CALCULATION SHOULD BE DONE OUTSIDE THE LOOP

Description:

On line https://github.com/code-423n4/2022-10-zksync/blob/main/ethereum/contracts/zksync/libraries/Diamond.sol#L160 there is a check _saveFacetIfNew(_facet); to see if the facet already exists and this is done inside the loop , so this is executed with every iteration and there is no need to do so as this value calculated by saveFacetIfNew(_facet); does not depend upon the selector so this can be taken outside the loop and gas can be saved as it will be executed just once.

Remediation:

Take the saveFacetIfNew(_facet); outside the loop

+= COSTS MORE GAS THAN = + FOR STATE VARIABLES

Description:

Using the addition operator instead of plus-equals saves 113 gas

Instances Of this Issue:

https://github.com/code-423n4/2022-10-zksync/blob/main/ethereum/contracts/zksync/facets/DiamondCut.sol#L29

SPLITTING REQUIRE() STATEMENTS THAT USE && SAVES GAS

Description:

See this issue which describes the fact that there is a larger deployment gas cost, but with enough runtime calls, the change ends up being cheaper by 3 gas.

Instances of this issue:

https://github.com/code-423n4/2022-10-zksync/blob/main/ethereum/contracts/common/AllowList.sol#L97

Split the require into multiple require statements.

MULTIPLE ADDRESS/ID MAPPINGS CAN BE COMBINED INTO A SINGLE MAPPING OF AN ADDRESS/ID TO A STRUCT, WHERE APPROPRIATE

Description:

Saves a storage slot for the mapping. Depending on the circumstances and sizes of types, can avoid a Gsset (20000 gas) per mapping combined. Reads and subsequent writes can also be cheaper when a function requires both values and they both fit in the same storage slot. Finally, if both fields are accessed in the same function, can save ~42 gas per access due to not having to recalculate the key’s keccak256 hash (Gkeccak256 - 30 gas) and that calculation’s associated stack operations.

Instances of this issue: https://github.com/code-423n4/2022-10-zksync/blob/main/ethereum/contracts/zksync/Storage.sol#L87 https://github.com/code-423n4/2022-10-zksync/blob/main/ethereum/contracts/zksync/Storage.sol#L89 These mappings can be combined into one

USING STORAGE INSTEAD OF MEMORY FOR STRUCTS/ARRAYS SAVES GAS

Description:

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.

Instances of this issue:

CALLDATA INSTEAD OF MEMORY FOR RO FUNCTION PARAMETERS

Description:

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,but it alleviates the compiler from the abi.decode() step that copies each index of the calldata to the memory index, each iteration costing 60 gas.

Instances of this issue:

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sakshamguruji-G.md

sakshamguruji-G.md

CALCULATION SHOULD BE DONE OUTSIDE THE LOOP

Description:

Remediation:

+= COSTS MORE GAS THAN = + FOR STATE VARIABLES

Description:

SPLITTING REQUIRE() STATEMENTS THAT USE && SAVES GAS

Description:

MULTIPLE ADDRESS/ID MAPPINGS CAN BE COMBINED INTO A SINGLE MAPPING OF AN ADDRESS/ID TO A STRUCT, WHERE APPROPRIATE

Description:

USING STORAGE INSTEAD OF MEMORY FOR STRUCTS/ARRAYS SAVES GAS

Description:

CALLDATA INSTEAD OF MEMORY FOR RO FUNCTION PARAMETERS

Description:

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CALCULATION SHOULD BE DONE OUTSIDE THE LOOP

Description:

Remediation:

+= COSTS MORE GAS THAN = + FOR STATE VARIABLES

Description:

SPLITTING REQUIRE() STATEMENTS THAT USE && SAVES GAS

Description:

MULTIPLE ADDRESS/ID MAPPINGS CAN BE COMBINED INTO A SINGLE MAPPING OF AN ADDRESS/ID TO A STRUCT, WHERE APPROPRIATE

Description:

USING STORAGE INSTEAD OF MEMORY FOR STRUCTS/ARRAYS SAVES GAS

Description:

CALLDATA INSTEAD OF MEMORY FOR RO FUNCTION PARAMETERS

Description: