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Comment by bunderbunder | Hacker News Reader

The snarky answer to that is that you just described a compiler with extra undefined behavior sprinkled in for extra excitement.

Compiled ones already translate to the theoretically fastest imperative language (machine code) using correctness preserving transforms. And plenty of them already occupy the top tier of performance for garbage collected languages. But being able to match the performance people can achieve with C, C++, etc. requires manual memory management, and that is a difficult nut for functional languages to crack because it interacts poorly with closures.

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But the undefined behavior would only apply to the performance, not to the correctness.

If we’re talking AI-assisted translation, and by AI you mean LLM, it would apply to everything.

You missed "correctness preserving transformations" in my first comment :)

If you want to be 100% sure of transformations being correctness preserving, then they need to be deterministic and formally proven to be correct.

We have had a good technology for doing that since the late 1950s, and, like I pointed out in my first reply, it already works very well.

Replacing it with a probabilistic model would not improve things. In this case, it would do the opposite of what you want because you would be replacing something that is provably and reliably able to produce correctness preserving translations with something that is fundamentally and inherently loosey-goosey.

Suppose at some point a classic algorithm can choose between doing 2 transforms. Both are correct, but one will lead to a better optimization than the other. You ask the LLM. No matter which one it chooses, you will get a correct output.

You're still describing a compiler. You want that decision to be deterministic. An LLM is a really bad solution for such a problem.

No, you use a profile-guided optimizer. Because you want that decision to be based on real empirical performance data, not a language model’s output based on conditional token probabilities.

> it already works very well.

Peephole optimization that can't be made global due to combinatorial explosion?

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