[PATCH] D100802: [PassManager] add late LICM to LTO pipeline to undo InstCombine sinking

[Roman Lebedev via Phabricator via llvm-commits]

lebedev.ri added a comment.

In D100802#2701348 <https://reviews.llvm.org/D100802#2701348>, @spatel wrote:

> Patch updated:
> Add explicit late LoopPassManager for LICM and disable MemorySSA usage from LICM pass on NewPM.
>
> Hopefully, that matches what was suggested in the inline comment. Let me know if not. I should learn more about how the new PM works... 
> It's not clear to me what the analogous change would look like for OldPM - set the Cap options to zero?

That didn't help:
https://llvm-compile-time-tracker.com/compare.php?from=8a6772f3aa92fdf6d01303adfef0e05f5651ea7d&to=b39f226e628eb2b58e63848985bf5c2af8a1a8d7&stat=instructions

I personally think the problem isn't MSSA, but the fact that we run this Loop pass manager
after main function pass manager finishes, thus losing cache locality.


CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D100802/new/

https://reviews.llvm.org/D100802