[Bug tree-optimization/121522] [14/15/16 Regression] wrong code at -O3 on x86_64-linux-gnu (the generated code hangs) since r14-6536

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

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=121522

--- Comment #4 from Filip Kastl <pheeck at gcc dot gnu.org> ---
>  just reference each other.

I mean that they reference each other or a single other value -- .MEM_42. 
That's why the pass replaces uses of these PHIs with uses of .MEM_42.