Gas Optimizations

[code423n4]

G-01 Using of custom errors than are came from 0.8.4 instead of require()/revert() strings will save deployment gas

Contracts use version 0.8.14 and can use custom errors that will save of deployment gas also when the trasaction failed duo to return the gas will be less.

There have 2 istance of this issues:

require(sfrxeth_recieved > 0, 'No sfrxETH was returned');

https://github.com/code-423n4/2022-09-frax/blob/55ea6b1ef3857a277e2f47d42029bc0f3d6f9173/src/frxETHMinter.sol#L79

require(numDeposits > 0, "Not enough ETH in contract");

https://github.com/code-423n4/2022-09-frax/blob/55ea6b1ef3857a277e2f47d42029bc0f3d6f9173/src/frxETHMinter.sol#L126

G-02 Use uncheck() in for loops whenere overflow and undeflow is not possible

Using of uncheck(i++)/uncheck(++i) will save about 30 gas per iteration because compiler not save check everytime. This feature come from 0.8

There have 5 istance of this issues:

for (uint i = 0; i < minters_array.length; i++){

https://github.com/code-423n4/2022-09-frax/blob/55ea6b1ef3857a277e2f47d42029bc0f3d6f9173/src/ERC20/ERC20PermitPermissionedMint.sol#L84

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

https://github.com/code-423n4/2022-09-frax/blob/55ea6b1ef3857a277e2f47d42029bc0f3d6f9173/src/OperatorRegistry.sol#L63

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

https://github.com/code-423n4/2022-09-frax/blob/55ea6b1ef3857a277e2f47d42029bc0f3d6f9173/src/OperatorRegistry.sol#L84

for (uint256 i = 0; i < original_validators.length; ++i) {

https://github.com/code-423n4/2022-09-frax/blob/55ea6b1ef3857a277e2f47d42029bc0f3d6f9173/src/OperatorRegistry.sol#L114

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

https://github.com/code-423n4/2022-09-frax/blob/55ea6b1ef3857a277e2f47d42029bc0f3d6f9173/src/OperatorRegistry.sol#L129

G-03 = + cost less than += for state variables

There have 5 istance of this issues:

currentWithheldETH += withheld_amt;

https://github.com/code-423n4/2022-09-frax/blob/55ea6b1ef3857a277e2f47d42029bc0f3d6f9173/src/frxETHMinter.sol#97

G-04 i++, i += 1 and i = i + 1 IN FOR LOOPS COSTS MORE GAS COMPARED TO ++i

++i will save about 5 gas for each iteration

There have 1 istance of this issues:

for (uint i = 0; i < minters_array.length; i++){

https://github.com/code-423n4/2022-09-frax/blob/55ea6b1ef3857a277e2f47d42029bc0f3d6f9173/src/ERC20/ERC20PermitPermissionedMint.sol#L84

G-05 Recomend to use uint256(1)/uint256(2) for true and false

If you don't use boolean for storage you will avoid Gwarmaccess 100 gas. Also boolean from true to false cost 20000 gas rather than uint256(2) to uint256(1) that cost less.

There have 4 istance of this issues:

File: ERC20PermitPermissionedMint.sol line 20

mapping(address => bool) public minters; // Mapping is also used for faster verification

https://github.com/code-423n4/2022-09-frax/blob/55ea6b1ef3857a277e2f47d42029bc0f3d6f9173/src/ERC20/ERC20PermitPermissionedMint.sol#L20

File: frxETHMinter.sol lines 43,49,50

mapping(bytes => bool) public activeValidators; // Tracks validators (via their pubkeys) that already have 32 ETH in them

https://github.com/code-423n4/2022-09-frax/blob/55ea6b1ef3857a277e2f47d42029bc0f3d6f9173/src/frxETHMinter.sol#L43

bool public submitPaused;

https://github.com/code-423n4/2022-09-frax/blob/55ea6b1ef3857a277e2f47d42029bc0f3d6f9173/src/frxETHMinter.sol#L49

bool public depositEtherPaused;

https://github.com/code-423n4/2022-09-frax/blob/55ea6b1ef3857a277e2f47d42029bc0f3d6f9173/src/frxETHMinter.sol#L50

G-06 Recomend to use one operator for comparison

If you use >= or <= this will cost more gas because in the EVM there is no implementation of Opcodes for >= and `<= and two operations are done.

There have 1 istance of this issues:

if (block.timestamp >= rewardsCycleEnd) { syncRewards(); } 

https://github.com/code-423n4/2022-09-frax/blob/55ea6b1ef3857a277e2f47d42029bc0f3d6f9173/src/sfrxETH.sol#L50

G-07 != cost 6 gas less than > in require

There have 2 istance of this issues:

File: frxETHMinter.sol lines 79, 126

require(sfrxeth_recieved > 0, 'No sfrxETH was returned');

https://github.com/code-423n4/2022-09-frax/blob/55ea6b1ef3857a277e2f47d42029bc0f3d6f9173/src/frxETHMinter.sol#L79

require(numDeposits > 0, "Not enough ETH in contract");

https://github.com/code-423n4/2022-09-frax/blob/55ea6b1ef3857a277e2f47d42029bc0f3d6f9173/src/frxETHMinter.sol#L126

G-08 Recommend to use short require string to save deployment gas

If you use longer require strings than 32 bytes that will cost more expensive than short require string.

File : frxETHMinter.sol line 167

There have 1 istance of this issues:

require(amount <= currentWithheldETH, "Not enough withheld ETH in contract");

https://github.com/code-423n4/2022-09-frax/blob/55ea6b1ef3857a277e2f47d42029bc0f3d6f9173/src/frxETHMinter.sol#L167

G-09 Use defualt value rather than overwriite variable with their default value.

Overriting varibles with defualt values with their default value will waste only gas and not necessary.

There have 5 istance of this issues:

for (uint i = 0; i < minters_array.length; i++){

https://github.com/code-423n4/2022-09-frax/blob/55ea6b1ef3857a277e2f47d42029bc0f3d6f9173/src/ERC20/ERC20PermitPermissionedMint.sol#L84

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

https://github.com/code-423n4/2022-09-frax/blob/55ea6b1ef3857a277e2f47d42029bc0f3d6f9173/src/OperatorRegistry.sol#L63

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

https://github.com/code-423n4/2022-09-frax/blob/55ea6b1ef3857a277e2f47d42029bc0f3d6f9173/src/OperatorRegistry.sol#L84

for (uint256 i = 0; i < original_validators.length; ++i) {

https://github.com/code-423n4/2022-09-frax/blob/55ea6b1ef3857a277e2f47d42029bc0f3d6f9173/src/OperatorRegistry.sol#L114

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

https://github.com/code-423n4/2022-09-frax/blob/55ea6b1ef3857a277e2f47d42029bc0f3d6f9173/src/OperatorRegistry.sol#L129

G-10 In for loop use outside variable for array length

For loop written like thisfor (uint256 i; i < array.length; ++i) { will cost more gas than for (uint256 i; i < _lengthOfArray; ++i) { because for every iteration we use mload and memory_offset that will cost about 6 gas

There are 2 instances of this issue:

for (uint i = 0; i < minters_array.length; i++){

https://github.com/code-423n4/2022-09-frax/blob/55ea6b1ef3857a277e2f47d42029bc0f3d6f9173/src/ERC20/ERC20PermitPermissionedMint.sol#L84

for (uint256 i = 0; i < original_validators.length; ++i) {

https://github.com/code-423n4/2022-09-frax/blob/55ea6b1ef3857a277e2f47d42029bc0f3d6f9173/src/OperatorRegistry.sol#L114