https://gcc.gnu.org/bugzilla/show_bug.cgi?id=19987 Bug 19987 depends on bug 95527, which changed state.
Bug 95527 Summary: Failure to optimize __builtin_ffs == 0 https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95527 What |Removed |Added ---------------------------------------------------------------------------- Status|NEW |RESOLVED Resolution|--- |FIXED