1. Unnecessary initialising with default values

        uint _growth = calculate_growth(weekly);             
        uint _teamEmissions = (teamRate * (_growth + weekly)) /
            (PRECISION - teamRate);
        uint _required = _growth + weekly + _teamEmissions;
        uint _balanceOf = _velo.balanceOf(address(this));
        if (_balanceOf < _required) {
            _velo.mint(address(this), _required - _balanceOf);
        }

        require(_velo.transfer(team, _teamEmissions));
        require(_velo.transfer(address(_rewards_distributor), _growth));
        _rewards_distributor.checkpoint_token(); // checkpoint token balance that was just minted in rewards distributor
        _rewards_distributor.checkpoint_total_supply(); // checkpoint supply

        _velo.approve(address(_voter), weekly);
        _voter.notifyRewardAmount(weekly);

        emit Mint(msg.sender, weekly, circulating_supply(), circulating_emission());

derivedBalances[account] can be replaced with _derivedBalance in

https://github.com/code-423n4/2022-05-velodrome/blob/7fda97c570b758bbfa7dd6724a336c43d4041740/contracts/contracts/Gauge.sol#L370

    _derivedBalance = derivedBalance(account);
    derivedBalances[account] = _derivedBalance;
    derivedSupply += _derivedBalance;

    _writeCheckpoint(account, derivedBalances[account]);

fantomSender can be cached and re-used

    require(fantomSender != address(0), "NOT_INITIALIZED");
    require(
        msg.sender == endpoint &&
            srcChainId == fantomChainId &&
            addressFromPackedBytes(srcAddress) == fantomSender,
        "UNAUTHORIZED_CALLER"
    );

Mitigation

Cache storage variable in a local variable and re-use

3. Cache array length to save gas

Array length can be stored in a local variable and re-used instead of querying it in every loop to save gas

Proof of concept

https://github.com/code-423n4/2022-05-velodrome/blob/7fda97c570b758bbfa7dd6724a336c43d4041740/contracts/contracts/Minter.sol#L57

https://github.com/code-423n4/2022-05-velodrome/blob/7fda97c570b758bbfa7dd6724a336c43d4041740/contracts/contracts/Voter.sol#L76

Mitigation

Store array length in a local variable and re-use

4. storage variable can be replaced with `msg.sender`

In VotingEscrow.sol#mintToRedemption since msg.sender is validation in the require statement, the second storage read of redemptionReceiver can be replaced with msg.sender as it consumes only 2 gas

Proof of concept

    require(msg.sender == redemptionReceiver);
    _mint(redemptionReceiver, amount);

Similarly in PairFactory.sol

L46        require(msg.sender == pendingPauser);
L47        pauser = pendingPauser;

L61    require(msg.sender == pendingFeeManager, 'not pending fee manager');
L62    feeManager = pendingFeeManager;

Minter.sol

L70        require(msg.sender == pendingTeam, "not pending team"); 
L71        team = pendingTeam;

Mitigation

Replace second storage read with msg.sender

5. Shorten revert strings

Revert string takes a minimum of 32 bytes, longer strings increases deployment gas as well as runtime gas when the require condition is met

Proof of concept

https://github.com/code-423n4/2022-05-velodrome/blob/7fda97c570b758bbfa7dd6724a336c43d4041740/contracts/contracts/VotingEscrow.sol#L398

https://github.com/code-423n4/2022-05-velodrome/blob/7fda97c570b758bbfa7dd6724a336c43d4041740/contracts/contracts/VotingEscrow.sol#L518

https://github.com/code-423n4/2022-05-velodrome/blob/7fda97c570b758bbfa7dd6724a336c43d4041740/contracts/contracts/VotingEscrow.sol#L774

https://github.com/code-423n4/2022-05-velodrome/blob/7fda97c570b758bbfa7dd6724a336c43d4041740/contracts/contracts/VotingEscrow.sol#L786

https://github.com/code-423n4/2022-05-velodrome/blob/7fda97c570b758bbfa7dd6724a336c43d4041740/contracts/contracts/VotingEscrow.sol#L821

https://github.com/code-423n4/2022-05-velodrome/blob/7fda97c570b758bbfa7dd6724a336c43d4041740/contracts/contracts/VotingEscrow.sol#L886

https://github.com/code-423n4/2022-05-velodrome/blob/7fda97c570b758bbfa7dd6724a336c43d4041740/contracts/contracts/VotingEscrow.sol#L942

https://github.com/code-423n4/2022-05-velodrome/blob/7fda97c570b758bbfa7dd6724a336c43d4041740/contracts/contracts/VotingEscrow.sol#L1017

https://github.com/code-423n4/2022-05-velodrome/blob/7fda97c570b758bbfa7dd6724a336c43d4041740/contracts/contracts/VotingEscrow.sol#L1146

https://github.com/code-423n4/2022-05-velodrome/blob/7fda97c570b758bbfa7dd6724a336c43d4041740/contracts/contracts/VotingEscrow.sol#L1317

https://github.com/code-423n4/2022-05-velodrome/blob/7fda97c570b758bbfa7dd6724a336c43d4041740/contracts/contracts/VotingEscrow.sol#L1380

https://github.com/code-423n4/2022-05-velodrome/blob/7fda97c570b758bbfa7dd6724a336c43d4041740/contracts/contracts/VotingEscrow.sol#L1384

https://github.com/code-423n4/2022-05-velodrome/blob/7fda97c570b758bbfa7dd6724a336c43d4041740/contracts/contracts/VotingEscrow.sol#L1388

https://github.com/code-423n4/2022-05-velodrome/blob/7fda97c570b758bbfa7dd6724a336c43d4041740/contracts/contracts/Router.sol#L341

https://github.com/code-423n4/2022-05-velodrome/blob/7fda97c570b758bbfa7dd6724a336c43d4041740/contracts/contracts/Router.sol#L406

Mitigation

Reduce revert strings to 32 bytes

6. `!= 0` is more efficient than `> 0` for unsigned integers

!= 0 costs less compared to >0 for unsigned integers in require statements with optimizer enabled

Proof of concept

https://github.com/code-423n4/2022-05-velodrome/blob/7fda97c570b758bbfa7dd6724a336c43d4041740/contracts/contracts/VotingEscrow.sol#L772

https://github.com/code-423n4/2022-05-velodrome/blob/7fda97c570b758bbfa7dd6724a336c43d4041740/contracts/contracts/PairFees.sol#L20

https://github.com/code-423n4/2022-05-velodrome/blob/7fda97c570b758bbfa7dd6724a336c43d4041740/contracts/contracts/Router.sol#L58-L59

https://github.com/code-423n4/2022-05-velodrome/blob/7fda97c570b758bbfa7dd6724a336c43d4041740/contracts/contracts/Gauge.sol#L512

https://github.com/code-423n4/2022-05-velodrome/blob/7fda97c570b758bbfa7dd6724a336c43d4041740/contracts/contracts/Gauge.sol#L592

https://github.com/code-423n4/2022-05-velodrome/blob/7fda97c570b758bbfa7dd6724a336c43d4041740/contracts/contracts/Gauge.sol#L613

https://github.com/code-423n4/2022-05-velodrome/blob/7fda97c570b758bbfa7dd6724a336c43d4041740/contracts/contracts/Gauge.sol#L665

https://github.com/code-423n4/2022-05-velodrome/blob/7fda97c570b758bbfa7dd6724a336c43d4041740/contracts/contracts/Gauge.sol#L672

https://github.com/code-423n4/2022-05-velodrome/blob/7fda97c570b758bbfa7dd6724a336c43d4041740/contracts/contracts/Gauge.sol#L679

https://github.com/code-423n4/2022-05-velodrome/blob/7fda97c570b758bbfa7dd6724a336c43d4041740/contracts/contracts/Voter.sol#L352

7. `i++` can be replaced with `++i`

pre-increment costs less compared to post-increment for unsigned integers.

Proof of concept

VotingEscrow.sol#L632
VotingEscrow.sol#L1193
VotingEscrow.sol#L1225
VotingEscrow.sol#L1249
VotingEscrow.sol#L1295
VotingEscrow.sol#L1320
VotingEscrow.sol#L1326
Router.sol#L90
Router.sol#L316
RewardsDistributor.sol#L75
RewardsDistributor.sol#L105
RewardsDistributor.sol#L121
RewardsDistributor.sol#L148
RewardsDistributor.sol#L195
RewardsDistributor.sol#L252
RewardsDistributor.sol#L301
Gauge.sol#L179
Gauge.sol#L353
Voter.sol#L143
Voter.sol#L147
Voter.sol#L266
Voter.sol#L304
Voter.sol#L310
Voter.sol#L346

Mitigation

Replace post-increment with pre-increment

code-423n4 / 2022-05-velodrome-findings

Gas Optimizations #180

1. Unnecessary initialising with default values

Proof of concept

Mitigation

2. Cache storage values and re-use to save gas

Proof of concept

Mitigation

3. Cache array length to save gas

Proof of concept

Mitigation

4. storage variable can be replaced with `msg.sender`

Proof of concept

Mitigation

5. Shorten revert strings

Proof of concept

Mitigation

6. `!= 0` is more efficient than `> 0` for unsigned integers

Proof of concept

7. `i++` can be replaced with `++i`

Proof of concept

Mitigation

code-423n4 / 2022-05-velodrome-findings

Gas Optimizations #180

1. Unnecessary initialising with default values

Proof of concept

Mitigation

2. Cache storage values and re-use to save gas

Proof of concept

Mitigation

3. Cache array length to save gas

Proof of concept

Mitigation

4. storage variable can be replaced with msg.sender

Proof of concept

Mitigation

5. Shorten revert strings

Proof of concept

Mitigation

6. != 0 is more efficient than > 0 for unsigned integers

Proof of concept

7. i++ can be replaced with ++i

Proof of concept

Mitigation

4. storage variable can be replaced with `msg.sender`

6. `!= 0` is more efficient than `> 0` for unsigned integers

7. `i++` can be replaced with `++i`