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

[Sjoerd Meijer via Phabricator via llvm-commits]

SjoerdMeijer added a comment.

Okay, if we want to do this here, then we need clarity on the exact problem, which is lacking at the moment. You mentioned "scary" a few times, but there's nothing scary here. ;-) First of all, this is an extra option that people need to buy into, so changes won't bother anyone.

About the suspected problem:

> I think the problem may come from there is no restriction between iterations.

I don't think this is the case. In next iterations, exactly the same cost-model and heuristics are applied. Thus, I expect that if a function was not specialised before, it won't be specialised in a next iteration. Except, for recursive functions that need to be triggered by a very specific optimisation first between iterations.

Thus, without exact clarity of the problem, this feels like a premature optimisation to me, so we can do 2 things:

- I guess it's up to me to show with performance numbers if there is a problem or not. Before doing that, I would appreciate if you can elaborate on the suspected problems (just to make sure I understand them).
- if you're happy with my explanation thus far, and that this is an opt-in anyway, we can defer the compile time analysis that I need to do anyway when I plan to look into enable function specialisation by default.


CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D106426/new/

https://reviews.llvm.org/D106426