[Bug 93681] GLSL compilation can be very slow

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=93681

Timothy Arceri <t_arceri at yahoo.com.au> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Assignee|idr at freedesktop.org         |jason at jlekstrand.net

--- Comment #10 from Timothy Arceri <t_arceri at yahoo.com.au> ---
(In reply to Timothy Arceri from comment #9)
> This shader now seems to be causing a crash which is more concerning than
> the original perf issues.

Bisected assert to:

commit 45912fb908f7a1d2efbce0f1dbe81e5bc975fbe1
Author: Jason Ekstrand <jason.ekstrand at intel.com>
Date:   Fri Dec 9 22:32:08 2016 -0800

    i965/compiler: Use the new nir_opt_copy_prop_vars pass

    We run this after nir_lower_vars_to_ssa so that as many load/store_var
    intrinsics as possible before copy_prop_vars executes.  This is because the
    pass isn't particularly efficient (it does a lot of linear walks of a
    linked list) so we'd like as much of the work as possible to be done before
    copy_prop_vars runs.

    Shader DB results on Sky Lake:

       total instructions in shared programs: 12020290 -> 12013627 (-0.06%)
       instructions in affected programs: 26033 -> 19370 (-25.59%)
       helped: 16
       HURT: 13

       total cycles in shared programs: 137772848 -> 137549012 (-0.16%)
       cycles in affected programs: 6955660 -> 6731824 (-3.22%)
       helped: 217
       HURT: 237

       total loops in shared programs: 3208 -> 3208 (0.00%)
       loops in affected programs: 0 -> 0
       helped: 0
       HURT: 0

       total spills in shared programs: 4112 -> 4057 (-1.34%)
       spills in affected programs: 483 -> 428 (-11.39%)
       helped: 2
       HURT: 0

       total fills in shared programs: 5519 -> 5102 (-7.56%)
       fills in affected programs: 993 -> 576 (-41.99%)
       helped: 2
       HURT: 0

       LOST:   0
       GAINED: 0

    Broadwell had similar results.  On older hardware, the impact isn't as
    large because they don't advertise GL 4.5.  Of the hurt programs, all but
    one are hurt by a single instruction and the one is hurt by 3 instructions.
    All of the helped programs, on the other hand, are helped by at least 3
    instructions and one kerbal space program shader is helped by 44.59%.

    The real star of the show, however, is the Gl43CSDof synmark2 benchmark
    which has two shaders which are cut by 28% and 40% and the over-all runtime
    performance of the benchmark on my Sky Lake laptop is improved by around
    25-30% (it's a bit hard to be exact due to thermal throttling).

    Reviewed-by: Timothy Arceri <timothy.arceri at collabora.com>

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