Update: downgraded llvm-libs and clang fixed xorg for now. Thus I will watch this issue like a hawk, but presently I wouldn't call this issue resolved. Is it possible to wait for mesa to update before upgrading llvm-libs?
Edit: found the problem. its yet another dependency hell problem . (eric: see
icu hell :))
taco@ zen ~ % pacman -Q mesa-nosystemd; pacman -Si mesa | egrep "Name|Version"
mesa-nosystemd 11.2.1-1
Name : mesa
Version : 11.2.2-1
Notice how mesa-nosystemd is missing a incremental update.
Well this is rather very depressing, because it seems no one has this specific error. Although it was relevant for mesa-testing but not libLLVM.so.3.8/mesa-stable (see above) Even if I had researched llvm prior to doing an upgrade it wouldn't matter, because the actual issues were for previous versions that ironically affected the latest. So researching against the latest wouldn't give me anything.
Basically this is what happened: I've proceeded to upgrade arch and of course llvm-libs had to be update, then after rebooting that's when everything went to shit.
gbm: failed to open any driver (search paths /usr/lib/xorg/modules/dri)
gbm: Last dlopen error: libLLVM.so.3.7: cannot open shared object file: no such file or directory
failed to load driver: r600
failed to load swrast driver
So at first I tried reinstalling mesa with pacman -Sy, didn't work. Next I tried removing (pacman -Rscn) and reinstalling mesa along with its dependencies (yaourt -S $(cat mesa)) prior with pactree -lr mesa-nosystemd > mesa
(as advised for mesa-git [1] by kerberizer ), Didn't work. Although I should have known it wouldn't work because its a binary package :(
Now I don't what to do ;_;, reinstall llvm-libs? downgrade llvm-libs, and wait till the problem is resolved for mesa? replace llvm and mesa with testing? I don't know, I feel like giving up because there isn't enough information. The arch forums (presently) show no help at all towards this issue [2] However I want to avoid linking libllvm for now, as reference to the forum posts.
TL;Dr Don't be a fucking idiot like me, don't upgrade llvm-libs...
[1]
https://aur.archlinux.org/pkgbase/mesa-git/?comments=all
[2]
https://bbs.archlinux.org/search.php?action=search&keywords=libllvm
References
https://bugs.archlinux.org/task/48973
https://bugs.freedesktop.org/show_bug.cgi?id=93103