Gas Optimizations

[code423n4]

In the file contracts/gateway/BridgeEscrow.sol:

public/external function names and public member variable names can be optimized to save gas. See this link for an example of how it works. Below are the interfaces/abstract contracts that can be optimized so that the most frequently-called functions use the least amount of gas possible during method lookup. Method IDs that have two leading zero bytes can save 128 gas each during deployment, and renaming functions to have lower method IDs will save 22 gas per call, per sorted position shifted

[!]DO NOT USE SOLIDITY VERSION LESS THAN 0.8.0 FOR SAFE CHECK

[!]USE A MORE RECENT VERSION OF SOLIDITY.

AVOID CONTRACT EXISTENCE CHECKS BY USING SOLIDITY VERSION 0.8.10 OR LATER
Prior to 0.8.10 the compiler inserted extra code, including EXTCODESIZE (100 gas), to check for contract existence for external calls. In more recent solidity versions, the compiler will not insert these checks if the external call has a return value

In the file contracts/upgrades/GraphUpgradeable.sol:

public/external function names and public member variable names can be optimized to save gas. See this link for an example of how it works. Below are the interfaces/abstract contracts that can be optimized so that the most frequently-called functions use the least amount of gas possible during method lookup. Method IDs that have two leading zero bytes can save 128 gas each during deployment, and renaming functions to have lower method IDs will save 22 gas per call, per sorted position shifted

[!]DO NOT USE SOLIDITY VERSION LESS THAN 0.8.0 FOR SAFE CHECK

[!]USE A MORE RECENT VERSION OF SOLIDITY.

AVOID CONTRACT EXISTENCE CHECKS BY USING SOLIDITY VERSION 0.8.10 OR LATER
Prior to 0.8.10 the compiler inserted extra code, including EXTCODESIZE (100 gas), to check for contract existence for external calls. In more recent solidity versions, the compiler will not insert these checks if the external call has a return value

Line 24: require(msg.sender == _proxy.admin(), "Caller must be the proxy admin");
REQUIRE() USED! USE CUSTOM ERRORS RATHER THAN REVERT()/REQUIRE()/ASSERT() STRINGS TO SAVE GAS.

Line 32: require(msg.sender == _implementation(), "Caller must be the implementation");
REQUIRE() USED! USE CUSTOM ERRORS RATHER THAN REVERT()/REQUIRE()/ASSERT() STRINGS TO SAVE GAS.

Line 32: require(msg.sender == _implementation(), "Caller must be the implementation");
REQUIRE()/REVERT() STRINGS LONGER THAN 32 BYTES COST EXTRA GAS

In the file contracts/governance/Governed.sol:

public/external function names and public member variable names can be optimized to save gas. See this link for an example of how it works. Below are the interfaces/abstract contracts that can be optimized so that the most frequently-called functions use the least amount of gas possible during method lookup. Method IDs that have two leading zero bytes can save 128 gas each during deployment, and renaming functions to have lower method IDs will save 22 gas per call, per sorted position shifted

[!]DO NOT USE SOLIDITY VERSION LESS THAN 0.8.0 FOR SAFE CHECK

[!]USE A MORE RECENT VERSION OF SOLIDITY.

AVOID CONTRACT EXISTENCE CHECKS BY USING SOLIDITY VERSION 0.8.10 OR LATER
Prior to 0.8.10 the compiler inserted extra code, including EXTCODESIZE (100 gas), to check for contract existence for external calls. In more recent solidity versions, the compiler will not insert these checks if the external call has a return value

STORAGE VARIABLES LOADED TWOCE SHOULD GET CACHED
In function transferOwnership:
pendingGovernor should be cached to save gas

Line 24: require(msg.sender == governor, "Only Governor can call");
REQUIRE() USED! USE CUSTOM ERRORS RATHER THAN REVERT()/REQUIRE()/ASSERT() STRINGS TO SAVE GAS.

Line 41: require(_newGovernor != address(0), "Governor must be set");
REQUIRE() USED! USE CUSTOM ERRORS RATHER THAN REVERT()/REQUIRE()/ASSERT() STRINGS TO SAVE GAS.

Line 54: require(
REQUIRE() USED! USE CUSTOM ERRORS RATHER THAN REVERT()/REQUIRE()/ASSERT() STRINGS TO SAVE GAS.

Line 46: emit NewPendingOwnership(oldPendingGovernor, pendingGovernor);
AVOID EMITTING A STORAGE VARIABLE WHEN A MEMORY VALUE IS AVAILABLE

Line 65: emit NewOwnership(oldGovernor, governor);
AVOID EMITTING A STORAGE VARIABLE WHEN A MEMORY VALUE IS AVAILABLE

Line 66: emit NewPendingOwnership(oldPendingGovernor, pendingGovernor);
AVOID EMITTING A STORAGE VARIABLE WHEN A MEMORY VALUE IS AVAILABLE

In the file contracts/governance/Pausable.sol:

public/external function names and public member variable names can be optimized to save gas. See this link for an example of how it works. Below are the interfaces/abstract contracts that can be optimized so that the most frequently-called functions use the least amount of gas possible during method lookup. Method IDs that have two leading zero bytes can save 128 gas each during deployment, and renaming functions to have lower method IDs will save 22 gas per call, per sorted position shifted

[!]DO NOT USE SOLIDITY VERSION LESS THAN 0.8.0 FOR SAFE CHECK

[!]USE A MORE RECENT VERSION OF SOLIDITY.

AVOID CONTRACT EXISTENCE CHECKS BY USING SOLIDITY VERSION 0.8.10 OR LATER
Prior to 0.8.10 the compiler inserted extra code, including EXTCODESIZE (100 gas), to check for contract existence for external calls. In more recent solidity versions, the compiler will not insert these checks if the external call has a return value

STORAGE VARIABLES LOADED TWOCE SHOULD GET CACHED
In function _setPartialPaused:
_partialPaused should be cached to save gas

STORAGE VARIABLES LOADED TWOCE SHOULD GET CACHED
In function _setPaused:
_paused should be cached to save gas

Line 8: bool internal _partialPaused;
USING BOOLS FOR STORAGE INCURS OVERHEAD: use uint256(1) uint256(2) instead.

Line 10: bool internal _paused;
USING BOOLS FOR STORAGE INCURS OVERHEAD: use uint256(1) uint256(2) instead.

Line 34: emit PartialPauseChanged(_partialPaused);
AVOID EMITTING A STORAGE VARIABLE WHEN A MEMORY VALUE IS AVAILABLE

Line 48: emit PauseChanged(_paused);
AVOID EMITTING A STORAGE VARIABLE WHEN A MEMORY VALUE IS AVAILABLE

Line 58: emit NewPauseGuardian(oldPauseGuardian, pauseGuardian);
AVOID EMITTING A STORAGE VARIABLE WHEN A MEMORY VALUE IS AVAILABLE

In the file contracts/l2/token/L2GraphToken.sol:

public/external function names and public member variable names can be optimized to save gas. See this link for an example of how it works. Below are the interfaces/abstract contracts that can be optimized so that the most frequently-called functions use the least amount of gas possible during method lookup. Method IDs that have two leading zero bytes can save 128 gas each during deployment, and renaming functions to have lower method IDs will save 22 gas per call, per sorted position shifted

[!]DO NOT USE SOLIDITY VERSION LESS THAN 0.8.0 FOR SAFE CHECK

[!]USE A MORE RECENT VERSION OF SOLIDITY.

AVOID CONTRACT EXISTENCE CHECKS BY USING SOLIDITY VERSION 0.8.10 OR LATER
Prior to 0.8.10 the compiler inserted extra code, including EXTCODESIZE (100 gas), to check for contract existence for external calls. In more recent solidity versions, the compiler will not insert these checks if the external call has a return value

Line 36: require(msg.sender == gateway, "NOT_GATEWAY");
REQUIRE() USED! USE CUSTOM ERRORS RATHER THAN REVERT()/REQUIRE()/ASSERT() STRINGS TO SAVE GAS.

Line 49: require(_owner != address(0), "Owner must be set");
REQUIRE() USED! USE CUSTOM ERRORS RATHER THAN REVERT()/REQUIRE()/ASSERT() STRINGS TO SAVE GAS.

Line 60: require(_gw != address(0), "INVALID_GATEWAY");
REQUIRE() USED! USE CUSTOM ERRORS RATHER THAN REVERT()/REQUIRE()/ASSERT() STRINGS TO SAVE GAS.

Line 70: require(_addr != address(0), "INVALID_L1_ADDRESS");
REQUIRE() USED! USE CUSTOM ERRORS RATHER THAN REVERT()/REQUIRE()/ASSERT() STRINGS TO SAVE GAS.

Line 62: emit GatewaySet(gateway);
AVOID EMITTING A STORAGE VARIABLE WHEN A MEMORY VALUE IS AVAILABLE

In the file contracts/upgrades/GraphProxyAdmin.sol:

public/external function names and public member variable names can be optimized to save gas. See this link for an example of how it works. Below are the interfaces/abstract contracts that can be optimized so that the most frequently-called functions use the least amount of gas possible during method lookup. Method IDs that have two leading zero bytes can save 128 gas each during deployment, and renaming functions to have lower method IDs will save 22 gas per call, per sorted position shifted

[!]DO NOT USE SOLIDITY VERSION LESS THAN 0.8.0 FOR SAFE CHECK

[!]USE A MORE RECENT VERSION OF SOLIDITY.

AVOID CONTRACT EXISTENCE CHECKS BY USING SOLIDITY VERSION 0.8.10 OR LATER
Prior to 0.8.10 the compiler inserted extra code, including EXTCODESIZE (100 gas), to check for contract existence for external calls. In more recent solidity versions, the compiler will not insert these checks if the external call has a return value

Line 34: require(success);
REQUIRE() USED! USE CUSTOM ERRORS RATHER THAN REVERT()/REQUIRE()/ASSERT() STRINGS TO SAVE GAS.

Line 47: require(success);
REQUIRE() USED! USE CUSTOM ERRORS RATHER THAN REVERT()/REQUIRE()/ASSERT() STRINGS TO SAVE GAS.

Line 59: require(success);
REQUIRE() USED! USE CUSTOM ERRORS RATHER THAN REVERT()/REQUIRE()/ASSERT() STRINGS TO SAVE GAS.

In the file contracts/upgrades/GraphProxyStorage.sol:

public/external function names and public member variable names can be optimized to save gas. See this link for an example of how it works. Below are the interfaces/abstract contracts that can be optimized so that the most frequently-called functions use the least amount of gas possible during method lookup. Method IDs that have two leading zero bytes can save 128 gas each during deployment, and renaming functions to have lower method IDs will save 22 gas per call, per sorted position shifted

[!]DO NOT USE SOLIDITY VERSION LESS THAN 0.8.0 FOR SAFE CHECK

[!]USE A MORE RECENT VERSION OF SOLIDITY.

AVOID CONTRACT EXISTENCE CHECKS BY USING SOLIDITY VERSION 0.8.10 OR LATER
Prior to 0.8.10 the compiler inserted extra code, including EXTCODESIZE (100 gas), to check for contract existence for external calls. In more recent solidity versions, the compiler will not insert these checks if the external call has a return value

Line 62: require(msg.sender == _admin(), "Caller must be admin");
REQUIRE() USED! USE CUSTOM ERRORS RATHER THAN REVERT()/REQUIRE()/ASSERT() STRINGS TO SAVE GAS.

In the file contracts/upgrades/GraphProxy.sol:

public/external function names and public member variable names can be optimized to save gas. See this link for an example of how it works. Below are the interfaces/abstract contracts that can be optimized so that the most frequently-called functions use the least amount of gas possible during method lookup. Method IDs that have two leading zero bytes can save 128 gas each during deployment, and renaming functions to have lower method IDs will save 22 gas per call, per sorted position shifted

[!]DO NOT USE SOLIDITY VERSION LESS THAN 0.8.0 FOR SAFE CHECK

[!]USE A MORE RECENT VERSION OF SOLIDITY.

AVOID CONTRACT EXISTENCE CHECKS BY USING SOLIDITY VERSION 0.8.10 OR LATER
Prior to 0.8.10 the compiler inserted extra code, including EXTCODESIZE (100 gas), to check for contract existence for external calls. In more recent solidity versions, the compiler will not insert these checks if the external call has a return value

Line 47: assert(ADMIN_SLOT == bytes32(uint256(keccak256("eip1967.proxy.admin")) - 1));
ASSERT() USED! ASSERT USES UP ALL REMAINING GAS WHEN REVERT!

Line 48: assert(
ASSERT() USED! ASSERT USES UP ALL REMAINING GAS WHEN REVERT!

Line 51: assert(
ASSERT() USED! ASSERT USES UP ALL REMAINING GAS WHEN REVERT!

Line 105: require(_newAdmin != address(0), "Cannot change the admin of a proxy to the zero address");
REQUIRE() USED! USE CUSTOM ERRORS RATHER THAN REVERT()/REQUIRE()/ASSERT() STRINGS TO SAVE GAS.

Line 105: require(_newAdmin != address(0), "Cannot change the admin of a proxy to the zero address");
REQUIRE()/REVERT() STRINGS LONGER THAN 32 BYTES COST EXTRA GAS

Line 133: require(success);
REQUIRE() USED! USE CUSTOM ERRORS RATHER THAN REVERT()/REQUIRE()/ASSERT() STRINGS TO SAVE GAS.

Line 141: require(Address.isContract(_pendingImplementation), "Implementation must be a contract");
REQUIRE() USED! USE CUSTOM ERRORS RATHER THAN REVERT()/REQUIRE()/ASSERT() STRINGS TO SAVE GAS.

Line 141: require(Address.isContract(_pendingImplementation), "Implementation must be a contract");
REQUIRE()/REVERT() STRINGS LONGER THAN 32 BYTES COST EXTRA GAS

Line 142-145: require(
_pendingImplementation != address(0) && msg.sender == _pendingImplementation,
"Caller must be the pending implementation"
);
REQUIRE() USED! USE CUSTOM ERRORS RATHER THAN REVERT()/REQUIRE()/ASSERT() STRINGS TO SAVE GAS.
REQUIRE()/REVERT() STRINGS LONGER THAN 32 BYTES COST EXTRA GAS

Line 157: require(msg.sender != _admin(), "Cannot fallback to proxy target");
REQUIRE() USED! USE CUSTOM ERRORS RATHER THAN REVERT()/REQUIRE()/ASSERT() STRINGS TO SAVE GAS.

Line 179: revert(ptr, size)
REVERT() USED! USE CUSTOM ERRORS RATHER THAN REVERT()/REQUIRE()/ASSERT() STRINGS TO SAVE GAS.

In the file contracts/governance/Managed.sol:

public/external function names and public member variable names can be optimized to save gas. See this link for an example of how it works. Below are the interfaces/abstract contracts that can be optimized so that the most frequently-called functions use the least amount of gas possible during method lookup. Method IDs that have two leading zero bytes can save 128 gas each during deployment, and renaming functions to have lower method IDs will save 22 gas per call, per sorted position shifted

[!]DO NOT USE SOLIDITY VERSION LESS THAN 0.8.0 FOR SAFE CHECK

[!]USE A MORE RECENT VERSION OF SOLIDITY.

AVOID CONTRACT EXISTENCE CHECKS BY USING SOLIDITY VERSION 0.8.10 OR LATER
Prior to 0.8.10 the compiler inserted extra code, including EXTCODESIZE (100 gas), to check for contract existence for external calls. In more recent solidity versions, the compiler will not insert these checks if the external call has a return value

Line 44: require(!controller.paused(), "Paused");
REQUIRE() USED! USE CUSTOM ERRORS RATHER THAN REVERT()/REQUIRE()/ASSERT() STRINGS TO SAVE GAS.

Line 45: require(!controller.partialPaused(), "Partial-paused");
REQUIRE() USED! USE CUSTOM ERRORS RATHER THAN REVERT()/REQUIRE()/ASSERT() STRINGS TO SAVE GAS.

Line 49: require(!controller.paused(), "Paused");
REQUIRE() USED! USE CUSTOM ERRORS RATHER THAN REVERT()/REQUIRE()/ASSERT() STRINGS TO SAVE GAS.

Line 53: require(msg.sender == controller.getGovernor(), "Caller must be Controller governor");
REQUIRE() USED! USE CUSTOM ERRORS RATHER THAN REVERT()/REQUIRE()/ASSERT() STRINGS TO SAVE GAS.

Line 53: require(msg.sender == controller.getGovernor(), "Caller must be Controller governor");
REQUIRE()/REVERT() STRINGS LONGER THAN 32 BYTES COST EXTRA GAS

Line 57: require(msg.sender == address(controller), "Caller must be Controller");
REQUIRE() USED! USE CUSTOM ERRORS RATHER THAN REVERT()/REQUIRE()/ASSERT() STRINGS TO SAVE GAS.

Line 104: require(_controller != address(0), "Controller must be set");
REQUIRE() USED! USE CUSTOM ERRORS RATHER THAN REVERT()/REQUIRE()/ASSERT() STRINGS TO SAVE GAS.

In the file contracts/l2/token/GraphTokenUpgradeable.sol:

public/external function names and public member variable names can be optimized to save gas. See this link for an example of how it works. Below are the interfaces/abstract contracts that can be optimized so that the most frequently-called functions use the least amount of gas possible during method lookup. Method IDs that have two leading zero bytes can save 128 gas each during deployment, and renaming functions to have lower method IDs will save 22 gas per call, per sorted position shifted

[!]DO NOT USE SOLIDITY VERSION LESS THAN 0.8.0 FOR SAFE CHECK

[!]USE A MORE RECENT VERSION OF SOLIDITY.

AVOID CONTRACT EXISTENCE CHECKS BY USING SOLIDITY VERSION 0.8.10 OR LATER
Prior to 0.8.10 the compiler inserted extra code, including EXTCODESIZE (100 gas), to check for contract existence for external calls. In more recent solidity versions, the compiler will not insert these checks if the external call has a return value

STORAGE VARIABLES LOADED TWOCE SHOULD GET CACHED
In function permit:
nonces[_owner] should be cached to save gas

Line 60: require(isMinter(msg.sender), "Only minter can call");
REQUIRE() USED! USE CUSTOM ERRORS RATHER THAN REVERT()/REQUIRE()/ASSERT() STRINGS TO SAVE GAS.

Line 94: require(_owner == recoveredAddress, "GRT: invalid permit");
REQUIRE() USED! USE CUSTOM ERRORS RATHER THAN REVERT()/REQUIRE()/ASSERT() STRINGS TO SAVE GAS.

Line 95: require(_deadline == 0 || block.timestamp <= _deadline, "GRT: expired permit");
REQUIRE() USED! USE CUSTOM ERRORS RATHER THAN REVERT()/REQUIRE()/ASSERT() STRINGS TO SAVE GAS.

Line 95: require(_deadline == 0 || block.timestamp <= _deadline, "GRT: expired permit");
REQUIRE() OR REVERT() STATEMENTS THAT CHECK INPUT ARGUMENTS SHOULD BE AT THE TOP OF THE FUNCTION

Line 106: require(_account != address(0), "INVALID_MINTER");
REQUIRE() USED! USE CUSTOM ERRORS RATHER THAN REVERT()/REQUIRE()/ASSERT() STRINGS TO SAVE GAS.

Line 115: require(_minters[_account], "NOT_A_MINTER");
REQUIRE() USED! USE CUSTOM ERRORS RATHER THAN REVERT()/REQUIRE()/ASSERT() STRINGS TO SAVE GAS.

Line 123: require(_minters[msg.sender], "NOT_A_MINTER");
REQUIRE() USED! USE CUSTOM ERRORS RATHER THAN REVERT()/REQUIRE()/ASSERT() STRINGS TO SAVE GAS.

Line 51: mapping(address => bool) private _minters;
USING BOOLS FOR STORAGE INCURS OVERHEAD: use uint256(1) uint256(2) instead.

Line 79: uint8 _v,
USAGE OF UINTS/INTS SMALLER THAN 32 BYTES (256 BITS) INCURS OVERHEAD: When using elements that are smaller than 32 bytes, your contract's gas usage may be higher. This is because the EVM operates on 32 bytes at a time. Therefore, if the element is smaller than that, the EVM must use more operations in order to reduce the size of the element from 32 bytes to the desired size.

In the file contracts/l2/gateway/L2GraphTokenGateway.sol:

public/external function names and public member variable names can be optimized to save gas. See this link for an example of how it works. Below are the interfaces/abstract contracts that can be optimized so that the most frequently-called functions use the least amount of gas possible during method lookup. Method IDs that have two leading zero bytes can save 128 gas each during deployment, and renaming functions to have lower method IDs will save 22 gas per call, per sorted position shifted

[!]DO NOT USE SOLIDITY VERSION LESS THAN 0.8.0 FOR SAFE CHECK

[!]USE A MORE RECENT VERSION OF SOLIDITY.

AVOID CONTRACT EXISTENCE CHECKS BY USING SOLIDITY VERSION 0.8.10 OR LATER
Prior to 0.8.10 the compiler inserted extra code, including EXTCODESIZE (100 gas), to check for contract existence for external calls. In more recent solidity versions, the compiler will not insert these checks if the external call has a return value

STORAGE VARIABLES LOADED TWOCE SHOULD GET CACHED
In function outboundTransfer:
l1GRT should be cached to save gas

STORAGE VARIABLES LOADED TWOCE SHOULD GET CACHED
In function finalizeInboundTransfer:
l1GRT should be cached to save gas

Line 69: require(
REQUIRE() USED! USE CUSTOM ERRORS RATHER THAN REVERT()/REQUIRE()/ASSERT() STRINGS TO SAVE GAS.

Line 98: require(_l2Router != address(0), "INVALID_L2_ROUTER");
REQUIRE() USED! USE CUSTOM ERRORS RATHER THAN REVERT()/REQUIRE()/ASSERT() STRINGS TO SAVE GAS.

Line 108: require(_l1GRT != address(0), "INVALID_L1_GRT");
REQUIRE() USED! USE CUSTOM ERRORS RATHER THAN REVERT()/REQUIRE()/ASSERT() STRINGS TO SAVE GAS.

Line 118: require(_l1Counterpart != address(0), "INVALID_L1_COUNTERPART");
REQUIRE() USED! USE CUSTOM ERRORS RATHER THAN REVERT()/REQUIRE()/ASSERT() STRINGS TO SAVE GAS.

Line 145: require(_l1Token == l1GRT, "TOKEN_NOT_GRT");
REQUIRE() USED! USE CUSTOM ERRORS RATHER THAN REVERT()/REQUIRE()/ASSERT() STRINGS TO SAVE GAS.

Line 146: require(_amount > 0, "INVALID_ZERO_AMOUNT");
REQUIRE() USED! USE CUSTOM ERRORS RATHER THAN REVERT()/REQUIRE()/ASSERT() STRINGS TO SAVE GAS.

Line 146: require(_amount > 0, "INVALID_ZERO_AMOUNT");
USING > 0 COSTS MORE GAS THAN != 0 WHEN USED ON A UINT IN A REQUIRE() STATEMENT

Line 147: require(msg.value == 0, "INVALID_NONZERO_VALUE");
REQUIRE() USED! USE CUSTOM ERRORS RATHER THAN REVERT()/REQUIRE()/ASSERT() STRINGS TO SAVE GAS.

Line 148: require(_to != address(0), "INVALID_DESTINATION");
REQUIRE() USED! USE CUSTOM ERRORS RATHER THAN REVERT()/REQUIRE()/ASSERT() STRINGS TO SAVE GAS.

Line 153: require(outboundCalldata.extraData.length == 0, "CALL_HOOK_DATA_NOT_ALLOWED");
REQUIRE() USED! USE CUSTOM ERRORS RATHER THAN REVERT()/REQUIRE()/ASSERT() STRINGS TO SAVE GAS.

Line 233: require(_l1Token == l1GRT, "TOKEN_NOT_GRT");
REQUIRE() USED! USE CUSTOM ERRORS RATHER THAN REVERT()/REQUIRE()/ASSERT() STRINGS TO SAVE GAS.

Line 234: require(msg.value == 0, "INVALID_NONZERO_VALUE");
REQUIRE() USED! USE CUSTOM ERRORS RATHER THAN REVERT()/REQUIRE()/ASSERT() STRINGS TO SAVE GAS.

In the file contracts/gateway/L1GraphTokenGateway.sol:

public/external function names and public member variable names can be optimized to save gas. See this link for an example of how it works. Below are the interfaces/abstract contracts that can be optimized so that the most frequently-called functions use the least amount of gas possible during method lookup. Method IDs that have two leading zero bytes can save 128 gas each during deployment, and renaming functions to have lower method IDs will save 22 gas per call, per sorted position shifted

[!]DO NOT USE SOLIDITY VERSION LESS THAN 0.8.0 FOR SAFE CHECK

[!]USE A MORE RECENT VERSION OF SOLIDITY.

AVOID CONTRACT EXISTENCE CHECKS BY USING SOLIDITY VERSION 0.8.10 OR LATER
Prior to 0.8.10 the compiler inserted extra code, including EXTCODESIZE (100 gas), to check for contract existence for external calls. In more recent solidity versions, the compiler will not insert these checks if the external call has a return value

STORAGE VARIABLES LOADED TWOCE SHOULD GET CACHED
In function removeFromCallhookWhitelist:
callhookWhitelist[_notWhitelisted] should be cached to save gas

STORAGE VARIABLES LOADED TWOCE SHOULD GET CACHED
In function finalizeInboundTransfer:
escrow should be cached to save gas

Line 74: require(inbox != address(0), "INBOX_NOT_SET");
REQUIRE() USED! USE CUSTOM ERRORS RATHER THAN REVERT()/REQUIRE()/ASSERT() STRINGS TO SAVE GAS.

Line 78: require(msg.sender == address(bridge), "NOT_FROM_BRIDGE");
REQUIRE() USED! USE CUSTOM ERRORS RATHER THAN REVERT()/REQUIRE()/ASSERT() STRINGS TO SAVE GAS.

Line 82: require(l2ToL1Sender == l2Counterpart, "ONLY_COUNTERPART_GATEWAY");
REQUIRE() USED! USE CUSTOM ERRORS RATHER THAN REVERT()/REQUIRE()/ASSERT() STRINGS TO SAVE GAS.

Line 110: require(_inbox != address(0), "INVALID_INBOX");
REQUIRE() USED! USE CUSTOM ERRORS RATHER THAN REVERT()/REQUIRE()/ASSERT() STRINGS TO SAVE GAS.

Line 111: require(_l1Router != address(0), "INVALID_L1_ROUTER");
REQUIRE() USED! USE CUSTOM ERRORS RATHER THAN REVERT()/REQUIRE()/ASSERT() STRINGS TO SAVE GAS.

Line 122: require(_l2GRT != address(0), "INVALID_L2_GRT");
REQUIRE() USED! USE CUSTOM ERRORS RATHER THAN REVERT()/REQUIRE()/ASSERT() STRINGS TO SAVE GAS.

Line 132: require(_l2Counterpart != address(0), "INVALID_L2_COUNTERPART");
REQUIRE() USED! USE CUSTOM ERRORS RATHER THAN REVERT()/REQUIRE()/ASSERT() STRINGS TO SAVE GAS.

Line 142: require(_escrow != address(0) && Address.isContract(_escrow), "INVALID_ESCROW");
REQUIRE() USED! USE CUSTOM ERRORS RATHER THAN REVERT()/REQUIRE()/ASSERT() STRINGS TO SAVE GAS.

Line 142: require(_escrow != address(0) && Address.isContract(_escrow), "INVALID_ESCROW");
SPLITTING REQUIRE() STATEMENTS THAT USE && SAVES GAS

Line 153: require(_newWhitelisted != address(0), "INVALID_ADDRESS");
REQUIRE() USED! USE CUSTOM ERRORS RATHER THAN REVERT()/REQUIRE()/ASSERT() STRINGS TO SAVE GAS.

Line 154: require(!callhookWhitelist[_newWhitelisted], "ALREADY_WHITELISTED");
REQUIRE() USED! USE CUSTOM ERRORS RATHER THAN REVERT()/REQUIRE()/ASSERT() STRINGS TO SAVE GAS.

Line 165: require(_notWhitelisted != address(0), "INVALID_ADDRESS");
REQUIRE() USED! USE CUSTOM ERRORS RATHER THAN REVERT()/REQUIRE()/ASSERT() STRINGS TO SAVE GAS.

Line 166: require(callhookWhitelist[_notWhitelisted], "NOT_WHITELISTED");
REQUIRE() USED! USE CUSTOM ERRORS RATHER THAN REVERT()/REQUIRE()/ASSERT() STRINGS TO SAVE GAS.

Line 200: require(_l1Token == address(token), "TOKEN_NOT_GRT");
REQUIRE() USED! USE CUSTOM ERRORS RATHER THAN REVERT()/REQUIRE()/ASSERT() STRINGS TO SAVE GAS.

Line 201: require(_amount > 0, "INVALID_ZERO_AMOUNT");
REQUIRE() USED! USE CUSTOM ERRORS RATHER THAN REVERT()/REQUIRE()/ASSERT() STRINGS TO SAVE GAS.

Line 201: require(_amount > 0, "INVALID_ZERO_AMOUNT");
USING > 0 COSTS MORE GAS THAN != 0 WHEN USED ON A UINT IN A REQUIRE() STATEMENT

Line 202: require(_to != address(0), "INVALID_DESTINATION");
REQUIRE() USED! USE CUSTOM ERRORS RATHER THAN REVERT()/REQUIRE()/ASSERT() STRINGS TO SAVE GAS.

Line 202: require(_to != address(0), "INVALID_DESTINATION");
REQUIRE() OR REVERT() STATEMENTS THAT CHECK INPUT ARGUMENTS SHOULD BE AT THE TOP OF THE FUNCTION

Line 213: require(
REQUIRE() USED! USE CUSTOM ERRORS RATHER THAN REVERT()/REQUIRE()/ASSERT() STRINGS TO SAVE GAS.

Line 217: require(maxSubmissionCost > 0, "NO_SUBMISSION_COST");
REQUIRE() USED! USE CUSTOM ERRORS RATHER THAN REVERT()/REQUIRE()/ASSERT() STRINGS TO SAVE GAS.

Line 217: require(maxSubmissionCost > 0, "NO_SUBMISSION_COST");
USING > 0 COSTS MORE GAS THAN != 0 WHEN USED ON A UINT IN A REQUIRE() STATEMENT

Line 224: require(msg.value >= expectedEth, "WRONG_ETH_VALUE");
REQUIRE() USED! USE CUSTOM ERRORS RATHER THAN REVERT()/REQUIRE()/ASSERT() STRINGS TO SAVE GAS.

Line 271: require(_l1Token == address(token), "TOKEN_NOT_GRT");
REQUIRE() USED! USE CUSTOM ERRORS RATHER THAN REVERT()/REQUIRE()/ASSERT() STRINGS TO SAVE GAS.

Line 275: require(_amount <= escrowBalance, "BRIDGE_OUT_OF_FUNDS");
REQUIRE() USED! USE CUSTOM ERRORS RATHER THAN REVERT()/REQUIRE()/ASSERT() STRINGS TO SAVE GAS.

Line 35: mapping(address => bool) public callhookWhitelist;
USING BOOLS FOR STORAGE INCURS OVERHEAD: use uint256(1) uint256(2) instead.