[Bug 109404] [ANV] The Witcher 3 shadows flickering

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=109404

--- Comment #25 from Ian Romanick <idr at freedesktop.org> ---
Fixed by :

commit 2dff9a66b629834bffad47e7a9025e0f1de5ffc3
Author: Matt Turner <mattst88 at gmail.com>
Date:   Mon Feb 11 16:02:15 2019 -0800

    intel/compiler: Avoid propagating inequality cmods if types are different

    v2: Fix silly bug in logic.  s/||/&&/

    All but one of the affected shaders is in an Unreal4 demo.  The other is
    in Tomb Raider.  All of the cases that Ian investigated appear to be
    sequences like the following

        if (int(uint(some_float)) < 0) /* other relations too */
            ...

    At least in Tomb Raider, it's not obvious that this sequence came from
    the original shader.

    In some of the Unreal demos, the shader contains code like

        if (int(uint(textureLod(...))) > 0)
            ...

    which explicitly generates the offending sequence.

    All Gen6+ platforms had similar results (Skylake shown):
    total instructions in shared programs: 15437170 -> 15437187 (<.01%)
    instructions in affected programs: 4492 -> 4509 (0.38%)
    helped: 0
    HURT: 17
    HURT stats (abs)   min: 1 max: 1 x̄: 1.00 x̃: 1
    HURT stats (rel)   min: 0.05% max: 0.73% x̄: 0.66% x̃: 0.73%
    95% mean confidence interval for instructions value: 1.00 1.00
    95% mean confidence interval for instructions %-change: 0.57% 0.75%
    Instructions are HURT.

    total cycles in shared programs: 383007996 -> 383007992 (<.01%)
    cycles in affected programs: 20542 -> 20538 (-0.02%)
    helped: 6
    HURT: 7
    helped stats (abs) min: 2 max: 6 x̄: 5.33 x̃: 6
    helped stats (rel) min: 0.11% max: 0.36% x̄: 0.32% x̃: 0.36%
    HURT stats (abs)   min: 4 max: 4 x̄: 4.00 x̃: 4
    HURT stats (rel)   min: 0.27% max: 0.27% x̄: 0.27% x̃: 0.27%
    95% mean confidence interval for cycles value: -3.30 2.69
    95% mean confidence interval for cycles %-change: -0.19% 0.19%
    Inconclusive result (value mean confidence interval includes 0).

    No changes on Iron Lake or GM45.

    Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=109404
    Reviewed-by: Ian Romanick <ian.d.romanick at intel.com>
    Reviewed-by: Jason Ekstrand <jason at jlekstrand.net>
    Tested-by: nagrigoriadis at gmail.com
    Tested-by: Danylo Piliaiev <danylo.piliaiev at gmail.com>

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