Frax Ether Liquid Staking contest - SooYa's results

Loops can be optimized in several ways

To optimize this loop and make it consume less gas, we can do the folowing things:

1. Use ++i instead of i++, which is a cheaper operation (in this case there is no difference between i++ and ++i because we dont use the return value of this expression, which is the only difference between these two expression).
2. There’s no need to initialize i to its default value, it will be done automatically and it will consume more gas if it will be done (I know, sounds stupid, but trust me - it works). So after applying all these changes, the loop will look something like this:

for (uint256 i; i < Variable; ++i) {

I suggest to change the code here: https://github.com/code-423n4/2022-09-frax/blob/main/src/ERC20/ERC20PermitPermissionedMint.sol#L84

> 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: While it may seem that > 0 is cheaper than !=, this is only true without the optimizer enabled and outside a require statement. If you enable the optimizer at 10k AND you’re in a require statement, this will save gas. You can see this tweet for more proofs: https://twitter.com/gzeon/status/1485428085885640706

I suggest changing > 0 with != 0 here: https://github.com/code-423n4/2022-09-frax/blob/main/src/frxETHMinter.sol#L79 https://github.com/code-423n4/2022-09-frax/blob/main/src/frxETHMinter.sol#L126

Cache The Length Of Arrays In Loops

The solidity compiler will always read the length of the array during each iteration. That is,

1.if it is a storage array, this is an extra sload operation (100 additional extra gas (EIP-2929 2) for each iteration except for the first), 2.if it is a memory array, this is an extra mload operation (3 additional gas for each iteration except for the first), 3.if it is a calldata array, this is an extra calldataload operation (3 additional gas for each iteration except for the first)

This extra costs can be avoided by caching the array length (in stack):

Here, I suggest storing the array’s length in a variable before the for-loop, and use it instead: https://github.com/code-423n4/2022-09-frax/blob/main/src/OperatorRegistry.sol#L114

No Need Initialize Variable Its Default Value

There’s no need to initialize variable to its default value, it will be done automatically and it will consume more gas if it will be done.

I suggest to change the code here: https://github.com/code-423n4/2022-09-frax/blob/main/src/OperatorRegistry.sol#L84 https://github.com/code-423n4/2022-09-frax/blob/main/src/OperatorRegistry.sol#L114 https://github.com/code-423n4/2022-09-frax/blob/main/src/OperatorRegistry.sol#L63 https://github.com/code-423n4/2022-09-frax/blob/main/src/frxETHMinter.sol#L94 https://github.com/code-423n4/2022-09-frax/blob/main/src/frxETHMinter.sol#L129