[llvm] [LV][EVL] Simplify EVL recipe transformation by using a single EVL mask. nfc (PR #152479)

[Mel Chen via llvm-commits]

Mel-Chen wrote:

> As an aside, its weird to begin with that there might be multiple header masks? From a quick check it only appears to happen when the data tail folding style is used, and we generate both a VPInstruction::ActiveLaneMask and a `icmp ule IV, BTC`?. I'll see if we can change this so that we only have one header mask max.

Yes, but I haven’t looked closely into the reason for having more than one header mask yet, since I’m out of office today. But I think there’s a chance we could unify them into a single header mask.


https://github.com/llvm/llvm-project/pull/152479