[Bug middle-end/32667] block copy with exact overlap is expanded as memcpy

[fw at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=32667

--- Comment #55 from Florian Weimer <fw at gcc dot gnu.org> ---
(In reply to post+gcc from comment #52)
> For the point discussed earlier with the `restrict` in the musl memcpy, I
> had another look at the definition of `restrict` and it's not entirely clear
> to me any more that there is UB here. The restrict rules only apply to
> objects that are "also modified (by any means)". Now the question is, does
> "*X = *X" modify the object?

C11 says this:

| NOTE: “Modify” includes the case where the new value being stored is the same
as the previous value.

So at least this should be quite clear (although I think notes are supposedly
informal).