Gas Optimizations #326
Labels
bug
Something isn't working
G (Gas Optimization)
G-10
grade-b
sponsor confirmed
Sponsor agrees this is a problem and intends to fix it (OK to use w/ "disagree with severity")
Summary
Gas Optimizations
address
/ID mappings can be combined into a singlemapping
of anaddress
/ID to astruct
, where appropriatestorage
instead ofmemory
for structs/arrays saves gasunchecked {}
for subtractions where the operands cannot underflow because of a previousrequire()
orif
-statement++i
/i++
should beunchecked{++i}
/unchecked{i++}
when it is not possible for them to overflow, as is the case when used infor
- andwhile
-loops>=
costs less gas than>
payable
Total: 121 instances over 11 issues with 50432 gas saved
Gas totals use lower bounds of ranges and count two iterations of each
for
-loop. All values above are runtime, not deployment, values; deployment values are listed in the individual issue descriptions. The table above and its gas values do not include any excluded findings.Gas Optimizations
[G‑01] Multiple
address
/ID mappings can be combined into a singlemapping
of anaddress
/ID to astruct
, where appropriateSaves 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.
There is 1 instance of this issue:
https://github.com/code-423n4/2022-10-traderjoe/blob/79f25d48b907f9d0379dd803fc2abc9c5f57db93/src/LBPair.sol#L68-L70
[G‑02] State variables can be packed into fewer storage slots
If variables occupying the same slot are both written the same function or by the constructor, avoids a separate Gsset (20000 gas). Reads of the variables can also be cheaper
There is 1 instance of this issue:
https://github.com/code-423n4/2022-10-traderjoe/blob/79f25d48b907f9d0379dd803fc2abc9c5f57db93/src/LBFactory.sol#L32
[G‑03] Using
storage
instead ofmemory
for structs/arrays saves gasWhen 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 additionalMLOAD
rather than a cheap stack read. Instead of declearing the variable with thememory
keyword, declaring the variable with thestorage
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 amemory
variable, is if the full struct/array is being returned by the function, is being passed to a function that requiresmemory
, or if the array/struct is being read from anothermemory
array/structThere are 11 instances of this issue:
https://github.com/code-423n4/2022-10-traderjoe/blob/79f25d48b907f9d0379dd803fc2abc9c5f57db93/src/LBFactory.sol#L197
https://github.com/code-423n4/2022-10-traderjoe/blob/79f25d48b907f9d0379dd803fc2abc9c5f57db93/src/LBPair.sol#L220
[G‑04] Avoid contract existence checks by using low level calls
Prior to 0.8.10 the compiler inserted extra code, including
EXTCODESIZE
(100 gas), to check for contract existence for external function calls. In more recent solidity versions, the compiler will not insert these checks if the external call has a return value. Similar behavior can be achieved in earlier versions by using low-level calls, since low level calls never check for contract existenceThere are 28 instances of this issue:
https://github.com/code-423n4/2022-10-traderjoe/blob/79f25d48b907f9d0379dd803fc2abc9c5f57db93/src/LBFactory.sol#L216
https://github.com/code-423n4/2022-10-traderjoe/blob/79f25d48b907f9d0379dd803fc2abc9c5f57db93/src/LBQuoter.sol#L77
https://github.com/code-423n4/2022-10-traderjoe/blob/79f25d48b907f9d0379dd803fc2abc9c5f57db93/src/LBRouter.sol#L718
https://github.com/code-423n4/2022-10-traderjoe/blob/79f25d48b907f9d0379dd803fc2abc9c5f57db93/src/libraries/BinHelper.sol#L44
https://github.com/code-423n4/2022-10-traderjoe/blob/79f25d48b907f9d0379dd803fc2abc9c5f57db93/src/libraries/TokenHelper.sol#L28
[G‑05] Multiple accesses of a mapping/array should use a local variable cache
The instances below point to the second+ access of a value inside a mapping/array, within a function. Caching a mapping's value in a local
storage
orcalldata
variable when the value is accessed multiple times, saves ~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. Caching an array's struct avoids recalculating the array offsets into memory/calldataThere is 1 instance of this issue:
https://github.com/code-423n4/2022-10-traderjoe/blob/79f25d48b907f9d0379dd803fc2abc9c5f57db93/src/LBPair.sol#L453
[G‑06] Add
unchecked {}
for subtractions where the operands cannot underflow because of a previousrequire()
orif
-statementrequire(a <= b); x = b - a
=>require(a <= b); unchecked { x = b - a }
There are 5 instances of this issue:
https://github.com/code-423n4/2022-10-traderjoe/blob/79f25d48b907f9d0379dd803fc2abc9c5f57db93/src/LBPair.sol#L225
[G‑07]
++i
/i++
should beunchecked{++i}
/unchecked{i++}
when it is not possible for them to overflow, as is the case when used infor
- andwhile
-loopsThe
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 loopThere are 5 instances of this issue:
https://github.com/code-423n4/2022-10-traderjoe/blob/79f25d48b907f9d0379dd803fc2abc9c5f57db93/src/LBQuoter.sol#L75
https://github.com/code-423n4/2022-10-traderjoe/blob/79f25d48b907f9d0379dd803fc2abc9c5f57db93/src/LBRouter.sol#L711
[G‑08] Optimize names to save gas
public
/external
function names andpublic
member variable names can be optimized to save gas. See this link for an example of how it works. Below are the interfaces/abstract contracts that can be optimized so that the most frequently-called functions use the least amount of gas possible during method lookup. Method IDs that have two leading zero bytes can save 128 gas each during deployment, and renaming functions to have lower method IDs will save 22 gas per call, per sorted position shiftedThere are 11 instances of this issue:
https://github.com/code-423n4/2022-10-traderjoe/blob/79f25d48b907f9d0379dd803fc2abc9c5f57db93/src/interfaces/IJoeFactory.sol#L7
https://github.com/code-423n4/2022-10-traderjoe/blob/79f25d48b907f9d0379dd803fc2abc9c5f57db93/src/interfaces/IJoePair.sol#L7
https://github.com/code-423n4/2022-10-traderjoe/blob/79f25d48b907f9d0379dd803fc2abc9c5f57db93/src/interfaces/IJoeRouter01.sol#L7
https://github.com/code-423n4/2022-10-traderjoe/blob/79f25d48b907f9d0379dd803fc2abc9c5f57db93/src/interfaces/IJoeRouter02.sol#L9
https://github.com/code-423n4/2022-10-traderjoe/blob/79f25d48b907f9d0379dd803fc2abc9c5f57db93/src/interfaces/ILBFactory.sol#L13
https://github.com/code-423n4/2022-10-traderjoe/blob/79f25d48b907f9d0379dd803fc2abc9c5f57db93/src/interfaces/ILBFlashLoanCallback.sol#L8
https://github.com/code-423n4/2022-10-traderjoe/blob/79f25d48b907f9d0379dd803fc2abc9c5f57db93/src/interfaces/ILBPair.sol#L13
https://github.com/code-423n4/2022-10-traderjoe/blob/79f25d48b907f9d0379dd803fc2abc9c5f57db93/src/interfaces/ILBRouter.sol#L13
https://github.com/code-423n4/2022-10-traderjoe/blob/79f25d48b907f9d0379dd803fc2abc9c5f57db93/src/interfaces/ILBToken.sol#L8
https://github.com/code-423n4/2022-10-traderjoe/blob/79f25d48b907f9d0379dd803fc2abc9c5f57db93/src/interfaces/IPendingOwnable.sol#L8
https://github.com/code-423n4/2022-10-traderjoe/blob/79f25d48b907f9d0379dd803fc2abc9c5f57db93/src/LBQuoter.sol#L17
[G‑09] Use a more recent version of solidity
Use a solidity version of at least 0.8.2 to get simple compiler automatic inlining
Use a solidity version of at least 0.8.3 to get better struct packing and cheaper multiple storage reads
Use a solidity version of at least 0.8.4 to get custom errors, which are cheaper at deployment than
revert()/require()
stringsUse a solidity version of at least 0.8.10 to have external calls skip contract existence checks if the external call has a return value
There are 37 instances of this issue:
https://github.com/code-423n4/2022-10-traderjoe/blob/79f25d48b907f9d0379dd803fc2abc9c5f57db93/src/interfaces/IJoeFactory.sol#L3
https://github.com/code-423n4/2022-10-traderjoe/blob/79f25d48b907f9d0379dd803fc2abc9c5f57db93/src/interfaces/IJoePair.sol#L3
https://github.com/code-423n4/2022-10-traderjoe/blob/79f25d48b907f9d0379dd803fc2abc9c5f57db93/src/interfaces/IJoeRouter01.sol#L3
https://github.com/code-423n4/2022-10-traderjoe/blob/79f25d48b907f9d0379dd803fc2abc9c5f57db93/src/interfaces/IJoeRouter02.sol#L3
https://github.com/code-423n4/2022-10-traderjoe/blob/79f25d48b907f9d0379dd803fc2abc9c5f57db93/src/interfaces/ILBFactory.sol#L3
https://github.com/code-423n4/2022-10-traderjoe/blob/79f25d48b907f9d0379dd803fc2abc9c5f57db93/src/interfaces/ILBFlashLoanCallback.sol#L3
https://github.com/code-423n4/2022-10-traderjoe/blob/79f25d48b907f9d0379dd803fc2abc9c5f57db93/src/interfaces/ILBPair.sol#L3
https://github.com/code-423n4/2022-10-traderjoe/blob/79f25d48b907f9d0379dd803fc2abc9c5f57db93/src/interfaces/ILBRouter.sol#L3
https://github.com/code-423n4/2022-10-traderjoe/blob/79f25d48b907f9d0379dd803fc2abc9c5f57db93/src/interfaces/ILBToken.sol#L3
https://github.com/code-423n4/2022-10-traderjoe/blob/79f25d48b907f9d0379dd803fc2abc9c5f57db93/src/interfaces/IPendingOwnable.sol#L3
https://github.com/code-423n4/2022-10-traderjoe/blob/79f25d48b907f9d0379dd803fc2abc9c5f57db93/src/interfaces/IWAVAX.sol#L3
https://github.com/code-423n4/2022-10-traderjoe/blob/79f25d48b907f9d0379dd803fc2abc9c5f57db93/src/LBErrors.sol#L3
https://github.com/code-423n4/2022-10-traderjoe/blob/79f25d48b907f9d0379dd803fc2abc9c5f57db93/src/LBFactory.sol#L3
https://github.com/code-423n4/2022-10-traderjoe/blob/79f25d48b907f9d0379dd803fc2abc9c5f57db93/src/LBPair.sol#L3
https://github.com/code-423n4/2022-10-traderjoe/blob/79f25d48b907f9d0379dd803fc2abc9c5f57db93/src/LBQuoter.sol#L3
https://github.com/code-423n4/2022-10-traderjoe/blob/79f25d48b907f9d0379dd803fc2abc9c5f57db93/src/LBRouter.sol#L3
https://github.com/code-423n4/2022-10-traderjoe/blob/79f25d48b907f9d0379dd803fc2abc9c5f57db93/src/LBToken.sol#L3
https://github.com/code-423n4/2022-10-traderjoe/blob/79f25d48b907f9d0379dd803fc2abc9c5f57db93/src/libraries/BinHelper.sol#L3
https://github.com/code-423n4/2022-10-traderjoe/blob/79f25d48b907f9d0379dd803fc2abc9c5f57db93/src/libraries/BitMath.sol#L3
https://github.com/code-423n4/2022-10-traderjoe/blob/79f25d48b907f9d0379dd803fc2abc9c5f57db93/src/libraries/Buffer.sol#L3
https://github.com/code-423n4/2022-10-traderjoe/blob/79f25d48b907f9d0379dd803fc2abc9c5f57db93/src/libraries/Constants.sol#L3
https://github.com/code-423n4/2022-10-traderjoe/blob/79f25d48b907f9d0379dd803fc2abc9c5f57db93/src/libraries/Decoder.sol#L3
https://github.com/code-423n4/2022-10-traderjoe/blob/79f25d48b907f9d0379dd803fc2abc9c5f57db93/src/libraries/Encoder.sol#L3
https://github.com/code-423n4/2022-10-traderjoe/blob/79f25d48b907f9d0379dd803fc2abc9c5f57db93/src/libraries/FeeDistributionHelper.sol#L3
https://github.com/code-423n4/2022-10-traderjoe/blob/79f25d48b907f9d0379dd803fc2abc9c5f57db93/src/libraries/FeeHelper.sol#L3
https://github.com/code-423n4/2022-10-traderjoe/blob/79f25d48b907f9d0379dd803fc2abc9c5f57db93/src/libraries/JoeLibrary.sol#L3
https://github.com/code-423n4/2022-10-traderjoe/blob/79f25d48b907f9d0379dd803fc2abc9c5f57db93/src/libraries/Math128x128.sol#L3
https://github.com/code-423n4/2022-10-traderjoe/blob/79f25d48b907f9d0379dd803fc2abc9c5f57db93/src/libraries/Math512Bits.sol#L3
https://github.com/code-423n4/2022-10-traderjoe/blob/79f25d48b907f9d0379dd803fc2abc9c5f57db93/src/libraries/Oracle.sol#L3
https://github.com/code-423n4/2022-10-traderjoe/blob/79f25d48b907f9d0379dd803fc2abc9c5f57db93/src/libraries/PendingOwnable.sol#L3
https://github.com/code-423n4/2022-10-traderjoe/blob/79f25d48b907f9d0379dd803fc2abc9c5f57db93/src/libraries/ReentrancyGuardUpgradeable.sol#L3
https://github.com/code-423n4/2022-10-traderjoe/blob/79f25d48b907f9d0379dd803fc2abc9c5f57db93/src/libraries/SafeCast.sol#L3
https://github.com/code-423n4/2022-10-traderjoe/blob/79f25d48b907f9d0379dd803fc2abc9c5f57db93/src/libraries/SafeMath.sol#L3
https://github.com/code-423n4/2022-10-traderjoe/blob/79f25d48b907f9d0379dd803fc2abc9c5f57db93/src/libraries/Samples.sol#L3
https://github.com/code-423n4/2022-10-traderjoe/blob/79f25d48b907f9d0379dd803fc2abc9c5f57db93/src/libraries/SwapHelper.sol#L3
https://github.com/code-423n4/2022-10-traderjoe/blob/79f25d48b907f9d0379dd803fc2abc9c5f57db93/src/libraries/TokenHelper.sol#L3
https://github.com/code-423n4/2022-10-traderjoe/blob/79f25d48b907f9d0379dd803fc2abc9c5f57db93/src/libraries/TreeMath.sol#L3
[G‑10]
>=
costs less gas than>
The compiler uses opcodes
GT
andISZERO
for solidity code that uses>
, but only requiresLT
for>=
, which saves 3 gasThere is 1 instance of this issue:
https://github.com/code-423n4/2022-10-traderjoe/blob/79f25d48b907f9d0379dd803fc2abc9c5f57db93/src/LBRouter.sol#L116
[G‑11] Functions guaranteed to revert when called by normal users can be marked
payable
If a function modifier such as
onlyOwner
is used, the function will revert if a normal user tries to pay the function. Marking the function aspayable
will lower the gas cost for legitimate callers because the compiler will not include checks for whether a payment was provided. The extra opcodes avoided areCALLVALUE
(2),DUP1
(3),ISZERO
(3),PUSH2
(3),JUMPI
(10),PUSH1
(3),DUP1
(3),REVERT
(0),JUMPDEST
(1),POP
(2), which costs an average of about 21 gas per call to the function, in addition to the extra deployment costThere are 20 instances of this issue:
https://github.com/code-423n4/2022-10-traderjoe/blob/79f25d48b907f9d0379dd803fc2abc9c5f57db93/src/LBFactory.sol#L215
https://github.com/code-423n4/2022-10-traderjoe/blob/79f25d48b907f9d0379dd803fc2abc9c5f57db93/src/LBPair.sol#L104-L110
https://github.com/code-423n4/2022-10-traderjoe/blob/79f25d48b907f9d0379dd803fc2abc9c5f57db93/src/LBRouter.sol#L622-L626
https://github.com/code-423n4/2022-10-traderjoe/blob/79f25d48b907f9d0379dd803fc2abc9c5f57db93/src/libraries/PendingOwnable.sol#L59
Excluded findings
These findings are excluded from awards calculations because there are publicly-available automated tools that find them. The valid ones appear here for completeness
[G‑01]
<array>.length
should not be looked up in every loop of afor
-loopThe overheads outlined below are PER LOOP, excluding the first loop
MLOAD
(3 gas)CALLDATALOAD
(3 gas)Caching the length changes each of these to a
DUP<N>
(3 gas), and gets rid of the extraDUP<N>
needed to store the stack offsetThere are 13 instances of this issue:
https://github.com/code-423n4/2022-10-traderjoe/blob/79f25d48b907f9d0379dd803fc2abc9c5f57db93/src/LBPair.sol#L274
https://github.com/code-423n4/2022-10-traderjoe/blob/79f25d48b907f9d0379dd803fc2abc9c5f57db93/src/LBQuoter.sol#L100
The text was updated successfully, but these errors were encountered: