Gas Optimizations

[code423n4]

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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[re1ro]

1

Good spot

2

Not applicable
abi.encode() is less secure than abi.encodePacked()

3 - 7

Dup #2

8

Dup #113

[GalloDaSballo]

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

Nope, constant / immutable save the same gas (except minor gas during deployment)
https://twitter.com/GalloDaSballo/status/1543729080926871557

Rest will save less than 300 gas