[llvm] [VPlan] Add simplifications to remove header masks in predicated AnyOf select reductions (PR #190196)

[Andrei Elovikov via llvm-commits]

eas wrote:

> The first transform on its own breaks some vp.merge patterns without the second one

> Then there's a separate existing combine in simplifyRecipes for  vp.merge true, (or x, y), x, evl -> vp.merge y, true, x, evl:

Then why do the first transformation with the root on `select` instead of matching larger single `vp.merge`/`select` pattern at once?


https://github.com/llvm/llvm-project/pull/190196