On 6 Jul, 2014, at 3:45 PM, Marc Glisse <marc.glisse@xxxxxxxx> wrote: > On Sat, 5 Jul 2014, Vincenzo Innocente wrote: > >> at the end of >> https://gcc.gnu.org/onlinedocs/gcc/Vector-Extensions.html >> I read >> "It is possible to cast from one vector type to another, provided they are of the same size" >> >> when I try, it looks to me that it is actually more a type-punning rather than a C-style cast. > > Indeed, I am not happy about that, but it seems hard to change that now. Understand. > If you could send a patch to gcc-patches improving the documentation, it would be welcome. I will try to think of something (maybe use "reinterpret" insted of cast, as in c++ reinterpret_cast.) The point is that there is no (more?) any equivalent for C/C++ type Of course adding __builtin_convertvector and its doc will ease to clarify the issue > > >> Is it possible to cast “vectors” as in C one casts intrinsic types? > > Not directly, no. You can cast element by element and hope gcc will vectorize it, but I don't even think that is likely. VF convert(itype i) { VF f; for (int j=0;j<N;++j) f[j]=i[j]; return f;} itype convert(VF f) { itype i; for (int j=0;j<N;++j) i[j]=f[j]; return i;} vectorize for N=8 and N=16, does not vectorize for N=4 (independently of the target architecture) > > From a language point of view, clang recently introduced __builtin_convertvector. It takes a type as second parameter, that may be an issue if we try to implement the same in gcc. strange syntax indeed. of course in c++ would be trivial… "__builtin_convertvector<T>” It that would be a very welcome addition whatever syntax you choose/manage-to-implement If you can also try to add something for “movemask” would be also great! Vincenzo > > From an implementation point of view, we seem to have most (all?) pieces (float_expr, vec_unpack_hi_expr, etc) to represent those in the middle-end. > > -- > Marc Glisse -
