$ ./bin/shader_runner generated_tests/spec/glsl-1.30/execution/interpolation/interpolation-noperspective-gl_BackColor-flat-distance.shader_test -auto
Probe at (159,45)
  Expected: 0.272727 0.181818 0.545455 1.000000
  Observed: 0.474510 0.160784 0.364706 1.000000
Probe at (192,38)
  Expected: 0.153846 0.153846 0.692308 1.000000
  Observed: 0.266667 0.133333 0.596078 1.000000
Probe at (216,33)
  Expected: 0.066667 0.133333 0.800000 1.000000
  Observed: 0.117647 0.117647 0.764706 1.000000
Probe at (166,83)
  Expected: 0.166667 0.333333 0.500000 1.000000
  Observed: 0.294118 0.294118 0.415686 1.000000
Probe at (196,71)
  Expected: 0.071429 0.285714 0.642857 1.000000
  Observed: 0.125490 0.250980 0.627451 1.000000
Probe at (136,136)
  Expected: 0.181818 0.545455 0.272727 1.000000
  Observed: 0.317647 0.478431 0.203922 1.000000
Probe at (173,115)
  Expected: 0.076923 0.461538 0.461538 1.000000
  Observed: 0.129412 0.403922 0.462745 1.000000
Probe at (145,166)
  Expected: 0.083333 0.666667 0.250000 1.000000
  Observed: 0.149020 0.603922 0.247059 1.000000
PIGLIT: {'result': 'fail' }


4a938ef7136a89c828ebb16effe1bc5bea08b7d7 is the first bad commit
commit 4a938ef7136a89c828ebb16effe1bc5bea08b7d7
Author: Brian Paul <brianp@vmware.com>
Date:   Mon Jan 21 11:32:49 2013 -0700

    draw: add new debug code and comments in clip code template
    
    In debug builds, set clipped vertex window coordinates to NaN values
    to help debugging.  Otherwise, we're just leaving the coordinate in clip
    space and it's invalid to use it later expecting it to be a window coord.
    
    Reviewed-by: José Fonseca <jfonseca@vmware.com>

:040000 040000 1c9a933b785f0a56ebf2f13874aacffc4183e976 b87acb6dca3e64abd30f9da1d7483ac61364fb9e M	src
bisect run success