Zbb static    Zbb dynamic   I baseline
clz       0.668032642   1.336072283   19.552376803
clzl      0.668092643   1.336181786   26.110855571
ctz       1.336208533   3.340209702   26.054869008
ctzl      1.336247784   3.340362457   26.055266290
(seconds for 1 billion iterations on a SiFive-U74 core)