gf_log_t
gf_log_t logsum;
logsum = (gf_log_t) vdev_raidz_log2[a] + (gf_log_t) vdev_raidz_log2[b];
gf_log_t logsum;
logsum = (gf_log_t) 255 + (gf_log_t) vdev_raidz_log2[a] -
(gf_log_t) vdev_raidz_log2[b];
gf_log_t logsum;
logsum = (gf_log_t) 255 - (gf_log_t) vdev_raidz_log2[a];
gf_exp2(gf_log_t exp)
gf_exp4(gf_log_t exp)