https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81476
--- Comment #5 from Hannes Hauswedell <h2+bugs at fsfe dot org> --- > Please clarify if the problem is in compilation time (how long the compiler > takes to compile the file), or in performance of generated code. Performance of code. > Please attach preprocessed testcase obtained with -E or -save-temps. I have added intermediate code. > For clang are you using GCC's libstdc++ or llvm's libc++? For clang I am using libc++ (FreeBSD). I has no immediate luck trying to use libstdc++ with clang (to exclude library issues), but I will give it another shot later.