Consider changing the _deployData architecture

[code423n4]

Handle

hrkrshnn

Vulnerability details

Consider changing the _deployData architecture

Currently, the factory contracts implements deployment in the following
fashion:

1. The argument to the external function has the type bytes memory.
2. This gets decoded using abi.decode(deploydata, args)

Example

Consider directly specifying the parameters.

modified   contracts/pool/ConstantProductPoolFactory.sol
@@ -10,8 +10,7 @@ import "./PoolDeployer.sol";
 contract ConstantProductPoolFactory is PoolDeployer {
     constructor(address _masterDeployer) PoolDeployer(_masterDeployer) {}

-    function deployPool(bytes memory _deployData) external returns (address pool) {
-        (address tokenA, address tokenB, uint256 swapFee, bool twapSupport) = abi.decode(_deployData, (address, address, uint256, bool));
+    function deployPool(address tokenA, address tokenB, uint256 swapFree, bool twapSupport) external returns (address pool) {
         if (tokenA > tokenB) {
             (tokenA, tokenB) = (tokenB, tokenA);
             _deployData = abi.encode(tokenA, tokenB, swapFee, twapSupport);

Advantages

1. Using _deployData instead of (address, address, uint256, uint256) needs larger calldata size. This is because the bytes
   also needs to store the length.
2. This avoids going via memory. For the byte array example, the value
   is first copied from calldata to memory (note: solidity
   currently does this in an inefficient for loop, instead of using
   calldatacopy; so if you really want to keep the architecture,
   writing it in assembly using calldatacopy would be even more
   efficient.) Effectively, this saves the cost to store in memory, as
   well as memory expansion costs. Since the function call does a
   contract deployment, the savings from memory expansion costs can be
   reasonably high, assuming that the quadratic pricing is reached.

This pattern seems to be used in several other places. All of them can
be better optimized.

1. https://github.com/sushiswap/trident/blob/9130b10efaf9c653d74dc7a65bde788ec4b354b5/contracts/pool/ConstantProductPool.sol#L124