Created attachment 112566 [details]
Test case

Hi,

on a R290X with a fresh fedora 21 install (Mesa 10.4.1) a fragment shader
sampling a cubemap texture with trilinear filtering is not correctly executed
on the edge of rasterized triangles.

I've included a patch against piglit that display the behaviour. On my system
the test display a small orange diagonal line on top of the color pattern. 
(the test doesn't check result atm)

I think it's related to some quad pattern : in my app that has a depth buffer
the line follows the edge of the geometry.