We have found a consistent issue with uniform buffer layout on our GLSL shaders on Catalyst drivers.
The GPU tested is a Radeon HD 7950 with Catalyst 15.7.1.
The effect is that a shader like this will have an unpredictable UBO layout for any member after the first one:
gl_Position = vec4(0, 0, 0, 0);
gl_Position += a0;
gl_Position += a1;
Both shader reflection (GL_OFFSET) and my experiments show that the offset of 'a1' inside 'a' is not the expected 16, but rather a random value, usually between 1200 and 1400.
This incidentally does not happen if we replace the the first line with:
Currently we use this as a workaround but it would be nice if the compiler did not have this kind of behavior with version 4.4 shaders, or at least issued an error on compilation.