[Mesa-dev] [Bug 105670] [regression][hang] Trine1EE hangs GPU after loading screen on Mesa3D-17.3 and later

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=105670

--- Comment #6 from Timothy Arceri <t_arceri at yahoo.com.au> ---
(In reply to Gert Wollny from comment #2)
> I can confirm this on Radeon 6870 HD. 
> 
> I was able to track the issue to the series beginning with  
> 
>    ab23b759f24 glsl: don't drop instructions from unreachable 
>                terminators continue branch
> 
> The first time around I had a few difficulties get the correct patch, it
> seems to be either 646621c66da9 or 7a7fb90af75. In any case, yes it is
> related to loop unrolling.
> 
> The original TGSI goes like 
> 
> BGNLOOP
>   ISGE TEMP[13].x, TEMP[8].xxxx, IMM[7].yyyy
>   UIF TEMP[13].xxxx
>      BRK
>   ENDIF
>   ...
> ENDLOOP
> 
> and with the series in question applied it is 
> 
> BGNLOOP
>   ISLT TEMP[13].x, TEMP[8].xxxx, IMM[7].yyyy
>   UIF TEMP[13].xxxx
>   ...
>   ENDI
> ENDLOOP
> 
> This UIF should have an else path with the BRK to resemble the original
> code. 
> (There are more BRK statements in the LOOP but they are the same in both
> versions.
> 
> Regarding bisecting this, after a failure one usually must reboot the
> system, otherwise the graphics card is in a bad state. But given the nature
> of the bug one should also be able to reproduce the endless loop with
> LIBGL_ALWAYS_SOFTWARE=1 thereby not clobbering the hardware.

Thanks for tracking down the problem. Do you think you would be able to create
a piglit test to reproduce the bug? Or failing that can you copy the full glsl
loop an attach it to the bug so that I can attempt to recreate the issue in
piglit. Thanks.

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