https://gcc.gnu.org/bugzilla/show_bug.cgi?id=118166
--- Comment #4 from Gero <gero.peterhoff at gmx dot net> --- Changing the register sets is of course a problem. But u/int128 could also be realized in xmm ? - Addition/subtraction can be implemented efficiently (see attachemant). - For multiplications/shl/shr/... this should also be possible ? - Division is a separate function. On other ISAs these problems may not occur and the operations can be implemented better/more efficiently. But you can judge this better than I can. Merry Christmas Gero