Re-commit r330627 "[libcxx] implement <experimental/simd> declarations based on P0214R7."

There are 3 changes:
* Renamed genertor.pass.cpp to generator.pass.cpp
* Removed nothing_to_do.pass.cpp
* Mark GCC 4.9 as UNSUPPORTED for the test files that have negative
  narrowing conversion SFINAE test (see GCC PR63723).

git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@330655 91177308-0d34-0410-b5e6-96231b3b80d8

test/std/experimental/simd/simd.cons/broadcast.pass.cpp

@@ -0,0 +1,58 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: c++98, c++03
+
+// See GCC PR63723.
+// UNSUPPORTED: gcc-4.9
+
+// <experimental/simd>
+//
+// [simd.class]
+// template <class U> simd(U&& value);
+
+#include <cstdint>
+#include <experimental/simd>
+
+using namespace std::experimental::parallelism_v2;
+
+template <class T, class... Args>
+auto not_supported_native_simd_ctor(Args&&... args)
+    -> decltype(native_simd<T>(std::forward<Args>(args)...), void()) = delete;
+
+template <class T>
+void not_supported_native_simd_ctor(...) {}
+
+template <class T, class... Args>
+auto supported_native_simd_ctor(Args&&... args)
+    -> decltype(native_simd<T>(std::forward<Args>(args)...), void()) {}
+
+template <class T>
+void supported_native_simd_ctor(...) = delete;
+
+void compile_narrowing_conversion() {
+  supported_native_simd_ctor<int8_t>(3);
+  supported_native_simd_ctor<int16_t>(3);
+  supported_native_simd_ctor<int32_t>(3);
+  supported_native_simd_ctor<int64_t>(3);
+  supported_native_simd_ctor<uint8_t>(3);
+  supported_native_simd_ctor<uint16_t>(3);
+  supported_native_simd_ctor<uint32_t>(3);
+  supported_native_simd_ctor<uint64_t>(3);
+  supported_native_simd_ctor<float>(3.f);
+  supported_native_simd_ctor<double>(3.);
+  supported_native_simd_ctor<long double>(3.);
+
+  not_supported_native_simd_ctor<float>(3.);
+  not_supported_native_simd_ctor<int8_t>(long(3));
+  not_supported_native_simd_ctor<float>(long(3));
+  not_supported_native_simd_ctor<int>(3.);
+}
+
+int main() {}