Gas Optimizations

[code423n4]

Gas Report

• G-01: use unchecked when incrementing for loop variable
• G-02: increment using ++i instead of i++ consistently
• G-03: use solmate's ERC20 contract
• G-04: remove unnecessary require statment in XC20Wrapper.sol

G-01: use unchecked when incrementing for loop variable

Since the loop's iterator can't realistically overflow because of the loop's condition, you can increment it in an unchecked block to save gas:

./contracts/auth/AxelarAuthWeighted.sol:17:        for (uint256 i; i < recentOperators.length; ++i) {
./contracts/auth/AxelarAuthWeighted.sol:69:        for (uint256 i = 0; i < weightsLength; ++i) {
./contracts/auth/AxelarAuthWeighted.sol:98:        for (uint256 i = 0; i < signatures.length; ++i) {
./contracts/auth/AxelarAuthWeighted.sol:116:        for (uint256 i; i < accounts.length - 1; ++i) {
./contracts/gas-service/AxelarGasService.sol:123:        for (uint256 i; i < tokens.length; i++) {
./contracts/deposit-service/AxelarDepositService.sol:114:        for (uint256 i; i < refundTokens.length; i++) {
./contracts/deposit-service/AxelarDepositService.sol:168:        for (uint256 i; i < refundTokens.length; i++) {
./contracts/deposit-service/AxelarDepositService.sol:204:        for (uint256 i; i < refundTokens.length; i++) {
./contracts/AdminMultisigBase.sol:51:        for (uint256 i; i < adminCount; ++i) {
./contracts/AdminMultisigBase.sol:158:        for (uint256 i; i < adminLength; ++i) {
./contracts/AxelarGateway.sol:195:        for (uint256 i; i < adminCount; ++i) {
./contracts/AxelarGateway.sol:207:        for (uint256 i = 0; i < symbols.length; i++) {
./contracts/AxelarGateway.sol:293:        for (uint256 i; i < commandsLength; ++i) {
./contracts/auth/AxelarAuthWeighted.sol:101:            for (; operatorIndex < operatorsLength && signer != operators[operatorIndex]; ++operatorIndex) {}

Just search for "for (" in your .sol files to find all the relevant instances

G-02: increment using ++i instead of i++ consistently

Using ++i saves gas because you don't have to cache the original value in memory. You already use it in some places but not consistently.

./contracts/gas-service/AxelarGasService.sol:123:        for (uint256 i; i < tokens.length; i++) {
./contracts/deposit-service/AxelarDepositService.sol:114:        for (uint256 i; i < refundTokens.length; i++) {
./contracts/deposit-service/AxelarDepositService.sol:168:        for (uint256 i; i < refundTokens.length; i++) {
./contracts/deposit-service/AxelarDepositService.sol:204:        for (uint256 i; i < refundTokens.length; i++) {
./contracts/AxelarGateway.sol:207:        for (uint256 i = 0; i < symbols.length; i++) {

G-03: use solmate's ERC20 contract

solmate's contracts are optimized for gas usage. They are more efficient than OZ's contracts. Consider switching to them. It will save gas for all the ERC20 transfers, burns, etc.

https://github.com/transmissions11/solmate

G-04: remove unnecessary require statement in XC20Wrapper.sol

In XC20Wrapper.unwrap() the function checks whether the caller has enough tokens to burn before calling the burn() function. But, the burn function will simply revert if the user doesn't have enough. Explicitly checking for that is a waste of gas.

https://github.com/code-423n4/2022-07-axelar/blob/main/xc20/contracts/XC20Wrapper.sol#L85

[re1ro]

1

Yup. Dup #2

2

Yup. Dup #2

3

Good spot. We might consider that

4

Good spot.

[GalloDaSballo]

3

Would like to see a benchmark in difference

Will give the report 350 gas