Gas Optimizations

[code423n4]

#1 Visibility

https://github.com/code-423n4/2022-08-foundation/blob/792e00df429b0df9ee5d909a0a5a6e72bd07cf79/contracts/mixins/nftDropMarket/NFTDropMarketFixedPriceSale.sol#L70

https://github.com/code-423n4/2022-08-foundation/blob/792e00df429b0df9ee5d909a0a5a6e72bd07cf79/contracts/mixins/roles/MinterRole.sol#L19

Reducing from public to private or internal can save gas when a constant isn’t used outside of its contract. I suggest changing the visibility from public to internal or private.

#2 Looping

https://github.com/code-423n4/2022-08-foundation/blob/792e00df429b0df9ee5d909a0a5a6e72bd07cf79/contracts/mixins/shared/MarketFees.sol#L126

https://github.com/code-423n4/2022-08-foundation/blob/792e00df429b0df9ee5d909a0a5a6e72bd07cf79/contracts/mixins/shared/MarketFees.sol#L198

https://github.com/code-423n4/2022-08-foundation/blob/792e00df429b0df9ee5d909a0a5a6e72bd07cf79/contracts/mixins/shared/MarketFees.sol#L484

default uint is 0 so remove unnecassary explicit can reduce gas.
caching the array length can reduce gas it caused access to a local variable is more cheap than query storage / calldata / memory in solidity.

#3 use calldata instead of memory

https://github.com/code-423n4/2022-08-foundation/blob/792e00df429b0df9ee5d909a0a5a6e72bd07cf79/contracts/libraries/BytesLibrary.sol#L16

https://github.com/code-423n4/2022-08-foundation/blob/792e00df429b0df9ee5d909a0a5a6e72bd07cf79/contracts/libraries/BytesLibrary.sol#L38

https://github.com/code-423n4/2022-08-foundation/blob/792e00df429b0df9ee5d909a0a5a6e72bd07cf79/contracts/mixins/shared/MarketFees.sol#L181-L182

https://github.com/code-423n4/2022-08-foundation/blob/792e00df429b0df9ee5d909a0a5a6e72bd07cf79/contracts/libraries/ArrayLibrary.sol#L13

https://github.com/code-423n4/2022-08-foundation/blob/792e00df429b0df9ee5d909a0a5a6e72bd07cf79/contracts/libraries/ArrayLibrary.sol#L25

https://github.com/code-423n4/2022-08-foundation/blob/792e00df429b0df9ee5d909a0a5a6e72bd07cf79/contracts/NFTCollectionFactory.sol#L371

When arguments are read-only on external functions, the function() has an inputed parameter that using memory, if this function didnt change the parameter, its cheaper to use calldata then memory. so we suggest to change it.

#4 Use storage instead memory

https://github.com/code-423n4/2022-08-foundation/blob/792e00df429b0df9ee5d909a0a5a6e72bd07cf79/contracts/libraries/AddressLibrary.sol#L29

https://github.com/code-423n4/2022-08-foundation/blob/792e00df429b0df9ee5d909a0a5a6e72bd07cf79/contracts/mixins/nftDropMarket/NFTDropMarketFixedPriceSale.sol#L284

https://github.com/code-423n4/2022-08-foundation/blob/792e00df429b0df9ee5d909a0a5a6e72bd07cf79/contracts/mixins/nftDropMarket/NFTDropMarketFixedPriceSale.sol#L180

https://github.com/code-423n4/2022-08-foundation/blob/792e00df429b0df9ee5d909a0a5a6e72bd07cf79/contracts/libraries/BytesLibrary.sol#L21-L22

https://github.com/code-423n4/2022-08-foundation/blob/792e00df429b0df9ee5d909a0a5a6e72bd07cf79/contracts/mixins/shared/MarketFees.sol#L112-L113

Use storage instead of memory to reduce the gas fee. i suggest to change this.

#5 Cache recipients.length

https://github.com/code-423n4/2022-08-foundation/blob/792e00df429b0df9ee5d909a0a5a6e72bd07cf79/contracts/mixins/shared/MarketFees.sol#L263

https://github.com/code-423n4/2022-08-foundation/blob/792e00df429b0df9ee5d909a0a5a6e72bd07cf79/contracts/mixins/shared/MarketFees.sol#L315

cache the recipients.length to the local too for saving the gas fee. because mload is cheaper than sload.

#6 Cache recipientBasisPoints.length

https://github.com/code-423n4/2022-08-foundation/blob/792e00df429b0df9ee5d909a0a5a6e72bd07cf79/contracts/mixins/shared/MarketFees.sol#L320

cache the recipientBasisPoints.length to the local too for saving the gas fee. because mload is cheaper than sload.

#7 Cache creatorRecipients.length
https://github.com/code-423n4/2022-08-foundation/blob/792e00df429b0df9ee5d909a0a5a6e72bd07cf79/contracts/mixins/shared/MarketFees.sol#L432-L465

cache the creatorRecipients.length to the local too for saving the gas fee. because mload is cheaper than sload.

#8 Reduce string

https://github.com/code-423n4/2022-08-foundation/blob/792e00df429b0df9ee5d909a0a5a6e72bd07cf79/contracts/NFTCollectionFactory.sol#L173

https://github.com/code-423n4/2022-08-foundation/blob/792e00df429b0df9ee5d909a0a5a6e72bd07cf79/contracts/NFTCollectionFactory.sol#L182

https://github.com/code-423n4/2022-08-foundation/blob/792e00df429b0df9ee5d909a0a5a6e72bd07cf79/contracts/NFTCollectionFactory.sol#L203

https://github.com/code-423n4/2022-08-foundation/blob/792e00df429b0df9ee5d909a0a5a6e72bd07cf79/contracts/NFTCollectionFactory.sol#L227

https://github.com/code-423n4/2022-08-foundation/blob/792e00df429b0df9ee5d909a0a5a6e72bd07cf79/contracts/libraries/AddressLibrary.sol#L31

https://github.com/code-423n4/2022-08-foundation/blob/792e00df429b0df9ee5d909a0a5a6e72bd07cf79/contracts/NFTDropCollection.sol#L88

https://github.com/code-423n4/2022-08-foundation/blob/792e00df429b0df9ee5d909a0a5a6e72bd07cf79/contracts/mixins/roles/AdminRole.sol#L19

https://github.com/code-423n4/2022-08-foundation/blob/792e00df429b0df9ee5d909a0a5a6e72bd07cf79/contracts/mixins/collections/SequentialMintCollection.sol#L63

https://github.com/code-423n4/2022-08-foundation/blob/792e00df429b0df9ee5d909a0a5a6e72bd07cf79/contracts/mixins/collections/SequentialMintCollection.sol#L74

https://github.com/code-423n4/2022-08-foundation/blob/792e00df429b0df9ee5d909a0a5a6e72bd07cf79/contracts/mixins/collections/SequentialMintCollection.sol#L87-L89

Shortening revert strings to fit in 32 bytes will decrease deployment time gas and will decrease runtime gas when the revert condition is met.
Revert strings that are longer than 32 bytes require at least one additional mstore, along with additional overhead for computing memory offset, etc.

#9 Use custom error instead revert string to save gas
https://github.com/code-423n4/2022-08-foundation/blob/792e00df429b0df9ee5d909a0a5a6e72bd07cf79/contracts/NFTCollectionFactory.sol#L173

https://github.com/code-423n4/2022-08-foundation/blob/792e00df429b0df9ee5d909a0a5a6e72bd07cf79/contracts/NFTCollectionFactory.sol#L182

https://github.com/code-423n4/2022-08-foundation/blob/792e00df429b0df9ee5d909a0a5a6e72bd07cf79/contracts/NFTCollectionFactory.sol#L203

https://github.com/code-423n4/2022-08-foundation/blob/792e00df429b0df9ee5d909a0a5a6e72bd07cf79/contracts/NFTCollectionFactory.sol#L227

https://github.com/code-423n4/2022-08-foundation/blob/792e00df429b0df9ee5d909a0a5a6e72bd07cf79/contracts/libraries/AddressLibrary.sol#L31

https://github.com/code-423n4/2022-08-foundation/blob/792e00df429b0df9ee5d909a0a5a6e72bd07cf79/contracts/NFTDropCollection.sol#L88

https://github.com/code-423n4/2022-08-foundation/blob/792e00df429b0df9ee5d909a0a5a6e72bd07cf79/contracts/mixins/roles/AdminRole.sol#L19

https://github.com/code-423n4/2022-08-foundation/blob/792e00df429b0df9ee5d909a0a5a6e72bd07cf79/contracts/mixins/collections/SequentialMintCollection.sol#L63

https://github.com/code-423n4/2022-08-foundation/blob/792e00df429b0df9ee5d909a0a5a6e72bd07cf79/contracts/mixins/collections/SequentialMintCollection.sol#L74

https://github.com/code-423n4/2022-08-foundation/blob/792e00df429b0df9ee5d909a0a5a6e72bd07cf79/contracts/mixins/collections/SequentialMintCollection.sol#L87-L89

Custom errors from Solidity 0.8.4 are cheaper than revert strings (cheaper deployment cost and runtime cost when the revert condition is met)

#10 Increment

https://github.com/code-423n4/2022-08-foundation/blob/792e00df429b0df9ee5d909a0a5a6e72bd07cf79/contracts/NFTCollectionFactory.sol#L207

https://github.com/code-423n4/2022-08-foundation/blob/792e00df429b0df9ee5d909a0a5a6e72bd07cf79/contracts/NFTCollectionFactory.sol#L230

pre increment e.g ++i more cheaper gas than post increment e.g i++. i suggest to use pre increment.

#11 Use != 0 instead >0

https://github.com/code-423n4/2022-08-foundation/blob/792e00df429b0df9ee5d909a0a5a6e72bd07cf79/contracts/NFTDropCollection.sol#L88

https://github.com/code-423n4/2022-08-foundation/blob/792e00df429b0df9ee5d909a0a5a6e72bd07cf79/contracts/NFTDropCollection.sol#L130-L131

!= 0 costs less gas compared to > 0 for unsigned integers in require statements with the optimizer enabled (6 gas)

[HardlyDifficult]

Using private rather than public for constants to saves gas.

Agree but won't fix. For ease of use and consistency we will continue to expose some constants publicly.

Don't initialize variables with default values.

Invalid. This optimization technique is no longer applicable with the current version of Solidity.

calldata

Valid & will fix. This saves ~50 gas on createNFTCollection and ~60 gas on createNFTDropCollectionWithPaymentFactory

Updated startsWith, NFTCollection, and the AddressLibrary & call
Invalid for capLength due to how that data is sourced. Same for replaceAtIf.

Use storage instead memory

For the encode examples this is invalid, storage cannot be used.
For mint, we tested and found this caused a small regression - maybe because all fields are being used here.
For the return values this is invalid, storage cannot be used.

Cache Array Length Outside of Loop

May be theoretically valid, but won't fix. I tested this: gas-reporter and our gas-stories suite is reporting a small regression using this technique. It also hurts readability a bit so we wouldn't want to include it unless it was a clear win.

Cache recipientBasisPoints.length

Cache creatorRecipients.length

Little to no benefit. And the comment is invalid, these are not sloads.

Use short error messages

Agree but won't fix. We use up to 64 bytes, aiming to respect the incremental cost but 32 bytes is a bit too short to provide descriptive error messages for our users.

Custom errors

Agree but won't fix at this time. We use these in the market but not in collections. Unfortunately custom errors are still not as good of an experience for users (e.g. on etherscan). We used them in the market originally because we were nearing the max contract size limit and this was a good way to reduce the bytecode. We'll consider this in the future as tooling continues to improve.

++i costs less than i++

Agree and will fix.

Use != 0 instead of > 0

Invalid. We tested the recommendation and got the following results:

createNFTDropCollection gas reporter results:
  using > 0 (current):
    - 319246  ·     319578  ·      319361
  using != 0 (recommendation):
    -  319252  ·     319584  ·      319367
  impact: +6 gas