Created attachment 137537 [details]
Alien: Isolation rendering on TURKS with Mesa git
With Mesa 18.1~git180219165200.f78fe98 in Alien: Isolation there is rendering artifacts - please look into attached screenshot. Issue is reproducible on Radeon HD 6620G and 6650M.
Graphical settings is all set to minimal, all visual effects is disabled.
Kubuntu 17.10 x86_64, Linux 4.15.5
By the way this issue looks like bug 100387, but I not sure if cause is the same.
On BARTS this looks fine with 4562a7b0e82bf664b30 (2018-02-23). Do you have any output from logs? On my Cedar based card I get "CS shader rejected" - and then the GPU to lock up (In any case, on that card even starting up the game is already only a slide show).
I might have been wrong, it is certain that eb96ba722ee7 worked, but checking out above commit after following Darius Spitznagel hint 
Disable it in the prefereces file in ~/.local/share/feral-interactive/AlienIsolation like below...
<value name="EnableShaderWarmer" type="integer">0</value>
I wasn't even able to start the game, because I got an LLVM error. Will bisect now ...
Well, after a clean reboot 4562a7b0e82bf664 works fine on BART. I guess the crash with the CEDAR card somehow triggered an instability that was responsible for the problems starting AI later (I use both cards in a dual head with separate X-screens setup).
I retested game on Mesa build 4562a7b0e82bf664, this time with "MESA_GL_VERSION_OVERRIDE=4.3 MESA_GLSL_VERSION_OVERRIDE=430 %command%" launch option in Steam settings - issue is no longer reproducible.