https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101188
--- Comment #7 from Georg-Johann Lay <gjl at gcc dot gnu.org> --- On branch releases/gcc-5.4.0, the wrong code is since r226119, which is a backport of r225918. Doesn't look like this caused the current PR; maybe that change just unmasked a bug in postreload that's even older.