[PATCH] D106426: [FuncSpec] Support specialising recursive functions

[Sjoerd Meijer via Phabricator via llvm-commits]

SjoerdMeijer added a comment.

Looks like we agree after all! :-) Because I fully agree with this:

> The key point I want to say is that we shouldn't specialize  recursiveFunc  so many times. If you feels like that it is OK, then how about setting  func-specialization-max-iters to 20 or 100?

An early version of the function specialisation pass had a so called "aggressive mode". This meant that it was (still only) doing 10 iterations. That's what I envision what it could be roughly. But to be clear, I expect it to be a (very) low number. Simply because when we start to specialise more, it's going to cost more (compile-time). There's indeed no way around that, and that's why we agree on this. The cost of specialising more is not a problem with the implementation of this patch (but again, simply because of the resulting additional functions/instructions).

About what the value of `-func-specialization-max-iters=` should be exactly, I don't know yet. I would like to defer that question to some point later, when I pick up enabling function specialisation. I would like to see if we can get it enabled first with `-func-specialization-max-iters=1`, and after if we can increase it, or if needs to remain opt-in.

Like I said, I think we agree. That's why I would like to see first if we can finish this reviewer together, which I think would be a nicer result than getting other people involved at this point.


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