opt: branchless MathUtils.add(uint,int)

[DhairyaSethi]

aave-v4/src/libraries/math/MathUtils.sol

Lines 46 to 56 in 63caec0

	/**
	* @notice Adds a signed integer to an unsigned integer.
	* @dev Reverts on underflow.
	* @param a The unsigned integer.
	* @param b The signed integer.
	* @return The result of the addition.
	*/
	function add(uint256 a, int256 b) internal pure returns (uint256) {
	if (b >= 0) return a + uint256(b);
	return a - uint256(-b);
	}

This can be optimised to be written branchless-ly. See min implementation above or oz for inspiration.

[DhairyaSethi]

existing tests are enough to model behaviour

aave-v4/tests/unit/MathUtils.t.sol

Lines 39 to 77 in 63caec0

	function test_add_positive_operand(uint256 a, int256 b) public {
	vm.assume(b >= 0);
	if (a > UINT256_MAX - uint256(b)) {
	vm.expectRevert(stdError.arithmeticError);
	MathUtils.add(a, b);
	} else {
	uint256 expected = a + uint256(b);
	assertEq(MathUtils.add(a, b), expected);
	}
	}
	function test_add_negative_operand(uint256 a, int256 b) public {
	b = bound(b, type(int256).min + 1, 0); // -b doesn't overflow uint256
	if (a < uint256(-b)) {
	vm.expectRevert(stdError.arithmeticError);
	MathUtils.add(a, b);
	} else {
	uint256 expected = a - uint256(-b);
	assertEq(MathUtils.add(a, b), expected);
	}
	}
	function test_add_edge_cases() public {
	assertEq(MathUtils.add(100, 0), 100);
	assertEq(MathUtils.add(0, 50), 50);
	vm.expectRevert(stdError.arithmeticError);
	MathUtils.add(0, -50);
	assertEq(MathUtils.add(0, INT256_MAX), uint256(INT256_MAX));
	vm.expectRevert(stdError.arithmeticError);
	MathUtils.add(0, type(int256).min);
	assertEq(MathUtils.add(uint256(INT256_MAX), type(int256).min + 1), 0);
	vm.expectRevert(stdError.arithmeticError);
	MathUtils.add(UINT256_MAX, 1);
	}