At my uni, 15 years ago, one postdoc reverse engineered NVIDIA chip and wrote more performant compiler. He did that by connecting oscyloscops to all chip's outputs and started with applying random current on inputs. Using ML and his genius he rediscoverd all opcodes including a few hidden ones. Eventually he got hired by some company that was doing a lot of GPU on supercomputers.
I was waiting for some writeup about permutation decyphering
but reminds me how we're going to find out on an industrial level when the Saudis give China some nvidia chips they were grifted
they've cloned lots of chips before but nothing that advanced