https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113234
--- Comment #1 from Joseph S. Myers <jsm28 at gcc dot gnu.org> --- Note that if flag_signaling_nans, __builtin_isnan should not raise exceptions for signaling NaN argument (bug 66462), but ==, != and __builtin_isunordered should raise exceptions for signaling NaN argument.