Gas Optimizations

[code423n4]

Use uint256 instead of uint8 at for loop at Swapper.sol and HopFacet.sol

Target codebase

https://github.com/code-423n4/2022-03-lifinance/blob/main/src/Facets/Swapper.sol#L14

for (uint8 i; i < _swapData.length; i++) {
    require(
        ls.dexWhitelist[_swapData[i].approveTo] == true && ls.dexWhitelist[_swapData[i].callTo] == true,
        "Contract call not allowed!"
    );

    LibSwap.swap(_lifiData.transactionId, _swapData[i]);
}

https://github.com/code-423n4/2022-03-lifinance/blob/main/src/Facets/HopFacet.sol#L48-L50

for (uint8 i; i < _tokens.length; i++) {
    s.hopBridges[_tokens[i]] = _bridgeConfigs[i];
}

Usage of uint8 increases the gas fee. If switching this to uint256 is possible for the product, it can reduce the gas fee.

Proposed implementations

Just use uint256 instead of uint8.

for (uint256 i; i < _swapData.length; i++) {
    require(
        ls.dexWhitelist[_swapData[i].approveTo] == true && ls.dexWhitelist[_swapData[i].callTo] == true,
        "Contract call not allowed!"
    );

    LibSwap.swap(_lifiData.transactionId, _swapData[i]);
}

for (uint256 i; i < _tokens.length; i++) {
    s.hopBridges[_tokens[i]] = _bridgeConfigs[i];
}

Gas improvements

Gas fees of methods and deployments are decreased by using uint256 instead of uint8.

Methods - average gas change

Contract	Methods	Before	After	Change
AnyswapFacet	swapAndStartBridgeTokensViaAnyswap	238904	238872	-32
CBridgeFacet	swapAndStartBridgeTokensViaCBridge	315598	315557	-41
DiamondCutFacet	diamondCut	252812	252800	-12
GenericSwapFacet	swapTokensGeneric	254149	254108	-41
HopFacet	startBridgeTokensViaHop	215293	215289	-4
HopFacet	swapAndStartBridgeTokensViaHop	357016	356975	-41
NXTPFacet	swapAndStartBridgeTokensViaNXTP	357455	357414	-

Deployments - average gas change

Contract	Before	After	Change
HopFacet	1482624	1476996	-5628
NXTPFacet	1754544	1750853	-3691

---

== true check is not needed at _executeSwaps function in Swapper.sol

Target codebase

https://github.com/code-423n4/2022-03-lifinance/blob/main/src/Facets/Swapper.sol#L16

require(
    ls.dexWhitelist[_swapData[i].approveTo] == true && ls.dexWhitelist[_swapData[i].callTo] == true,
    "Contract call not allowed!"
);

When checking boolean value, it does not need to check == true.

Proposed implementations

Following code has same meaning.

require(
    ls.dexWhitelist[_swapData[i].approveTo] && ls.dexWhitelist[_swapData[i].callTo],
    "Contract call not allowed!"
);

Gas improvements

Confirmed that the gas fees of deployments and methods decreased.

---

Usage of != 0 instead of > 0 can reduce the gas fee slightly

Target codebase

https://github.com/code-423n4/2022-03-lifinance/blob/main/src/Facets/HopFacet.sol#L109
https://github.com/code-423n4/2022-03-lifinance/blob/main/src/Facets/AnyswapFacet.sol#L92
https://github.com/code-423n4/2022-03-lifinance/blob/main/src/Facets/AnyswapFacet.sol#L105
https://github.com/code-423n4/2022-03-lifinance/blob/main/src/Facets/CBridgeFacet.sol#L105
https://github.com/code-423n4/2022-03-lifinance/blob/main/src/Facets/CBridgeFacet.sol#L116
https://github.com/code-423n4/2022-03-lifinance/blob/main/src/Facets/NXTPFacet.sol#L98
https://github.com/code-423n4/2022-03-lifinance/blob/main/src/Libraries/LibAsset.sol#L67
https://github.com/code-423n4/2022-03-lifinance/blob/main/src/Libraries/LibDiamond.sol#L84
https://github.com/code-423n4/2022-03-lifinance/blob/main/src/Libraries/LibDiamond.sol#L102
https://github.com/code-423n4/2022-03-lifinance/blob/main/src/Libraries/LibDiamond.sol#L121
https://github.com/code-423n4/2022-03-lifinance/blob/main/src/Libraries/LibDiamond.sol#L189
https://github.com/code-423n4/2022-03-lifinance/blob/main/src/Libraries/LibDiamond.sol#L196
https://github.com/code-423n4/2022-03-lifinance/blob/main/src/Libraries/LibDiamond.sol#L212

Proposed implementations

Use != 0 instead of > 0. Example code is as follows:

require(contractSize != 0, _errorMessage);

Gas improvements

Confirmed that the gas fees of deployments and methods decreased.

---

Avoid using == true or == false at DexManagerFacet.sol

Target codebase

Where == true is used

https://github.com/code-423n4/2022-03-lifinance/blob/main/src/Facets/DexManagerFacet.sol#L20

if (s.dexWhitelist[_dex] == true) {
    return;
}

https://github.com/code-423n4/2022-03-lifinance/blob/main/src/Facets/DexManagerFacet.sol#L34

if (s.dexWhitelist[_dexs[i]] == true) {
    continue;
}

Where == false is used

https://github.com/code-423n4/2022-03-lifinance/blob/main/src/Facets/DexManagerFacet.sol#L47

if (s.dexWhitelist[_dex] == false) {
    return;
}

https://github.com/code-423n4/2022-03-lifinance/blob/main/src/Facets/DexManagerFacet.sol#L66

if (s.dexWhitelist[_dexs[i]] == false) {
    continue;
}

Proposed implementations

Where == true is used

if (s.dexWhitelist[_dex]) {
    return;
}

if (s.dexWhitelist[_dexs[i]]) {
    continue;
}

Where == false is used

if (!s.dexWhitelist[_dex]) {
    return;
}

if (!s.dexWhitelist[_dexs[i]]) {
    continue;
}

Gas improvements

Confirmed that the gas fees of deployments and methods slightly decreased.

---

[H3xept]

Re: uint8 -> uint256

Fixed in lifinance/lifi-contracts@3c1558ef50a19cfbbdd6d616d18322dae0bef6ba

[H3xept]

Re uintx to uint256

Duplicate of #196