This shader https://gist.github.com/igv/a015fc885d5c22e6891820ad89555637 (5th of September revision, crossbilateral only) used to crash the radeon driver and bring the whole system down, whilst the previous version did not. 
After this was magically fixed, the only issue has been extremely low performance, visible through low render times and a few dropped frames.

Test case: https://www.youtube.com/watch?v=6v2L2UGZJAM (it is important that you use my settings for the 1080p version to be selected)

Using any revision of this shader after the introduction of the 5th of September commit, on mpv, I get render times in the order of 31000 and lots of dropped, mistimed frames (as per lua-stats). Using the version immediately before this one ( https://gist.github.com/igv/a015fc885d5c22e6891820ad89555637/15a6623d61b4030ed4d8dce637e509b7433f39c2 ) I get 6700 on the same video.

CPU+GPU: i5-4690, R9-280x
mpv, ffmpeg, mesa, llvm and xf86-video-ati are all git.

SSIMsuperres can be found here https://gist.github.com/igv/2364ffa6e81540f29cb7ab4c9bc05b6b
Relevant bits of mpv.conf for reproduction purposes:


profile=opengl-hq
opengl-pbo=yes

# Scaling
scale=ewa_lanczossharp
opengl-shaders="~~/shaders/ssimsuperres.glsl,~~/shaders/crossbilateral.glsl" #cscale

# Interpolation
tscale=sinc
interpolation=yes
video-sync=display-resample
tscale-clamp=yes

# Misc
temporal-dither=yes
dither-depth=8
deband-iterations=2
deband-range=12
blend-subtitles=no
hwdec=no
framedrop=vo

# Web media
ytdl=yes
ytdl-format=0/(bestvideo[vcodec=vp9]/bestvideo[height>720]/bestvideo[fps>30])[tbr<13000]+(bestaudio[acodec=opus]/bestaudio)/best