Just tried -clKernel 3 on a RX580 and it doesn't work...

Get the following message:
GPU1: Radeon RX 580 Series (pcie 1), OpenCL 2.0, 8 GB VRAM, 36 CUs
Light cache generated in 5.2 s (12.8 MB/s)
The option -clKernel 3 is ignored for GPU1
GPU1: Free VRAM: 7.948 GB; used: 0.052 GB