https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67145
--- Comment #2 from Alan Modra <amodra at gmail dot com> --- Note that r224768 was specifically about keeping register order (association and commutation) when simplify_plus_minus does not simplify an expression, because ordering matters for machine insn matching when an expression contains fixed regs. It would be possible to modify the r224768 change so that expressions not containing fixed regs are sorted, but I think that would be the wrong fix due to points (2) and (3) above.
