unchecked{
finalBalance = postSwapBalance - startingBalance;
}

#10 Unnecessary receivingAssetIdBalance MSTORE https://github.com/code-423n4/2022-03-lifinance/blob/main/src/Facets/GenericSwapFacet.sol#L23 receivingAssetIdBalance var was merely called once in the function. Just pass LibAsset.getOwnBalance(_lifiData.receivingAssetId) value directly to L28:

uint256 postSwapBalance = LibAsset.getOwnBalance(_lifiData.receivingAssetId) - LibAsset.getOwnBalance(_lifiData.receivingAssetId);

#11 Custom errors from Solidity 0.8.4 are cheaper than revert strings By defined using error statement, and using if(condition)revert() to check the condition. It can be implemented for all require() check

#12 Function can set external https://github.com/code-423n4/2022-03-lifinance/blob/main/src/Facets/AnyswapFacet.sol#L35 https://github.com/code-423n4/2022-03-lifinance/blob/main/src/Facets/AnyswapFacet.sol#L78 https://github.com/code-423n4/2022-03-lifinance/blob/main/src/Facets/CBridgeFacet.sol#L57 https://github.com/code-423n4/2022-03-lifinance/blob/main/src/Facets/CBridgeFacet.sol#L96 Some function can set external to save gas