Created attachment 142649 [details]
Pertinent system logs

Upgraded Ubuntu 16.04 to 18.04.1.  VLC worked correctly prior to the upgrade; no hardware changes were made.
VLC plays music files correctly.
Any video files cause "Segmentation fault (core dumped)"
Happens if 2x-clicking a video file, or if dropping a video file onto a running VLC window, or if selecting a video from Media -> Open File.
Specific file format does not matter - I have confirmed with mp4, mkv, webm, avi, mov
Turning hardware acceleration off does not correct the issue.

Full output:
VLC media player 3.0.4 Vetinari (revision 3.0.4-0-gf615db6332)
[0000557badb0d570] main libvlc: Running vlc with the default interface. Use 'cvlc' to use vlc without interface.
[0000557badb114e0] main playlist: playlist is empty
Gtk-Message: 10:02:40.800: GtkDialog mapped without a transient parent. This is discouraged.
Segmentation fault (core dumped)


Videos play correctly with xine.

Possibly related symptoms:
Videos viewed on Chrome exhibit tearing (with hw accel on or off) but not in Firefox.
After the initial upgrade, the system would freeze at every boot - screen would flicker and attempt to launch the GUI, but would drop back to the terminal.  Safe Mode from the recovery console would flicker the screen and return to the recovery console. ***This behavior was the same when booting to a live Ubuntu 18.04.1 disc.***  Ultimately required amdgpu-uninstall from recovery console CLI to get to a login/desktop.
Currently running the latest AMDGPU driver, and have removed and re-installed it multiple times. ("amdgpu-pro-18.40-676022-ubuntu-18.04.tar.xz")
No other graphics issues are apparent with the system; Geeks3d GPUtest runs very smoothly and gives very impressive results.