[Bug 91730] [ivb blorp?] GPU hang in witcher.EXE

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=91730

--- Comment #2 from Matt Turner <mattst88 at gmail.com> ---
(In reply to Pavel Ondračka from comment #1)
> I can reproduce a similar behavior in Total War: Shogun2.
> GPU hangs and "intel_do_flush_locked failed: Input/output error" is printed
> in the terminal. Hopefully it is the same bug, however for me this is 100%
> reproducible.

Why do you believe it's the same bug? Are Shogun2 and Witcher based on the same
engine or something?

> I've managed to bisect it to:
> commit f5cf74d8ba8ce30b9d53b2198e5122ed72f1dcff
> Author: Matt Turner <mattst88 at gmail.com>
> Date:   Tue May 5 20:25:07 2015 -0700
> 
>     nir: Recognize (a < c || b < c) as min(a, b) < c.
>     
>     ... and (a >= c) || (b >= c) as max(a, b) >= c.
>     
>     Similar to commit 97e6c1b9.
>     
>     total instructions in shared programs: 6182276 -> 6182180 (-0.00%)
>     instructions in affected programs:     6400 -> 6304 (-1.50%)
>     helped:                                68
>     HURT:                                  4
>     
>     Reviewed-by: Jordan Justen <jordan.l.justen at intel.com>
>     Reviewed-by: Glenn Kennard <glenn.kennard at gmail.com>
> 
> Tim can you confirm this with your testcases?
> 
> It can be reproduced with this trace: http://pavel.ondracka.cz/Shogun2.trace

I couldn't get a hang by running this trace on Haswell, but I did confirm that
3 of the shaders were affected (hurt, actually...) by the patch you bisected
the problem to.

I'll see if I can get someone to run the trace on BDW, and I'll look more
closely at the differences in the shaders to see if we're doing something
suspicious.

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