Gas Optimizations #167

code423n4 · 2022-05-23T01:34:18Z

Gas Optimizations

Use unchecked{++i} instead of i++ in loops

When using i++ there is an extra operation that can be skipped if you use unchecked{++i}. This saves gas every iteration.

You can also use assembly to save much more gas. This may be challenging though in some for loops due to limitations of inline assembly, however this will save much more gas when applicable.

Examples

^^ many other instances like this throughout the codebase.

Optimization

contract Unoptimized {
    function unoptimizedGasTest(uint256[] calldata _toPids) public pure {
        uint256 j = 0;
        for (uint256 i = 0; i < _toPids.length; i++) {
            j++;
        }
    }
}

contract Optimized {
    function optimizedGasTest(uint256[] calldata _toPids) public pure {
        uint256 j = 0;
        for (uint256 i = 0; i < _toPids.length;) {
            j++;

            unchecked{
                ++i;
            }
        }
    }
}


contract OptimizedAssembly {
    function optimizedAssemblyGasTest(uint256[] calldata _toPids) public pure {
        uint256 j = 0;
        assembly {
            for {let i := 0} lt(i, _toPids.length) {i := add(i, 0x01)} {
                //code goes here
                j := add(j, 0x01)
            }
        }
    }
}

Gas report

╭──────────────────────┬─────────────────┬─────┬────────┬─────┬─────────╮
│ Unoptimized contract ┆                 ┆     ┆        ┆     ┆         │
╞══════════════════════╪═════════════════╪═════╪════════╪═════╪═════════╡
│ Deployment Cost      ┆ Deployment Size ┆     ┆        ┆     ┆         │
├╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌┤
│ 65917                ┆ 361             ┆     ┆        ┆     ┆         │
├╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌┤
│ Function Name        ┆ min             ┆ avg ┆ median ┆ max ┆ # calls │
├╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌┤
│ unoptimizedGasTest   ┆ 800             ┆ 800 ┆ 800    ┆ 800 ┆ 1       │
╰──────────────────────┴─────────────────┴─────┴────────┴─────┴─────────╯
╭────────────────────┬─────────────────┬─────┬────────┬─────┬─────────╮
│ Optimized contract ┆                 ┆     ┆        ┆     ┆         │
╞════════════════════╪═════════════════╪═════╪════════╪═════╪═════════╡
│ Deployment Cost    ┆ Deployment Size ┆     ┆        ┆     ┆         │
├╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌┤
│ 60311              ┆ 333             ┆     ┆        ┆     ┆         │
├╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌┤
│ Function Name      ┆ min             ┆ avg ┆ median ┆ max ┆ # calls │
├╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌┤
│ optimizedGasTest   ┆ 658             ┆ 658 ┆ 658    ┆ 658 ┆ 1       │
╰────────────────────┴─────────────────┴─────┴────────┴─────┴─────────╯
╭────────────────────────────┬─────────────────┬─────┬────────┬─────┬─────────╮
│ OptimizedAssembly contract ┆                 ┆     ┆        ┆     ┆         │
╞════════════════════════════╪═════════════════╪═════╪════════╪═════╪═════════╡
│ Deployment Cost            ┆ Deployment Size ┆     ┆        ┆     ┆         │
├╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌┤
│ 51299                      ┆ 288             ┆     ┆        ┆     ┆         │
├╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌┤
│ Function Name              ┆ min             ┆ avg ┆ median ┆ max ┆ # calls │
├╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌┤
│ optimizedAssemblyGasTest   ┆ 534             ┆ 534 ┆ 534    ┆ 534 ┆ 1       │
╰────────────────────────────┴─────────────────┴─────┴────────┴─────┴─────────╯

Use Solmate ERC20 vs Openzeppelin

Link to Solmate ERC20

Use assembly to check for address(0) or any other 0 value

When requiring that an address is not address(0), instead of using require(_address!=address(0)), you can use assembly to save gas. You can package the optimized assembly logic below into a function and call it instead of the require statement.
One limitation to this approach is that there is a limit to the error message length that you can pass in, however this forces you to make the revert message 32 bytes, ensuring that only one 256 bit slot is used.

Examples

Occurence0

Occurrence1

Occurrence2

^^ many other instances like this throughout the codebase.

Optimization

contract Unoptimized {
    function unoptimizedGasTest(address owner) public view {
        require(owner != address(0), "ERC4626: approve from address(0)");
    }
}

contract Optimized {
    function optimizedGasTest(address owner) public view {
        assembly {
            if iszero(owner) {
                mstore(0x00, "ERC4626: approve from address(0)")
                revert(0x00, 0x20)
            }
        }
    }
}

Gas report

╭──────────────────────┬─────────────────┬─────┬────────┬─────┬─────────╮
│ Unoptimized contract ┆                 ┆     ┆        ┆     ┆         │
╞══════════════════════╪═════════════════╪═════╪════════╪═════╪═════════╡
│ Deployment Cost      ┆ Deployment Size ┆     ┆        ┆     ┆         │
├╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌┤
│ 50899                ┆ 285             ┆     ┆        ┆     ┆         │
├╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌┤
│ Function Name        ┆ min             ┆ avg ┆ median ┆ max ┆ # calls │
├╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌┤
│ unoptimizedGasTest   ┆ 282             ┆ 282 ┆ 282    ┆ 282 ┆ 1       │
╰──────────────────────┴─────────────────┴─────┴────────┴─────┴─────────╯
╭────────────────────┬─────────────────┬─────┬────────┬─────┬─────────╮
│ Optimized contract ┆                 ┆     ┆        ┆     ┆         │
╞════════════════════╪═════════════════╪═════╪════════╪═════╪═════════╡
│ Deployment Cost    ┆ Deployment Size ┆     ┆        ┆     ┆         │
├╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌┤
│ 42293              ┆ 242             ┆     ┆        ┆     ┆         │
├╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌┤
│ Function Name      ┆ min             ┆ avg ┆ median ┆ max ┆ # calls │
├╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌┤
│ optimizedGasTest   ┆ 264             ┆ 264 ┆ 264    ┆ 264 ┆ 1       │
╰────────────────────┴─────────────────┴─────┴────────┴─────┴─────────╯

Use assembly to check if msg.sender == owner (or check any stored value)

When requiring that the msg.sender is the owner of the contract, use assembly instead of a require statement. You can package this logic into a function and call the function instead of the require statement.
Using assembly to check any stored value will save gas.

Examples

^^ many other instances like this throughout the codebase.

Optimization

contract Unoptimized {
    address owner = 0xb4c79daB8f259C7Aee6E5b2Aa729821864227e84;

    function unoptimizedGasTest() public view {
        require(msg.sender == owner, "!auth");
    }
}

contract Optimized {
    address owner = 0xb4c79daB8f259C7Aee6E5b2Aa729821864227e84;

    function optimizedGasTest() public view {
        assembly {
            if iszero(eq(sload(owner.slot), caller())) {
                mstore(0x00, "!auth")
                revert(0x00, 0x20)
            }
        }
    }
}

Gas report

╭──────────────────────┬─────────────────┬──────┬────────┬──────┬─────────╮
│ Unoptimized contract ┆                 ┆      ┆        ┆      ┆         │
╞══════════════════════╪═════════════════╪══════╪════════╪══════╪═════════╡
│ Deployment Cost      ┆ Deployment Size ┆      ┆        ┆      ┆         │
├╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌┤
│ 57823                ┆ 247             ┆      ┆        ┆      ┆         │
├╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌┤
│ Function Name        ┆ min             ┆ avg  ┆ median ┆ max  ┆ # calls │
├╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌┤
│ unoptimizedGasTest   ┆ 2262            ┆ 2262 ┆ 2262   ┆ 2262 ┆ 1       │
╰──────────────────────┴─────────────────┴──────┴────────┴──────┴─────────╯
╭────────────────────┬─────────────────┬──────┬────────┬──────┬─────────╮
│ Optimized contract ┆                 ┆      ┆        ┆      ┆         │
╞════════════════════╪═════════════════╪══════╪════════╪══════╪═════════╡
│ Deployment Cost    ┆ Deployment Size ┆      ┆        ┆      ┆         │
├╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌┤
│ 49217              ┆ 203             ┆      ┆        ┆      ┆         │
├╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌┤
│ Function Name      ┆ min             ┆ avg  ┆ median ┆ max  ┆ # calls │
├╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌┤
│ optimizedGasTest   ┆ 2244            ┆ 2244 ┆ 2244   ┆ 2244 ┆ 1       │
╰────────────────────┴─────────────────┴──────┴────────┴──────┴─────────╯

Use assembly to update state variables

Using assembly to update the stored value will save gas with sstore(owner.slot, newOwnerAddress) instead of owner = newOwner;.

Examples

Occurrence0

Occurrence1

Occurrence2

^^ many other instances like this throughout the codebase.

Optimization

contract Unoptimized {
    address owner = 0xb4c79daB8f259C7Aee6E5b2Aa729821864227e84;

    function unoptimizedGasTest(address newOwner) public {
        owner = newOwner;
    }
}

contract Optimized {
    address owner = 0xb4c79daB8f259C7Aee6E5b2Aa729821864227e84;

    function optimizedGasTest(address newOwner) public {
        assembly {
            sstore(owner.slot, newOwner)
        }
    }
}

Gas report

╭──────────────────────┬─────────────────┬──────┬────────┬──────┬─────────╮
│ Unoptimized contract ┆                 ┆      ┆        ┆      ┆         │
╞══════════════════════╪═════════════════╪══════╪════════╪══════╪═════════╡
│ Deployment Cost      ┆ Deployment Size ┆      ┆        ┆      ┆         │
├╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌┤
│ 60623                ┆ 261             ┆      ┆        ┆      ┆         │
├╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌┤
│ Function Name        ┆ min             ┆ avg  ┆ median ┆ max  ┆ # calls │
├╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌┤
│ unoptimizedGasTest   ┆ 5302            ┆ 5302 ┆ 5302   ┆ 5302 ┆ 1       │
╰──────────────────────┴─────────────────┴──────┴────────┴──────┴─────────╯
╭────────────────────┬─────────────────┬──────┬────────┬──────┬─────────╮
│ Optimized contract ┆                 ┆      ┆        ┆      ┆         │
╞════════════════════╪═════════════════╪══════╪════════╪══════╪═════════╡
│ Deployment Cost    ┆ Deployment Size ┆      ┆        ┆      ┆         │
├╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌┤
│ 54823              ┆ 232             ┆      ┆        ┆      ┆         │
├╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌┤
│ Function Name      ┆ min             ┆ avg  ┆ median ┆ max  ┆ # calls │
├╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌┤
│ optimizedGasTest   ┆ 5236            ┆ 5236 ┆ 5236   ┆ 5236 ┆ 1       │
╰────────────────────┴─────────────────┴──────┴────────┴──────┴─────────╯

Break up one multi-condition require statement into multiple require statements

When checking multiple conditions in a single require statement, break it up into multiple require statements.

Examples

Optimization

contract Unoptimized {
    address check0 = 0x158B28A1b1CB1BE12C6bD8f5a646a0e3B2024734;
    address check1 = 0x158B28A1b1CB1BE12C6bD8f5a646a0e3B2024734;
    uint256 check2 = 100;

    function unoptimizedGasTest() public returns (uint256 incr) {
        require(check0 != address(0) && check1 != address(0) && check2 > 50);
    }
}

contract Optimized {
    address check0 = 0x158B28A1b1CB1BE12C6bD8f5a646a0e3B2024734;
    address check1 = 0x158B28A1b1CB1BE12C6bD8f5a646a0e3B2024734;
    uint256 check2 = 100;

    function optimizedGasTest() public returns (uint256 incr) {
        require(check0 != address(0));
        require(check1 != address(0));
        require(check2 > 50);
    }
}

Gas report

╭──────────────────────┬─────────────────┬──────┬────────┬──────┬─────────╮
│ Unoptimized contract ┆                 ┆      ┆        ┆      ┆         │
╞══════════════════════╪═════════════════╪══════╪════════╪══════╪═════════╡
│ Deployment Cost      ┆ Deployment Size ┆      ┆        ┆      ┆         │
├╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌┤
│ 103068               ┆ 273             ┆      ┆        ┆      ┆         │
├╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌┤
│ Function Name        ┆ min             ┆ avg  ┆ median ┆ max  ┆ # calls │
├╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌┤
│ unoptimizedGasTest   ┆ 6594            ┆ 6594 ┆ 6594   ┆ 6594 ┆ 1       │
╰──────────────────────┴─────────────────┴──────┴────────┴──────┴─────────╯
╭────────────────────┬─────────────────┬──────┬────────┬──────┬─────────╮
│ Optimized contract ┆                 ┆      ┆        ┆      ┆         │
╞════════════════════╪═════════════════╪══════╪════════╪══════╪═════════╡
│ Deployment Cost    ┆ Deployment Size ┆      ┆        ┆      ┆         │
├╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌┤
│ 102668             ┆ 271             ┆      ┆        ┆      ┆         │
├╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌┤
│ Function Name      ┆ min             ┆ avg  ┆ median ┆ max  ┆ # calls │
├╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌┤
│ optimizedGasTest   ┆ 6566            ┆ 6566 ┆ 6566   ┆ 6566 ┆ 1       │
╰────────────────────┴─────────────────┴──────┴────────┴──────┴─────────╯

You don't have to use the Safemath library when you are using Solidity version >= 0.8.0

Solidity >= 0.8.0 uses safe math by default. Using Safemath on top of versions >= 0.8.0 is redundant.

contract Unoptimized {
    using SafeMath for uint256;

    function unoptimizedGasTest(uint256 a, uint256 b) public {
        uint256 c = a.add(b);
    }
}

contract Optimized {
    function optimizedGasTest(uint256 a, uint256 b) public {
        uint256 c = a + b;
    }
}

Gas report

╭──────────────────────┬─────────────────┬─────┬────────┬─────┬─────────╮
│ Unoptimized contract ┆                 ┆     ┆        ┆     ┆         │
╞══════════════════════╪═════════════════╪═════╪════════╪═════╪═════════╡
│ Deployment Cost      ┆ Deployment Size ┆     ┆        ┆     ┆         │
├╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌┤
│ 43893                ┆ 250             ┆     ┆        ┆     ┆         │
├╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌┤
│ Function Name        ┆ min             ┆ avg ┆ median ┆ max ┆ # calls │
├╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌┤
│ unoptimizedGasTest   ┆ 348             ┆ 348 ┆ 348    ┆ 348 ┆ 1       │
╰──────────────────────┴─────────────────┴─────┴────────┴─────┴─────────╯
╭────────────────────┬─────────────────┬─────┬────────┬─────┬─────────╮
│ Optimized contract ┆                 ┆     ┆        ┆     ┆         │
╞════════════════════╪═════════════════╪═════╪════════╪═════╪═════════╡
│ Deployment Cost    ┆ Deployment Size ┆     ┆        ┆     ┆         │
├╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌┤
│ 40493              ┆ 233             ┆     ┆        ┆     ┆         │
├╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌┤
│ Function Name      ┆ min             ┆ avg ┆ median ┆ max ┆ # calls │
├╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌┤
│ optimizedGasTest   ┆ 303             ┆ 303 ┆ 303    ┆ 303 ┆ 1       │
╰────────────────────┴─────────────────┴─────┴────────┴─────┴─────────╯

Pack structs by putting data types in ascending size

When defining a struct, pack the values so that the data types are in ascending order. This will make sure that data types that can be put into the same slot are packed together instead of each variable having a separate storage slot.

Examples

Optimization

contract Unoptimized {

    struct NewStruct {
        uint112 data0;
        uint256 data1;
        uint8 data2;
    }

}

contract Optimized {

    struct NewStruct {
        uint8 data0;
        uint112 data1;
        uint256 data2;
    }

}

Use assembly for add, sub, mul, div and other math library operations

In the Aura math lib, use assembly instead of solidity to save gas during arithmetic.

Examples

Occurrences

Optimization

contract Unoptimized {
    function unoptimizedGasTest(uint256 a, uint256 b) public {
        uint256 c = a + b;
    }
}

contract Optimized {
    function optimizedGasTest(uint256 a, uint256 b) public {
        assembly {
            let c := add(a, b)
        }
    }
}

Gas report

╭──────────────────────┬─────────────────┬─────┬────────┬─────┬─────────╮
│ Unoptimized contract ┆                 ┆     ┆        ┆     ┆         │
╞══════════════════════╪═════════════════╪═════╪════════╪═════╪═════════╡
│ Deployment Cost      ┆ Deployment Size ┆     ┆        ┆     ┆         │
├╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌┤
│ 40493                ┆ 233             ┆     ┆        ┆     ┆         │
├╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌┤
│ Function Name        ┆ min             ┆ avg ┆ median ┆ max ┆ # calls │
├╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌┤
│ unoptimizedGasTest   ┆ 303             ┆ 303 ┆ 303    ┆ 303 ┆ 1       │
╰──────────────────────┴─────────────────┴─────┴────────┴─────┴─────────╯
╭────────────────────┬─────────────────┬─────┬────────┬─────┬─────────╮
│ Optimized contract ┆                 ┆     ┆        ┆     ┆         │
╞════════════════════╪═════════════════╪═════╪════════╪═════╪═════════╡
│ Deployment Cost    ┆ Deployment Size ┆     ┆        ┆     ┆         │
├╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌┤
│ 29881              ┆ 179             ┆     ┆        ┆     ┆         │
├╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌┤
│ Function Name      ┆ min             ┆ avg ┆ median ┆ max ┆ # calls │
├╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌┤
│ optimizedGasTest   ┆ 214             ┆ 214 ┆ 214    ┆ 214 ┆ 1       │
╰────────────────────┴─────────────────┴─────┴────────┴─────┴─────────╯

Use assembly for merkle proof verification

Instead of using openzeppelin's merkle proof verification, use assembly to save significant gas.

Examples

Occurrences

Optimization

Here is a link to my optimized merkle proof verification implementation

Gas report

╭──────────────────────┬─────────────────┬──────┬────────┬──────┬─────────╮
│ OZ MerkleProof       ┆                 ┆      ┆        ┆      ┆         │
╞══════════════════════╪═════════════════╪══════╪════════╪══════╪═════════╡
│ Deployment Cost      ┆ Deployment Size ┆      ┆        ┆      ┆         │
├╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌┤
│ 105953               ┆ 561             ┆      ┆        ┆      ┆         │
├╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌┤
│ Function Name        ┆ min             ┆ avg  ┆ median ┆ max  ┆ # calls │
├╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌┤
│ verify               ┆ 1437            ┆ 1437 ┆ 1437   ┆ 1437 ┆ 1       │
╰──────────────────────┴─────────────────┴──────┴────────┴──────┴─────────╯
╭───────────────────────────────┬─────────────────┬─────┬────────┬─────┬─────────╮
│ OptimizedMerkleProof          ┆                 ┆     ┆        ┆     ┆         │
╞═══════════════════════════════╪═════════════════╪═════╪════════╪═════╪═════════╡
│ Deployment Cost               ┆ Deployment Size ┆     ┆        ┆     ┆         │
├╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌┤
│ 66517                         ┆ 364             ┆     ┆        ┆     ┆         │
├╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌┤
│ Function Name                 ┆ min             ┆ avg ┆ median ┆ max ┆ # calls │
├╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌┤
│ verifyProof                   ┆ 893             ┆ 893 ┆ 893    ┆ 893 ┆ 1       │
╰───────────────────────────────┴─────────────────┴─────┴────────┴─────┴─────────╯

The text was updated successfully, but these errors were encountered:

code423n4 added bug Something isn't working G (Gas Optimization) labels May 23, 2022

code423n4 added a commit that referenced this issue May 23, 2022

0xKitsune issue #167

a08700e

0xMaharishi added the duplicate This issue or pull request already exists label May 28, 2022

This was referenced May 29, 2022

code4rena aurafinance/aura-contracts#84

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All code4rena fixes code-423n4/2022-05-aura#6

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dmvt removed the duplicate This issue or pull request already exists label Jun 25, 2022

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Gas Optimizations #167

Gas Optimizations #167

code423n4 commented May 23, 2022

Gas Optimizations #167

Gas Optimizations #167

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code423n4 commented May 23, 2022

Gas Optimizations

Use unchecked{++i} instead of i++ in loops

Examples

Optimization

Gas report

Use Solmate ERC20 vs Openzeppelin

Use assembly to check for address(0) or any other 0 value

Examples

Optimization

Gas report

Use assembly to check if msg.sender == owner (or check any stored value)

Examples

Optimization

Gas report

Use assembly to update state variables

Examples

Optimization

Gas report

Break up one multi-condition require statement into multiple require statements

Examples

Optimization

Gas report

You don't have to use the Safemath library when you are using Solidity version >= 0.8.0

Gas report

Pack structs by putting data types in ascending size

Examples

Optimization

Use assembly for add, sub, mul, div and other math library operations

Examples

Optimization

Gas report

Use assembly for merkle proof verification

Examples

Optimization

Gas report