[PATCH] Use __builtin_memmove for trivially copy assignable types

[Glen Fernandes]

On Sat, Jun 16, 2018 at 9:10 AM Jonathan Wakely wrote:
> I'll review the patch later, just a quick comment for now.
>
> Every use of memcpy, memmove etc. makes it harder to make everything in <algorithm> constexpr (as we're now required to do). But that's an existing problem, and probably needs to be solved by teaching the built-ins to expand inside constant expression evaluation.

Understood. The existing implementation currently already uses the
built-in for only trivial types, but this relaxes that to
trivially-copy-assignable types.