Index: clang/lib/Headers/__clang_cuda_cmath.h
===================================================================
--- clang/lib/Headers/__clang_cuda_cmath.h
+++ clang/lib/Headers/__clang_cuda_cmath.h
@@ -72,6 +72,10 @@
 __DEVICE__ float frexp(float __arg, int *__exp) {
   return ::frexpf(__arg, __exp);
 }
+
+// For inscrutible reasons, the CUDA headers define these functions for us on
+// Windows.
+#ifndef _MSC_VER
 __DEVICE__ bool isinf(float __x) { return ::__isinff(__x); }
 __DEVICE__ bool isinf(double __x) { return ::__isinf(__x); }
 __DEVICE__ bool isfinite(float __x) { return ::__finitef(__x); }
@@ -79,6 +83,10 @@
 // __finitef, does not exist when compiling for MacOS.  __isfinited is available
 // everywhere and is just as good.
 __DEVICE__ bool isfinite(double __x) { return ::__isfinited(__x); }
+__DEVICE__ bool isnan(float __x) { return ::__isnanf(__x); }
+__DEVICE__ bool isnan(double __x) { return ::__isnan(__x); }
+#endif
+
 __DEVICE__ bool isgreater(float __x, float __y) {
   return __builtin_isgreater(__x, __y);
 }
@@ -109,8 +117,6 @@
 __DEVICE__ bool islessgreater(double __x, double __y) {
   return __builtin_islessgreater(__x, __y);
 }
-__DEVICE__ bool isnan(float __x) { return ::__isnanf(__x); }
-__DEVICE__ bool isnan(double __x) { return ::__isnan(__x); }
 __DEVICE__ bool isnormal(float __x) { return __builtin_isnormal(__x); }
 __DEVICE__ bool isnormal(double __x) { return __builtin_isnormal(__x); }
 __DEVICE__ bool isunordered(float __x, float __y) {