https://bugzilla.kernel.org/show_bug.cgi?id=204725
--- Comment #35 from Dmitri Seletski (drjoms@gmail.com) --- we got some progress. Or may be not. Since I suspect original issue is still not solved. Still get black screen when amdgpu is loaded. This time, however, I can start Xorg, with no 3d or 2d acceleration, but not using VESA driver, but using AMDGPU.
My guess is, we fixed second problem, I did not know existed. Which is good all the same. Because I had several versions of LLVM, older one was used by default and only newer was showing up as installed by portage(gentoo packaging system). It shows only last installed. Shame on me, I hsould have known better. To my defence, there are very a few packages where you have several versions of same package installed and they usually can be chosed using 'eselect' command.
eselect |grep llvm (nothing)
this is now me sitting under: uname -a Linux (none)dimko's Desktop 5.3.0-rc6+ #8 SMP PREEMPT Sun Sep 1 07:39:44 IST 2019 x86_64 AMD Ryzen 5 1600 Six-Core Processor AuthenticAMD GNU/Linux
glxinfo name of display: :0.0 Error: couldn't find RGB GLX visual or fbconfig
glxgears Error: couldn't get an RGB, Double-buffered visual
see new dmesg(nothing interesting there) and new Xorg.log files in next message.(a lot of interesting there)