https://gcc.gnu.org/bugzilla/show_bug.cgi?id=31485
--- Comment #21 from Jakub Jelinek <jakub at gcc dot gnu.org> --- (In reply to Joel Yliluoma from comment #20) > Which exceptions would be generated by data in an unused portion of a > register? addps adds 4 float elements, there is no "unused" portion. If some of the elements contain garbage, it can trigger for e.g. the addition FE_INVALID, FE_OVERFLOW, FE_UNDERFLOW or FE_INEXACT (FE_DIVBYZERO obviously isn't relevant to addition). Please read the standard about floating point exceptions, fenv.h etc.
