https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94833
--- Comment #2 from Carl Love <carll at gcc dot gnu.org> --- The ABI has the builtin VEC_FIRST_MATCH_OR_EOS_ INDEX (ARG1, ARG2) which says Returns the element index of the position of either the first character match or an end-of-string (EOS) terminator. If no match or terminator, returns the number of characters as an element count in the vector argument. So, I do agree the builtin in question should be treating the EOS (null) as any other number for comparison purposes.
