http://gcc.gnu.org/bugzilla/show_bug.cgi?id=51744
--- Comment #5 from Richard Biener <rguenth at gcc dot gnu.org> --- It also (sadly) means this "works" with -fno-use-linker-plugin. It also means that not outputting the UNDEF into the LTO symbol table for this case doesn't work as the executable will not link (we optimize the symbol away) if we don't fold away the reference to it later. I see no better way than either forcing the linker to re-scan needed symbols and warn at a "second" stage only or to fold __builtin_constant_p earlier.
