Gas Optimizations - Githubissues

[G-01] ++i costs less gas than i++, especially when it's used in for loops (same for ++j vs j++)

Instances include: 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

[G-02] ++i/i++ should be unchecked{++i}/unchecked{i++} when it is not possible for them to overflow, as is the case when used in for- and while-loops The unchecked keyword is new in solidity version 0.8.0, so this only applies to that version or higher, which these instances are. This saves 30-40 gas per loop: https://gist.github.com/hrkrshnn/ee8fabd532058307229d65dcd5836ddc#the-increment-in-for-loop-post-condition-can-be-made-unchecked

[G-03] .length should not be looked up in every loop of a for-loop The overheads outlined below are PER LOOP, excluding the first loop storage arrays incur a Gwarmaccess (100 gas) memory arrays use MLOAD (3 gas) calldata arrays use CALLDATALOAD (3 gas) Caching the length changes each of these to a DUP (3 gas), and gets rid of the extra DUP needed to store the stack offset.

[G-04] calldata instead of memory for read-only function parameter If a reference type function parameter is read-only, it is cheaper in gas to use calldata instead of memory. Calldata is a non-modifiable, non-persistent area where function arguments are stored, and behaves mostly like memory. Try to use calldata as a data location because it will avoid copies and also makes sure that the data cannot be modified.

[G-05] Reduce the size of error messages (Long revert Strings) Shortening revert strings to fit in 32 bytes will decrease deployment time gas and will decrease runtime gas when the revert condition is met. Revert strings that are longer than 32 bytes require at least one additional mstore, along with additional overhead for computing memory offset, etc.

Instances include: https://github.com/code-423n4/2022-07-fractional/blob/e2c5a962a94106f9495eb96769d7f60f7d5b14c9/src/utils/MerkleBase.sol#L62 https://github.com/code-423n4/2022-07-fractional/blob/e2c5a962a94106f9495eb96769d7f60f7d5b14c9/src/utils/MerkleBase.sol#L78

Mitigation: I suggest shortening the revert strings to fit in 32 bytes

[G-06] += costs more gas than = + for state variables (also -= vs = - )

[G-07] Usage of uints/ints smaller than 32 bytes (256 bits) incurs overhead

Instances include: https://github.com/code-423n4/2022-07-fractional/blob/e2c5a962a94106f9495eb96769d7f60f7d5b14c9/src/FERC1155.sol#L104 https://github.com/code-423n4/2022-07-fractional/blob/e2c5a962a94106f9495eb96769d7f60f7d5b14c9/src/FERC1155.sol#L150 https://github.com/code-423n4/2022-07-fractional/blob/e2c5a962a94106f9495eb96769d7f60f7d5b14c9/src/utils/SelfPermit.sol#L23 https://github.com/code-423n4/2022-07-fractional/blob/e2c5a962a94106f9495eb96769d7f60f7d5b14c9/src/utils/SelfPermit.sol#L50

[G-08] Using private rather than public for constants saves gas If needed, the value can be read from the verified contract source code. Savings are due to the compiler not having to create non-payable getter functions for deployment calldata, and not adding another entry to the method ID table.

Instances include: https://github.com/code-423n4/2022-07-fractional/blob/e2c5a962a94106f9495eb96769d7f60f7d5b14c9/src/FERC1155.sol#L15 https://github.com/code-423n4/2022-07-fractional/blob/e2c5a962a94106f9495eb96769d7f60f7d5b14c9/src/FERC1155.sol#L17 https://github.com/code-423n4/2022-07-fractional/blob/e2c5a962a94106f9495eb96769d7f60f7d5b14c9/src/modules/Buyout.sol#L35 https://github.com/code-423n4/2022-07-fractional/blob/e2c5a962a94106f9495eb96769d7f60f7d5b14c9/src/modules/Buyout.sol#L37 https://github.com/code-423n4/2022-07-fractional/blob/e2c5a962a94106f9495eb96769d7f60f7d5b14c9/src/modules/Migration.sol#L43 https://github.com/code-423n4/2022-07-fractional/blob/e2c5a962a94106f9495eb96769d7f60f7d5b14c9/src/utils/SafeSend.sol#L11

[G-09] Multiplication/division by two should use bit shifting

* 2 is equivalent to << 1 and / 2 is the same as >> 1. The MUL and DIV opcodes cost 5 gas, whereas SHL and SHR only cost 3 gas. Instances include: https://github.com/code-423n4/2022-07-fractional/blob/e2c5a962a94106f9495eb96769d7f60f7d5b14c9/src/utils/MerkleBase.sol#L100 https://github.com/code-423n4/2022-07-fractional/blob/e2c5a962a94106f9495eb96769d7f60f7d5b14c9/src/utils/MerkleBase.sol#L136 https://github.com/code-423n4/2022-07-fractional/blob/e2c5a962a94106f9495eb96769d7f60f7d5b14c9/src/utils/MerkleBase.sol#L142 [G-10] Use custom errors rather than revert()/require() strings to save deployment gas Custom errors are available from solidity version 0.8.4. The instances below match or exceed that version. Instances include: https://github.com/code-423n4/2022-07-fractional/blob/e2c5a962a94106f9495eb96769d7f60f7d5b14c9/src/utils/MerkleBase.sol#L62 https://github.com/code-423n4/2022-07-fractional/blob/e2c5a962a94106f9495eb96769d7f60f7d5b14c9/src/utils/MerkleBase.sol#L78 [G-11] 'internal' functions only called once can be inlined to save gas Not inlining costs 20 to 40 gas because of two extra JUMP instructions and additional stack operations needed for function calls. Instances include: https://github.com/code-423n4/2022-07-fractional/blob/e2c5a962a94106f9495eb96769d7f60f7d5b14c9/src/Vault.sol#L115

code-423n4 / 2022-07-fractional-findings

Gas Optimizations #613