[Bug 103258] [GEN9+] 5% performance drop + misrendering in GfxBench Manhattan 3.0 & CarChase from "i965: Disable auxiliary buffers when there are self-dependencies"

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=103258

Kenneth Graunke <kenneth at whitecape.org> changed:

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

--- Comment #12 from Kenneth Graunke <kenneth at whitecape.org> ---
The performance regression should be fixed by the series ending in:

commit 82144b7392d1651167cbfd4746aea6a14d5aff46
Author: Kenneth Graunke <kenneth at whitecape.org>
Date:   Thu Oct 12 20:47:41 2017 -0700

    i965: Don't disable aux buffers for non-overlapping miplevels.

    Meta's GenerateMipmap implementation binds the same image for both
    sampling and rendering - but it samples from one miplevel while
    rendering the next.  This is a false self-dependency, and there's
    no need to disable auxiliary buffers in this case.  In fact, we really
    want to leave it enabled so the new miplevels gain color compression.

    Thankfully, the texture object's _MaxLevel is always one shy of the
    miplevel being rendered.  So we can simply check if irb->mt_level is
    overlaps with the texture's defined levels.  If not, there's no self-
    dependency and we can leave the auxiliary buffers enabled.

    Fixes a performance regression in GFXBench4 Car Chase, which apparently
    calls glGenerateMipmap() on every frame.

    Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=103247
    Reviewed-by: Topi Pohjolainen <topi.pohjolainen at intel.com>
    Reviewed-by; Jason Ekstrand <jason at jlekstrand.net>

I'm still not sure why the rendering changed - there's probably a bug there
still - but I don't have time to investigate that right now.

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