[Bug tree-optimization/84859] [8 Regression] bogus -Warray-bounds on a memcpy in a loop

[jakub at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=84859

--- Comment #4 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
Note, even teaching VRP to look through stores and loads from memory wouldn't
help here, not even for the first function, because it uses *a as the length,
but also overwrites it (potentially or for real) with the memcpy, so the
compiler can't really know anything about *a in the second and following
iterations, except that it is unsigned char and thus [0, 255].  n can wrap
around.