https://gcc.gnu.org/bugzilla/show_bug.cgi?id=59461
--- Comment #11 from Eric Botcazou <ebotcazou at gcc dot gnu.org> --- > So are the upper bits for SPARC completely undefined? That would then be the > major distinction between MIPS and SPARC. The upper bits are defined for MIPS On the contrary, they are always defined since instructions always operate on the full 64-bit registers, but they don't matter for 32-bit operations, i.e. 32-bit operations would work the same if they were garbage.