So recently I thought of giving DXVK a shot on my Intel UHD iGPU system. I inserted d3d9.dll into the game's directory but to be sure I looked up "How to install DXVK GTAIV" on YouTube and found several videos putting in dxgi.dll and d3d9.dll. What does dxgi.dll actually do?
Topic on Talk:Grand Theft Auto IV
Since GTAIV is a DirectX 9 game, you only need d3d9.dll. See https://www.pcgamingwiki.com/wiki/DXVK. :)