https://gcc.gnu.org/bugzilla/show_bug.cgi?id=100801
--- Comment #2 from Joel Linn <jl_gccbugs at conductive dot de> --- Great. In the meantime I will use > if (count % 4 == 0) __builtin_unreachable(); at the start of the for loop to suppress the warning as suggested by Martin Sebor https://gcc.gnu.org/pipermail/gcc-help/2021-May/140339.html
