Gas Optimizations

[code423n4]

1. IT COSTS MORE GAS TO INITIALIZE VARIABLES TO ZERO THAN TO LET THE DEFAULT OF ZERO BE APPLIED

// Links to github files
https://github.com/code-423n4/2022-07-axelar/blob/main/contracts/auth/AxelarAuthWeighted.sol#L68
https://github.com/code-423n4/2022-07-axelar/blob/main/contracts/auth/AxelarAuthWeighted.sol#L94
https://github.com/code-423n4/2022-07-axelar/blob/main/contracts/auth/AxelarAuthWeighted.sol#L95

// actual codes
contracts/auth/AxelarAuthWeighted.sol:68:        uint256 totalWeight = 0;+
contracts/auth/AxelarAuthWeighted.sol:94:        uint256 operatorIndex = 0;
contracts/auth/AxelarAuthWeighted.sol:95:        uint256 weight = 0;

2. ARRAY .LENGTH SHOULD NOT BE LOOKED UP IN EVERY LOOP OF A FOR-LOOP

The overheads outlined below are PER LOOP, excluding the first loop storage arrays incur a Gwarmaccess (100 gas) memory arrays use MLOAD (3 gas)
calldata arrays use CALLDATALOAD (3 gas).
Caching the length changes each of these to a DUP (3 gas), and gets rid of the extra DUP needed to store the stack offset

// Links to githubfile
https://github.com/code-423n4/2022-07-axelar/blob/main/contracts/deposit-service/AxelarDepositService.sol#L114
https://github.com/code-423n4/2022-07-axelar/blob/main/contracts/deposit-service/AxelarDepositService.sol#L168
https://github.com/code-423n4/2022-07-axelar/blob/main/contracts/deposit-service/AxelarDepositService.sol#L204
https://github.com/code-423n4/2022-07-axelar/blob/main/contracts/auth/AxelarAuthWeighted.sol#L17
https://github.com/code-423n4/2022-07-axelar/blob/main/contracts/auth/AxelarAuthWeighted.sol#L98
https://github.com/code-423n4/2022-07-axelar/blob/main/contracts/auth/AxelarAuthWeighted.sol#L17
https://github.com/code-423n4/2022-07-axelar/blob/main/contracts/AxelarGateway.sol#L207
https://github.com/code-423n4/2022-07-axelar/blob/main/contracts/gas-service/AxelarGasService.sol#L123

// actual codes
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/auth/AxelarAuthWeighted.sol:17:        for (uint256 i; i < recentOperators.length; ++i) {
contracts/auth/AxelarAuthWeighted.sol:98:        for (uint256 i = 0; i < signatures.length; ++i) 
contracts/AxelarGateway.sol:207:        for (uint256 i = 0; i < symbols.length; i++) 
contracts/gas-service/AxelarGasService.sol:123:        for (uint256 i; i < tokens.length; i++) 

[GalloDaSballo]

Less than 100 gas saved