[Bug c++/110167] excessive compile time when optimizing std::to_array

[redi at gcc dot gnu.org via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110167

Jonathan Wakely <redi at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
     Ever confirmed|0                           |1
   Last reconfirmed|                            |2023-06-08
           Keywords|                            |compile-time-hog
             Status|UNCONFIRMED                 |NEW
          Component|libstdc++                   |c++

--- Comment #1 from Jonathan Wakely <redi at gcc dot gnu.org> ---
Reduced:

template<unsigned long N>
struct array
{
  int data[N];
};

template<unsigned long...> struct seq { };


template<unsigned long... Idx>
array<sizeof...(Idx)>
to_array_impl(int (&a)[sizeof...(Idx)], seq<Idx...>)
{
  return {{a[Idx]...}};
}


template<unsigned long N>
array<N>
to_array(int (&a)[N])
{
  return to_array_impl(a, seq<__integer_pack(N)...>{});
}

int f[262144];

auto g(void) { return to_array(f); }