http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53987
--- Comment #1 from Oleg Endo <olegendo at gcc dot gnu.org> 2012-08-31 18:14:28 UTC --- On a second thought, it might be not safe to omit zero/sign extensions if values are compared after calculations, where the regs hold values < SImode.
