[Bug libstdc++/114958] use __builtin_shufflevector for std::experimental::simd split and concat (at least the common cases) to enable better optimizations

[jakub at gcc dot gnu.org via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114958

--- Comment #4 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
Strange, the __builtin_shufflevector in GCC has been added for Clang
compatibility.
__builtin_shuffle is the original native GCC builtin (which Clang doesn't
implement).