[Bug tree-optimization/99954] [8/9/10/11 Regression] Copy loop over array of unions at -O3 generates memcpy instead of memmove, resulting in incorrect code

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

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99954

--- Comment #2 from Jonathan Wakely <redi at gcc dot gnu.org> ---
> using -O2 "fixes" the issue on GCC 9 and below but not on 10.

And that changed with r271553

        PR tree-optimization/88440
        * opts.c (default_options_table): Enable
-ftree-loop-distribute-patterns
        at -O[2s]+.
        * tree-loop-distribution.c (generate_memset_builtin): Fold the
        generated call.
        (generate_memcpy_builtin): Likewise.
        (distribute_loop): Pass in whether to only distribute patterns.
        (prepare_perfect_loop_nest): Also allow size optimization.
        (pass_loop_distribution::execute): When optimizing a loop
        nest for size allow pattern replacement.