Gas Optimizations

[code423n4]

X = X + Y / X = X - Y IS CHEAPER THAN X += Y / X -= Y

The demo of the gas comparison can be seen here.

Consider use X = X + Y / X = X - Y to save gas.

Instances number of this issue:

268        pledgeAvailableRewardAmounts[pledgeId] -= rewardAmount;

340        pledgeAvailableRewardAmounts[vars.newPledgeID] += vars.totalRewardAmount;
401        pledgeAvailableRewardAmounts[pledgeId] += totalRewardAmount;
445        pledgeAvailableRewardAmounts[pledgeId] += totalRewardAmount;

Update value order can be adjusted to simplify the code and save gas

For example, to update the num variable with newVal, the current way is as following:

    uint oldVal = num;
    num = newVal;
    emit update(oldVal, newVal);

If the execution order is adjusted, some operations can be saved (memory space allocation, variable assignment), reducing both the deployment and run time gas cost.

    emit update(num, newVal);
    num = newVal;

The operation saved: 1 sload, 1 memory allocation, 1 mstore.

The demo of the gas comparison can be seen here.

There are multiple places can use this trick for optimization, since the updates of parameters are widely and frequently used, the optimization can be beneficial.

Instances number of this issue: 3

    function updateChest(address chest) external onlyOwner {
        if(chest == address(0)) revert Errors.ZeroAddress();
        address oldChest = chestAddress;
        chestAddress = chest;

        emit ChestUpdated(oldChest, chest);
    }

    function updateMinTargetVotes(uint256 newMinTargetVotes) external onlyOwner {
        if(newMinTargetVotes == 0) revert Errors.InvalidValue();
        uint256 oldMinTarget = minTargetVotes;
        minTargetVotes = newMinTargetVotes;

        emit MinTargetUpdated(oldMinTarget, newMinTargetVotes);
    }

    function updatePlatformFee(uint256 newFee) external onlyOwner {
        if(newFee > 500) revert Errors.InvalidValue();
        uint256 oldfee = protocalFeeRatio;
        protocalFeeRatio = newFee;

        emit PlatformFeeUpdated(oldfee, newFee);
    }

Code reuse

Some function codes overlap.
Consider reuse the common part and save deployment gas.

• retrievePledgeRewards() and closePledge() codes overlap a lot, only a few lines of difference.

• the following are used in extendPledge(), increasePledgeRewardPerVote() and _pledge():

        Pledge storage pledgeParams = pledges[pledgeId];
        if(pledgeParams.closed) revert Errors.PledgeClosed();
        if(pledgeParams.endTimestamp <= block.timestamp) revert Errors.ExpiredPledge();

pledgeParams.closed could be deleted

This variable does not seem useful, since the check for if(pledgeParams.endTimestamp <= block.timestamp) can serve the purpose of pledgeParams.closed.

Consider delete pledgeParams.closed.

[c4-judge]

kirk-baird marked the issue as grade-b