openmw runs 100x slower on zink compared to radeonsi

The best game ever created (Morrowind, 2002) has an open source modern engine re-implementation called openmw and apparently doesn't run well on zink 😞

I compiled openmw from git master and the openmw fork of openscenegraph from git master as well (not mandatory, you can use a released vanilla version as well). I also use mesa from git master to get the latest version of zink available (zink-wip didn't compile). I use Gentoo ppc64le (4K page size) on my IBM Power9 8-cores + AMD RX 570.

Morrowind graphics are 20 years old, but once you crank all the settings up you can get as low as 30 fps with radeonsi on my system, even without mods. This is my ~/.config/openmw/settings.cfg that you can use.

In the openmw-launcher go to Advanced, Testing and enable Skip menu and generate default character, then set Start default character at to Balmora and click Play.

With an RX 570 I get about ~30 fps with the settings I attached, while with Zink I only get ~0.33 fps, 100x slower.

It would be awesome if Zink could be made faster because on MacOSX openmw is severely limited by the crippled Apple OpenGL driver and MoltenVK+Zink would be a way better option.