Gas Optimizations

[code423n4]

[S]: Suggested optimation, save a decent amount of gas without compromising readability;

[M]: Minor optimation, the amount of gas saved is minor, change when you see fit;

[N]: Non-preferred, the amount of gas saved is at cost of readability, only apply when gas saving is a top priority.

ISSUE LIST

C4-001: Revert String Size Optimization - [S]

C4-002 : Adding unchecked directive can save gas - [S]

C4-003 : Check if amount > 0 before token transfer can save gas - [S]

C4-004 : There is no need to assign default values to variables - [N]

C4-005 : Using operator && used more gas - [M]

C4-006 : Non-strict inequalities are cheaper than strict ones - [N]

C4-007 : Use Custom Errors instead of Revert Strings to save Gas - [S]

C4-008 : Use Shift Right/Left instead of Division/Multiplication if possible [N]

C4-009 : State Variables that can be changed to immutable - [N]

C4-010 : Keccak functions in constants waste gas - [M]

C4-011 : > 0 can be replaced with != 0 for gas optimization - [S]

C4-001: Revert String Size Optimization

Impact

Shortening revert strings to fit in 32 bytes will decrease deploy time gas and will decrease runtime gas when the revert condition has been met.

Revert strings that are longer than 32 bytes require at least one additional mstore, along with additional overhead for computing memory offset, etc.

Proof of Concept

Revert strings > 32 bytes are here:

https://github.com/code-423n4/2022-06-infinity/blob/main/contracts/core/InfinityExchange.sol#L395

https://github.com/code-423n4/2022-06-infinity/blob/main/contracts/core/InfinityExchange.sol#L1141

Tools Used

Manual Review

Recommended Mitigation Steps

Shorten the revert strings to fit in 32 bytes. That will affect gas optimization.

C4-002 : Adding unchecked directive can save gas

Impact

For the arithmetic operations that will never over/underflow, using the unchecked directive (Solidity v0.8 has default overflow/underflow checks) can save some gas from the unnecessary internal over/underflow checks.

Proof of Concept

https://github.com/code-423n4/2022-06-infinity/blob/main/contracts/core/InfinityOrderBookComplication.sol#L201

Tools Used

None

Recommended Mitigation Steps

Consider applying unchecked arithmetic where overflow/underflow is not possible. Example can be seen from below.

Unchecked{i++};

C4-003 : Check if amount > 0 before token transfer can save gas

Impact

Since _amount can be 0. Checking if (_amount != 0) before the transfer can potentially save an external call and the unnecessary gas cost of a 0 token transfer.

Proof of Concept

https://github.com/code-423n4/2022-06-infinity/blob/main/contracts/staking/InfinityStaker.sol#L346

All Contracts

Tools Used

None

Recommended Mitigation Steps

Consider checking amount != 0.

C4-004 : There is no need to assign default values to variables

Impact - Gas Optimization

Boolean is default initialized to false. There is no need assign false to variable.

Proof of Concept

  2022-06-infinity/contracts/core/InfinityExchange.sol::148 => for (uint256 i = 0; i < numMakerOrders; ) {
  2022-06-infinity/contracts/core/InfinityExchange.sol::200 => for (uint256 i = 0; i < ordersLength; ) {
  2022-06-infinity/contracts/core/InfinityExchange.sol::219 => for (uint256 i = 0; i < ordersLength; ) {
  2022-06-infinity/contracts/core/InfinityExchange.sol::272 => for (uint256 i = 0; i < numSells; ) {
  2022-06-infinity/contracts/core/InfinityExchange.sol::308 => for (uint256 i = 0; i < numMakerOrders; ) {
  2022-06-infinity/contracts/core/InfinityExchange.sol::349 => for (uint256 i = 0; i < ordersLength; ) {
  2022-06-infinity/contracts/core/InfinityExchange.sol::393 => for (uint256 i = 0; i < numNonces; ) {
  2022-06-infinity/contracts/core/InfinityExchange.sol::1048 => for (uint256 i = 0; i < numNfts; ) {
  2022-06-infinity/contracts/core/InfinityExchange.sol::1086 => for (uint256 i = 0; i < numTokens; ) {
  2022-06-infinity/contracts/core/InfinityExchange.sol::1109 => for (uint256 i = 0; i < numNfts; ) {
  2022-06-infinity/contracts/core/InfinityExchange.sol::1190 => for (uint256 i = 0; i < numNfts; ) {
  2022-06-infinity/contracts/core/InfinityExchange.sol::1206 => for (uint256 i = 0; i < numTokens; ) {
  2022-06-infinity/contracts/core/InfinityOrderBookComplication.sol::76 => for (uint256 i = 0; i < ordersLength; ) {
  2022-06-infinity/contracts/core/InfinityOrderBookComplication.sol::82 => for (uint256 j = 0; j < nftsLength; ) {
  2022-06-infinity/contracts/core/InfinityOrderBookComplication.sol::197 => uint256 numConstructedItems = 0;
  2022-06-infinity/contracts/core/InfinityOrderBookComplication.sol::199 => for (uint256 i = 0; i < nftsLength; ) {
  2022-06-infinity/contracts/core/InfinityOrderBookComplication.sol::214 => uint256 numTakerItems = 0;
  2022-06-infinity/contracts/core/InfinityOrderBookComplication.sol::216 => for (uint256 i = 0; i < nftsLength; ) {
  2022-06-infinity/contracts/core/InfinityOrderBookComplication.sol::244 => uint256 numCollsMatched = 0;
  2022-06-infinity/contracts/core/InfinityOrderBookComplication.sol::246 => for (uint256 i = 0; i < order2NftsLength; ) {
  2022-06-infinity/contracts/core/InfinityOrderBookComplication.sol::247 => for (uint256 j = 0; j < order1NftsLength; ) {
  2022-06-infinity/contracts/core/InfinityOrderBookComplication.sol::289 => uint256 numTokenIdsPerCollMatched = 0;
  2022-06-infinity/contracts/core/InfinityOrderBookComplication.sol::290 => for (uint256 k = 0; k < item2TokensLength; ) {
  2022-06-infinity/contracts/core/InfinityOrderBookComplication.sol::291 => for (uint256 l = 0; l < item1TokensLength; ) {
  2022-06-infinity/contracts/core/InfinityOrderBookComplication.sol::318 => uint256 sum = 0;
  2022-06-infinity/contracts/core/InfinityOrderBookComplication.sol::320 => for (uint256 i = 0; i < ordersLength; ) {

Tools Used

Code Review

Recommended Mitigation Steps

bool x = false costs more gas than bool x without having any different functionality.

C4-005 : Using operator && used more gas

Impact

Using double require instead of operator && can save more gas.

Proof of Concept

1. Navigate to the following contracts.

https://github.com/code-423n4/2022-06-infinity/blob/main/contracts/staking/InfinityStaker.sol#L215-L220

Tools Used

Code Review

Recommended Mitigation Steps

Example

using &&:

function check(uint x)public view{
require(x == 0 && x < 1 );
}
// gas cost 21630

using double require:

require(x == 0 );
require( x < 1);
}
}
// gas cost 21622

C4-006 : Non-strict inequalities are cheaper than strict ones

Impact

Strict inequalities add a check of non equality which costs around 3 gas.

Proof of Concept

  2022-06-infinity/contracts/MockERC721.sol::11 => for (uint256 i = 0; i < 100; i++) {
  2022-06-infinity/contracts/core/InfinityExchange.sol::148 => for (uint256 i = 0; i < numMakerOrders; ) {
  2022-06-infinity/contracts/core/InfinityExchange.sol::200 => for (uint256 i = 0; i < ordersLength; ) {
  2022-06-infinity/contracts/core/InfinityExchange.sol::219 => for (uint256 i = 0; i < ordersLength; ) {
  2022-06-infinity/contracts/core/InfinityExchange.sol::272 => for (uint256 i = 0; i < numSells; ) {
  2022-06-infinity/contracts/core/InfinityExchange.sol::308 => for (uint256 i = 0; i < numMakerOrders; ) {
  2022-06-infinity/contracts/core/InfinityExchange.sol::349 => for (uint256 i = 0; i < ordersLength; ) {
  2022-06-infinity/contracts/core/InfinityExchange.sol::393 => for (uint256 i = 0; i < numNonces; ) {
  2022-06-infinity/contracts/core/InfinityExchange.sol::1048 => for (uint256 i = 0; i < numNfts; ) {
  2022-06-infinity/contracts/core/InfinityExchange.sol::1086 => for (uint256 i = 0; i < numTokens; ) {
  2022-06-infinity/contracts/core/InfinityExchange.sol::1109 => for (uint256 i = 0; i < numNfts; ) {
  2022-06-infinity/contracts/core/InfinityExchange.sol::1190 => for (uint256 i = 0; i < numNfts; ) {
  2022-06-infinity/contracts/core/InfinityExchange.sol::1206 => for (uint256 i = 0; i < numTokens; ) {
  2022-06-infinity/contracts/core/InfinityOrderBookComplication.sol::76 => for (uint256 i = 0; i < ordersLength; ) {
  2022-06-infinity/contracts/core/InfinityOrderBookComplication.sol::82 => for (uint256 j = 0; j < nftsLength; ) {
  2022-06-infinity/contracts/core/InfinityOrderBookComplication.sol::197 => uint256 numConstructedItems = 0;
  2022-06-infinity/contracts/core/InfinityOrderBookComplication.sol::199 => for (uint256 i = 0; i < nftsLength; ) {
  2022-06-infinity/contracts/core/InfinityOrderBookComplication.sol::214 => uint256 numTakerItems = 0;
  2022-06-infinity/contracts/core/InfinityOrderBookComplication.sol::216 => for (uint256 i = 0; i < nftsLength; ) {
  2022-06-infinity/contracts/core/InfinityOrderBookComplication.sol::244 => uint256 numCollsMatched = 0;
  2022-06-infinity/contracts/core/InfinityOrderBookComplication.sol::246 => for (uint256 i = 0; i < order2NftsLength; ) {
  2022-06-infinity/contracts/core/InfinityOrderBookComplication.sol::247 => for (uint256 j = 0; j < order1NftsLength; ) {
  2022-06-infinity/contracts/core/InfinityOrderBookComplication.sol::289 => uint256 numTokenIdsPerCollMatched = 0;
  2022-06-infinity/contracts/core/InfinityOrderBookComplication.sol::290 => for (uint256 k = 0; k < item2TokensLength; ) {
  2022-06-infinity/contracts/core/InfinityOrderBookComplication.sol::291 => for (uint256 l = 0; l < item1TokensLength; ) {
  2022-06-infinity/contracts/core/InfinityOrderBookComplication.sol::318 => uint256 sum = 0;
  2022-06-infinity/contracts/core/InfinityOrderBookComplication.sol::320 => for (uint256 i = 0; i < ordersLength; ) {

Tools Used

Code Review

Recommended Mitigation Steps

Use >= or <= instead of > and < when possible.

C4-007 : Use Custom Errors instead of Revert Strings to save Gas

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

Source Custom Errors in Solidity:

Starting from Solidity v0.8.4, there is a convenient and gas-efficient way to explain to users why an operation failed through the use of custom errors. Until now, you could already use strings to give more information about failures (e.g., revert("Insufficient funds.");), but they are rather expensive, especially when it comes to deploy cost, and it is difficult to use dynamic information in them.

Custom errors are defined using the error statement, which can be used inside and outside of contracts (including interfaces and libraries).

Instances include:

All require Statements

Tools Used

Code Review

Recommended Mitigation Steps

Recommended to replace revert strings with custom errors.

C4-008 : Use Shift Right/Left instead of Division/Multiplication if possible

Impact

A division/multiplication by any number x being a power of 2 can be calculated by shifting log2(x) to the right/left.

While the DIV opcode uses 5 gas, the SHR opcode only uses 3 gas. Furthermore, Solidity's division operation also includes a division-by-0 prevention which is bypassed using shifting.

Proof of Concept

  2022-06-infinity/contracts/staking/InfinityStaker.sol::39 => /// the user will get back 100/4 tokens.
  2022-06-infinity/contracts/staking/InfinityStaker.sol::235 => (userstakedAmounts[user][Duration.THREE_MONTHS].amount * 2) +
  2022-06-infinity/contracts/staking/InfinityStaker.sol::237 => (userstakedAmounts[user][Duration.TWELVE_MONTHS].amount * 4)) / (10**18);

Tools Used

None

Recommended Mitigation Steps

A division/multiplication by any number x being a power of 2 can be calculated by shifting log2(x) to the right/left.

C4-009 : State Variables that can be changed to immutable

Impact

Solidity 0.6.5 introduced immutable as a major feature. It allows setting contract-level variables at construction time which gets stored in code rather than storage.

Consider the following generic example:

contract C {
   /// The owner is set during contruction time, and never changed afterwards.
   address public owner = msg.sender;
}

In the above example, each call to the function owner() reads from storage, using a sload. After EIP-2929, this costs 2100 gas cold or 100 gas warm. However, the following snippet is more gas efficient:

contract C {
   /// The owner is set during contruction time, and never changed afterwards.
   address public immutable owner = msg.sender;
}

In the above example, each storage read of the owner state variable is replaced by the instruction push32 value, where value is set during contract construction time. Unlike the last example, this costs only 3 gas.

Code Location

https://github.com/code-423n4/2022-06-infinity/blob/main/contracts/staking/InfinityStaker.sol#L25

Tools Used

None

Recommended Mitigation Steps

Consider using immutable variable.

C4-010 : Keccak functions in constants waste gas

Impact

The contracts assigns two constants to the result of a keccak operation, which results in gas waste since the expression is computed each time the constant is accessed.

See this issue for more context: ethereum/solidity#9232 (https://github.com/ethereum/solidity/issues/9232)

Proof of Concept

  2022-06-infinity/contracts/core/InfinityExchange.sol::1186 => // keccak256('OrderItem(address collection,TokenInfo[] tokens)TokenInfo(uint256 tokenId,uint256 numTokens)')
  2022-06-infinity/contracts/core/InfinityExchange.sol::1191 => bytes32 hash = keccak256(abi.encode(ORDER_ITEM_HASH, nfts[i].collection, _tokensHash(nfts[i].tokens)));
  2022-06-infinity/contracts/core/InfinityExchange.sol::1197 => bytes32 nftsHash = keccak256(abi.encodePacked(hashes));
  2022-06-infinity/contracts/core/InfinityExchange.sol::1202 => // keccak256('TokenInfo(uint256 tokenId,uint256 numTokens)')
  2022-06-infinity/contracts/core/InfinityExchange.sol::1207 => bytes32 hash = keccak256(abi.encode(TOKEN_INFO_HASH, tokens[i].tokenId, tokens[i].numTokens));
  2022-06-infinity/contracts/core/InfinityExchange.sol::1213 => bytes32 tokensHash = keccak256(abi.encodePacked(hashes));
  2022-06-infinity/contracts/libs/SignatureChecker.sol::61 => bytes32 digest = keccak256(abi.encodePacked('\x19\x01', domainSeparator, orderHash));
  2022-06-infinity/contracts/token/InfinityToken.sol::25 => bytes32 public constant EPOCH_INFLATION = keccak256('Inflation');
  2022-06-infinity/contracts/token/InfinityToken.sol::26 => bytes32 public constant EPOCH_DURATION = keccak256('EpochDuration');
  2022-06-infinity/contracts/token/InfinityToken.sol::27 => bytes32 public constant EPOCH_CLIFF = keccak256('Cliff');
  2022-06-infinity/contracts/token/InfinityToken.sol::28 => bytes32 public constant MAX_EPOCHS = keccak256('MaxEpochs');
  2022-06-infinity/contracts/token/TimelockConfig.sol::9 => bytes32 public constant ADMIN = keccak256('Admin');
  2022-06-infinity/contracts/token/TimelockConfig.sol::10 => bytes32 public constant TIMELOCK = keccak256('Timelock');

Tools Used

None

Recommended Mitigation Steps

Replace the constant directive with immutable, or assign the already hashed value to the constants

C4-011 : > 0 can be replaced with != 0 for gas optimization

Impact

!= 0 is a cheaper operation compared to > 0, when dealing with uint.

Proof of Concept

1. Navigate to the following contract sections.

  2022-06-infinity/contracts/core/InfinityExchange.sol::392 => require(numNonces > 0, 'cannot be empty');

Tools Used

None

Recommended Mitigation Steps

Consider to replace > 0 with != 0 for gas optimization.