[llvm] [PGO][ICP] Add separate hot count threshold for indirect call promotion (PR #206656)

[Aiden Grossman via llvm-commits]

https://github.com/boomanaiden154 commented:

Does tuning the hot count in general not provide similar wins?

This also seems like it would be pretty fragile as an optimization win. I'm also not a huge fan of generalizing `isHotCount` with a boolean flag. A `cl::opt` inside ICP I think would be cleanest.

https://github.com/llvm/llvm-project/pull/206656