https://gcc.gnu.org/bugzilla/show_bug.cgi?id=45217
--- Comment #3 from Richard Biener <rguenth at gcc dot gnu.org> --- Note that alternatively we do allow BIT_FIELD_REF on the LHS if it operates on memory... (we're inserting into a global variable for the testcase). But indeed a RMW cycle might be prefered on targets that cannot do stv on memory.
