[Bug rtl-optimization/69904] [6 Regression] shrink-wrapping creates weird atomic compare exchange loop on arm

[segher at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=69904

--- Comment #2 from Segher Boessenkool <segher at gcc dot gnu.org> ---
If you disallow this memory clobber from being copied (via the
cannot_copy_insn_p hook), do you then get what you want?