https://gcc.gnu.org/bugzilla/show_bug.cgi?id=61747
--- Comment #3 from Marc Glisse <glisse at gcc dot gnu.org> --- (In reply to vincenzo Innocente from comment #2) > > I think you need -fno-signed-zeros for the transformation to be valid. > possible. > but then is the O2 code that is wrong? > in any case adding -fno-signed-zeros makes no difference w/r/t O2 alone -fno-signed-zeros comes in addition to some flag saying there are no NaNs (-ffinite-math-only for instance).