Gas Optimizations

[code423n4]

USE A MORE RECENT VERSION OF SOLIDITY

Use a solidity version of at least 0.8.0 to get overflow protection without LowGasSafeMath Use a solidity version of at least 0.8.2 to get simple compiler automatic inlining Use a solidity version of at least 0.8.3 to get better struct packing and cheaper multiple storage reads Use a solidity version of at least 0.8.4 to get custom errors, which are cheaper at deployment than revert()/require() strings Use a solidity version of at least 0.8.10 to have external calls skip contract existence checks if the external call has a return value

Instances include:
contracts/gateway/BridgeEscrow.sol:3
contracts/upgrades/GraphUpgradeable.sol:3
contracts/governance/Governed.sol:3
contracts/governance/Pausable.sol:3
contracts/l2/token/L2GraphToken.sol:3
contracts/upgrades/GraphProxyAdmin.sol:3
contracts/upgrades/GraphProxyStorage.sol:3
contracts/upgrades/GraphProxy.sol:3
contracts/governance/Managed.sol:3
contracts/l2/token/GraphTokenUpgradeable.sol:3
contracts/l2/gateway/L2GraphTokenGateway.sol:3
contracts/gateway/L1GraphTokenGateway.sol:3
contracts/gateway/GraphTokenGateway.sol:3
contracts/curation/IGraphCurationToken.sol:3
contracts/gateway/ICallhookReceiver.sol:9
contracts/upgrades/IGraphProxy.sol:3
contracts/epochs/IEpochManager.sol:3
contracts/governance/IController.sol:3
contracts/token/IGraphToken.sol:3
contracts/rewards/IRewardsManager.sol:3
contracts/staking/IStakingData.sol:3
contracts/curation/ICuration.sol:3
contracts/staking/IStaking.sol:3

Require/Revert strings longer than 32 bytes cost additional gas

Instances include:
contracts/upgrades/GraphUpgradeable.sol:32
contracts/upgrades/GraphProxy.sol:105
contracts/upgrades/GraphProxy.sol:141
contracts/upgrades/GraphProxy.sol:144
contracts/governance/Managed.sol:53
contracts/gateway/GraphTokenGateway.sol:21

Use assembly to check for address(0)

Saves 6 gas per instance if using assembly to check for address(0)
e.g.

assembly {
 if iszero(_addr) {
  mstore(0x00, "zero address")
  revert(0x00, 0x20)
 }
}

Instances include:
contracts/governance/Governed.sol:41
contracts/governance/Governed.sol:55
contracts/l2/token/L2GraphToken.sol:49
contracts/l2/token/L2GraphToken.sol:60
contracts/l2/token/L2GraphToken.sol:70
contracts/upgrades/GraphProxy.sol:105
contracts/upgrades/GraphProxy.sol:143
contracts/governance/Managed.sol:104
contracts/l2/token/GraphTokenUpgradeable.sol:106
contracts/l2/gateway/L2GraphTokenGateway.sol:98
contracts/l2/gateway/L2GraphTokenGateway.sol:108
contracts/l2/gateway/L2GraphTokenGateway.sol:118
contracts/l2/gateway/L2GraphTokenGateway.sol:148
contracts/gateway/L1GraphTokenGateway.sol:74
contracts/gateway/L1GraphTokenGateway.sol:110
contracts/gateway/L1GraphTokenGateway.sol:111
contracts/gateway/L1GraphTokenGateway.sol:122
contracts/gateway/L1GraphTokenGateway.sol:132
contracts/gateway/L1GraphTokenGateway.sol:142
contracts/gateway/L1GraphTokenGateway.sol:153
contracts/gateway/L1GraphTokenGateway.sol:165
contracts/gateway/L1GraphTokenGateway.sol:202
contracts/gateway/GraphTokenGateway.sol:31

In require(), Use != 0 Instead of > 0 With Uint Values

In a require, when checking a uint, using != 0 instead of > 0 saves 6 gas. This will jump over or avoid an extra ISZERO opcode.

Instances include:
contracts/gateway/L1GraphTokenGateway.sol:201
contracts/gateway/L1GraphTokenGateway.sol:217

Splitting require() statements that use && saves gas

Saves 16 gas per instance. If you're using the Optimizer at 200, instead of using the && operator in a single require statement to check multiple conditions, multiple require statements with 1 condition per require statement should be used to save gas:

contracts/governance/Governed.sol:55
contracts/upgrades/GraphProxy.sol:143
contracts/l2/gateway/L2GraphTokenGateway.sol:146
contracts/gateway/L1GraphTokenGateway.sol:142

Calls to keccak256 should use immutable instead of constants

Instances include:
contracts/l2/token/GraphTokenUpgradeable.sol:34
contracts/l2/token/GraphTokenUpgradeable.sol:38
contracts/l2/token/GraphTokenUpgradeable.sol:39
contracts/l2/token/GraphTokenUpgradeable.sol:40
contracts/l2/token/GraphTokenUpgradeable.sol:42

abi.encode() is less efficient than abi.encodepacked()

Instances include:
contracts/l2/token/GraphTokenUpgradeable.sol:162
contracts/l2/token/GraphTokenUpgradeable.sol:88
contracts/l2/gateway/L2GraphTokenGateway.sol:174
contracts/l2/gateway/L2GraphTokenGateway.sol:275
contracts/gateway/L1GraphTokenGateway.sol:249
contracts/gateway/L1GraphTokenGateway.sol:342