feat: return uint64 from XDM's baseGas

.changeset/chatty-impalas-report.md

+---
+'@eth-optimism/contracts-bedrock': patch
+---
+
+Use uint64 for arithmetic in XDM's baseGas

packages/contracts-bedrock/.gas-snapshot

@@ -9,6 +9,8 @@ GasBenchMark_L1StandardBridge_Finalize:test_finalizeETHWithdrawal_benchmark() (g
 GasBenchMark_L2OutputOracle:test_proposeL2Output_benchmark() (gas: 68671)
 GasBenchMark_OptimismPortal:test_depositTransaction_benchmark() (gas: 74964)
 GasBenchMark_OptimismPortal:test_depositTransaction_benchmark_1() (gas: 35777)
+CrossDomainMessenger_Test:testFuzz_baseGas(uint32) (runs: 256, μ: 20263, ~: 20263)
+CrossDomainMessenger_Test:test_baseGas() (gas: 20100)
 CrossDomainOwnableThroughPortal_Test:test_depositTransaction_crossDomainOwner() (gas: 61850)
 CrossDomainOwnable_Test:test_onlyOwner() (gas: 34945)
 CrossDomainOwnable_Test:test_revertOnlyOwner() (gas: 10619)
@@ -61,7 +63,7 @@ L1CrossDomainMessenger_Test:test_L1MessengerRelayMessageToSystemContract() (gas:
 L1CrossDomainMessenger_Test:test_L1MessengerRelayMessageV0Fails() (gas: 33258)
 L1CrossDomainMessenger_Test:test_L1MessengerRelayShouldRevertIfPaused() (gas: 60526)
 L1CrossDomainMessenger_Test:test_L1MessengerReplayMessageWithValue() (gas: 38193)
-L1CrossDomainMessenger_Test:test_L1MessengerSendMessage() (gas: 299481)
+L1CrossDomainMessenger_Test:test_L1MessengerSendMessage() (gas: 299487)
 L1CrossDomainMessenger_Test:test_L1MessengerTwiceSendMessage() (gas: 1490366)
 L1CrossDomainMessenger_Test:test_L1MessengerUnpause() (gas: 41003)
 L1CrossDomainMessenger_Test:test_L1MessengerXDomainSenderReverts() (gas: 24283)
@@ -91,7 +93,7 @@ L2CrossDomainMessenger_Test:test_L2MessengerRelayMessageSucceeds() (gas: 53115)
 L2CrossDomainMessenger_Test:test_L2MessengerRelayMessageToSystemContract() (gas: 36217)
 L2CrossDomainMessenger_Test:test_L2MessengerRelayMessageV0Fails() (gas: 18871)
 L2CrossDomainMessenger_Test:test_L2MessengerRelayShouldRevertIfPaused() (gas: 41637)
-L2CrossDomainMessenger_Test:test_L2MessengerSendMessage() (gas: 120636)
+L2CrossDomainMessenger_Test:test_L2MessengerSendMessage() (gas: 120648)
 L2CrossDomainMessenger_Test:test_L2MessengerTwiceSendMessage() (gas: 136338)
 L2CrossDomainMessenger_Test:test_L2MessengerXDomainSenderReverts() (gas: 10576)
 L2CrossDomainMessenger_Test:test_L2MessengerxDomainMessageSenderResets() (gas: 50459)

packages/contracts-bedrock/contracts/test/CrossDomainMessenger.t.sol

+// SPDX-License-Identifier: MIT
+pragma solidity 0.8.15;
+
+import { Messenger_Initializer, Reverter, CallerCaller } from "./CommonTest.t.sol";
+
+// CrossDomainMessenger_Test is for testing functionality which is common to both the L1 and L2
+// CrossDomainMessenger contracts. For simplicity, we use the L1 Messenger as the test contract.
+contract CrossDomainMessenger_Test is Messenger_Initializer {
+    // Ensure that baseGas passes for the max value of _minGasLimit,
+    // this is about 4 Billion.
+    function test_baseGas() external {
+        L1Messenger.baseGas(hex"ff", type(uint32).max);
+    }
+
+    // Fuzz for other values which might cause a revert in baseGas.
+    function testFuzz_baseGas(uint32 _minGasLimit) external {
+        L1Messenger.baseGas(hex"ff", _minGasLimit);
+    }
+}

packages/contracts-bedrock/contracts/universal/CrossDomainMessenger.sol

@@ -53,22 +53,22 @@ abstract contract CrossDomainMessenger is
     /**
      * @notice Constant overhead added to the base gas for a message.
      */
-    uint32 public constant MIN_GAS_CONSTANT_OVERHEAD = 200_000;
+    uint64 public constant MIN_GAS_CONSTANT_OVERHEAD = 200_000;
 
     /**
      * @notice Numerator for dynamic overhead added to the base gas for a message.
      */
-    uint32 public constant MIN_GAS_DYNAMIC_OVERHEAD_NUMERATOR = 1016;
+    uint64 public constant MIN_GAS_DYNAMIC_OVERHEAD_NUMERATOR = 1016;
 
     /**
      * @notice Denominator for dynamic overhead added to the base gas for a message.
      */
-    uint32 public constant MIN_GAS_DYNAMIC_OVERHEAD_DENOMINATOR = 1000;
+    uint64 public constant MIN_GAS_DYNAMIC_OVERHEAD_DENOMINATOR = 1000;
 
     /**
      * @notice Extra gas added to base gas for each byte of calldata in a message.
      */
-    uint32 public constant MIN_GAS_CALLDATA_OVERHEAD = 16;
+    uint64 public constant MIN_GAS_CALLDATA_OVERHEAD = 16;
 
     /**
      * @notice Minimum amount of gas required to relay a message.
@@ -369,13 +369,16 @@ abstract contract CrossDomainMessenger is
      *
      * @return Amount of gas required to guarantee message receipt.
      */
-    function baseGas(bytes calldata _message, uint32 _minGasLimit) public pure returns (uint32) {
+    function baseGas(bytes calldata _message, uint32 _minGasLimit) public pure returns (uint64) {
+        // We peform the following math on uint64s to avoid overflow errors. Multiplying the
+        //  by MIN_GAS_DYNAMIC_OVERHEAD_NUMERATOR would otherwise limit the _mingasLimit to
+        // approximately 4.2 MM.
         return
             // Dynamic overhead
-            ((_minGasLimit * MIN_GAS_DYNAMIC_OVERHEAD_NUMERATOR) /
+            ((uint64(_minGasLimit) * MIN_GAS_DYNAMIC_OVERHEAD_NUMERATOR) /
                 MIN_GAS_DYNAMIC_OVERHEAD_DENOMINATOR) +
             // Calldata overhead
-            (uint32(_message.length) * MIN_GAS_CALLDATA_OVERHEAD) +
+            (uint64(_message.length) * MIN_GAS_CALLDATA_OVERHEAD) +
             // Constant overhead
             MIN_GAS_CONSTANT_OVERHEAD;
     }