[Bug 110412] Over 15% performance lost on large branching shader

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=110412

            Bug ID: 110412
           Summary: Over 15% performance lost on large branching shader
           Product: Mesa
           Version: git
          Hardware: Other
                OS: All
            Status: NEW
          Severity: normal
          Priority: medium
         Component: Drivers/DRI/i965
          Assignee: intel-3d-bugs at lists.freedesktop.org
          Reporter: kevin.rogovin at intel.com
        QA Contact: intel-3d-bugs at lists.freedesktop.org

Created attachment 143948
  --> https://bugs.freedesktop.org/attachment.cgi?id=143948&action=edit
output from Mesa 18.2

A large branching shader suffers an over 15% performance loss comparing Mesa
GIT (revision a182adfd83ad00e326153b00a725a014e0359bf0) against Mesa 18.2.8 (on
Ubuntu 18.04).

To replicate,

 1. Build painter-glyph-test-GL-debug from the project
https://github.com/intel/fastuidraw
 2. Run (adjusting width and height options to match ones monitor) with

     vblank_mode=0 LD_LIBRARY_PATH=. ./painter-glyph-test-GL-release fullscreen
true width 1920 height 1200 use_file true text
demo_data/txt/wall_of_text_caps_no_numbers.txt

On my Iris Pro Graphics 580 (Skylake GT4e), I see (with fluctuations):

   Mesa 18.2.8: 5.6 ms/frame [178 FPS]
   a182adfd83ad00e326153b00a725a014e0359bf0: 6.5 ms/frame [153 FPS]

The shader being executed is a large uber-shader. In both tested Mesa's above,
the uber-shader is realized as only SIMD8 with no spilling.

Attached are the outputs when running with MESA_GLSL_CACHE_DISABLE=true
INTEL_DEBUG=fs for the offending fragment shader.

-- 
You are receiving this mail because:
You are the QA Contact for the bug.
You are the assignee for the bug.
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <https://lists.freedesktop.org/archives/intel-3d-bugs/attachments/20190412/7bdae3c3/attachment.html>