Gas Optimizations

[code423n4]

Findings: Use assembly when getting a contract’s balance of eth

Code:  src/auction/Auction.sol - line 346

Explanation Non-critical gas optimisation. You can use selfbalance() instead of address(this).balance when getting your contract’s balance of ETH to save gas.

----

Findings: Using private rather than public for constants, saves gas

Code: src/governance/governor/Governor.sol - line 27

Explanation: If needed, the value can be read from the verified contract source code.

----

Findings: It costs more gas to initialize non-constant/non-immutable variables to zero than to let the default of zero be applied.

Code: 
src/governance/treasury/Treasure.sol - line 162
src/token/metadata/MetadataRenderer.sol - line 119, line 136, line 193, line 234

Explanation: 

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

Use instead

  for (uint256 i; i < numTargets; ++i) {

----

Findings: Empty blocks should be removed or emit something (external receive & fallback)

Code:  src/governance/treasury/Treasure.sol - line 269

Explanation: The code should be refactored such that they no longer exist, or the block should do something useful, such as emitting an event or reverting.

Mitigation: Either remove, or implement an emit event.

----

Findings: Multiplication/division by two should use bit shifting
Code: src/lib/token/ERC721Votes.sol

Explanation: 
<x> * 2 is equivalent to <x> << 1 and <x> / 2 is the same as <x> >> 1. The MUL and DIV opcodes cost 5 gas, whereas SHL and SHR only cost 3 gas. DIVISION BY TWO SHOULD USE BIT SHIFTING. Given this is an openzeppelin library modification is at the developers discretion.

Mitigation: Use Bit Shifting.

[GalloDaSballo]

Less than 50 gas