http://gcc.gnu.org/bugzilla/show_bug.cgi?id=48016
--- Comment #1 from Richard Guenther <rguenth at gcc dot gnu.org> 2011-03-07 14:13:10 UTC --- The gimple middle-end only knows one pointer type mode, ptr_type_mode. If we want to save Pmode then we need to use an appropriate integer type and a proper alias set. I guess this code should be simply replaced to emit RTL directly instead of going through expansion of an ARRAY_REF.
