[Bug 99850] Tessellation bug on Carrizo

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=99850

            Bug ID: 99850
           Summary: Tessellation bug on Carrizo
           Product: Mesa
           Version: unspecified
          Hardware: Other
                OS: All
            Status: NEW
          Severity: normal
          Priority: medium
         Component: Drivers/Gallium/radeonsi
          Assignee: dri-devel at lists.freedesktop.org
          Reporter: tom.stdenis at amd.com
        QA Contact: dri-devel at lists.freedesktop.org

Created attachment 129692
  --> https://bugs.freedesktop.org/attachment.cgi?id=129692&action=edit
carrizo run with HEAD

Tessellation is broken on Carrizo (A12-9800) hardware and apparently has been
for a while.  The offending commit is 

commit a4e2146a9d24592ed7e3bf778e3c21c6cfb89330
Author: Bas Nieuwenhuizen <bas at basnieuwenhuizen.nl>
Date:   Mon May 2 14:55:52 2016 +0200

    radeonsi: Use buffer loads and stores for passing data from TCS to TES.

    We always try to use 4-component loads, as LLVM does not combine loads
    and they bypass the L1 cache.

    We can't use a similar strategy for stores and this is especially
    notable with the tess factors, as they are often set with separate
    MOV's per component in the TGSI.

    We keep storing to LDS and the LDS space, so we can load the outputs
    later, either due to the shader, of for wrting the tess factors.

    Signed-off-by: Bas Nieuwenhuizen <bas at basnieuwenhuizen.nl>
    Reviewed-by: Nicolai Hähnle <nicolai.haehnle at amd.com>
    Reviewed-by: Marek Olšák <marek.olsak at amd.com>

I found it via running Unigine-Heaven with tessellation enabled.

The bug doesn't occur on other VI hardware (Polaris10, FIJI).

I can confirm that the HEAD~ commit leads to spec/arb_tessellation_shader/*
tests (in piglit) passing compared to running with HEAD.

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