On Mon, Jan 21, 2019 at 10:14 AM Alexander Monakov <amona...@ispras.ru> wrote: > > On Mon, 21 Jan 2019, Richard Biener wrote: > > > I'm not sure whether it's permitted to use this in C++ or not (and whether > > the C usage is now officially sanctioned other than via a non-normative > > footnote) - but at least GCC will guarantee that it works. > > My impression is that, via the "active member" wording, C++ standard says > clearly this is UB. I assume on the GCC side the intention is to treat it > like in C (for POD types only?..), but I don't want to go there in the > "Vector Extensions" section. Hence my patch limits the suggestion to C. > > I think in C++ it's a bit less of an issue anyway, because people can use > operator overloading to achieve a similar end result, with some extra legwork. > > Do you want me to change the text somehow?
No, it was just a note from my side. > > Might be interesting to show how to do argument marshalling with the > > same union. > > Sorry, I don't see what you mean here; can you give an example or elaborate? when you call a function with v4si signature but want to pass it a result from a __mm intrinsic you'd need a temporary union to do the marshalling. I think you can use a union argument in the function itself and you can elide the temporary then if you use transparent_union. But I didn't try. Richard. > Thanks! > Alexander
