Gas Optimizations

[code423n4]

G001 - Don't Initialize Variables with Default Value

Description

Uninitialized variables are assigned with the types default value.

Explicitly initializing a variable with it's default value costs unnecessary gas.

uint112 vestAmt = 0;

https://github.com/code-423n4/2022-09-vtvl/blob/f68b7f3e61dad0d873b5b5a1e8126b839afeab5f/contracts/VTVLVesting.sol#L148

for (uint256 i = 0; i < length; i++) {

https://github.com/code-423n4/2022-09-vtvl/blob/f68b7f3e61dad0d873b5b5a1e8126b839afeab5f/contracts/VTVLVesting.sol#L353

background info

https://mudit.blog/solidity-tips-and-tricks-to-save-gas-and-reduce-bytecode-size/

G002 - ++I COSTS LESS GAS COMPARED TO I++ OR I += 1 (SAME FOR --I VS I-- OR I -= 1)

Pre-increments and pre-decrements are cheaper.

For a uint256 i variable, the following is true with the Optimizer enabled at 10k:

Increment:

• i += 1 is the most expensive form
• i++ costs 6 gas less than i += 1
• ++i costs 5 gas less than i++ (11 gas less than i += 1)

Decrement:

• i -= 1 is the most expensive form
• i-- costs 11 gas less than i -= 1
• --i costs 5 gas less than i-- (16 gas less than i -= 1)

for (uint256 i = 0; i < length; i++) {

https://github.com/code-423n4/2022-09-vtvl/blob/f68b7f3e61dad0d873b5b5a1e8126b839afeab5f/contracts/VTVLVesting.sol#L353

G003 - ++I/I++ SHOULD BE UNCHECKED{++I}/UNCHECKED{I++} WHEN IT IS NOT POSSIBLE FOR THEM TO OVERFLOW, AS IS THE CASE WHEN USED IN FORAND WHILELOOPS

The unchecked keyword is new in solidity version 0.8.0, so this only applies to that version or higher, which these instances are. This saves 30-40 gas per loop

for (uint256 i = 0; i < length; i++) {

https://github.com/code-423n4/2022-09-vtvl/blob/f68b7f3e61dad0d873b5b5a1e8126b839afeab5f/contracts/VTVLVesting.sol#L353

G004 - USING > 0 COSTS MORE GAS THAN != 0 WHEN USED ON A UINT IN A REQUIRE() STATEMENT

This change saves 6 gas per instance

require(_claim.startTimestamp > 0, "NO_ACTIVE_CLAIM");

https://github.com/code-423n4/2022-09-vtvl/blob/f68b7f3e61dad0d873b5b5a1e8126b839afeab5f/contracts/VTVLVesting.sol#L107

require(_linearVestAmount + _cliffAmount > 0, "INVALID_VESTED_AMOUNT");

https://github.com/code-423n4/2022-09-vtvl/blob/f68b7f3e61dad0d873b5b5a1e8126b839afeab5f/contracts/VTVLVesting.sol#L256

require(_startTimestamp > 0, "INVALID_START_TIMESTAMP");

https://github.com/code-423n4/2022-09-vtvl/blob/f68b7f3e61dad0d873b5b5a1e8126b839afeab5f/contracts/VTVLVesting.sol#L257

require(_releaseIntervalSecs > 0, "INVALID_RELEASE_INTERVAL");

https://github.com/code-423n4/2022-09-vtvl/blob/f68b7f3e61dad0d873b5b5a1e8126b839afeab5f/contracts/VTVLVesting.sol#L263

_cliffReleaseTimestamp > 0 &&
_cliffAmount > 0 &&

https://github.com/code-423n4/2022-09-vtvl/blob/f68b7f3e61dad0d873b5b5a1e8126b839afeab5f/contracts/VTVLVesting.sol#L272

require(bal > 0, "INSUFFICIENT_BALANCE");

https://github.com/code-423n4/2022-09-vtvl/blob/f68b7f3e61dad0d873b5b5a1e8126b839afeab5f/contracts/VTVLVesting.sol#L449

require(supply_ > 0, "NO_ZERO_MINT");

https://github.com/code-423n4/2022-09-vtvl/blob/f68b7f3e61dad0d873b5b5a1e8126b839afeab5f/contracts/token/FullPremintERC20Token.sol#L11

require(initialSupply_ > 0 || maxSupply_ > 0, "INVALID_AMOUNT");

https://github.com/code-423n4/2022-09-vtvl/blob/f68b7f3e61dad0d873b5b5a1e8126b839afeab5f/contracts/token/VariableSupplyERC20Token.sol#L27