[Bug middle-end/86471] GCC/libstdc++ outputs inferior code for std::fill and std::fill_n vs std::memset on c-style arrays

[mattreecebentley at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=86471

--- Comment #10 from Matt Bentley <mattreecebentley at gmail dot com> ---
(In reply to Marc Glisse from comment #9)
> (In reply to Andrew Pinski from comment #7)
> We could also use __builtin_constant_p, if the function is inlined often
> enough (don't know if it is).

Right - so then the proposed function becomes:

template<typename _ForwardIterator, typename _Tp>
    inline typename
    __gnu_cxx::__enable_if<__is_pointer_helper<_Tp>::__value ||
__is_integral_helper<_Tp>::__value, void>::__type
    __fill_a(_ForwardIterator __first, _ForwardIterator __last,
             const _Tp& __value)
    {
      if (__builtin_constant_p(__value) == 1)
      {
                        if (__value != reinterpret_cast<_Tp>(0))
              {
                      const _Tp __tmp = __value;
                      for (; __first != __last; ++__first)
                        *__first = __tmp;
                        }
                        else
                        {
                      if (const size_t __len = __last - __first)
                        __builtin_memset(reinterpret_cast<void *>(__first), 0,
__len *
        sizeof(_Tp));
                        }
                }
                else
                {
                      const _Tp __tmp = __value;
                      for (; __first != __last; ++__first)
                        *__first = __tmp;
                }
    }

, if I'm getting the enable_if syntax correct?