https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109029
--- Comment #5 from Hongtao.liu <crazylht at gmail dot com> --- We need to support signbit<mode>2 for vector double/_Float16. Also similar like popcnt, there's a mismatch of input and output between builtin and signbit_optab, it could be handled in vectorizer pattern match.
