Gas Optimizations

[code423n4]

More efficient Struct packing of SwapCalculationCache in the contract AlgebraPool.sol

    The following structs could change the order of their stored elements to decrease memory uses.
    and number of occupied slots. Therefore will save gas at every store and load from memory.

In AlgebraPool.sol, SwapCalculationCache is optimized to: 8 slots from: 9 slots.
The new order of types (you choose the actual variables):
1. uint256
2. int256
3. int256
4. uint256
5. uint256
6. IAlgebraVirtualPool.Status
7. uint160
8. int56
9. int24
10. uint16
11. uint128
12. uint16
13. bool
14. bool

State variables that could be set immutable

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

Code instance:

    owner in AlgebraPoolDeployer.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:

    AlgebraPoolDeployer.sol, parameters
    Constants.sol, RESOLUTION
    Constants.sol, Q96
    Constants.sol, MAX_LIQUIDITY_COOLDOWN
    Constants.sol, COMMUNITY_FEE_DENOMINATOR
    Constants.sol, MAX_COMMUNITY_FEE
    Constants.sol, BASE_FEE
    PoolState.sol, tickTable
    PoolState.sol, liquidityCooldown
    PoolState.sol, totalFeeGrowth0Token
    PoolState.sol, volumePerLiquidityInBlock
    PoolState.sol, activeIncentive
    Constants.sol, Q128
    PoolState.sol, ticks
    PoolState.sol, totalFeeGrowth1Token
    Constants.sol, MAX_LIQUIDITY_PER_TICK

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 instance:

    DataStorage.sol, secondsAgos, 307

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 instance:

    change to prefix increment and unchecked: DataStorage.sol, i, 307

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 instance:

    DataStorage.sol, 307

Rearrange state variables

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

Code instance:

In Constants.sol,rearranging the storage fields can optimize to: 4 slots from: 5 slots.
The new order of types (you choose the actual variables):
1. uint256
2. uint256
3. uint256
4. uint128
5. uint32
6. int24
7. uint16
8. uint8
9. uint8

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:

    AlgebraPool.sol, 734: change 'amountRequired > 0' to 'amountRequired != 0'
    AlgebraPool.sol, 911: change 'amount1 > 0' to 'amount1 != 0'
    PriceMovementMath.sol, 52: change 'price > 0' to 'price != 0'
    AlgebraPool.sol, 237: change 'liquidityDelta > 0' to 'liquidityDelta != 0'
    AlgebraPool.sol, 645: change 'balance > 0' to 'balance != 0'
    FullMath.sol, 114: change 'denominator > 0' to 'denominator != 0'
    DataStorageOperator.sol, 138: change 'liquidity > 0' to 'liquidity != 0'
    PriceMovementMath.sol, 53: change 'liquidity > 0' to 'liquidity != 0'
    AlgebraPool.sol, 451: change 'balance > 0' to 'balance != 0'
    AlgebraPool.sol, 454: change 'balance > 0' to 'balance != 0'
    AlgebraPool.sol, 455: change 'balance > 0' to 'balance != 0'
    DataStorage.sol, 80: change 'liquidity > 0' to 'liquidity != 0'
    TickMath.sol, 52: change 'tick > 0' to 'tick != 0'
    AlgebraPool.sol, 434: change 'liquidityDesired > 0' to 'liquidityDesired != 0'
    AlgebraPool.sol, 641: change 'balance > 0' to 'balance != 0'
    AlgebraPool.sol, 452: change 'balance > 0' to 'balance != 0'
    DataStorageOperator.sol, 139: change 'liquidity > 0' to 'liquidity != 0'
    AlgebraPool.sol, 904: change 'amount0 > 0' to 'amount0 != 0'

Unnecessary cast

Code instances:

    int128 TokenDeltaMath.sol.getToken1Delta - unnecessary casting int128(liquidity)
    int128 LiquidityMath.sol.addDelta - unnecessary casting int128(y)
    int128 TokenDeltaMath.sol.getToken0Delta - unnecessary casting int128(liquidity)
    int256 PriceMovementMath.sol.movePriceTowardsTarget - unnecessary casting int256(amountAvailable)

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

    AlgebraPool.sol, balanceToken1, { return IERC20Minimal(token1).balanceOf(address(this)); }
    AlgebraPool.sol, balanceToken0, { return IERC20Minimal(token0).balanceOf(address(this)); }
    PoolState.sol, _blockTimestamp, { return uint32(block.timestamp); // truncation is desired }
    PriceMovementMath.sol, getNewPriceAfterInput, { return getNewPrice(price, liquidity, input, zeroToOne, true); }

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:

    FullMath.sol, mulDiv
    AlgebraPool.sol, _recalculatePosition
    DataStorage.sol, _volatilityOnRange
    DataStorage.sol, binarySearch
    LowGasSafeMath.sol, sub
    LowGasSafeMath.sol, add
    PriceMovementMath.sol, getNewPriceAfterInput
    PriceMovementMath.sol, getNewPriceAfterOutput
    TickTable.sol, getMostSignificantBit

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:

    IAlgebraFactory.sol
    AlgebraPool.sol
    IAlgebraPoolActions.sol
    Sqrt.sol
    AlgebraFactory.sol
    DataStorage.sol
    IAlgebraPoolState.sol
    IAlgebraPoolImmutables.sol
    AdaptiveFee.sol
    IAlgebraPool.sol
    PoolState.sol
    DataStorageOperator.sol
    TransferHelper.sol
    PoolImmutables.sol
    IAlgebraPoolDerivedState.sol
    IERC20Minimal.sol
    TickTable.sol
    Constants.sol
    TickManager.sol
    IAlgebraFlashCallback.sol
    IAlgebraPoolPermissionedActions.sol
    TokenDeltaMath.sol
    IAlgebraPoolDeployer.sol
    AlgebraPoolDeployer.sol
    IAlgebraVirtualPool.sol
    IAlgebraSwapCallback.sol
    IDataStorageOperator.sol
    TickMath.sol
    LowGasSafeMath.sol
    PriceMovementMath.sol
    FullMath.sol
    IAlgebraPoolEvents.sol
    SafeCast.sol
    IAlgebraMintCallback.sol
    LiquidityMath.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-423n4/2022-09-quickswap/tree/main/src/core/contracts/AlgebraFactory.sol#L52
    https://github.com/code-423n4/2022-09-quickswap/tree/main/src/core/contracts/DataStorageOperator.sol#L33
    https://github.com/code-423n4/2022-09-quickswap/tree/main/src/core/contracts/AlgebraPoolDeployer.sol#L33