https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99918
--- Comment #4 from Martin Sebor <msebor at gcc dot gnu.org> --- (In reply to Andrew Pinski from comment #1) > This comes down to lowering bitfields too soon. > my bet it will happen even integer bitfields will have a problem. Yes, unsigned bit-fields suffer the same problem but unlike for _Bool, GCC never emitted optimal code for those for this test case.