Gas Optimizations

[code423n4]

Unnecessary equals boolean

Boolean variables can be checked within conditionals directly without the use of equality operators to true/false.

Code instances:

    RewardFactory.sol, 40: require(rewardAccess[msg.sender] == true, "!auth");
    ExtraRewardStashV1.sol, 152: if (token == address(0)) return true;
    RewardFactory.sol, 103: require(operators.contains(_msgSender()) || rewardAccess[_msgSender()] == true, "!auth");
    VoterProxy.sol, 96: if (protectedTokens[_gauge] == false) {
    Booster.sol, 498: require(pool.shutdown == false, "pool is closed");

State variables that could be set immutable

In the following files there are state variables that could be set immutable to save gas.

Code instances:

    _symbol in VE3DLocker.sol
    veToken in VeTokenMinter.sol
    _name in VE3DLocker.sol
    rewardFactory in StashFactory.sol
    totalCliffs in VeTokenMinter.sol

Unused state variables

Unused state variables are gas consuming at deployment (since they are located in storage) and are
a bad code practice. Removing those variables will decrease deployment gas cost and improve code quality.
This is a full list of all the unused storage variables we found in your code base.

Code instances:

    ExtraRewardStashV1.sol, maxRewards
    ExtraRewardStashV3.sol, WEEK

Unused declared local variables

Unused local variables are gas consuming, since the initial value assignment costs gas. And are
a bad code practice. Removing those variables will decrease the gas cost and improve code quality.
This is a full list of all the unused storage variables we found in your code base.

Code instances:

    VE3DLocker.sol, _checkpointEpoch, nextEpochDate
    VE3DLocker.sol, constructor, currentEpoch

Caching array length can save gas

Caching the array length is more gas efficient.
This is because access to a local variable in solidity is more efficient than query storage / calldata / memory.
We recommend to change from:

for (uint256 i=0; i<array.length; i++) { ... }

to:

uint len = array.length  
for (uint256 i=0; i<len; i++) { ... }

Code instances:

    BaseRewardPool.sol, extraRewards, 218
    Booster.sol, poolInfo, 329
    VE3DLocker.sol, userRewards, 286
    VE3DLocker.sol, locks, 457
    VE3DLocker.sol, rewardTokens, 720

Prefix increments are cheaper than postfix increments

Prefix increments are cheaper than postfix increments.
Further more, using unchecked {++x} is even more gas efficient, and the gas saving accumulates every iteration and can make a real change
There is no risk of overflow caused by increamenting the iteration index in for loops (the ++i in for (uint256 i = 0; i < numIterations; ++i)).
But increments perform overflow checks that are not necessary in this case.
These functions use not using prefix increments (++x) or not using the unchecked keyword:

Code instances:

    change to prefix increment and unchecked: VE3DRewardPool.sol, i, 257
    change to prefix increment and unchecked: VE3DLocker.sol, i, 720
    change to prefix increment and unchecked: Booster.sol, i, 329
    change to prefix increment and unchecked: ExtraRewardStashV2.sol, i, 213
    change to prefix increment and unchecked: VE3DLocker.sol, i, 457

Unnecessary index init

In for loops you initialize the index to start from 0, but it already initialized to 0 in default and this assignment cost gas.
It is more clear and gas efficient to declare without assigning 0 and will have the same meaning:

Code instances:

    ExtraRewardStashV2.sol, 137
    RewardFactory.sol, 49
    ExtraRewardStashV3.sol, 84
    BaseRewardPool.sol, 199
    VE3DRewardPool.sol, 148

Unnecessary default assignment

Unnecessary default assignments, you can just declare and it will save gas and have the same meaning.

Code instances:

    BaseRewardPool.sol (L#70) : uint256 public queuedRewards = 0;
    VeAssetDepositor.sol (L#28) : uint256 public incentiveVeAsset = 0;
    VirtualBalanceRewardPool.sol (L#74) : uint256 public periodFinish = 0;
    BaseRewardPool.sol (L#71) : uint256 public currentRewards = 0;
    VirtualBalanceRewardPool.sol (L#78) : uint256 public queuedRewards = 0;

Rearrange state variables

You can change the order of the storage variables to decrease memory uses.

Code instances:

In VoterProxy.sol,rearranging the storage fields can optimize to: 9 slots from: 10 slots.
The new order of types (you choose the actual variables):
1. string
2. IVoteEscrow.EscrowModle
3. address
4. bytes4
5. address
6. address
7. address
8. address
9. address
10. address

In VE3DLocker.sol,rearranging the storage fields can optimize to: 11 slots from: 12 slots.
The new order of types (you choose the actual variables):
1. IERC20
2. EnumerableSet.AddressSet
3. uint256
4. uint256
5. uint256
6. uint256
7. uint256
8. uint256
9. string
10. string
11. uint8
12. bool

Short the following require messages

The following require messages are of length more than 32 and we think are short enough to short
them into exactly 32 characters such that it will be placed in one slot of memory and the require
function will cost less gas.
The list:

Code instances:

    Solidity file: BitMath.sol, In line 45, Require message length to shorten: 34, The message: BitMath::leastSignificantBit: zero
    Solidity file: FixedPoint.sol, In line 85, Require message length to shorten: 33, The message: FixedPoint::muluq: upper overflow
    Solidity file: FixedPoint.sol, In line 105, Require message length to shorten: 35, The message: FixedPoint::divuq: division by zero
    Solidity file: BitMath.sol, In line 8, Require message length to shorten: 33, The message: BitMath::mostSignificantBit: zero
    Solidity file: FixedPoint.sol, In line 131, Require message length to shorten: 38, The message: FixedPoint::fraction: division by zero

Use != 0 instead of > 0

Using != 0 is slightly cheaper than > 0. (see code-423n4/2021-12-maple-findings#75 for similar issue)

Code instances:

    BaseRewardPool.sol, 196: change '_amount > 0' to '_amount != 0'
    VE3DLocker.sol, 649: change '_checkDelay > 0' to '_checkDelay != 0'
    VE3DLocker.sol, 626: change '_checkDelay > 0' to '_checkDelay != 0'
    Booster.sol, 590: change 'stakerLockFeesIncentive > 0' to 'stakerLockFeesIncentive != 0'
    BitMath.sol, 8: change 'x > 0' to 'x != 0'

Use unchecked to save gas for certain additive calculations that cannot overflow

You can use unchecked in the following calculations since there is no risk to overflow:

Code instances:

    VeAssetDepositor.sol (L#73) - uint256 unlockAt = block.timestamp + maxTime;
    ExtraRewardStashV1.sol (L#106) - if (block.timestamp > tokenInfo.lastActiveTime + WEEK) { 
    VeAssetDepositor.sol (L#102) - uint256 unlockAt = block.timestamp + maxTime;
    ExtraRewardStashV2.sol (L#187) - if (block.timestamp <= t.lastActiveTime + WEEK) {
    ExtraRewardStashV2.sol (L#101) - if (block.timestamp > tokenInfo[i].lastActiveTime + WEEK) { 

Consider inline the following functions to save gas

You can inline the following functions instead of writing a specific function to save gas.
(see https://github.com/code-423n4/2021-11-nested-findings/issues/167 for a similar issue.)

Code instances

    FixedPoint.sol, decode, { return uint112(self._x >> RESOLUTION); }
    FixedPoint.sol, decode144, { return uint144(self._x >> RESOLUTION); }
    FixedPoint.sol, encode144, { return uq144x112(uint256(x) << RESOLUTION); }
    FixedPoint.sol, encode, { return uq112x112(uint224(x) << RESOLUTION); }
    VE3DLocker.sol, _lastTimeRewardApplicable, { return Math.min(block.timestamp, _finishTime); }

Inline one time use functions

The following functions are used exactly once. Therefore you can inline them and save gas and improve code clearness.

Code instances:

    VE3DLocker.sol, _notifyReward
    ExtraRewardStashV3.sol, checkForNewRewardTokens
    VoterProxy.sol, _withdrawSome
    Booster.sol, _earmarkRewards
    ExtraRewardStashV1.sol, setToken

Upgrade pragma to at least 0.8.4

Using newer compiler versions and the optimizer gives gas optimizations
and additional safety checks are available for free.

The advantages of versions 0.8.* over <0.8.0 are:

    1. Safemath by default from 0.8.0 (can be more gas efficient than library based safemath.)
    2. Low level inliner : from 0.8.2, leads to cheaper runtime gas. Especially relevant when the contract has small functions. For example, OpenZeppelin libraries typically have a lot of small helper functions and if they are not inlined, they cost an additional 20 to 40 gas because of 2 extra jump instructions and additional stack operations needed for function calls.
    3. Optimizer improvements in packed structs: Before 0.8.3, storing packed structs, in some cases used an additional storage read operation. After EIP-2929, if the slot was already cold, this means unnecessary stack operations and extra deploy time costs. However, if the slot was already warm, this means additional cost of 100 gas alongside the same unnecessary stack operations and extra deploy time costs.
    4. Custom errors from 0.8.4, leads to cheaper deploy time cost and run time cost. Note: the run time cost is only relevant when the revert condition is met. In short, replace revert strings by custom errors.

Code instances:

    FullMath.sol
    Babylonian.sol
    FixedPoint.sol
    BitMath.sol
    Migrations.sol

Do not cache msg.sender

We recommend not to cache msg.sender since calling it is 2 gas while reading a variable is more.

Code instances:

    https://github.com/code-423n4/2022-05-vetoken/tree/main/contracts/VoterProxy.sol#L52
    https://github.com/code-423n4/2022-05-vetoken/tree/main/contracts/VeAssetDepositor.sol#L48
    https://github.com/code-423n4/2022-05-vetoken/tree/main/contracts/token/VE3Token.sol#L19
    https://github.com/code-423n4/2022-05-vetoken/tree/main/contracts/token/VeToken.sol#L16
    https://github.com/code-423n4/2022-05-vetoken/tree/main/contracts/Booster.sol#L112

[GalloDaSballo]

5 immutables will save 2.1k * 5 = 10500 gas

Rest will save less than 500 gas

Let's estimate at 11k saved