System Environment:
--------------------------
Platform: Ironlake
Libdrm:		(master)libdrm-2.4.52-10-g1cb5fc706cf5913d9dee33c939f65a23ecea17a5
Mesa:		(master)7683fce8781ef0169333c5ee1276392d058cfaa8
Xserver:	(master)xorg-server-1.15.99.901-129-gbf087659f0fb747c471e26c5b287c35877818040
Xf86_video_intel:(master)2.99.911-3-g220accd828c5a0054ae9e3b491a434f7a6c750e0
Cairo:		(master)bb17403622e9ea474017e0039af8ee48b2b285db
Libva:		(staging)bf2e1773d4373619232c4c653b8cda19ea329441
Libva_intel_driver:(staging)b1319c7f7cb9d20179b20dac2308330bd0e51ffe
Kernel:	(drm-intel-nightly)84295583b8322f96a187c4fc5cca5dd7d511f57e

Bug detailed description:
-----------------------------
It fails on Ironlake, Sandybridge, Ivybridge, Haswell, Baytrail and broadwell with mesa master branch.It doesn't happen on mesa 10.1 branch.

Bisect shows:9cd51bb0c4608258199c69bc7738e72f055799d2 is the first bad commit.
commit 9cd51bb0c4608258199c69bc7738e72f055799d2
Author:     Matt Turner <mattst88@gmail.com>
AuthorDate: Tue Mar 11 13:16:37 2014 -0700
Commit:     Matt Turner <mattst88@gmail.com>
CommitDate: Mon Mar 24 11:06:26 2014 -0700

    i965/vec4: Eliminate writes that are never read.

    With an awful O(n^2) algorithm that searches previous instructions for
    dead writes.

    total instructions in shared programs: 805582 -> 788074 (-2.17%)
    instructions in affected programs:     144561 -> 127053 (-12.11%)

    Reviewed-by: Eric Anholt <eric@anholt.net>

output:
Probe color at (75,75)
  Expected: 1.000000 0.000000 1.000000 1.000000
  Observed: 0.000000 0.000000 1.000000 1.000000
Test /GFX/Test/Piglit/piglit/tests/shaders/generic/vp-sge-alias.vpfp:16 failed
PIGLIT: {'result': 'fail' }


Reproduce steps:
---------------------------- 
1. xinit
2. ./bin/vpfp-generic /GFX/Test/Piglit/piglit/tests/shaders/generic/vp-sge-alias.vpfp -fbo -auto