Submission Details
Severity:
Use assembly to emit events
Summary
We can use assembly to emit events efficiently by utilizing scratch space and the free memory pointer. This will allow us to potentially avoid memory expansion costs. Note: In order to do this optimization safely, we will need to cache and restore the free memory pointer.
For example, for a generic emit event for eventSentAmountExample:
// uint256 id, uint256 value, uint256 amount
emit eventSentAmountExample(id, value, amount);
We can use the following assembly emit events:
assembly {
let memptr := mload(0x40)
mstore(0x00, calldataload(0x44))
mstore(0x20, calldataload(0xa4))
mstore(0x40, amount)
log1(
0x00,
0x60,
// keccak256("eventSentAmountExample(uint256,uint256,uint256)")
0xa622cf392588fbf2cd020ff96b2f4ebd9c76d7a4bc7f3e6b2f18012312e76bc3
)
mstore(0x40, memptr)
}
Gas saved per Instance: ~38
Tools Used
Manual Review
Recommendations
Use assembly to emit events
Prize pool breakdown
Total prize
40,000 USDC
nSLOC
186215 USDC / LOC
37,000 USDC
3,000 USDC
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