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:

• AaveVault.sol#updateTvls()

  https://github.com/code-423n4/2021-12-mellow/blob/6679e2dd118b33481ee81ad013ece4ea723327b5/mellow-vaults/contracts/AaveVault.sol#L51-L55

• AaveVault.sol#_push()

  https://github.com/code-423n4/2021-12-mellow/blob/6679e2dd118b33481ee81ad013ece4ea723327b5/mellow-vaults/contracts/AaveVault.sol#L68-L75

• AaveVault.sol#_pull()

  https://github.com/code-423n4/2021-12-mellow/blob/6679e2dd118b33481ee81ad013ece4ea723327b5/mellow-vaults/contracts/AaveVault.sol#L86-L86

• ERC20Vault.sol#tvl()

  https://github.com/code-423n4/2021-12-mellow/blob/6679e2dd118b33481ee81ad013ece4ea723327b5/mellow-vaults/contracts/ERC20Vault.sol#L26-L26

• ERC20Vault.sol#_postReclaimTokens()

  https://github.com/code-423n4/2021-12-mellow/blob/6679e2dd118b33481ee81ad013ece4ea723327b5/mellow-vaults/contracts/ERC20Vault.sol#L93-L93

• ERC20Vault.sol#_pull()

  https://github.com/code-423n4/2021-12-mellow/blob/6679e2dd118b33481ee81ad013ece4ea723327b5/mellow-vaults/contracts/ERC20Vault.sol#L86-L86

• GatewayVault.sol#_push()

  https://github.com/code-423n4/2021-12-mellow/blob/6679e2dd118b33481ee81ad013ece4ea723327b5/mellow-vaults/contracts/GatewayVault.sol#L131-L168

• GatewayVault.sol#_pull()

  https://github.com/code-423n4/2021-12-mellow/blob/6679e2dd118b33481ee81ad013ece4ea723327b5/mellow-vaults/contracts/GatewayVault.sol#L187-L199

• LpIssuer.sol#_chargeFees()

  https://github.com/code-423n4/2021-12-mellow/blob/6679e2dd118b33481ee81ad013ece4ea723327b5/mellow-vaults/contracts/LpIssuer.sol#L220-L233

• LpIssuer.sol#_getLpAmount()

  https://github.com/code-423n4/2021-12-mellow/blob/6679e2dd118b33481ee81ad013ece4ea723327b5/mellow-vaults/contracts/LpIssuer.sol#L276-L303

• Vault.sol#transferAndPush()

  https://github.com/code-423n4/2021-12-mellow/blob/6679e2dd118b33481ee81ad013ece4ea723327b5/mellow-vaults/contracts/Vault.sol#L109-L115

• Vault.sol#reclaimTokens()

  https://github.com/code-423n4/2021-12-mellow/blob/6679e2dd118b33481ee81ad013ece4ea723327b5/mellow-vaults/contracts/Vault.sol#L151-L151

• UniV3Vault.sol#_push()

  https://github.com/code-423n4/2021-12-mellow/blob/6679e2dd118b33481ee81ad013ece4ea723327b5/mellow-vaults/contracts/UniV3Vault.sol#L130-L130

• YearnVault.sol#_push()

  https://github.com/code-423n4/2021-12-mellow/blob/6679e2dd118b33481ee81ad013ece4ea723327b5/mellow-vaults/contracts/YearnVault.sol#L65-L65

• YearnVault.sol#tvl()

  https://github.com/code-423n4/2021-12-mellow/blob/6679e2dd118b33481ee81ad013ece4ea723327b5/mellow-vaults/contracts/YearnVault.sol#L53-L53

• YearnVault.sol#_pull()

  https://github.com/code-423n4/2021-12-mellow/blob/6679e2dd118b33481ee81ad013ece4ea723327b5/mellow-vaults/contracts/YearnVault.sol#L84-L84

[0xleastwood]

duplicate of #73