Nouveau - Jun 2016 - [Bug 96565] New: Clive Barker's Jericho displays strange, vivid colors when motion blur enabled

https://bugs.freedesktop.org/show_bug.cgi?id=96565

            Bug ID: 96565
           Summary: Clive Barker's Jericho displays strange,vivid colors
                    when motion blur enabled
           Product: Mesa
           Version: 11.2
          Hardware: Other
                OS: All
            Status: NEW
          Keywords: bisected, regression
          Severity: normal
          Priority: medium
         Component: Drivers/DRI/nouveau
          Assignee: nouveau at lists.freedesktop.org
          Reporter: gyebro69 at gmail.com
        QA Contact: nouveau at lists.freedesktop.org
                CC: imirkin at alum.mit.edu

Created attachment 124580
  --> https://bugs.freedesktop.org/attachment.cgi?id=124580&action=edit
screenshot

When motion blur effect is enabled in the game, the screen is filled with red,
yellow and green colors (both the menus and midgame).
The problem doesn't exist with the software renderer.

Bisecting revealed that the problem is present since

commit 7752bbc44e78e982de3cd4c34862adc38a338234
Author: Ilia Mirkin <imirkin at alum.mit.edu>
Date:   Thu Dec 10 18:19:44 2015 -0500

    gk104/ir: simplify and fool-proof texbar algorithm

    With the current algorithm, we only look at tex uses. However there's a
    write-after-write hazard where we might decide to, on some path, not use
    a texture's output at all, but instead to write a different value to
    that register. However without the barrier, the texture might complete
    later and overwrite that value.

    This fixes Unreal Elemental demo on GK110/GK208, flightgear on GK10x,
    and likely other random-looking failures.

The game renders properly with the previous commit.

Trace (uncompressed 138M):
https://drive.google.com/open?id=0B-tTbLKBl-tOaVRvNmMwQW8zYlk

OpenGL vendor string: nouveau
OpenGL renderer string: Gallium 0.4 on NV106
OpenGL core profile version string: 4.3 (Core Profile) Mesa 12.1.0-devel
(git-5a64549)
OpenGL core profile shading language version string: 4.30

Fedora 23
Libdrm 2.4.68+git
Linux kernel 4.7.0-rc3

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--- Comment #1 from Samuel Pitoiset <samuel.pitoiset at gmail.com> ---
The trace replays fine on my GF119. I guess it's a Kepler issue.

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--- Comment #2 from Ilia Mirkin <imirkin at alum.mit.edu> ---
Created attachment 124590
  --> https://bugs.freedesktop.org/attachment.cgi?id=124590&action=edit
failing tgsi shader

Somehow the attached shader manages to generate

BB:11 (4 instructions) - idom = BB:8, df = { BB:5 }
 -> BB:26 (tree)
 -> BB:12 (tree)
 45: mov u32 $r4 $r14 (8)
 46: mov u32 $r5 $r15 (8)
 47: tex 2D $r1 $s0 f32 $r4t $r4d (8)
 48: set ftz u8 $p0 neu f32 $r7 neg $r7 (8)
BB:12 (4 instructions) - idom = BB:11, df = { BB:13 }
 -> BB:13 (forward)
 49: $p0 add ftz f32 $r17 $r17 $r4 (8)
 50: $p0 add ftz f32 $r18 $r18 $r5 (8)
 51: $p0 add ftz f32 $r19 $r19 $r6 (8)
 52: $p0 add ftz f32 $r16 $r16 1.000000 (8)

Which is obviously missing a texbar. Investigating.

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--- Comment #3 from Ilia Mirkin <imirkin at alum.mit.edu> ---
https://patchwork.freedesktop.org/patch/94103/

That fixes the trace for me. Technically the issue wasn't *caused* by that
commit... the bad logic existed already. But the old logic didn't pick up
the
"uses" at the top of the loop, which in turn meant that it kept the
uses after
the tex. Oh well.

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--- Comment #4 from Ilia Mirkin <imirkin at alum.mit.edu> ---
v2 here:

https://patchwork.freedesktop.org/patch/94106/

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Béla Gyebrószki <gyebro69 at gmail.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |gyebro69 at gmail.com

--- Comment #5 from Béla Gyebrószki <gyebro69 at gmail.com> ---
(In reply to Ilia Mirkin from comment #4)
> v2 here:
> 
> https://patchwork.freedesktop.org/patch/94106/
The patch fixes the problem in the game, thank you.

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Ilia Mirkin <imirkin at alum.mit.edu> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
         Resolution|---                         |FIXED
             Status|NEW                         |RESOLVED

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