System Environment:
--------------------------
Arch:           i386
Platform:       Sandy bridge
Libdrm:		(master)libdrm-2.4.42-7-g36a2daad2416ad55a859c483b0d7ed93a5eff6e0
Mesa:		(master)de315f76a266ce51ca0638b9ea2ec3ccfd31f03b
Xserver:(master)xorg-server-1.14.0-36-gcc3d1a5a6120e721a46c67446ba68f5596055633
Xf86_video_intel:(master)2.21.4-31-g308f0208de59620190dd3cb65b3243d2e8a7bd87
Cairo:	(master)ff233fd706e62edf267bee66113e2cb35183bcd9
Libva:	(staging)620ab8401d2970e2a83e345ab1379ae03e1c1943
Libva_intel_driver:(staging)825c76ee544cd35cd459d86068f5301cd5319108
Kernel:	(drm-intel-nightly) 0d98e68d373eac2948d5619369f072af2e3f52d7

Bug detailed description:
-------------------------
It fails on sandy bridge with mesa master branch.It doesn't happen on 9.1 branch.
Case glean_polygonOffset also fails with same bisect commit.
Bisect shows:c07c18081e3b21070c7db3aea0c7a31a31ff20ce is the first bad commit.
commit c07c18081e3b21070c7db3aea0c7a31a31ff20ce
Author:     Philipp Brüschweiler <blei42@gmail.com>
AuthorDate: Fri Mar 8 21:32:36 2013 +0100
Commit:     Brian Paul <brianp@vmware.com>
CommitDate: Fri Mar 15 06:50:23 2013 -0600

    wayland: fix segfault when using software rendering

    wayland_roundtrip() was given an incorrect parameter.

    Fixes https://bugs.freedesktop.org/show_bug.cgi?id=62362

    Note: This is a candidate for the stable branches.

    Signed-off-by: Brian Paul <brianp@vmware.com>

output:
Probe at (0,0)
  Expected: 1.000000 0.000000 0.000000
  Observed: 0.000000 0.000000 0.000000
Probe at (25,25)
  Expected: 0.000000 1.000000 0.000000
  Observed: 0.000000 0.000000 0.000000
PIGLIT: {'result': 'fail' }

Reproduce steps:
----------------
1. xinit
2. ./bin/glx-copy-sub-buffer -auto