Added a test for and WAR'd the clang&C++11 constant eval builtin, tes…

…t may need to be moved.

.upstream-tests/test/std/utilities/utilities.general/broken_constant_eval.pass.cpp

@@ -0,0 +1,35 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+//
+// This test serves as a canary for when this issue is fixed in NVCC
+//
+// UNSUPPORTED: windows, icc, pgi
+// XFAIL: clang-9 && c++11
+// XFAIL: clang-10 && c++11
+// XFAIL: gcc-9 && c++11
+// XFAIL: gcc-10 && c++11
+
+
+#if defined(__has_builtin)
+#if __has_builtin(__builtin_is_constant_evaluated)
+#define BUILTIN_CONSTANT_EVAL() __builtin_is_constant_evaluated()
+#endif
+#endif
+
+#ifndef BUILTIN_CONSTANT_EVAL
+#define BUILTIN_CONSTANT_EVAL() true
+#endif
+
+__device__ __host__ inline constexpr bool constant_eval() {
+  return BUILTIN_CONSTANT_EVAL();
+}
+
+int main(int, char**) {
+  static_assert(constant_eval(), "");
+  return 0;
+}

libcxx/include/__config

@@ -647,6 +647,14 @@ typedef __char32_t char32_t;
 #define _LIBCUDACXX_IS_CONSTANT_EVALUATED(...) __builtin_is_constant_evaluated(__VA_ARGS__)
 #endif
 
+// TODO: Builtin is not constexpr, this can be tested with an integral_constant
+//       but _only_ in C++11 mode. (fix for NVCC+clang-9 and up)
+#if defined(__CUDACC__)
+#if __cplusplus < 201402L
+#undef _LIBCUDACXX_IS_CONSTANT_EVALUATED
+#endif
+#endif
+
 #if __has_builtin(__builtin_addressof)
 #define _LIBCUDACXX_ADDRESSOF(...) __builtin_addressof(__VA_ARGS__)
 #endif