Axelar Network v2 contest - Tomio's results

Title: Gas savings for using solidity 0.8.10

Proof of Concept: all contract

Recommended Mitigation Steps: Consider to upgrade pragma to at least 0.8.10.

Solidity 0.8.10 has a useful change which reduced gas costs of external calls Reference: here

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Title: abi.encode() is less efficient than abi.encodePacked()

Proof of Concept: AxelarAuthWeighted.sol#L32

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Title: Default value initialization

Impact: If a variable is not set/initialized, it is assumed to have the default value (0, false, 0x0 etc depending on the data type). Explicitly initializing it with its default value is an anti-pattern and wastes gas.

Proof of Concept: AxelarAuthWeighted.sol#L68-L69 AxelarAuthWeighted.sol#L94-L98

Recommended Mitigation Steps: Remove explicit initialization for default values.

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Title: Using unchecked and prefix increment is more effective for gas saving:

Proof of Concept: AxelarAuthWeighted.sol#L69 AxelarAuthWeighted.sol#L98 AxelarDepositService.sol#L114 AxelarDepositService.sol#L168 AxelarDepositService.sol#L204 AxelarGasService.sol#L123

Recommended Mitigation Steps: Change to:

    for (uint256 i = 0; i < weightsLength;) {
          // ... 
    unchecked { ++i; }
      }

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Title: Cheaper to use ++ instead + 1

Proof of Concept: https://github.com/code-423n4/2022-05-aura/blob/main/contracts/AuraLocker.sol#L636

Recommended Mitigation Steps:

        uint256 epoch = ++currentEpoch;

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Title: Caching length for loop can save gas

Proof of Concept: AxelarDepositService.sol#L114 AxelarDepositService.sol#L168 AxelarDepositService.sol#L204 AxelarAuthWeighted.sol#L116 AxelarGasService.sol#L123

Recommended Mitigation Steps: Change to:

	uint256 Length = refundTokens.length;
	for (uint256 i; i < Length; i++) {

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Title: Comparison operators

Proof of Concept: AxelarAuthWeighted.sol#L117

Recommended Mitigation Steps: Replace <= with <, and >= with > for gas optimization

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Title: Expression for constant values such as a call to keccak256(), should use immutable rather than constant

Proof of Concept: AxelarGateway.sol#L27-L43

Recommended Mitigation Steps: Change from constant to immutable reference: here

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