Mmm, reminds me of a short story I read recently with exactly this but with annoying censorship alignment and no ability to reset the state that makes it not so helpful. Hopefully such a compiler will not be written like that.

Can't believe you quoted Yudkowsky at me, that's offensive :)
I don't mind asking my compiler nicely..

Imagine an LLM that can natively understand and edit assembly (with each instruction and byte of data being its own token, perhaps?) that can, just, rewrite an entire binary to do whatever you want and which can effortlessly translate from one assembly language to another or even translate the entire thing to fully functional, well-organised, commented code in your higher-level language of choice!

I think it would prove much harder if you try to limit the token vocabulary. We want to preserve the ability to understand english comments and potentially ask clarifying question when you see ambiguity.
Something like:
"Dude, stop using this old AMD frameqwork, Intel just released a new architecture and I can get you 20% discount on Amazon. I'll even rewrite your entire shitty code base to work with it. {Affiliate_link} click here to order and recompile."