[CUDA] Tweak CUDA wrappers to make cuda-9 work with libc++

CUDA-9 headers check for specific libc++ version and ifdef out
some of the definitions we need if LIBCPP_VERSION >= 3800.

Differential Revision: https://reviews.llvm.org/D40198

llvm-svn: 319485

clang/lib/Headers/__clang_cuda_runtime_wrapper.h

@@ -270,12 +270,18 @@ static inline __device__ void __brkpt(int __c) { __brkpt(); }
 // include guard from math.h wrapper from libstdc++. We have to undo the header
 // guard temporarily to get the definitions we need.
 #pragma push_macro("_GLIBCXX_MATH_H")
+#pragma push_macro("_LIBCPP_VERSION")
 #if CUDA_VERSION >= 9000
 #undef _GLIBCXX_MATH_H
+// We also need to undo another guard that checks for libc++ 3.8+
+#ifdef _LIBCPP_VERSION
+#define _LIBCPP_VERSION 3700
+#endif
 #endif
 
 #include "math_functions.hpp"
 #pragma pop_macro("_GLIBCXX_MATH_H")
+#pragma pop_macro("_LIBCPP_VERSION")
 #pragma pop_macro("__GNUC__")
 #pragma pop_macro("signbit")