[llvm] [polly] [SimpleLoopUnswitch] Don't use BlockFrequencyInfo to skip cold loops (PR #159522)

[Teresa Johnson via llvm-commits]

teresajohnson wrote:

Thanks for the data. That does look pretty compelling. We may have some binary size or compile time increase for loops that still are cold in non-cold functions - do you have any data on how many cold loops (after forcing BFI/BPA invalidation before the pass as above) will be unnecessarily unswitched after this change due to being in non-cold functions?

Also can you check a couple of instances where the loop was cold until BFI/BPA were invalidated and see why they were cold - were they new loops created by previous loop transformations? With any eventual support for loop attributes we'd need to ensure they were copied or synthesized on such new loop nests appropriately.

But generally I think this change makes sense. However, I have a question on a test change - it isn't clear to me whether the effects of this PR are being captured in a test currently.

https://github.com/llvm/llvm-project/pull/159522