[Bug 88906] [BDW Bisected]Ogles3conform ES3-CTS.shaders.uniform_block.random.nested_structs_arrays_instance_arrays.9 fails

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=88906

lu hua <huax.lu at intel.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEEDINFO                    |NEW
                 CC|                            |idr at freedesktop.org
           Assignee|idr at freedesktop.org         |mattst88 at gmail.com
            Summary|[BDW]Ogles3conform          |[BDW Bisected]Ogles3conform
                   |ES3-CTS.shaders.uniform_blo |ES3-CTS.shaders.uniform_blo
                   |ck.random.nested_structs_ar |ck.random.nested_structs_ar
                   |rays_instance_arrays.9      |rays_instance_arrays.9
                   |fails                       |fails

--- Comment #2 from lu hua <huax.lu at intel.com> ---
Run binary, it always pass, run this case via infrastructure, I can reproduce
the fail. Bisected it.
Bisect shows: c638ea3d19d46cfe65739af2c78373146ed50737 is the first bad commit
commit c638ea3d19d46cfe65739af2c78373146ed50737
Author:     Matt Turner <mattst88 at gmail.com>
AuthorDate: Wed Apr 9 13:38:14 2014 -0700
Commit:     Matt Turner <mattst88 at gmail.com>
CommitDate: Fri Jan 23 17:57:39 2015 -0800

    i965: Don't make instructions with a null dest a barrier to scheduling.

    Now that we properly track accumulator dependencies, the scheduler is
    able to schedule instructions between the mach and mov in the common
    the integer multiplication pattern:

       mul  acc0, x, y
       mach null, x, y
       mov  dest, acc0

    Since a null destination implies no dependency on the destination, we
    can also safely schedule instructions (that don't write the accumulator)
    between the mul and mach.

    GAINED:                                103
    LOST:                                  43

    Causes one program to spill (643 -> 1076 instructions).

    I committed this patch last year (commit 42a26cb5) but reverted it
    (commit 0d3f83f4) after inexplicable artifacts in Kerbal Space Program
    (bug 78648). Tapani reapplied this patch and could not reproduce the bug
    with current Mesa.

    Reviewed-by: Kenneth Graunke <kenneth at whitecape.org>
    Reviewed-by: Jason Ekstrand <jason.ekstrand at intel.com>

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