Gas Optimizations

[code423n4]

Unneeded check in Oracle getPrice function

The twoDayLow > 0 check in line 136 isn't needed since twoDayLow will always take at least the current normalizedPrice value, which is greater than 0 due to the check in line 117.

Move check condition in expansion function of FED contract to save gas

The check in line 93 can be moved up in the stack to early exit the function in case the condition fails in order to save gas.

uint256 newGlobalSupply = globalSupply + amount;
require(newGlobalSupply <= supplyCeiling);
...
globalSupply = newGlobalSupply;
emit Expansion(market, amount);

Use unchecked math in function contraction of FED contract

Lines 110 and 111 can be placed under an unchecked math group since amount <= supply due to check in line 107 and can't possibly underflow these two updates.

Force replenish checks are done twice in Market and DBR contracts

The checks around the deficit value (deficit > 0 and deficit >= amount) are done twice and repeated over the Market and DBR contracts in the functions forceReplenish and onForceReplenish respectively.

Store result of debts[borrower] += amount in borrowInternal function of Market contract

The calculation executed in line 395 is stored in storage and re-read from storage in the next line to check against the credit limit. Store the calculation locally to prevent an unnecessary re-read to storage.

name and symbol variables in DolaBorrowingRights contract can be changed to immutable to save gas

These two variables are defined at construction time and can't be updated. Consider defining them as immutable to avoid reading from storage to save gas.

Use unchecked math in transfer and transferFrom functions of DolaBorrowingRights contract

The updates in lines 172 and 196 can be done using unchecked math since balances[msg.sender] >= amount and balances[from] >= amount due to the checks in lines 171 and 195 respectively.

Store lastUpdated[user] locally to prevent a second read in function accrueDueTokens of DolaBorrowingRights contract

Value is loaded in line 286 and read again in the next line. Store the first read locally to avoid a second sload.

Check if debt is zero in accrueDueTokens to skip unnecessary calculations and save gas

If debt is zero in the accrueDueTokens function (line 285), then operations in lines 287, 288 and 290 can be skipped to save gas.

Use unchecked math in _burn function of DolaBorrowingRights contract

The update in line 374 can be done using unchecked math since balances[from] >= amount due to the check in line 373.

[c4-judge]

0xean marked the issue as grade-b