LooksRare Aggregator contest - shark's results

x = x + y is more efficient than x += y (same for subtracting)

The amount of gas saved can be sizeable when repeated in a loop.

For example:

File: SeaportProxy.sol Line 145-161

150                fee += orderFee;

Instead, you can change the code to the following:

150                fee = fee + orderFee;

Here are some more instances of this issue:

File: SeaportProxy.sol Line 109 File: SeaportProxy.sol Line 209

Math should be unchecked if overflowing is not a possibility

Consider the following example:

File: SeaportProxy.sol Line 145-161

145        for (uint256 i; i < ordersLength; ) {
146            address currency = orders[i].currency;
147            uint256 orderFee = (orders[i].price * feeBp) / 10000;
148
149            if (currency == lastOrderCurrency) {
150                fee += orderFee;
151            } else {
152                if (fee > 0) _transferFee(fee, lastOrderCurrency, feeRecipient);
153
154                lastOrderCurrency = currency;
155                fee = orderFee;
156            }
157
158            unchecked {
159                ++i;
160            }
161        }

Since we know that fee (Line 150) will not overflow, we can uncheck math and save the gas.

Instead, you can rewrite the code to the following:

    unchecked {
        for (uint256 i; i < ordersLength; ++i) {
            address currency = orders[i].currency;
            uint256 orderFee = (orders[i].price * feeBp) / 10000;

            if (currency == lastOrderCurrency) {
                fee += orderFee;
            } else {
                if (fee > 0) _transferFee(fee, lastOrderCurrency, feeRecipient);

                lastOrderCurrency = currency;
                fee = orderFee;
            }
        }
    }

Here are the rest of the instances:

File: SeaportProxy.sol Line 102-114 File: SeaportProxy.sol Line 187-222

Use calldata instead of memory

If you are not going to modify the parameter, you can pass it as calldata to save gas (about 60 gas).

For example:

File: LooksRareProxy.sol Line 108-109

        OrderTypes.TakerOrder memory takerBid,
        OrderTypes.MakerOrder memory makerAsk,

Since these parameters aren't going to be modified, they can be passed as calldata instead:

        OrderTypes.TakerOrder calldata takerBid,
        OrderTypes.MakerOrder calldata makerAsk,

Here is another instance of this issue:

File: SeaportProxy.sol Line 227

Use storage instead of memory for structs and arrays

storage costs less gas since copying a state struct in memory would incur as many SLOADs and MSTOREs as there are slots.

For example:

File: LooksRareProxy.sol Line 90

            OrderTypes.TakerOrder memory takerBid;

Instead of memory, you can use storage:

            OrderTypes.TakerOrder storage takerBid;

Here are the rest of the instances:

File: LooksRareProxy.sol Line 65-69 File: SeaportProxy.sol Line 97-103 File: SeaportProxy.sol Line 188-189 File: SeaportProxy.sol Line 244-254