Index: libcxx/include/numeric
===================================================================
--- libcxx/include/numeric
+++ libcxx/include/numeric
@@ -531,15 +531,9 @@
 midpoint(_Tp __a, _Tp __b) noexcept
 _LIBCPP_DISABLE_UBSAN_UNSIGNED_INTEGER_CHECK
 {
-    using _Up = std::make_unsigned_t<_Tp>;
-    constexpr _Up __bitshift = std::numeric_limits<_Up>::digits - 1;
-
-    _Up __diff = _Up(__b) - _Up(__a);
-    _Up __sign_bit = __b < __a;
-
-    _Up __half_diff = (__diff / 2) + (__sign_bit << __bitshift) + (__sign_bit & __diff);
-
-    return __a + __half_diff;
+    _Tp floored_avg = (__a & __b) + ((__a ^ __b) >> 1);
+    _Tp shift =  (__a ^ __b)&(__a >__b);
+    return floored_avg + shift;
 }