[llvm] [NFC][LV]: Differentiate between Pred and Unpred masked operations. (PR #169509)

[Florian Hahn via llvm-commits]

fhahn wrote:

> > Could you add a bit of additional context on how this may be used in the future?
> 
> As @hassnaaHamdi says, the goal is to add support for eliminating the scalar tail by using predicated vector epilogues in combination with an unpredicated vector body. We believe this to be a more optimal configuration since we get the best of worlds, namely:
> 
>     1. For larger runtime trip counts an unpredicated vector body is usually the best option and gives greater flexibility in terms of choice of VF and interleave factor.
> 
>     2. For low runtime trip counts we get the benefit of eliminating the scalar tail, as we'll skip the unpredicated vector body and jump straight to the predicated vector epilogue.
> 
>     3. Where we would previously have created a vector epilogue+scalar tail, we now create just a vector tail which is reduced code size.
> 
> 
> This PR is a requirement for such follow-on work.

Thanks for clarifying the goal, could you also sketch how this would be integrated a bit more concretely with the changes? I'd like to better understand how those changes will enable the new functionality.

https://github.com/llvm/llvm-project/pull/169509