[llvm] [LTO] Run Argument Promotion before IPSCCP (PR #111163)

[Hari Limaye via llvm-commits]

hazzlim wrote:

> I tested this a while ago but didn't post here: https://llvm-compile-time-tracker.com/compare.php?from=bf488ed6e1fbe4c494a1dc0dd199a3d03405784e&to=a4fe1ec912f4a2479218fc2d30ccbc8cf82cf782&stat=instructions:u It's indeed surprisingly cheap to run these extra passes.
> 
> A question I have here if this problem is somehow specific to LTO, or whether you just happen to be optimizing for LTO?

Thanks for sharing these results, they seem mostly in line with what I have been seeing so that's good!

We just happened to be concentrating on improving the LTO pipeline here - I think that this would also be beneficial to non-LTO, provided the compile-time impact wasn't prohibitive there either. 

Would it be preferred to make pipeline changes like this to LTO and non-LTO in separate PRs, or all in one go?

https://github.com/llvm/llvm-project/pull/111163