Numoen contest - cryptostellar5's results

G-01 X += Y COSTS MORE GAS THAN X = X + Y FOR STATE VARIABLES

Number of Instances Identified: 10

Using the addition operator instead of plus-equals saves 113 gas

https://github.com/code-423n4/2023-01-numoen/blob/main/src/core/Lendgine.sol

91: totalLiquidityBorrowed += liquidity;
114: totalLiquidityBorrowed -= liquidity;
176: totalPositionSize -= size;
257: rewardPerPositionStored += FullMath.mulDiv(dilutionSpeculative, 1e18, totalPositionSize);

https://github.com/code-423n4/2023-01-numoen/blob/main/src/periphery/LiquidityManager.sol

178: position.tokensOwed += FullMath.mulDiv(position.size, rewardPerPositionPaid - position.rewardPerPositionPaid, 1e18);
180: position.size += size;
214: position.tokensOwed += FullMath.mulDiv(position.size, rewardPerPositionPaid - position.rewardPerPositionPaid, 1e18);
216: position.size -= params.size;
238: position.tokensOwed += FullMath.mulDiv(position.size, rewardPerPositionPaid - position.rewardPerPositionPaid, 1e18);
242: position.tokensOwed -= amount;

G-02 SPLITTING REQUIRE() STATEMENTS THAT USE && SAVES GAS

Number of Instances Identified: 2

See this issue which describes the fact that there is a larger deployment gas cost, but with enough runtime calls, the change ends up being cheaper by 3 gas

https://github.com/code-423n4/2023-01-numoen/blob/main/src/periphery/UniswapV2/libraries/UniswapV2Library.sol

61: require(reserveIn > 0 && reserveOut > 0, "UniswapV2Library: INSUFFICIENT_LIQUIDITY");
79: require(reserveIn > 0 && reserveOut > 0, "UniswapV2Library: INSUFFICIENT_LIQUIDITY");

G-03 DUPLICATED REQUIRE() or REVERT() CHECKS SHOULD BE REFACTORED TO A MODIFIER OR FUNCTION

Number of Instances Identified: 2

Saves deployment costs

61: require(reserveIn > 0 && reserveOut > 0, "UniswapV2Library: INSUFFICIENT_LIQUIDITY");
79: require(reserveIn > 0 && reserveOut > 0, "UniswapV2Library: INSUFFICIENT_LIQUIDITY");

G-04 USING BOTH NAMED RETURNS AND A RETURN STATEMENT ISNT NECESSARY

Number of Instances Identified: 3

Removing unused named returns variables can reduce gas usage (MSTOREs/MLOADs) and improve code clarity. To save gas and improve code quality: consider using only one of those. Each MLOAD and MSTORE costs 3 additional gas

https://github.com/code-423n4/2023-01-numoen/blob/main/src/core/JumpRate.sol

13-23: function getBorrowRate(uint256 borrowedLiquidity, uint256 totalLiquidity) public pure override returns (uint256 rate) { 
    uint256 util = utilizationRate(borrowedLiquidity, totalLiquidity);

    if (util <= kink) {
      return (util * multiplier) / 1e18;
    } else {
      uint256 normalRate = (kink * multiplier) / 1e18;
      uint256 excessUtil = util - kink;
      return ((excessUtil * jumpMultiplier) / 1e18) + normalRate;
    }
  }

25-38: unction getSupplyRate(
    uint256 borrowedLiquidity,
    uint256 totalLiquidity
  )
    external
    pure
    override
    returns (uint256 rate)
  {
    uint256 util = utilizationRate(borrowedLiquidity, totalLiquidity);
    uint256 borrowRate = getBorrowRate(borrowedLiquidity, totalLiquidity);

    return (borrowRate * util) / 1e18;
  }

40-43: function utilizationRate(uint256 borrowedLiquidity, uint256 totalLiquidity) private pure returns (uint256 rate) { 
    if (totalLiquidity == 0) return 0;
    return (borrowedLiquidity * 1e18) / totalLiquidity;
  }

G-05 INTERNAL FUNCTIONS ONLY CALLED ONCE CAN BE INLINED TO SAVE GAS

Number of Instances Identified: 6

Not inlining costs 20 to 40 gas because of two extra JUMP instructions and additional stack operations needed for function calls.

https://github.com/code-423n4/2023-01-numoen/blob/main/src/core/libraries/Position.sol

69: function newTokensOwed(Position.Info memory position, uint256 rewardPerPosition) internal

73-78: function convertLiquidityToPosition(
    uint256 liquidity,
    uint256 totalLiquiditySupplied,
    uint256 totalPositionSize
  )
    internal

86-91: function convertPositionToLiquidity(
    uint256 position,
    uint256 totalLiquiditySupplied,
    uint256 totalPositionSize
  )
    internal

https://github.com/code-423n4/2023-01-numoen/blob/main/src/core/libraries/PositionMath.sol

12: function addDelta(uint256 x, int256 y) internal

https://github.com/code-423n4/2023-01-numoen/blob/main/src/periphery/UniswapV2/libraries/UniswapV2Library.sol

51-56: function getAmountOut(
    uint256 amountIn,
    uint256 reserveIn,
    uint256 reserveOut
  )
    internal

69-74: function getAmountIn(
    uint256 amountOut,
    uint256 reserveIn,
    uint256 reserveOut
  )
    internal