https://gcc.gnu.org/bugzilla/show_bug.cgi?id=106809
--- Comment #8 from Richard Biener <rguenth at gcc dot gnu.org> --- A real speed improvement to dominated_by_w_unex would record the single known executable predecessor and successor of each block, for example in rpo_state, but that's released before PRE eventually calls into it again via eliminate_with_rpo_vn. Some less hackish plumbing to manage lifetime is necessary here.
