Description:
Infinity can also be represented via `2**255, it's hex representation is 0x8000000000000000000000000000000000000000000000000000000000000000 while 2**256 - 1 is 0xffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff. Then main difference is and where the gas savings come from is, zeros are cheaper than non-zero values in hex representation.
Recommendation:
Use 2**255 instead of 2**256 - 1 to save gas on deployment.
Use of The memory Keyword When storage Should Be Used
Description:
When copying a state struct in memory, there are as many SLOADs and MSTOREs as there are fields. When reading the whole struct multiple times is not needed, it's better to actually only read the relevant field(s). When only some of the fields are read several times, these particular values should be cached instead of the whole state struct.
Recommendation:
Use the storage keyword instead of the memory keyword in these situations.
Description:
Functions that read state variables more than once can cache it into a local variable for repeated reads saving gas by converting expensive SLOADs into much cheaper MLOADs.
Recommendation:
It's best to cach the state variables into memory when read more than once.
Description:
Solidity 0.6.5 introduced immutable as a major feature. It allows setting contract-level variables at construction time which gets stored in code rather than storage. Each call to it reads from storage, using a sload costing 2100 gas cold or 100 gas warm. Setting it to immutable will have each storage read of the state variable to be replaced by the instruction push32 value, where value is set during contract construction time and this costs only 3 gas.
Recommendation:
Set the state variable to immutable
Description:
You can cut out 10 opcodes in the creation-time EVM bytecode if you declare a constructor payable. Making the constructor payable eliminates the need for an initial check of msg.value == 0 and saves 21 gas on deployment with no security risks.
Description:
Contracts most called functions could simply save gas by function ordering via Method ID. Calling a function at runtime will be cheaper if the function is positioned earlier in the order (has a relatively lower Method ID) because 22 gas are added to the cost of a function for every position that came before it. The caller can save on gas if you prioritize most called functions. One could use This tool to help find alternative function names with lower Method IDs while keeping the original name intact.
Recommendation:
Find a lower method ID name for the most called functions for example mostCalled() vs. mostCalled_41q() is cheaper by 44 gas.
robrobbins
commented
2 years ago
Use of
2**256 - 1When2**255Should Be UsedContext:
Swivel.sol#L549Description: Infinity can also be represented via
`2**255, it's hex representation is0x8000000000000000000000000000000000000000000000000000000000000000while2**256 - 1is0xffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff. Then main difference is and where the gas savings come from is, zeros are cheaper than non-zero values in hex representation.Recommendation: Use
2**255instead of2**256 - 1to save gas on deployment.Use of The
memoryKeyword WhenstorageShould Be UsedContext:
MarketPlace.sol#L91,MarketPlace.sol#L132,MarketPlace.sol#L216,MarketPlace.sol#L228,MarketPlace.sol#L248,MarketPlace.sol#L266,MarketPlace.sol#L284Description: When copying a state struct in memory, there are as many SLOADs and MSTOREs as there are fields. When reading the whole struct multiple times is not needed, it's better to actually only read the relevant field(s). When only some of the fields are read several times, these particular values should be cached instead of the whole state struct.
Recommendation: Use the
storagekeyword instead of thememorykeyword in these situations.Same State Variable Read More Than Once
Context:
VaultTracker.sol#L49-L77 (maturityRate),VaultTracker.sol#L82-L109 (maturityRate),VaultTracker.sol#L113-L139 (maturityRate),VaultTracker.sol#L152-L203 (maturityRate),VaultTracker.sol#L208-L239 (maturityRate),ZcToken.sol#L43-L48 (maturity, redeemer, protocol),ZcToken.sol#L52-L57 (maturity, redeemer, protocol),ZcToken.sol#L70-L75 (maturity, redeemer, protocol),ZcToken.sol#L79-L84 (maturity, redeemer, protocol),ZcToken.sol#L88-L93 (maturity, redeemer, protocol),ZcToken.sol#L98-L119 (maturity, redeemer, protocol),ZcToken.sol#L124-L137 (maturity, redeemer, protocol)Description: Functions that read state variables more than once can cache it into a local variable for repeated reads saving gas by converting expensive
SLOADs into much cheaperMLOADs.Recommendation: It's best to cach the state variables into memory when read more than once.
State Variables That Can Be Set To
ImmutableContext:
Swivel.sol#L33Description: Solidity
0.6.5introducedimmutableas a major feature. It allows setting contract-level variables at construction time which gets stored in code rather than storage. Each call to it reads from storage, using asloadcosting 2100 gas cold or 100 gas warm. Setting it toimmutablewill have each storage read of the state variable to be replaced by the instructionpush32 value, wherevalueis set during contract construction time and this costs only 3 gas.Recommendation: Set the state variable to
immutableSetting The Constructor To Payable
Context:
All ContractsDescription: You can cut out 10 opcodes in the creation-time EVM bytecode if you declare a constructor payable. Making the constructor payable eliminates the need for an initial check of
msg.value == 0and saves 21 gas on deployment with no security risks.Recommendation: Set the constructor to payable.
Function Ordering via Method ID
Context:
All ContractsDescription: Contracts most called functions could simply save gas by function ordering via Method ID. Calling a function at runtime will be cheaper if the function is positioned earlier in the order (has a relatively lower Method ID) because 22 gas are added to the cost of a function for every position that came before it. The caller can save on gas if you prioritize most called functions. One could use
This toolto help find alternative function names with lower Method IDs while keeping the original name intact.Recommendation: Find a lower method ID name for the most called functions for example
mostCalled()vs.mostCalled_41q()is cheaper by 44 gas.