System Environment:
--------------------------
Platform: BSW
Libdrm:		(master)libdrm-2.4.58-4-g00847fa48b83a85b0cb882594a12ed1511f780db
Mesa:		(master)16b53005a7df4249fecb6641af0934c32181fdea
Xserver:	(master)xorg-server-1.16.0-386-g95a5b92e37f73f497d547fd91c543c16d2cc73de
Xf86_video_intel:(master)2.99.916-84-gec2b9ac81aed0d2dda2948171ca1c260184bf221
Libva:		(master)cdf8636d5fc5b1558570fede347e1599e0d6af3d
Libva_intel_driver:(master)f11176415ec26eb5960ba6841d2d9c22f2cabc60
Kernel:   (drm-intel-nightly)eabc0c8db15f9ba4d727aee5e0612a68cafe1ab5

Bug detailed description:
-----------------------------
It fails on BSW with Xserver master branch.

good commit:d3d845ca9e92f0a2ccde93f4242d7769cfe14164
bad commit: 95a5b92e37f73f497d547fd91c543c16d2cc73de

Probe color at (40,20)
  Expected: 0.812500 0.600000 0.100000
  Observed: 0.000000 0.000000 0.000000
Wrong color for viewport i,j 0 0
Probe color at (40,60)
  Expected: 0.500000 0.600000 0.200000
  Observed: 0.000000 0.000000 0.000000
Wrong color for viewport i,j 0 1
Probe color at (40,100)
  Expected: 0.843750 0.600000 0.300000
  Observed: 0.000000 0.000000 0.000000
Wrong color for viewport i,j 0 2
Probe color at (40,140)
  Expected: 0.612500 0.600000 0.400000
  Observed: 0.000000 0.000000 0.000000
Wrong color for viewport i,j 0 3
Probe color at (120,20)
  Expected: 0.637500 0.600000 0.500000
  Observed: 0.000000 0.000000 0.000000
Wrong color for viewport i,j 1 0
Probe color at (120,60)
  Expected: 0.400000 0.600000 0.600000
  Observed: 0.000000 0.000000 0.000000
Wrong color for viewport i,j 1 1
Probe color at (120,100)
  Expected: 0.600000 0.600000 0.700000
  Observed: 0.000000 0.000000 0.000000
Wrong color for viewport i,j 1 2
Probe color at (120,140)
  Expected: 0.325000 0.600000 0.800000
  Observed: 0.000000 0.000000 0.000000
Wrong color for viewport i,j 1 3
PIGLIT: {"result": "fail" }

Reproduce steps:
---------------------------- 
1. xinit
2. bin/arb_viewport_array-render-depthrange -fbo -auto