DiamondLib Code Style Findings

DLI-01C: Inefficient mapping Lookups

Type	Severity	Location
Gas Optimization		DiamondLib.sol:L247, L250, L279, L286, L289, L299, L307, L321

Description:

The linked statements perform key-based lookup operations on mapping declarations from storage multiple times for the same key redundantly.

Example:

Copy
235/// @notice Adds a function to the diamond
236/// @param ds The diamond storage pointer
237/// @param _selector The function selector to add
238/// @param _selectorPosition The function selector position
239/// @param _facetAddress The facet address
240function addFunction(
241  DiamondStorage storage ds,
242  bytes4 _selector,
243  uint96 _selectorPosition,
244  address _facetAddress
245) internal {
246  ds
247    .selectorToFacetAndPosition[_selector]
248    .functionSelectorPosition = _selectorPosition;
249  ds.facetFunctionSelectors[_facetAddress].functionSelectors.push(_selector);
250  ds.selectorToFacetAndPosition[_selector].facetAddress = _facetAddress;
251}

Recommendation:

As the lookups internally perform an expensive keccak256 operation, we advise the lookups to be cached wherever possible to a single local declaration that either holds the value of the mapping in case of primitive types or holds a storage pointer to the struct contained.

Alleviation (3dd3d7bf0c2693b2f9c23bacedfa420393f7ea84):

All referenced mapping lookups have been optimized as advised, utilizing interim variables for iterative mapping declarations and caching values to local variables where applicable.