Hardware ctz instructions are available in the RISC-V Zbb and XTheadBb extension. With special `-march` flags defined, we can generate more simplified code compared to the generic implementation of `ffs`/`ffsll`.
Signed-off-by: Julian Zhu <julian.oerv@isrc.iscas.ac.cn>
Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
