Cache array length in for loops can save gas

[code423n4]

Handle

WatchPug

Vulnerability details

Reading array length at each iteration of the loop takes 6 gas (3 for mload and 3 to place memory_offset) in the stack.

Caching the array length in the stack saves around 3 gas per iteration.

Instances include:

• ActivePool.sol#sendCollaterals()

  https://github.com/code-423n4/2021-12-yetifinance/blob/5f5bf61209b722ba568623d8446111b1ea5cb61c/packages/contracts/contracts/ActivePool.sol#L167

• BorrowerOperations.sol#_getTotalVariableDepositFee()

  https://github.com/code-423n4/2021-12-yetifinance/blob/5f5bf61209b722ba568623d8446111b1ea5cb61c/packages/contracts/contracts/BorrowerOperations.sol#L699

• DefaultPool.sol#sendCollsToActivePool()

  https://github.com/code-423n4/2021-12-yetifinance/blob/5f5bf61209b722ba568623d8446111b1ea5cb61c/packages/contracts/contracts/DefaultPool.sol#L133

• TroveManager.sol#_updateTroveRewardSnapshots()

  https://github.com/code-423n4/2021-12-yetifinance/blob/5f5bf61209b722ba568623d8446111b1ea5cb61c/packages/contracts/contracts/TroveManager.sol#L348

• StabilityPool.sol#_computeRewardsPerUnitStaked()

  https://github.com/code-423n4/2021-12-yetifinance/blob/5f5bf61209b722ba568623d8446111b1ea5cb61c/packages/contracts/contracts/StabilityPool.sol#L562

[kingyetifinance]

Duplicate #14

[alcueca]

Taking as main