https://gcc.gnu.org/bugzilla/show_bug.cgi?id=92597
--- Comment #4 from Jakub Jelinek <jakub at gcc dot gnu.org> --- If it would use %0 and %1, it would find they are different and would need to use an instruction that can copy that in between those. Whether this PR is valid or invalid is unclear, matching constraints for "m" are unsupported, we even warn on "=m" (...) : "0" (...) which is the reason why "+m" is lowered to "=m" (...) : "m" (...).
