https://gcc.gnu.org/bugzilla/show_bug.cgi?id=88598
--- Comment #6 from rsandifo at gcc dot gnu.org <rsandifo at gcc dot gnu.org> --- I think a general fix for this would involve tracking the set of nonzero vector elements and adding a match.pd rule that uses that to replace REDUC functions in which only one element of the argument is nonzero.
