Nouns Builder contest - Saintcode_'s results

USE CALLDATA INSTEAD OF MEMORY

When a function with a memory array is called externally, the abi.decode() step has to use a for-loop to copy each index of the calldata to the memory index. Each iteration of this for-loop costs at least 60 gas (i.e. 60 * <mem_array>.length). Using calldata directly, obliviates the need for such a loop in the contract code and runtime execution.

When arguments are read-only on external functions, the data location should be calldata

19 Instances: -Governance.sol lines 99, 100, 101, 102, 117, 118, 119, 120 -ERC1967Proxy.sol line 21 -ERC1967Upgrade.sol lines 35, 56 -UUPS.sol line 55 -Address.sol lines 37, 46 -MetadataRenderer.sol lines 255, 308, 347, 355, 363

USING STORAGE INSTEAD OF MEMORY FOR STRUCTS/ARRAYS SAVES GAS

When fetching data from a storage location, assigning the data to a memory variable causes all fields of the struct/array to be read from storage, which incurs a Gcoldsload (2100 gas) for each field of the struct/array. If the fields are read from the new memory variable, they incur an additional MLOAD rather than a cheap stack read. Instead of declearing the variable with the memory keyword, declaring the variable with the storage keyword and caching any fields that need to be re-read in stack variables, will be much cheaper, only incuring the Gcoldsload for the fields actually read. The only time it makes sense to read the whole struct/array into a memory variable, is if the full struct/array is being returned by the function, is being passed to a function that requires memory, or if the array/struct is being read from another memory array/struct

6 Instances: -Governor.sol lines 358, 415, 508 -MetadataRenderer.sol 216, 234, 240

<X> += <Y> COSTS MORE GAS THAN <X> = <X> + <Y> FOR STATE VARIABLES

3 Instances: -Governor.sol lines 280, 285, 290

IT COSTS MORE GAS TO INITIALIZE VARIABLES WITH THEIR DEFAULT VALUE THAN LETTING THE DEFAULT VALUE BE APPLIED

If a variable is not set/initialized, it is assumed to have the default value (0 for uint, false for bool, address(0) for address…). Explicitly initializing it with its default value is an anti-pattern and wastes gas.

As an example: for (uint256 i = 0; i < numIterations; ++i) { should be replaced with for (uint256 i; i < numIterations; ++i) {

5 Instances: -Treasury.sol line 162 -MetadataRenderer.sol lines 119, 133, 189, 229

>= COSTS LESS GAS THAN >

The compiler uses opcodes GT and ISZERO for solidity code that uses >, but only requires LT for >=, which saves 3 gas

3 Instances: -Governor.sol line 261 -ERC721Votes.sol line 203 -Address.sol line 50

++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 ` for (uint256 i = 0; i < orders.length; /** NOTE: Removed i++ **/ ) {

       unchecked { ++i; }   

} `

8 Instances: -Treasury.sol line 162 -Token.sol lines 80, 108, 261 -MetadataRenderer.sol lines 119, 133, 189, 229