Incomplete SYCL 2020 math functions marray support

[JackAKirk]

Table 161 of the SYCL 2020 spec revision 4 provides the following relevant descriptions:

floatn: float{n}, mfloat{n}, marray<{N},float>
genfloatf: float, floatn
genfloat: genfloatf, genfloatd, genfloath

where

{N} means any positive value of size_t type.

The spec then defines math functions such as:

genfloat acos (genfloat x)

which are implemented in intel/llvm as (https://github.com/intel/llvm/blob/sycl/sycl/include/CL/sycl/builtins.hpp):

// genfloat acos (genfloat x)
template <typename T>
detail::enable_if_t<detail::is_genfloat<T>::value, T> acos(T x) __NOEXC {
  return __sycl_std::__invoke_acos<T>(x);
}

Now if we follow the definition of genfloat type trait and sub traits eventually we get that the subset of marray types contained within genfloat is defined by marray_float_list as:

using marray_float_list =
    type_list<marray<float, 1>, marray<float, 2>, marray<float, 3>,
              marray<float, 4>, marray<float, 8>, marray<float, 16>>;

i.e. this covers the set {n} : (from the sycl spec)

where {n} means 2,3,4,8,16

which does not match the set from the sycl spec which covers {N} defined above.

This means that we should increase marray_float_list to cover the complete set {N}, unless there is a good reason that only the limited {n} is supported by the sycl Math functions (In which case the SYCL spec should be updated)?

[JackAKirk]

Resolved by #6038.