Gas Optimizations

[code423n4]

Title: Caching .length for loop can save gas

Proof of Concept:
https://github.com/code-423n4/2022-05-backd/blob/main/protocol/contracts/access/RoleManager.sol#L82
https://github.com/code-423n4/2022-05-backd/blob/main/protocol/contracts/zaps/PoolMigrationZap.sol#L39

Recommended Mitigation Steps:
Change to:

	uint256 Length = roles.length;
	for (uint256 i; i < Length; i = i.uncheckedInc()) {

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Title: Using != is more gas efficient

Proof of Concept:
https://github.com/code-423n4/2022-05-backd/blob/main/protocol/contracts/BkdLocker.sol#L91
https://github.com/code-423n4/2022-05-backd/blob/main/protocol/contracts/BkdLocker.sol#L254

Recommended Mitigation Steps:
Change to !=

	require(amount != 0, Error.INVALID_AMOUNT);

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Title: Using delete statement to empty curRewardTokenData.userShares can save gas

Proof of Concept:
https://github.com/code-423n4/2022-05-backd/blob/main/protocol/contracts/BkdLocker.sol#L215
https://github.com/code-423n4/2022-05-backd/blob/main/protocol/contracts/utils/Preparable.sol#L87-L88

Recommended Mitigation Steps:

	delete curRewardTokenData.userShares[msg.sender];

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Title: Gas improvement on returning totalEthRequired value

Proof of Concept:
https://github.com/code-423n4/2022-05-backd/blob/main/protocol/contracts/Controller.sol#L121-L130

Recommended Mitigation Steps:
by set totalEthRequired in returns and delete L#123 can save gas

function getTotalEthRequiredForGas(address payer) external view override returns (uint256 totalEthRequired) { //@audit-info: set here
        // solhint-disable-previous-line ordering
	//@audit-info: remove this line
        address[] memory actions = addressProvider.allActions();
        uint256 numActions = actions.length;
        for (uint256 i = 0; i < numActions; i++) {
            totalEthRequired += IAction(actions[i]).getEthRequiredForGas(payer);
        }
	return totalEthRequired;
    }

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Title: Using unchecked to calculate

Proof of Concept:
https://github.com/code-423n4/2022-05-backd/blob/main/protocol/contracts/StakerVault.sol#L124

Recommended Mitigation Steps:
balances[msg.sender] value was checked that it >= than amount so using unchecked can save gas:

unchecked{
	balances[msg.sender] -= amount;
}

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Title: Unnecessary MSTORE timeElapsed

Proof of Concept:
https://github.com/code-423n4/2022-05-backd/blob/main/protocol/contracts/tokenomics/AmmGauge.sol#L144-L149

Recommended Mitigation Steps:
By passing block.timestamp - uint256(ammLastUpdated) directly to L#148 without storing it to timeElapsed can save gas without damaging readability of the code

	ammStakedIntegral += (currentRate * (block.timestamp - uint256(ammLastUpdated)).scaledDiv(totalStaked);

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Title: Unnecessary MSTORE

Proof of Concept:
https://github.com/code-423n4/2022-05-backd/blob/main/protocol/contracts/BkdLocker.sol#L138-L144

Recommended Mitigation Steps:
instead of caching length to i. use it directly can save gas
delete L#138 and replace i with `length

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Title: Use allowance_ directly to substract

Proof of Concept:
https://github.com/code-423n4/2022-05-backd/blob/main/protocol/contracts/StakerVault.sol#L387

Recommended Mitigation Steps:

	_allowances[src][msg.sender] = allowance_ - unstaked;

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Title: Unnecessary bool var set

Proof of Concept:
https://github.com/code-423n4/2022-05-backd/blob/main/protocol/contracts/tokenomics/InflationManager.sol#L412

Recommended Mitigation Steps:
the default value of bool is false

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Title: Using > instead >= can save gas

Proof of Concept:
https://github.com/code-423n4/2022-05-backd/blob/main/protocol/contracts/tokenomics/VestedEscrow.sol#L57
https://github.com/code-423n4/2022-05-backd/blob/main/protocol/contracts/utils/Preparable.sol#L110

Recommended Mitigation Steps:
1 second difference can be ignored to validate. using > operator can save gas

	require(starttime_ > block.timestamp, "start must be future");

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Title: Use custom errors rather than revert()/require() strings to save deployment gas

Proof of Concept:
https://github.com/code-423n4/2022-05-backd/blob/main/protocol/contracts/tokenomics/VestedEscrowRevocable.sol#L53-L54

reference: https://blog.soliditylang.org/2021/04/21/custom-errors/

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Title: Using += to increase value

Proof of Concept:
https://github.com/code-423n4/2022-05-backd/blob/main/protocol/contracts/tokenomics/VestedEscrow.sol#L145

Recommended Mitigation Steps:
Change to:

	totalClaimed[msg.sender] += claimable;

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14
Title: Unnecessary MSTORE

Proof of Concept:
https://github.com/code-423n4/2022-05-backd/blob/main/protocol/contracts/tokenomics/VestedEscrow.sol#L155-L156

Recommended Mitigation Steps:
instead of caching to elapsed. calculate directly can save gas
delete L#155

	return Math.min((locked * (_time - startTime)) / totalTime, locked);

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[GalloDaSballo]

Title: Caching .length for loop can save gas

3 per instance
6

Title: Using != is more gas efficient

Saves 3 gas, only for require, solidity < 0.8.13, when using optimizer
3

Title: Using delete statement to empty curRewardTokenData.userShares can save gas

Disagree, delete is the same as setting to default value

## Title: Gas improvement on returning totalEthRequired value
I don't believe it will save gas, it's just syntactic sugar, in lack of math I can only give it 0 gas saved

Title: Using unchecked to calculate

Agree, this will save 20 gas
20

Title: Unnecessary MSTORE timeElapsed

Saves 6 gas but does make the code more complex to scan

Title: Unnecessary MSTORE

I guess, saves 6 gas, notice that the sponsor forgot to use the cached length inside the loop, that would be a more rational refactoring

## Title: Use allowance_ directly to substract
Avoiding the =- saves a SLOAD which saves 100 gas

Title: Unnecessary bool var set

Saves 3 gas

Title: Using > instead >= can save gas

I assume this will save the extra eq, hence saves 3 gas

Use custom errors rather than revert()/require() strings to save deployment gas

In lack of POC i can't give it points

Title: Using += to increase value

Doesn't save gas

Title: Unnecessary MSTORE

Saves 6 gas and makes the code pretty ugly

Total Gas Saved
153