[PATCH] D36432: [IPSCCP] Add function specialization ability

Daniel Berlin via Phabricator via llvm-commits llvm-commits at lists.llvm.org
Fri Aug 11 13:24:34 PDT 2017

dberlin added a comment.

In https://reviews.llvm.org/D36432#839506, @mssimpso wrote:

> Danny/Davide,
> Thanks very much for the feedback. I have some replies to your comments below (abridged, so it's easier to read in Phab.), but I thought I would first summarize things so far. It sounds like your main points are that (1) the cost model for function specialization is difficult to get right in practice, and that (2) our current IPSCCP infrastructure could be improved to do better than pass-through for arguments and returns. I agree with both of these points. So do we think we should iterate on this patch and add function specialization to our current infrastructure?

I'm not opposed if we have cases where it matters.
But if we can't find these cases, it's not gonna be turned on by default, and then i think our time would be better spent elsewhere.
IE i don't think it will be horribly useful to have function specialization but not have it good enough to be worth it by default.
At that point, i think'd we better off exploring different kinds of improvements (IE store function argument range info) to IPSCCP or different mechanisms of using the existing info (IE inlining)


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