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WTF Gas Optimization

Solidity gas optimization techniques, verified with Foundry.

总结 Solidity 智能合约省 gas 技巧，并使用 Foundry 验证。

Lead by @0xKaso

Outline

1. use constant and immutable

2. use calldata over memory

3. use Bitmap

4. use unchecked

5. use uint256 over uint8

6. use custom error over require/assert

7. use local variable over storage

8. use clone over new/create2 to deploy contracts

9. packing storage slots

10. use ++i as better increment

11. use uint in reentrancy guard

12. use < over <=

13. optimized selector/method id

14. selector/method-id order matters

15. use shorter string in require()

16. use short circuit in logic operation || or &&

17. delete variables to get gas refund

18. do not initialize state variables with default values

19. swap 2 variables in 1 line with destructuring assignment

20. set constructor to payable to save gas

21. use bytes32 for short string

22. use fixed-size array over dynamic array

23. use event to store data when possible

24. use mapping over array when possible

1. use constant and immutable

Code | 文章

Testing

forge test --contracts 01_Constant/Constant.t.sol --gas-report

Gas report

2. use calldata over memory

Code | 文章

Testing

forge test --contracts 02_CalldataAndMemory/CalldataAndMemory.T.sol --gas-report

Gas report

3. use Bitmap

Code | 文章

Testing

forge test --contracts 03_Bitmap/Bitmap.T.sol --gas-report

Gas report

4. use unchecked

Code | 文章

Testing

forge test --contracts 04_unchecked/Unchecked.T.sol --gas-report

Gas report

5. use uint256 over uint8

Code | 文章

Testing

forge test --contracts 05_Uint/Uint.T.sol --gas-report

Gas report

6. use custom error over require/assert

Code | 文章

Testing

forge test --contracts 06_Error/Error.T.sol --gas-report

Gas report

7. use local variable over storage

Code | 文章

Testing

forge test --contracts 07_LocalData/LocalData.T.sol --gas-report

Gas report

8. use clone over new/create2 to deploy contract

Code | 文章

Testing

forge test --contracts 08_Clone/Clone.T.sol --gas-report

Gas report

9. packing storage slots

Code | 文章

Testing

forge test --contracts 09_Packing/Packing.T.sol --gas-report

Gas report

10. use ++i as better increment

Code | 文章

forge test --contracts 10_Increment/Increment.T.sol --gas-report

Gas report

11. use Uint in Reentrancy Guard

Code | 文章

Testing

forge test --contracts 11_ReentrancyGuard/ReentrancyGuard.T.sol --gas-report

Gas report

12. use < over <=

Code | 文章

Testing

forge test --contracts 12_LessThan/LessThan.t.sol --gas-report

Gas report

13 optimized selector

Code | 文章

Testing

forge test --contracts 13_MethodName/MethodName.t.sol --gas-report

Gas report

14 selector order

Code | 文章

Testing

forge test --contracts 14_MethodIdSort/MethodIdSort.t.sol --gas-report

Gas report

15 shorter string in require()

Code｜文章

Testing

forge test --contracts 15_RequireString/RequireString.t.sol --gas-report

Gas report

16. short circuit in logic operation

Code | 文章

Testing

forge test --contracts 16_ShortCircuit/ShortCircuit.t.sol --gas-report

Gas report

17. delete variables to get gas refund

Code | 文章

Testing

forge test --contracts 17_DeleteVar/DeleteVar.t.sol --gas-report

Gas report

18. do not initialize state variables with default values

Code

Testing

forge test --contracts 18_InitDefault/InitDefault.t.sol --gas-report

Gas report

19. swap 2 variables in 1 line with destructuring assignment

Code

Testing

forge test --contracts 19_SwapVars/SwapVars.t.sol --gas-report

Gas report

This technique will not save gas, but it makes your code look better :p

20. set constructor to payable to save gas

You can cut out 10 opcodes in the creation-time EVM bytecode if you declare a constructor payable. The following opcodes are cut out:

• CALLVALUE
• DUP1
• ISZERO
• PUSH2
• JUMPI
• PUSH1
• DUP1
• REVERT
• JUMPDEST
• POP

In Solidity, this chunk of assembly would mean the following:

if(msg.value != 0) revert();

Code

Testing

forge test --contracts 20_PayableConstructor/PayableConstructor.t.sol --gas-report

Gas report

21. use bytes32 for short string

Code

Testing

forge test --contracts 21_Bytes32String/Bytes32String.t.sol --gas-report

Gas report

22. use fixed-size array over dynamic array

Code

Testing

forge test --contracts 22_FixedSize/FixedSize.t.sol --gas-report

Gas report

23. use event to store data when possible

Code

Testing

forge test --contracts 23_Event/Event.t.sol --gas-report

Gas report

24. use mapping over array when possible

Code

Testing

forge test --contracts 24_MappingArray/MappingArray.t.sol --gas-report

Gas report

WTF Gas Optimization 贡献者

Reference

1. Solidity-Gas-Optimization-Tips