Easy one: under r600_bind_sampler_states(), there is an assert. Since I'm
building with --enable-debug, I hit it.

    if (shader != PIPE_SHADER_VERTEX &&
        shader != PIPE_SHADER_FRAGMENT) {
        assert(!"Only vertex/fragment sampler are implemented.");
        return;
    }

I suggest we should/could print out an error message if needed, but it
shouldn't be an assert() since we return just after that without doing anything
if the shader is not of the supported type. In fact, I tested mesa with the
assert commented out and everything was back to the way it used to be, so we
really don't need an assert() there. A R600_ERR() seems to do the trick here:

    if (shader != PIPE_SHADER_VERTEX &&
        shader != PIPE_SHADER_FRAGMENT) {
        R600_ERR("!Only vertex/fragment sampler are implemented.\n");
        return;
    }