> I don’t really see how it helps here. It doesn't help at all. That issue is entirely orthogonal to "open vs proprietary" ISA. The ways a compromise can be

> I don’t really see how it helps here. It doesn't help at all. That issue is entirely orthogonal to "open vs proprietary" ISA. The ways a compromise can be implemented are effectively infinite and need not be anything as obvious as an undocumented instruction. A predictor, for instance, can detect a specific sequence of instructions and fill the pipeline with whatever it wants: no undocumented instructions involved at all.