PoolTogether contest - 0x4non's results

Gas optimizations

Preincrement nonce and set in _nonce all using unchecked

Replace

nonce++;
uint256 _nonce = nonce;

For

// set add also `returns (uint256 _nonce)`
unchecked { _nonce = ++nonce; }

Gas diff;

testRelayCallsFail() (gas: 8 (0.012%)) 
testProcessCallsFail() (gas: 8 (0.013%)) 
testConstructorMaxGasLimitFail() (gas: -6 (-0.014%)) 
testConstructorInboxFail() (gas: -6 (-0.014%)) 
testGetTxHashFail() (gas: 8 (0.024%)) 
testGetTxHash() (gas: 8 (0.025%)) 
testExecuteCalls() (gas: -2200 (-0.080%)) 
testCallFailure() (gas: -2200 (-0.081%)) 
testGasLimitTooHigh() (gas: -2200 (-0.083%)) 
testSetGreetingError() (gas: -2200 (-0.083%)) 
testRelayCalls() (gas: -2362 (-0.087%)) 
testRelayer() (gas: -2200 (-0.097%)) 
testExecutor() (gas: -2200 (-0.097%)) 
testProcessCalls() (gas: -142 (-0.112%)) 
testRelayCalls() (gas: -150 (-0.129%)) 
testRelayCalls() (gas: -10171 (-0.713%)) 
testExecuteCalls() (gas: -10012 (-0.717%)) 
testIsAuthorized() (gas: -10012 (-0.777%)) 
testGasLimitTooHigh() (gas: -10012 (-0.778%)) 
testSetGreetingError() (gas: -10012 (-0.781%)) 
testRelayer() (gas: -10012 (-1.168%)) 
testExecutor() (gas: -10012 (-1.169%)) 
Overall gas change: -86077 (-6.905%)

Suggested changes;

src/ethereum-arbitrum/EthereumToArbitrumRelayer.sol

diff --git a/src/ethereum-arbitrum/EthereumToArbitrumRelayer.sol b/src/ethereum-arbitrum/EthereumToArbitrumRelayer.sol
index f88674d..2a08ee6 100644
--- a/src/ethereum-arbitrum/EthereumToArbitrumRelayer.sol
+++ b/src/ethereum-arbitrum/EthereumToArbitrumRelayer.sol
@@ -67,7 +67,7 @@ contract CrossChainRelayerArbitrum is ICrossChainRelayer {
   function relayCalls(CallLib.Call[] calldata _calls, uint256 _gasLimit)
     external
     payable
-    returns (uint256)
+    returns (uint256 _nonce)
   {
     uint256 _maxGasLimit = maxGasLimit;
 
@@ -75,15 +75,11 @@ contract CrossChainRelayerArbitrum is ICrossChainRelayer {
       revert GasLimitTooHigh(_gasLimit, _maxGasLimit);
     }
 
-    nonce++;
-
-    uint256 _nonce = nonce;
+    unchecked { _nonce = ++nonce; }
 
     relayed[_getTxHash(_nonce, _calls, msg.sender, _gasLimit)] = true;
 
     emit RelayedCalls(_nonce, msg.sender, _calls, _gasLimit);
-
-    return _nonce;
   }
 
   /**

src/ethereum-optimism/EthereumToOptimismRelayer.sol

diff --git a/src/ethereum-optimism/EthereumToOptimismRelayer.sol b/src/ethereum-optimism/EthereumToOptimismRelayer.sol
index ac70501..d5f9fa3 100644
--- a/src/ethereum-optimism/EthereumToOptimismRelayer.sol
+++ b/src/ethereum-optimism/EthereumToOptimismRelayer.sol
@@ -49,7 +49,7 @@ contract CrossChainRelayerOptimism is ICrossChainRelayer {
   function relayCalls(CallLib.Call[] calldata _calls, uint256 _gasLimit)
     external
     payable
-    returns (uint256)
+    returns (uint256 _nonce)
   {
     uint256 _maxGasLimit = maxGasLimit;
 
@@ -57,9 +57,7 @@ contract CrossChainRelayerOptimism is ICrossChainRelayer {
       revert GasLimitTooHigh(_gasLimit, _maxGasLimit);
     }
 
-    nonce++;
-
-    uint256 _nonce = nonce;
+    unchecked { _nonce = ++nonce; }
 
     crossDomainMessenger.sendMessage(
       address(executor),
@@ -73,8 +71,6 @@ contract CrossChainRelayerOptimism is ICrossChainRelayer {
     );
 
     emit RelayedCalls(_nonce, msg.sender, _calls, _gasLimit);
-
-    return _nonce;
   }
 
   /**

src/ethereum-polygon/EthereumToPolygonRelayer.sol

diff --git a/src/ethereum-polygon/EthereumToPolygonRelayer.sol b/src/ethereum-polygon/EthereumToPolygonRelayer.sol
index 2867314..f9feafb 100644
--- a/src/ethereum-polygon/EthereumToPolygonRelayer.sol
+++ b/src/ethereum-polygon/EthereumToPolygonRelayer.sol
@@ -45,7 +45,7 @@ contract CrossChainRelayerPolygon is ICrossChainRelayer, FxBaseRootTunnel {
   function relayCalls(CallLib.Call[] calldata _calls, uint256 _gasLimit)
     external
     payable
-    returns (uint256)
+    returns (uint256 _nonce)
   {
     uint256 _maxGasLimit = maxGasLimit;
 
@@ -53,15 +53,11 @@ contract CrossChainRelayerPolygon is ICrossChainRelayer, FxBaseRootTunnel {
       revert GasLimitTooHigh(_gasLimit, _maxGasLimit);
     }
 
-    nonce++;
-
-    uint256 _nonce = nonce;
+    unchecked { _nonce = ++nonce; }
 
     _sendMessageToChild(abi.encode(_nonce, msg.sender, _calls));
 
     emit RelayedCalls(_nonce, msg.sender, _calls, _gasLimit);
-
-    return _nonce;
   }
 
   /* ============ Internal Functions ============ */

Set executor as immutable

You can set the executor address variavle as immutable on CrossChainRelayerOptimism and CrossChainRelayerArbitrum. But you also have to change your deploy method and precalculate deployed address. Also you could remove the setExecutor function.

You can set the relayer address variavle as immutable on CrossChainExecutorOptimism and CrossChainExecutorArbitrum. But you also have to change your deploy method and precalculate deployed address. Also you could remove the setRelayer function.

Suggested changes;

src/ethereum-arbitrum/EthereumToArbitrumExecutor.sol

diff --git a/src/ethereum-arbitrum/EthereumToArbitrumExecutor.sol b/src/ethereum-arbitrum/EthereumToArbitrumExecutor.sol
index bfee411..fe6c906 100644
--- a/src/ethereum-arbitrum/EthereumToArbitrumExecutor.sol
+++ b/src/ethereum-arbitrum/EthereumToArbitrumExecutor.sol
@@ -16,7 +16,7 @@ contract CrossChainExecutorArbitrum is ICrossChainExecutor {
   /* ============ Variables ============ */
 
   /// @notice Address of the relayer contract on the Ethereum chain.
-  ICrossChainRelayer public relayer;
+  ICrossChainRelayer public immutable relayer;
 
   /**
    * @notice Nonce to uniquely identify the batch of calls that were executed.
@@ -25,6 +25,11 @@ contract CrossChainExecutorArbitrum is ICrossChainExecutor {
    */
   mapping(uint256 => bool) public executed;
 
+  constructor(ICrossChainRelayer _relayer) {
+    require(address(_relayer) != address(0), "Executor/relayer-already-set");
+    relayer = _relayer;
+  }
+
   /* ============ External Functions ============ */
 
   /// @inheritdoc ICrossChainExecutor
@@ -33,25 +38,14 @@ contract CrossChainExecutorArbitrum is ICrossChainExecutor {
     address _sender,
     CallLib.Call[] calldata _calls
   ) external {
-    ICrossChainRelayer _relayer = relayer;
-    _isAuthorized(_relayer);
+    _isAuthorized(relayer);
 
     bool _executedNonce = executed[_nonce];
     executed[_nonce] = true;
 
     CallLib.executeCalls(_nonce, _sender, _calls, _executedNonce);
 
-    emit ExecutedCalls(_relayer, _nonce);
-  }
-
-  /**
-   * @notice Set relayer contract address.
-   * @dev Will revert if it has already been set.
-   * @param _relayer Address of the relayer contract on the Ethereum chain
-   */
-  function setRelayer(ICrossChainRelayer _relayer) external {
-    require(address(relayer) == address(0), "Executor/relayer-already-set");
-    relayer = _relayer;
+    emit ExecutedCalls(relayer, _nonce);
   }
 
   /* ============ Internal Functions ============ */

src/ethereum-arbitrum/EthereumToArbitrumRelayer.sol

diff --git a/src/ethereum-arbitrum/EthereumToArbitrumRelayer.sol b/src/ethereum-arbitrum/EthereumToArbitrumRelayer.sol
index f88674d..80acb68 100644
--- a/src/ethereum-arbitrum/EthereumToArbitrumRelayer.sol
+++ b/src/ethereum-arbitrum/EthereumToArbitrumRelayer.sol
@@ -31,7 +31,7 @@ contract CrossChainRelayerArbitrum is ICrossChainRelayer {
   IInbox public immutable inbox;
 
   /// @notice Address of the executor contract on the Arbitrum chain.
-  ICrossChainExecutor public executor;
+  ICrossChainExecutor public immutable executor;
 
   /// @notice Gas limit provided for free on Arbitrum.
   uint256 public immutable maxGasLimit;
@@ -53,11 +53,13 @@ contract CrossChainRelayerArbitrum is ICrossChainRelayer {
    * @param _inbox Address of the Arbitrum inbox on Ethereum
    * @param _maxGasLimit Gas limit provided for free on Arbitrum
    */
-  constructor(IInbox _inbox, uint256 _maxGasLimit) {
+  constructor(IInbox _inbox, ICrossChainExecutor _executor, uint256 _maxGasLimit) {
     require(address(_inbox) != address(0), "Relayer/inbox-not-zero-address");
+    require(address(_executor) != address(0), "Relayer/executor-already-set");
     require(_maxGasLimit > 0, "Relayer/max-gas-limit-gt-zero");
 
     inbox = _inbox;
+    executor = _executor;
     maxGasLimit = _maxGasLimit;
   }
 
@@ -131,15 +133,6 @@ contract CrossChainRelayerArbitrum is ICrossChainRelayer {
     return _ticketID;
   }
 
-  /**
-   * @notice Set executor contract address.
-   * @dev Will revert if it has already been set.
-   * @param _executor Address of the executor contract on the Arbitrum chain
-   */
-  function setExecutor(ICrossChainExecutor _executor) external {
-    require(address(executor) == address(0), "Relayer/executor-already-set");
-    executor = _executor;
-  }
 
   /**
    * @notice Get transaction hash.

src/ethereum-optimism/EthereumToOptimismExecutor.sol

diff --git a/src/ethereum-optimism/EthereumToOptimismExecutor.sol b/src/ethereum-optimism/EthereumToOptimismExecutor.sol
index 1aba9c1..1988009 100644
--- a/src/ethereum-optimism/EthereumToOptimismExecutor.sol
+++ b/src/ethereum-optimism/EthereumToOptimismExecutor.sol
@@ -19,7 +19,7 @@ contract CrossChainExecutorOptimism is ICrossChainExecutor {
   ICrossDomainMessenger public immutable crossDomainMessenger;
 
   /// @notice Address of the relayer contract on the Ethereum chain.
-  ICrossChainRelayer public relayer;
+  ICrossChainRelayer public immutable relayer;
 
   /**
    * @notice Nonce to uniquely identify the batch of calls that were executed
@@ -34,9 +34,11 @@ contract CrossChainExecutorOptimism is ICrossChainExecutor {
    * @notice CrossChainExecutorOptimism constructor.
    * @param _crossDomainMessenger Address of the Optimism cross domain messenger on the Optimism chain
    */
-  constructor(ICrossDomainMessenger _crossDomainMessenger) {
+  constructor(ICrossDomainMessenger _crossDomainMessenger, ICrossChainRelayer _relayer) {
     require(address(_crossDomainMessenger) != address(0), "Executor/CDM-not-zero-address");
+    require(address(_relayer) != address(0), "Executor/relayer-already-set");
     crossDomainMessenger = _crossDomainMessenger;
+    relayer = _relayer;
   }
 
   /* ============ External Functions ============ */
@@ -47,25 +49,14 @@ contract CrossChainExecutorOptimism is ICrossChainExecutor {
     address _sender,
     CallLib.Call[] calldata _calls
   ) external {
-    ICrossChainRelayer _relayer = relayer;
-    _isAuthorized(_relayer);
+    _isAuthorized(relayer);
 
     bool _executedNonce = executed[_nonce];
     executed[_nonce] = true;
 
     CallLib.executeCalls(_nonce, _sender, _calls, _executedNonce);
 
-    emit ExecutedCalls(_relayer, _nonce);
-  }
-
-  /**
-   * @notice Set relayer contract address.
-   * @dev Will revert if it has already been set.
-   * @param _relayer Address of the relayer contract on the Ethereum chain
-   */
-  function setRelayer(ICrossChainRelayer _relayer) external {
-    require(address(relayer) == address(0), "Executor/relayer-already-set");
-    relayer = _relayer;
+    emit ExecutedCalls(relayer, _nonce);
   }
 
   /* ============ Internal Functions ============ */

src/ethereum-optimism/EthereumToOptimismRelayer.sol

diff --git a/src/ethereum-optimism/EthereumToOptimismRelayer.sol b/src/ethereum-optimism/EthereumToOptimismRelayer.sol
index ac70501..d9ffd3d 100644
--- a/src/ethereum-optimism/EthereumToOptimismRelayer.sol
+++ b/src/ethereum-optimism/EthereumToOptimismRelayer.sol
@@ -20,7 +20,7 @@ contract CrossChainRelayerOptimism is ICrossChainRelayer {
   ICrossDomainMessenger public immutable crossDomainMessenger;
 
   /// @notice Address of the executor contract on the Optimism chain.
-  ICrossChainExecutor public executor;
+  ICrossChainExecutor public immutable executor;
 
   /// @notice Gas limit provided for free on Optimism.
   uint256 public immutable maxGasLimit;
@@ -35,11 +35,13 @@ contract CrossChainRelayerOptimism is ICrossChainRelayer {
    * @param _crossDomainMessenger Address of the Optimism cross domain messenger
    * @param _maxGasLimit Gas limit provided for free on Optimism
    */
-  constructor(ICrossDomainMessenger _crossDomainMessenger, uint256 _maxGasLimit) {
+  constructor(ICrossDomainMessenger _crossDomainMessenger, ICrossChainExecutor _executor, uint256 _maxGasLimit) {
     require(address(_crossDomainMessenger) != address(0), "Relayer/CDM-not-zero-address");
+    require(address(_executor) != address(0), "Relayer/executor-already-set");
     require(_maxGasLimit > 0, "Relayer/max-gas-limit-gt-zero");
 
     crossDomainMessenger = _crossDomainMessenger;
+    executor = _executor;
     maxGasLimit = _maxGasLimit;
   }
 
@@ -77,13 +79,4 @@ contract CrossChainRelayerOptimism is ICrossChainRelayer {
     return _nonce;
   }
 
-  /**
-   * @notice Set executor contract address.
-   * @dev Will revert if it has already been set.
-   * @param _executor Address of the executor contract on the Optimism chain
-   */
-  function setExecutor(ICrossChainExecutor _executor) external {
-    require(address(executor) == address(0), "Relayer/executor-already-set");
-    executor = _executor;
-  }
 }

Use calldata instead of memory for read-only arguments functions saves gas (CallLib.sol)

For this you will need to create another function to support the call on polygon, but its worth it;

testExecuteCalls() (gas: -253 (-0.241%)) 
testRelayCalls() (gas: -14418 (-1.010%)) 
testExecuteCalls() (gas: -14671 (-1.051%)) 
testIsAuthorized() (gas: -14418 (-1.119%)) 
testGasLimitTooHigh() (gas: -14418 (-1.121%)) 
testSetGreetingError() (gas: -14418 (-1.124%)) 
testExecuteCallsAlreadyExecuted() (gas: -1245 (-1.253%)) 
testGreeter() (gas: -14418 (-1.659%)) 
testRelayer() (gas: -14424 (-1.683%)) 
testExecutor() (gas: -14424 (-1.684%)) 
Overall gas change: -117107 (-11.945%)

Suggested changes;

src/ethereum-polygon/EthereumToPolygonExecutor.sol

diff --git a/src/ethereum-polygon/EthereumToPolygonExecutor.sol b/src/ethereum-polygon/EthereumToPolygonExecutor.sol
index 29bc54f..924bf7e 100644
--- a/src/ethereum-polygon/EthereumToPolygonExecutor.sol
+++ b/src/ethereum-polygon/EthereumToPolygonExecutor.sol
@@ -54,7 +54,7 @@ contract CrossChainExecutorPolygon is FxBaseChildTunnel {
     bool _executedNonce = executed[_nonce];
     executed[_nonce] = true;
 
-    CallLib.executeCalls(_nonce, _callsSender, _calls, _executedNonce);
+    CallLib.executeCallsMemory(_nonce, _callsSender, _calls, _executedNonce);
 
     emit ExecutedCalls(_sender, _nonce);
   }

src/libraries/CallLib.sol

diff --git a/src/libraries/CallLib.sol b/src/libraries/CallLib.sol
index 18d8cdc..52bad30 100644
--- a/src/libraries/CallLib.sol
+++ b/src/libraries/CallLib.sol
@@ -47,6 +47,31 @@ library CallLib {
    * @param _executedNonce Whether `_calls` have already been executed or not
    */
   function executeCalls(
+    uint256 _nonce,
+    address _sender,
+    Call[] calldata _calls,
+    bool _executedNonce
+  ) internal {
+    if (_executedNonce) {
+      revert CallsAlreadyExecuted(_nonce);
+    }
+
+    uint256 _callsLength = _calls.length;
+
+    for (uint256 _callIndex; _callIndex < _callsLength; _callIndex++) {
+      Call memory _call = _calls[_callIndex];
+
+      (bool _success, bytes memory _returnData) = _call.target.call(
+        abi.encodePacked(_call.data, _nonce, _sender)
+      );
+
+      if (!_success) {
+        revert CallFailure(_callIndex, _returnData);
+      }
+    }
+  }
+
+  function executeCallsMemory(