Gas Optimizations

[code423n4]

Title: Using != is more gas efficient

Proof of Concept:
https://github.com/code-423n4/2022-05-aura/blob/main/contracts/Aura.sol#L68
https://github.com/code-423n4/2022-05-aura/blob/main/contracts/AuraBalRewardPool.sol#L139
https://github.com/code-423n4/2022-05-aura/blob/main/contracts/AuraBalRewardPool.sol#L210

Recommended Mitigation Steps:

    require(_amount != 0, "Must mint something");

========================================================================

Title: unnecessary variable set. the default value of uint is 0

Proof of Concept:
https://github.com/code-423n4/2022-05-aura/blob/main/contracts/AuraBalRewardPool.sol#L35
https://github.com/code-423n4/2022-05-aura/blob/main/contracts/AuraBalRewardPool.sol#L38-L39

Recommended Mitigation Steps:
remove 0 value

========================================================================

Title: Using delete statement to empty rewards[msg.sender] can save gas

Proof of Concept:
https://github.com/code-423n4/2022-05-aura/blob/main/contracts/AuraBalRewardPool.sol#L179
https://github.com/code-423n4/2022-05-aura/blob/main/contracts/AuraClaimZap.sol#L191-L192

Recommended Mitigation Steps:

    delete rewards[msg.sender];

========================================================================

Title: Using unchecked and prefix increment

Proof of Concept:
https://github.com/code-423n4/2022-05-aura/blob/main/contracts/AuraClaimZap.sol#L143-L153
https://github.com/code-423n4/2022-05-aura/blob/main/contracts/AuraLocker.sol#L773

Recommended Mitigation Steps:

for (uint256 i = 0; i < rewardContracts.length;) {
            IBasicRewards(rewardContracts[i]).getReward(msg.sender, true);
        }
    unchecked{
        ++i; //@audit-info: Place here with unchecked
        }

========================================================================

Title: Unnecessary variable set of bool

Proof of Concept:
https://github.com/code-423n4/2022-05-aura/blob/main/contracts/AuraLocker.sol#L114
https://github.com/code-423n4/2022-05-aura/blob/main/contracts/AuraVestedEscrow.sol#L33

Recommended Mitigation Steps:
the default value of bool is false. remove it for gas opt

========================================================================

Title: Use reward that already been cache

Proof of Concept:
https://github.com/code-423n4/2022-05-aura/blob/main/contracts/AuraBalRewardPool.sol#L177-L179

Recommended Mitigation Steps:

if (reward > 0) {
            reward = 0;

========================================================================

Title: Using > is cheaper than >=

Proof of Concept:
https://github.com/code-423n4/2022-05-aura/blob/main/contracts/AuraLocker.sol#L216-L217
https://github.com/code-423n4/2022-05-aura/blob/main/contracts/AuraLocker.sol#L829

Recommended Mitigation Steps:
just use > can save gas

	require(_delay > 1, "min delay"); //minimum 2 epochs of grace

========================================================================

Title: Gas opt to substract

Proof of Concept:
https://github.com/code-423n4/2022-05-aura/blob/main/contracts/AuraLocker.sol#L484

Recommended Mitigation Steps:

	uint256 i = --len;

========================================================================

Title: Using calldata to store struct data type can save gas

Proof of Concept:
https://github.com/code-423n4/2022-05-aura/blob/main/contracts/AuraLocker.sol#L583
https://github.com/code-423n4/2022-05-aura/blob/main/contracts/AuraLocker.sol#L627
https://github.com/code-423n4/2022-05-aura/blob/main/contracts/AuraLocker.sol#L769

Recommended Mitigation Steps:

	function checkpoints(address account, uint32 pos) external view virtual returns (DelegateeCheckpoint calldata) {

========================================================================

Title: Using storage to declare Struct variable inside function

Proof of Concept:
https://github.com/code-423n4/2022-05-aura/blob/main/contracts/AuraLocker.sol#L521
https://github.com/code-423n4/2022-05-aura/blob/main/contracts/AuraLocker.sol#L600
https://github.com/code-423n4/2022-05-aura/blob/main/contracts/AuraLocker.sol#L794

Recommended Mitigation Steps:

    DelegateeCheckpoint storage ckpt = _checkpointsLookup(_checkpointedVotes[account], epoch);

========================================================================

Title: Using SafeMath for solidity >0.8

Proof of Concept:
https://github.com/code-423n4/2022-05-aura/blob/main/contracts/AuraBalRewardPool.sol#L24
https://github.com/code-423n4/2022-05-aura/blob/main/contracts/AuraStakingProxy.sol#L35

Recommended Mitigation Steps:
it's better to remove using SafeMath for uint256 for solidity >0.8
reference: OpenZeppelin/openzeppelin-contracts#2465

========================================================================

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:

	low = ++mid;

========================================================================

Title: set as immutable

Proof of Concept:
https://github.com/code-423n4/2022-05-aura/blob/main/contracts/AuraMerkleDrop.sol#L26

Recommended Mitigation Steps:
add immutable

========================================================================

Title: Using multiple require instead && can save gas

Proof of Concept:
https://github.com/code-423n4/2022-05-aura/blob/main/contracts/AuraStakingProxy.sol#L159
https://github.com/code-423n4/2022-05-aura/blob/main/contracts/AuraStakingProxy.sol#L203
https://github.com/code-423n4/2022-05-aura/blob/main/contracts/BalLiquidityProvider.sol#L48
https://github.com/code-423n4/2022-05-aura/blob/main/contracts/BalLiquidityProvider.sol#L57

Recommended Mitigation Steps:

	require(_token != crv, "not allowed");
	require(_token != cvx, "not allowed");
	require(_token != cvxCrv, "not allowed");

========================================================================

Title: Using unchecked can save gas

Proof of Concept:
https://github.com/code-423n4/2022-05-aura/blob/main/contracts/AuraVestedEscrow.sol#L162

Recommended Mitigation Steps:

unchecked{
	uint256 elapsed = _time - startTime;
}

========================================================================

Title: better increment

Proof of Concept:
https://github.com/code-423n4/2022-05-aura/blob/main/contracts/AuraVestedEscrow.sol#L100

Recommended Mitigation Steps:
Change i++ to ++i

========================================================================

Title: Gas improvement on calling SafeERC20.function

Proof of Concept:
https://github.com/code-423n4/2022-05-aura/blob/main/contracts/ExtraRewardsDistributor.sol#L15

Recommended Mitigation Steps:
by removing L#15 and directly call SafeERC20

Example L#93:

    SafeERC20.safeTransferFrom(_token, msg.sender, address(this), _amount);

========================================================================