Gas Optimizations

[code423n4]

Use defualt value rather than overwriite variable with their default value.

Overriting varibles with defualt values with their default value will waste only gas and not necessary.

There are 3 instances of this issue:

Findings:

File: ./src/Kernel.sol
397:    for (uint256 i = 0; i < reqLength; ) {

https://github.com/code-423n4/2022-08-olympus/blob/b5e139d732eb4c07102f149fb9426d356af617aa/src/Kernel.sol#L397

File: ./src/utils/KernelUtils.sol
43:     for (uint256 i = 0; i < 5; ) {

58:     for (uint256 i = 0; i < 32; ) {

https://github.com/code-423n4/2022-08-olympus/blob/b5e139d732eb4c07102f149fb9426d356af617aa/src/utils/KernelUtils.sol#L43

In for loop use outside variable for array length

For loop written like thisfor (uint256 i; i < array.length; ++i) { will cost more gas than for (uint256 i; i < _lengthOfArray; ++i) { because for every iteration we use mload and memory_offset
that will cost about 6 gas

There are 2 instances of this issue:

Findings:

File: ./src/policies/Governance.sol

278: for (uint256 step; step < instructions.length; ) {

https://github.com/code-423n4/2022-08-olympus/blob/b5e139d732eb4c07102f149fb9426d356af617aa/src/policies/Governance.sol#L278

File: ./src/utils/KernelUtils.sol

58:     for (uint256 i = 0; i < 32; ) {

https://github.com/code-423n4/2022-08-olympus/blob/b5e139d732eb4c07102f149fb9426d356af617aa/src/utils/KernelUtils.sol#L58

++i/--i are more cheap operations than i++/i--

Using a ++i/--i operations can save about 6 gas for loop/instance because compiler will make less operations

There are 2 instances of this issue:

File: ./src/utils/KernelUtils.sol

49:     i++;

64:     i++;

https://github.com/code-423n4/2022-08-olympus/blob/b5e139d732eb4c07102f149fb9426d356af617aa/src/utils/KernelUtils.sol#L49

If you use bit shifting will save some gas

Use of bit shifting operations are more cheap than normal multiplication/division operations. MUL and DIV costs 5 gas rather than SHL and SHR that costs 3 gas. You can use them where is possible

There are 3 instances of this issue:

Findings:

File: ./src/policies/Operator.sol

372:    int8 scaleAdjustment = int8(ohmDecimals) - int8(reserveDecimals) + (priceDecimals / 2);

419:    uint256 invCushionPrice = 10**(oracleDecimals * 2) / range.cushion.low.price;

420:    uint256 invWallPrice = 10**(oracleDecimals * 2) / range.wall.low.price;

427:    int8 scaleAdjustment = int8(reserveDecimals) - int8(ohmDecimals) + (priceDecimals / 2);

786:    ) * (FACTOR_SCALE + RANGE.spread(true) * 2)) /

https://github.com/code-423n4/2022-08-olympus/blob/b5e139d732eb4c07102f149fb9426d356af617aa/src/policies/Operator.sol#L372