Index: libcxx/include/cmath
===================================================================
--- libcxx/include/cmath
+++ libcxx/include/cmath
@@ -550,26 +550,6 @@
 }
 #endif
 
-template <class _A1>
-_LIBCPP_INLINE_VISIBILITY
-_LIBCPP_CONSTEXPR typename enable_if<is_floating_point<_A1>::value, bool>::type
-__libcpp_isnan_or_builtin(_A1 __lcpp_x) _NOEXCEPT
-{
-#if __has_builtin(__builtin_isnan)
-    return __builtin_isnan(__lcpp_x);
-#else
-    return isnan(__lcpp_x);
-#endif
-}
-
-template <class _A1>
-_LIBCPP_INLINE_VISIBILITY
-_LIBCPP_CONSTEXPR typename enable_if<!is_floating_point<_A1>::value, bool>::type
-__libcpp_isnan_or_builtin(_A1 __lcpp_x) _NOEXCEPT
-{
-    return isnan(__lcpp_x);
-}
-
 template <class _A1>
 _LIBCPP_INLINE_VISIBILITY
 _LIBCPP_CONSTEXPR typename enable_if<is_floating_point<_A1>::value, bool>::type
Index: libcxx/include/complex
===================================================================
--- libcxx/include/complex
+++ libcxx/include/complex
@@ -599,16 +599,16 @@
     _Tp __bc = __b * __c;
     _Tp __x = __ac - __bd;
     _Tp __y = __ad + __bc;
-    if (__libcpp_isnan_or_builtin(__x) && __libcpp_isnan_or_builtin(__y))
+    if (__libcpp_isnan(__x) && __libcpp_isnan(__y))
     {
         bool __recalc = false;
         if (__libcpp_isinf_or_builtin(__a) || __libcpp_isinf_or_builtin(__b))
         {
             __a = copysign(__libcpp_isinf_or_builtin(__a) ? _Tp(1) : _Tp(0), __a);
             __b = copysign(__libcpp_isinf_or_builtin(__b) ? _Tp(1) : _Tp(0), __b);
-            if (__libcpp_isnan_or_builtin(__c))
+            if (__libcpp_isnan(__c))
                 __c = copysign(_Tp(0), __c);
-            if (__libcpp_isnan_or_builtin(__d))
+            if (__libcpp_isnan(__d))
                 __d = copysign(_Tp(0), __d);
             __recalc = true;
         }
@@ -616,22 +616,22 @@
         {
             __c = copysign(__libcpp_isinf_or_builtin(__c) ? _Tp(1) : _Tp(0), __c);
             __d = copysign(__libcpp_isinf_or_builtin(__d) ? _Tp(1) : _Tp(0), __d);
-            if (__libcpp_isnan_or_builtin(__a))
+            if (__libcpp_isnan(__a))
                 __a = copysign(_Tp(0), __a);
-            if (__libcpp_isnan_or_builtin(__b))
+            if (__libcpp_isnan(__b))
                 __b = copysign(_Tp(0), __b);
             __recalc = true;
         }
         if (!__recalc && (__libcpp_isinf_or_builtin(__ac) || __libcpp_isinf_or_builtin(__bd) ||
                           __libcpp_isinf_or_builtin(__ad) || __libcpp_isinf_or_builtin(__bc)))
         {
-            if (__libcpp_isnan_or_builtin(__a))
+            if (__libcpp_isnan(__a))
                 __a = copysign(_Tp(0), __a);
-            if (__libcpp_isnan_or_builtin(__b))
+            if (__libcpp_isnan(__b))
                 __b = copysign(_Tp(0), __b);
-            if (__libcpp_isnan_or_builtin(__c))
+            if (__libcpp_isnan(__c))
                 __c = copysign(_Tp(0), __c);
-            if (__libcpp_isnan_or_builtin(__d))
+            if (__libcpp_isnan(__d))
                 __d = copysign(_Tp(0), __d);
             __recalc = true;
         }
@@ -683,9 +683,9 @@
     _Tp __denom = __c * __c + __d * __d;
     _Tp __x = scalbn((__a * __c + __b * __d) / __denom, -__ilogbw);
     _Tp __y = scalbn((__b * __c - __a * __d) / __denom, -__ilogbw);
-    if (__libcpp_isnan_or_builtin(__x) && __libcpp_isnan_or_builtin(__y))
+    if (__libcpp_isnan(__x) && __libcpp_isnan(__y))
     {
-        if ((__denom == _Tp(0)) && (!__libcpp_isnan_or_builtin(__a) || !__libcpp_isnan_or_builtin(__b)))
+        if ((__denom == _Tp(0)) && (!__libcpp_isnan(__a) || !__libcpp_isnan(__b)))
         {
             __x = copysign(_Tp(INFINITY), __c) * __a;
             __y = copysign(_Tp(INFINITY), __c) * __b;
@@ -993,9 +993,9 @@
 complex<_Tp>
 polar(const _Tp& __rho, const _Tp& __theta = _Tp())
 {
-    if (__libcpp_isnan_or_builtin(__rho) || signbit(__rho))
+    if (__libcpp_isnan(__rho) || signbit(__rho))
         return complex<_Tp>(_Tp(NAN), _Tp(NAN));
-    if (__libcpp_isnan_or_builtin(__theta))
+    if (__libcpp_isnan(__theta))
     {
         if (__libcpp_isinf_or_builtin(__rho))
             return complex<_Tp>(__rho, __theta);
@@ -1008,10 +1008,10 @@
         return complex<_Tp>(_Tp(NAN), _Tp(NAN));
     }
     _Tp __x = __rho * cos(__theta);
-    if (__libcpp_isnan_or_builtin(__x))
+    if (__libcpp_isnan(__x))
         __x = 0;
     _Tp __y = __rho * sin(__theta);
-    if (__libcpp_isnan_or_builtin(__y))
+    if (__libcpp_isnan(__y))
         __y = 0;
     return complex<_Tp>(__x, __y);
 }
@@ -1047,8 +1047,8 @@
     if (__libcpp_isinf_or_builtin(__x.real()))
     {
         if (__x.real() > _Tp(0))
-            return complex<_Tp>(__x.real(), __libcpp_isnan_or_builtin(__x.imag()) ? __x.imag() : copysign(_Tp(0), __x.imag()));
-        return complex<_Tp>(__libcpp_isnan_or_builtin(__x.imag()) ? __x.imag() : _Tp(0), copysign(__x.real(), __x.imag()));
+            return complex<_Tp>(__x.real(), __libcpp_isnan(__x.imag()) ? __x.imag() : copysign(_Tp(0), __x.imag()));
+        return complex<_Tp>(__libcpp_isnan(__x.imag()) ? __x.imag() : _Tp(0), copysign(__x.real(), __x.imag()));
     }
     return polar(sqrt(abs(__x)), arg(__x) / _Tp(2));
 }
@@ -1074,7 +1074,7 @@
             return complex<_Tp>(__x.real(), __i);
         }
     }
-    else if (__libcpp_isnan_or_builtin(__x.real()) && __x.imag() == 0)
+    else if (__libcpp_isnan(__x.real()) && __x.imag() == 0)
         return __x;
     _Tp __e = exp(__x.real());
     return complex<_Tp>(__e * cos(__i), __e * sin(__i));
@@ -1145,13 +1145,13 @@
     const _Tp __pi(atan2(+0., -0.));
     if (__libcpp_isinf_or_builtin(__x.real()))
     {
-        if (__libcpp_isnan_or_builtin(__x.imag()))
+        if (__libcpp_isnan(__x.imag()))
             return __x;
         if (__libcpp_isinf_or_builtin(__x.imag()))
             return complex<_Tp>(__x.real(), copysign(__pi * _Tp(0.25), __x.imag()));
         return complex<_Tp>(__x.real(), copysign(_Tp(0), __x.imag()));
     }
-    if (__libcpp_isnan_or_builtin(__x.real()))
+    if (__libcpp_isnan(__x.real()))
     {
         if (__libcpp_isinf_or_builtin(__x.imag()))
             return complex<_Tp>(__x.imag(), __x.real());
@@ -1174,7 +1174,7 @@
     const _Tp __pi(atan2(+0., -0.));
     if (__libcpp_isinf_or_builtin(__x.real()))
     {
-        if (__libcpp_isnan_or_builtin(__x.imag()))
+        if (__libcpp_isnan(__x.imag()))
             return complex<_Tp>(abs(__x.real()), __x.imag());
         if (__libcpp_isinf_or_builtin(__x.imag()))
         {
@@ -1187,7 +1187,7 @@
             return complex<_Tp>(-__x.real(), copysign(__pi, __x.imag()));
         return complex<_Tp>(__x.real(), copysign(_Tp(0), __x.imag()));
     }
-    if (__libcpp_isnan_or_builtin(__x.real()))
+    if (__libcpp_isnan(__x.real()))
     {
         if (__libcpp_isinf_or_builtin(__x.imag()))
             return complex<_Tp>(abs(__x.imag()), __x.real());
@@ -1210,13 +1210,13 @@
     {
         return complex<_Tp>(copysign(_Tp(0), __x.real()), copysign(__pi/_Tp(2), __x.imag()));
     }
-    if (__libcpp_isnan_or_builtin(__x.imag()))
+    if (__libcpp_isnan(__x.imag()))
     {
         if (__libcpp_isinf_or_builtin(__x.real()) || __x.real() == 0)
             return complex<_Tp>(copysign(_Tp(0), __x.real()), __x.imag());
         return complex<_Tp>(__x.imag(), __x.imag());
     }
-    if (__libcpp_isnan_or_builtin(__x.real()))
+    if (__libcpp_isnan(__x.real()))
     {
         return complex<_Tp>(__x.real(), __x.real());
     }
@@ -1276,7 +1276,7 @@
             return complex<_Tp>(_Tp(1), _Tp(0));
         return complex<_Tp>(_Tp(1), copysign(_Tp(0), sin(_Tp(2) * __x.imag())));
     }
-    if (__libcpp_isnan_or_builtin(__x.real()) && __x.imag() == 0)
+    if (__libcpp_isnan(__x.real()) && __x.imag() == 0)
         return __x;
     _Tp __2r(_Tp(2) * __x.real());
     _Tp __2i(_Tp(2) * __x.imag());
@@ -1307,7 +1307,7 @@
     const _Tp __pi(atan2(+0., -0.));
     if (__libcpp_isinf_or_builtin(__x.real()))
     {
-        if (__libcpp_isnan_or_builtin(__x.imag()))
+        if (__libcpp_isnan(__x.imag()))
             return complex<_Tp>(__x.imag(), __x.real());
         if (__libcpp_isinf_or_builtin(__x.imag()))
         {
@@ -1319,7 +1319,7 @@
             return complex<_Tp>(__pi, signbit(__x.imag()) ? -__x.real() : __x.real());
         return complex<_Tp>(_Tp(0), signbit(__x.imag()) ? __x.real() : -__x.real());
     }
-    if (__libcpp_isnan_or_builtin(__x.real()))
+    if (__libcpp_isnan(__x.real()))
     {
         if (__libcpp_isinf_or_builtin(__x.imag()))
             return complex<_Tp>(__x.real(), -__x.imag());
Index: libcxx/test/libcxx/numerics/c.math/constexpr-fns.pass.cpp
===================================================================
--- libcxx/test/libcxx/numerics/c.math/constexpr-fns.pass.cpp
+++ libcxx/test/libcxx/numerics/c.math/constexpr-fns.pass.cpp
@@ -24,9 +24,9 @@
 
 #include "test_macros.h"
 
-static_assert(std::__libcpp_isnan_or_builtin(0.) == false, "");
-static_assert(std::__libcpp_isinf_or_builtin(0.0) == false, "");
-static_assert(std::__libcpp_isfinite_or_builtin(0.0) == true, "");
+static_assert(std::__libcpp_isnan(0.) == false, "");
+static_assert(std::__libcpp_isinf(0.0) == false, "");
+static_assert(std::__libcpp_isfinite(0.0) == true, "");
 
 int main(int, char**)
 {