[llvm] [IR] Update `PHINode::removeIncomingValueIf()` to use the swap strategy like `PHINode::removeIncomingValue()` (PR #172639)

[Ricardo Jesus via llvm-commits]

rj-jesus wrote:

That makes sense, thanks for the explanation. I don't have a use case for index-based predicates; I came across this PR while examining a few performance regressions that were flagged recently, but I'll continue looking into them next year. :) I believe there are a couple of uses of index-based predicates in LoopSimplify and LoopUtils, but they appear to be correct since they use Idx to remove all incoming values except the first.

https://github.com/llvm/llvm-project/pull/172639