On Fri, 12 Mar 2021, 18:14 Joseph Myers, <jos...@codesourcery.com> wrote:
> On Fri, 12 Mar 2021, Joseph Myers wrote: > > > On Fri, 12 Mar 2021, Jonathan Wakely wrote: > > > > > On Fri, 12 Mar 2021 at 12:26, Sjoerd Meijer via Gcc <gcc@gcc.gnu.org> > wrote: > > > > So here's finally my concrete question: what do we think about > making _Float16 available in C++ mode? > > > > > > I think GCC should do it. > > > > What about types with the same format as an existing type (but which are > > nevertheless distinct types in C), such as _Float64 (typically same > format > > as double) or _Float32 (typically same format as float, but not promoted > > when passed in variable arguments)? > > And also the _Float32x, _Float64x types (we don't have any targets > supporting _Float128x). (On all systems supporting those types in GCC, > _Float32x has the same format as double and _Float64, and _Float64x has > the same format as either long double or _Float128, but again they are > different types.) > I see less value in adding additional distinct types that don't add anything you can't already do. _Float16 gives you access to an entirely new data type. _Float32 just complicates overloading of it's a new type with the same representation as an existing one. With the proposed std::float32 typedef for C++ users will still be able to write code that definitely uses an IEEE binary32 type without needing a new type to be introduced. ISTM that what users really want is "a type guaranteed to be IEEE binary32" and whether that is float or _Float32 is mostly irrelevant.
