[llvm] [PredicateInfo] Support existing `PredicateType` by adding `PredicatePHI` when needing introduction of phi nodes (PR #151132)

[Rajveer Singh Bharadwaj via llvm-commits]

Rajveer100 wrote:

@nikic 
I was just wondering if we could simply add a fold or case based optimization like what instcombine does by recognizing patterns rather than making changes in predicate info?

>From your point of view, do you think generalizing this covers many cases potentially apart from generalizing and using existing code?

https://github.com/llvm/llvm-project/pull/151132