Yeah, sorry, everything you're saying is right. Compilers won't do the work for you. I just took issue with the wording about it being unsolved. If we can produce optimal binaries for a given process for multiple architectures we can also swap them as needed. I don't think any big new ideas need to come around, just work to implement ideas we have.
By the way, compilers can conceivably do "lowest common denominator" architecture optimization to get decent perf on heterogenous cores as a compromise, without leaning into every optimization for both core types.
