perf(libraries): branchless MathUtils.add(uint256,int256)

snapshots/ConfigPositionManager.Operations.json

@@ -9,5 +9,5 @@
   "setGlobalPermission": "50110",
   "setUsingAsCollateralOnBehalfOf": "77828",
   "updateUserDynamicConfigOnBehalfOf": "52342",
-  "updateUserRiskPremiumOnBehalfOf": "140135"
+  "updateUserRiskPremiumOnBehalfOf": "139975"
 }

snapshots/GiverPositionManager.Operations.json

@@ -1,4 +1,4 @@
 {
-  "repayOnBehalfOf": "176497",
+  "repayOnBehalfOf": "176258",
   "supplyOnBehalfOf": "143072"
 }

snapshots/Hub.Operations.json

@@ -6,13 +6,13 @@
   "eliminateDeficit: partial": "87146",
   "mintFeeShares": "87668",
   "payFee": "75720",
-  "refreshPremium": "75289",
+  "refreshPremium": "75141",
   "remove: full": "80564",
   "remove: partial": "85702",
-  "reportDeficit": "116908",
-  "restore: full": "81488",
-  "restore: full - with transfer": "188919",
-  "restore: partial": "90198",
-  "restore: partial - with transfer": "148213",
+  "reportDeficit": "116708",
+  "restore: full": "81288",
+  "restore: full - with transfer": "188719",
+  "restore: partial": "90050",
+  "restore: partial - with transfer": "148065",
   "transferShares": "74540"
 }

snapshots/NativeTokenGateway.Operations.json

@@ -1,6 +1,6 @@
 {
-  "borrowNative": "238707",
-  "repayNative": "172321",
+  "borrowNative": "238547",
+  "repayNative": "172082",
   "supplyAsCollateralNative": "165113",
   "supplyNative": "139728",
   "withdrawNative: full": "129898",

snapshots/SignatureGateway.Operations.json

@@ -1,10 +1,10 @@
 {
-  "borrowWithSig": "222144",
-  "repayWithSig": "192513",
+  "borrowWithSig": "221984",
+  "repayWithSig": "192274",
   "setSelfAsUserPositionManagerWithSig": "75138",
   "setUsingAsCollateralWithSig": "85380",
   "supplyWithSig": "155914",
   "updateUserDynamicConfigWithSig": "63113",
-  "updateUserRiskPremiumWithSig": "61995",
+  "updateUserRiskPremiumWithSig": "62007",
   "withdrawWithSig": "135124"
 }

snapshots/Spoke.Operations.ZeroRiskPremium.json

@@ -1,16 +1,16 @@
 {
   "borrow: first": "199509",
   "borrow: second action, same reserve": "179375",
-  "liquidationCall (receiveShares): full": "314227",
-  "liquidationCall (receiveShares): partial": "313645",
-  "liquidationCall (reportDeficit): full": "380307",
-  "liquidationCall: full": "332763",
-  "liquidationCall: partial": "332181",
-  "permitReserve + repay (multicall)": "169938",
+  "liquidationCall (receiveShares): full": "314007",
+  "liquidationCall (receiveShares): partial": "313425",
+  "liquidationCall (reportDeficit): full": "379867",
+  "liquidationCall: full": "332543",
+  "liquidationCall: partial": "331961",
+  "permitReserve + repay (multicall)": "169766",
   "permitReserve + supply (multicall)": "151663",
-  "permitReserve + supply + enable collateral (multicall)": "166114",
-  "repay: full": "129276",
-  "repay: partial": "134234",
+  "permitReserve + supply + enable collateral (multicall)": "166090",
+  "repay: full": "129116",
+  "repay: partial": "134074",
   "setUserPositionManagersWithSig: disable": "46772",
   "setUserPositionManagersWithSig: enable": "68684",
   "supply + enable collateral (multicall)": "146316",

snapshots/Spoke.Operations.json

@@ -1,16 +1,16 @@
 {
-  "borrow: first": "269297",
-  "borrow: second action, same reserve": "212163",
-  "liquidationCall (receiveShares): full": "347124",
-  "liquidationCall (receiveShares): partial": "346542",
-  "liquidationCall (reportDeficit): full": "372507",
-  "liquidationCall: full": "365660",
-  "liquidationCall: partial": "365078",
-  "permitReserve + repay (multicall)": "166334",
+  "borrow: first": "269137",
+  "borrow: second action, same reserve": "212003",
+  "liquidationCall (receiveShares): full": "346644",
+  "liquidationCall (receiveShares): partial": "346062",
+  "liquidationCall (reportDeficit): full": "371867",
+  "liquidationCall: full": "365180",
+  "liquidationCall: partial": "364598",
+  "permitReserve + repay (multicall)": "166133",
   "permitReserve + supply (multicall)": "151663",
-  "permitReserve + supply + enable collateral (multicall)": "166114",
-  "repay: full": "123355",
-  "repay: partial": "142713",
+  "permitReserve + supply + enable collateral (multicall)": "166090",
+  "repay: full": "123116",
+  "repay: partial": "142474",
   "setUserPositionManagersWithSig: disable": "46772",
   "setUserPositionManagersWithSig: enable": "68684",
   "supply + enable collateral (multicall)": "146316",
@@ -19,16 +19,16 @@
   "supply: second action, same reserve": "110653",
   "updateUserDynamicConfig: 1 collateral": "76251",
   "updateUserDynamicConfig: 2 collaterals": "92825",
-  "updateUserRiskPremium: 1 borrow": "158658",
-  "updateUserRiskPremium: 2 borrows": "210210",
+  "updateUserRiskPremium: 1 borrow": "158498",
+  "updateUserRiskPremium: 2 borrows": "209890",
   "usingAsCollateral: 0 borrows, enable": "59616",
-  "usingAsCollateral: 1 borrow, disable": "168699",
+  "usingAsCollateral: 1 borrow, disable": "168539",
   "usingAsCollateral: 1 borrow, enable": "42504",
-  "usingAsCollateral: 2 borrows, disable": "241825",
+  "usingAsCollateral: 2 borrows, disable": "241505",
   "usingAsCollateral: 2 borrows, enable": "42516",
   "withdraw: 0 borrows, full": "135058",
   "withdraw: 0 borrows, partial": "140394",
-  "withdraw: 1 borrow, partial": "221298",
-  "withdraw: 2 borrows, partial": "270470",
+  "withdraw: 1 borrow, partial": "221138",
+  "withdraw: 2 borrows, partial": "270150",
   "withdraw: non collateral": "111299"
 }

snapshots/TakerPositionManager.Operations.json

@@ -1,9 +1,9 @@
 {
   "approveBorrow": "49807",
-  "approveBorrowWithSig": "65689",
+  "approveBorrowWithSig": "65677",
   "approveWithdraw": "49816",
   "approveWithdrawWithSig": "65643",
-  "borrowOnBehalfOf": "332512",
+  "borrowOnBehalfOf": "332352",
   "renounceBorrowAllowance": "27929",
   "renounceWithdrawAllowance": "27983",
   "withdrawOnBehalfOf: full": "127209",

src/libraries/math/MathUtils.sol

@@ -45,10 +45,20 @@ library MathUtils {
   }
 
   /// @notice Returns the sum of an unsigned and signed integer.
-  /// @dev Reverts on underflow.
-  function add(uint256 a, int256 b) internal pure returns (uint256) {
-    if (b >= 0) return a + uint256(b);
-    return a - uint256(-b);
+  /// @dev Reverts with an arithmetic panic (0x11) on overflow or underflow.
+  function add(uint256 a, int256 b) internal pure returns (uint256 c) {
+    assembly ('memory-safe') {
+      // `add` wraps modulo 2**256, so reinterpreting `b` as its two's-complement
+      // word yields the correct result for both signs when it fits in a uint256.
+      c := add(a, b)
+      // Overflow (b >= 0) leaves `c < a`; underflow (b < 0) leaves `c >= a`.
+      // Either case is invalid, i.e. exactly when `(c < a) != (b < 0)`.
+      if xor(lt(c, a), slt(b, 0)) {
+        mstore(0x00, 0x4e487b71) // `Panic(uint256)` selector.
+        mstore(0x20, 0x11) // Arithmetic overflow/underflow panic code.
+        revert(0x1c, 0x24)
+      }
+    }
   }
 
   /// @notice Returns the sum of two unsigned integers.

tests/contracts/libraries/math/MathUtils.t.sol

@@ -92,6 +92,39 @@ contract MathUtilsTest is Base {
     }
   }
 
+  function test_fuzz_add(uint256 a, int256 b) public {
+    // Reference: full-range model, including `type(int256).min`.
+    if (b >= 0) {
+      if (a > UINT256_MAX - uint256(b)) {
+        vm.expectRevert(stdError.arithmeticError);
+        MathUtils.add(a, b);
+      } else {
+        assertEq(MathUtils.add(a, b), a + uint256(b));
+      }
+    } else {
+      // `-b` overflows for `type(int256).min`; derive `|b|` without negating.
+      uint256 magnitude = uint256(~b) + 1;
+      if (a < magnitude) {
+        vm.expectRevert(stdError.arithmeticError);
+        MathUtils.add(a, b);
+      } else {
+        assertEq(MathUtils.add(a, b), a - magnitude);
+      }
+    }
+  }
+
+  function test_add_int256_min_edge() public {
+    uint256 magnitude = uint256(type(int256).max) + 1; // 2**255
+
+    // Below the magnitude underflows and reverts.
+    vm.expectRevert(stdError.arithmeticError);
+    MathUtils.add(magnitude - 1, type(int256).min);
+
+    // At or above, `a + type(int256).min == a - 2**255` fits in a uint256.
+    assertEq(MathUtils.add(magnitude, type(int256).min), 0);
+    assertEq(MathUtils.add(UINT256_MAX, type(int256).min), UINT256_MAX - magnitude);
+  }
+
   function test_add_edge_cases() public {
     assertEq(MathUtils.add(100, 0), 100);
     assertEq(MathUtils.add(0, 50), 50);