https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95528
--- Comment #6 from rsandifo at gcc dot gnu.org <rsandifo at gcc dot gnu.org> --- (In reply to Jakub Jelinek from comment #4) > I'd say the vectorizer/simplify_vector_constructor just shouldn't attempt to > use these (e.g. vec_pack*, vec_unpack* optabs) for !VEC_MODE_P unless it is > VECTOR_BOOLEAN_TYPE_P type. > For i386 it would be the right thing as the patterns really assume that it > is vector booleans and have their properties. > Though, aarch64 seems to have vec_pack_trunc_di and vec_pack_trunc_df > expanders, it is unclear to me what they are for and if they are really used. > Other targets seem to only define these for vector modes. Yeah, I agree those look odd. The covering note for the patch that added them was: https://gcc.gnu.org/pipermail/gcc-patches/2013-April/361636.html which talks about fixing gcc.dg/vect failures. But as James says, only the 128-bit patterns should be needed for that. Maybe the the 64-bit patterns were just added for completeness. Perhaps one justification for _di is that there is no V1DI mode. Instead a vector of 1 DImode would itself have mode DImode. So in principle, vec_pack_trunc_di is probably the right name for a (V1)DI->V2SI truncate. The same doesn't apply to _df since we don't use scalar float modes for V1 vectors. And (unlike at the time of the patch) we now have V1DF. So I agree that the _df one looks dead. That said, for AArch64 we'd now try to mix 128-bit and 64-bit vectors instead of vectorising with 2 64-bit vectors. So the _di pattern probably isn't useful in practice either. In summary: from an AArch64 perspective, it's probably fine to check !VECTOR_MODE_P || VECTOR_BOOLEAN_TYPE_P. But given the V1 thing, maybe it would be better to add || m == GET_MODE_INNER (m) as well (unless that defeats the fix).
