https://gcc.gnu.org/bugzilla/show_bug.cgi?id=70307
--- Comment #4 from Marek Polacek <mpolacek at gcc dot gnu.org> --- I think we need to teach c_fully_fold how to fold VEC_COND_EXPR. Until r229128 this wasn't necessary as the C FE never saw any VEC_COND_EXPRs. But since that revision we create a VEC_COND_EXPR when building a vector comparison.
