HS/SW setup:
- HSW GT3e
- Mesa git from 2014-09-30
- Ubuntu 14.04

Test-case:
- Build ogl-samples test-suite from:
  https://github.com/g-truc/ogl-samples.git
- Run following test:
  build/Release/gl-400-fbo-rtt-texture-array

Actual result:
- "Vertex shader triggered register spilling.  Try reducing number of live vec4 value to improve performance."

Expected result:
- No register spilling with this simple vertex shader


Vertex shader is this:
https://github.com/g-truc/ogl-samples/blob/master/data/gl-400/rtt-array.vert

Code for the test is here:
https://github.com/g-truc/ogl-samples/blob/master/tests/gl-400-fbo-rtt-texture-array.cpp


Same thing happens also with the other tests using gl_VertexID as array index to small const array, for example with gl-320-draw-without-vertex-attrib test:
https://github.com/g-truc/ogl-samples/blob/master/data/gl-320/draw-without-vertex-attrib.vert

(which doesn't require setting these like gl-400-fbo-rtt* tests do:
  MESA_GL_VERSION_OVERRIDE=4.00
  MESA_GLSL_VERSION_OVERRIDE=400
)