If you got the Tahiti GPUs like the 7950/7970/280x the only miner I could get to work on V8 was XMR-Stak and the speeds are horrible compared to the RX/Vega GPUs.
Basically the most I can get is 400H/s while i've gotten 600H/s with V7.
Im using xmrig-amd-2.8.1-win64 miner for tahiti`s, i get 430-450hs average and best ones doing +500hs.
Edit* v8 and crimson 15.12