Mesa's GLSL compiler ignores the "invariant" keyword. This needs to be implemented.
Some tests in dEQP-GLES3.functional.shaders.invariance.* currently fail because of this. Some pass by luck. Handling "invariant" correctly should fix all of these.
*** Bug 90901 has been marked as a duplicate of this bug. ***
Jason has patches on the mailing list for this.
commit 4e060d80ff92b7fcf9b54cdd5ed00f549db3f573 and earlier fix this.