Y2k Finance contest - ReyAdmirado's results

1. state variables only set in the constructor should be declared immutable

avoids a gsset (20000 gas)

• Controller.sol#L13

• PegOracle.sol#L10

• PegOracle.sol#L11

• PegOracle.sol#L13

• PegOracle.sol#L15

• PegOracle.sol#L16

• SemiFungibleVault.sol#L20

• SemiFungibleVault.sol#L21

• StakingRewards.sol#L41

• RewardsFactory.sol#L9

• RewardsFactory.sol#L10

• RewardsFactory.sol#L11

2. state variables should be cached in stack variables rather than re-reading them from storage

asset

• Vault.sol#L189

treasury and controller should be cached beforehand

• VaultFactory.sol#L203
• VaultFactory.sol#L206

marketIndex should be cached after line 195

• VaultFactory.sol#L195

rewardsDuration

• StakingRewards.sol#L190

admin

• RewardsFactory.sol#L100

govToken

• RewardsFactory.sol#L102

3. <x> += <y> costs more gas than <x> = <x> + <y> for state variables

• VaultFactory.sol#L195

4. not using the named return variables when a function returns, wastes deployment gas

• Controller.sol#L264

• PegOracle.sol#L49

• PegOracle.sol#L89

• PegOracle.sol#L112

• Vault.sol#L162

• Vault.sol#L185

• Vault.sol#L213

• Vault.sol#L263

• Vault.sol#L381

• Vault.sol#L448

• VaultFactory.sol#L186

• VaultFactory.sol#L388

• RewardsFactory.sol#L86

• RewardsFactory.sol#L148

5. ++i costs less gas than i++, especially when it’s used in for-loops (--i/i-- too)

Saves 6 gas per loop

• Vault.sol#L443

6. it costs more gas to initialize non-constant/non-immutable variables to zero than to let the default of zero be applied

• Vault.sol#L443

• VaultFactory.sol#L159

• StakingRewards.sol#L36

7. ++i/i++ should be unchecked{++i}/unchecked{i++} when it is not possible for them to overflow, as is the case when used in for-loop and while-loops

In Solidity 0.8+, there’s a default overflow check on unsigned integers. It’s possible to uncheck this in for-loops and save some gas at each iteration, but at the cost of some code readability, as this uncheck cannot be made inline.

• Vault.sol#L443

8. require()/revert() strings longer than 32 bytes cost extra gas

• PegOracle.sol#L23

• PegOracle.sol#L24

• SemiFungibleVault.sol#L116

• StakingRewards.sol#L217

• StakingRewards.sol#L226

9. using > 0 costs more gas than != 0 when used on a uint in a require() statement

• PegOracle.sol#L98

• PegOracle.sol#L121

• Vault.sol#L187

10. use custom errors rather than revert()/require() strings to save deployment gas

https://blog.soliditylang.org/2021/04/21/custom-errors/

all the require()s need this change

11. using bool for storage incurs overhead

https://github.com/OpenZeppelin/openzeppelin-contracts/blob/58f635312aa21f947cae5f8578638a85aa2519f5/contracts/security/ReentrancyGuard.sol#L23-L27 Use uint256(1) and uint256(2) for true/false to avoid a Gwarmaccess (100 gas) for the extra SLOAD, and to avoid Gsset (20000 gas) when changing from ‘false’ to ‘true’, after having been ‘true’ in the past

• Controller.sol#L277

• Vault.sol#L52

• Vault.sol#L54

• Vault.sol#L336

12. abi.encode() is less efficient than abi.encodepacked()

• RewardsFactory.sol#L118
• RewardsFactory.sol#L150

13. usage of uint/int smaller than 32 bytes (256 bits) incurs overhead

When using elements that are smaller than 32 bytes, your contract’s gas usage may be higher. This is because the EVM operates on 32 bytes at a time. Therefore, if the element is smaller than that, the EVM must use more operations in order to reduce the size of the element from 32 bytes to the desired size. https://docs.soliditylang.org/en/v0.8.11/internals/layout_in_storage.html Use a larger size then downcast where needed

• Controller.sol#L292

• Controller.sol#L296

• PegOracle.sol#L13

• PegOracle.sol#L58

• PegOracle.sol#L62

• PegOracle.sol#L91

• PegOracle.sol#L95

• PegOracle.sol#L114

• PegOracle.sol#L118

14. using private rather than public for constants, saves gas

If needed, the values can be read from the verified contract source code, or if there are multiple values there can be a single getter function that returns a tuple of the values of all currently-public constants. Saves 3406-3606 gas in deployment gas due to the compiler not having to create non-payable getter functions for deployment calldata, not having to store the bytes of the value outside of where it’s used, and not adding another entry to the method ID table

• Controller.sol#L16

15. bytes constants are more efficient than string constants

If data can fit into 32 bytes, then you should use bytes32 datatype rather than bytes or strings as it is cheaper in solidity.

• SemiFungibleVault.sol#L20

• SemiFungibleVault.sol#L21

• SemiFungibleVault.sol#L66

• SemiFungibleVault.sol#L67

• Vault.sol#L116

• Vault.sol#L117

• VaultFactory.sol#L185