Gas Optimizations #32
Labels
bug
Warden finding
G (Gas Optimization)
sponsor acknowledged
Technically the issue is correct, but we're not going to resolve it for XYZ reasons
for loop optimisations
description
Uninitialized variables are assigned with the types default value.
Explicitly initializing a variable with it's default value costs unnecessary gas.
Suggest not initializing the for loop counter to 0.
An array’s length should be cached to save gas in for-loops
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.
Suggest storing the array’s length in a variable before the for-loop, and use it instead:
++i costs less gas compared to i++
++i costs less gas compared to i++ for unsigned integer, as pre-increment is cheaper (about 5 gas per iteration)
Suggest using ++i instead of i++ to increment the value of an uint variable.
Increments can be unchecked
In Solidity 0.8+, there’s a default overflow check on unsigned integers. It’s possible to uncheck this in for-loops and save some gas at each iteration, but at the cost of some code readability, as this uncheck cannot be made inline.
taking all of the above, the recommended format for gas savings is
findings
https://github.com/code-423n4/2022-07-fractional/blob/e2c5a962a94106f9495eb96769d7f60f7d5b14c9/src/Vault.sol#L78
https://github.com/code-423n4/2022-07-fractional/blob/e2c5a962a94106f9495eb96769d7f60f7d5b14c9/src/Vault.sol#L104
https://github.com/code-423n4/2022-07-fractional/blob/e2c5a962a94106f9495eb96769d7f60f7d5b14c9/src/modules/protoforms/BaseVault.sol#L64
https://github.com/code-423n4/2022-07-fractional/blob/e2c5a962a94106f9495eb96769d7f60f7d5b14c9/src/modules/protoforms/BaseVault.sol#L83
https://github.com/code-423n4/2022-07-fractional/blob/e2c5a962a94106f9495eb96769d7f60f7d5b14c9/src/modules/protoforms/BaseVault.sol#L107
https://github.com/code-423n4/2022-07-fractional/blob/e2c5a962a94106f9495eb96769d7f60f7d5b14c9/src/utils/MerkleBase.sol#L51
use calldata instead of memory
description
Use calldata instead of memory for function parameters saves gas if the function argument is only read.
findings
https://github.com/code-423n4/2022-07-fractional/blob/e2c5a962a94106f9495eb96769d7f60f7d5b14c9/src/Vault.sol#L73
https://github.com/code-423n4/2022-07-fractional/blob/e2c5a962a94106f9495eb96769d7f60f7d5b14c9/src/Vault.sol#L101
https://github.com/code-423n4/2022-07-fractional/blob/e2c5a962a94106f9495eb96769d7f60f7d5b14c9/src/VaultRegistry.sol#L53-L54
https://github.com/code-423n4/2022-07-fractional/blob/e2c5a962a94106f9495eb96769d7f60f7d5b14c9/src/VaultRegistry.sol#L70-L71
https://github.com/code-423n4/2022-07-fractional/blob/e2c5a962a94106f9495eb96769d7f60f7d5b14c9/src/VaultRegistry.sol#L85-L86
https://github.com/code-423n4/2022-07-fractional/blob/e2c5a962a94106f9495eb96769d7f60f7d5b14c9/src/VaultRegistry.sol#L105-L106
https://github.com/code-423n4/2022-07-fractional/blob/e2c5a962a94106f9495eb96769d7f60f7d5b14c9/src/VaultRegistry.sol#L150-L151
https://github.com/code-423n4/2022-07-fractional/blob/e2c5a962a94106f9495eb96769d7f60f7d5b14c9/src/VaultRegistry.sol#L168-L169
https://github.com/code-423n4/2022-07-fractional/blob/e2c5a962a94106f9495eb96769d7f60f7d5b14c9/src/utils/Metadata.sol#L24
https://github.com/code-423n4/2022-07-fractional/blob/e2c5a962a94106f9495eb96769d7f60f7d5b14c9/src/utils/MerkleBase.sol#L61
https://github.com/code-423n4/2022-07-fractional/blob/e2c5a962a94106f9495eb96769d7f60f7d5b14c9/src/utils/MerkleBase.sol#L125
cache in variables instead of loading
description
The code can be optimized by minimising the number of SLOADs. SLOADs are expensive (100 gas) compared to MLOADs/MSTOREs (3 gas).
findings
array.length
https://github.com/code-423n4/2022-07-fractional/blob/e2c5a962a94106f9495eb96769d7f60f7d5b14c9/src/modules/Buyout.sol#L454
https://github.com/code-423n4/2022-07-fractional/blob/e2c5a962a94106f9495eb96769d7f60f7d5b14c9/src/modules/protoforms/BaseVault.sol#L130
https://github.com/code-423n4/2022-07-fractional/blob/e2c5a962a94106f9495eb96769d7f60f7d5b14c9/src/modules/protoforms/BaseVault.sol#L132
https://github.com/code-423n4/2022-07-fractional/blob/e2c5a962a94106f9495eb96769d7f60f7d5b14c9/src/utils/MerkleBase.sol#L110
use shift operator
description
Gas can be saved by using >> operator instead of dividing by 2
use >> operator
findings
https://github.com/code-423n4/2022-07-fractional/blob/e2c5a962a94106f9495eb96769d7f60f7d5b14c9/src/utils/MerkleBase.sol#L100
using prefix increments save gas
description
Prefix increments are cheaper than postfix increments,
eg ++i rather than i++
findings
https://github.com/code-423n4/2022-07-fractional/blob/e2c5a962a94106f9495eb96769d7f60f7d5b14c9/src/utils/MerkleBase.sol#L188
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