QuickSwap and StellaSwap contest - Fitraldys's results

1. Useage of uint / int smaller than 32 bytes incurs overhead

When using elements that are smaller than 32 bytes, your contract’s gas usage may be higher. This is because the EVM operates on 32 bytes at a time. Therefore, if the element is smaller than that, the EVM must use more operations in order to reduce the size of the element from 32 bytes to the desired size.

POC :

https://github.com/code-423n4/2022-09-quickswap/blob/main/src/core/contracts/AlgebraFactory.sol#L99 https://github.com/code-423n4/2022-09-quickswap/blob/main/src/core/contracts/AlgebraFactory.sol#L100 https://github.com/code-423n4/2022-09-quickswap/blob/main/src/core/contracts/AlgebraFactory.sol#L103 https://github.com/code-423n4/2022-09-quickswap/blob/main/src/core/contracts/AlgebraFactory.sol#L104 https://github.com/code-423n4/2022-09-quickswap/blob/main/src/core/contracts/AlgebraFactory.sol#L106 https://github.com/code-423n4/2022-09-quickswap/blob/main/src/core/contracts/AlgebraFactory.sol#L107 https://github.com/code-423n4/2022-09-quickswap/blob/main/src/core/contracts/AlgebraPool.sol#L276 https://github.com/code-423n4/2022-09-quickswap/blob/main/src/core/contracts/AlgebraPool.sol#L277

2. use abi.encodepacked for gas optimization

Changing the abi.encode function to abi.encodePacked can save gas since the abi.encode function pads extra null bytes at the end of the call data, which is unnecessary. Also, in general, abi.encodePacked is more gas-efficient.

POC :

https://github.com/code-423n4/2022-09-quickswap/blob/main/src/core/contracts/AlgebraFactory.sol#L123 https://github.com/code-423n4/2022-09-quickswap/blob/main/src/core/contracts/AlgebraPoolDeployer.sol#L51

3. != is more efficient than > in require

!= 0 cost less gas compare to > 0 for unsigned integers in require statement with optimizer enable save 6 gas

because for uint the minimum value would be 0 and never a negative value, that mean check > 0 is essentially checking that the value is not 0.

resource : https://twitter.com/gzeon/status/1485428085885640706

i suggest changing > 0 to != 0

POC :

https://github.com/code-423n4/2022-09-quickswap/blob/main/src/core/contracts/AlgebraPool.sol#L434 https://github.com/code-423n4/2022-09-quickswap/blob/main/src/core/contracts/AlgebraPool.sol#L469 https://github.com/code-423n4/2022-09-quickswap/blob/main/src/core/contracts/AlgebraPool.sol#L898

4. Splitting require() statements that use && save gas

see https://github.com/code-423n4/2022-01-xdefi-findings/issues/128 which describes the fact that there is a larger deployment gas cost, but with enough runtime calls, the change ends up being cheaper

POC :

https://github.com/code-423n4/2022-09-quickswap/blob/main/src/core/contracts/AlgebraPool.sol#L739 https://github.com/code-423n4/2022-09-quickswap/blob/main/src/core/contracts/AlgebraPool.sol#L743 https://github.com/code-423n4/2022-09-quickswap/blob/main/src/core/contracts/AlgebraPool.sol#L953

5. cheaper foor loops

You can get cheaper for loops (at least 25 gas, however can be up to 80 gas under certain conditions), by rewriting:

for (uint256 i = 0; i < orders.length; /** NOTE: Removed i++ **/ ) {
        // Do the thing
        // Unchecked pre-increment is cheapest
        unchecked { ++i; }
}     

POC :

https://github.com/code-423n4/2022-09-quickswap/blob/main/src/core/contracts/libraries/DataStorage.sol#L307