Badger eBTC Audit + Certora Formal Verification Competition - Collinsoden's results

Gas Optimization

Gas 01: In contract/BorrowOperations.sol

Link to code

Gas can be optimized if the call _requireSufficientEbtcTokenBalance is made first before getCdpCollShares and getCdpLiquidatorRewardShares as those two values may not be needed until after the check. If the _requireSufficientEbtcTokenBalance call fails, the gas spent on making those calls will be lost. This can save about 82,864 gas if the check fails.

       uint256 collShares = cdpManager.getCdpCollShares(_cdpId);
       uint256 debt = cdpManager.getCdpDebt(_cdpId);
       uint256 liquidatorRewardShares = cdpManager.getCdpLiquidatorRewardShares(_cdpId);

       _requireSufficientEbtcTokenBalance(msg.sender, debt)

The code can be optimized thus:

  function decreaseSystemDebt(uint256 _amount) external override { 
       _requireCallerIsBOorCdpM();
       uint256 debt = cdpManager.getCdpDebt(_cdpId);
       
       _requireSufficientEbtcTokenBalance(msg.sender, debt)
       
       uint256 collShares = cdpManager.getCdpCollShares(_cdpId);
       uint256 liquidatorRewardShares = cdpManager.getCdpLiquidatorRewardShares(_cdpId);

Gas 02: In contracts/ActivePool.sol

Link to code

In the code below, assigning systemDebt as systemDebt -= _amount would save gas and a variable.

So this is recommended:

function decreaseSystemDebt(uint256 _amount) external override {
   _requireCallerIsBOorCdpM();
   systemDebt -= _amount
   emit ActivePoolEBTCDebtUpdated(systemDebt);

Instead of this:

   function decreaseSystemDebt(uint256 _amount) external override { 
       _requireCallerIsBOorCdpM();

       uint256 cachedSystemDebt = systemDebt - _amount;

       systemDebt = cachedSystemDebt;
       emit ActivePoolEBTCDebtUpdated(cachedSystemDebt);
   }