https://gcc.gnu.org/bugzilla/show_bug.cgi?id=91836
--- Comment #1 from Richard Biener <rguenth at gcc dot gnu.org> ---
It's likely been one of the vectorizer changes and fixed by
2019-09-20 Richard Biener <rguent...@suse.de>
PR tree-optimization/91821
* tree-vect-loop.c (check_reduction_path): Check we can compute
reduc_idx.
(vect_is_simple_reduction): Set STMT_VINFO_REDUC_IDX.
* tree-vect-patterns.c (vect_reassociating_reduction_p): Return
operands in canonical order.
* tree-vectorizer.c (vec_info::new_stmt_vec_info): Initialize
STMT_VINFO_REDUC_IDX.
* tree-vectorizer.h (_stmt_vec_info::reduc_idx): New.
(STMT_VINFO_REDUC_IDX): Likewise.
