Acc to article Intel driver is 381k kines. Two orders of magnitude less. There might some minor inefficiencies in AMD code, but nobody will read 34 mln of lines of code so we will never know ;-)

Meanwhile the open-source NVIDIA “Nouveau” driver is around 201k (21.7k blank lines, 24.3k lines of comments, and 155k lines of code). Or the Intel i915 DRM kernel graphics driver is around 381k lines via the same cloc judgment.

It’s open source. If there were backdoors people would’ve noticed.