[llvm] [LV] Use original trip-count as the vector-trip-count if use predicated EVL instructions for tail-folding. (PR #132675)

[Pengcheng Wang via llvm-commits]

wangpc-pp wrote:

> I thought the consensus is that we want to keep canonical IV alive through the entire duration of loop vectorizer. And that's exactly why I chose to add a Pass right after LV to replace canonical IV with EVL IV in #131005

I understand but why we should keep the canonical IV? I did a similar change based on llvm-epi and haven't encounter any problem yet.

https://github.com/llvm/llvm-project/pull/132675