https://gcc.gnu.org/bugzilla/show_bug.cgi?id=69720
--- Comment #5 from Richard Biener <rguenth at gcc dot gnu.org> --- vect_finalize_reduction: ... /* 2.5 Adjust the final result by the initial value of the reduction variable. (When such adjustment is not needed, then 'adjustment_def' is zero). For example, if code is PLUS we create: new_temp = loop_exit_def + adjustment_def */ if (adjustment_def) { gcc_assert (!slp_reduc); misses support for ncopies > 1. Bah, stupid spaghetti in this function.