[llvm] [PassBuilder] VectorizerEnd Extension Points (PR #123494)

[Min-Yih Hsu via llvm-commits]

mshockwave wrote:

> the patch looks good, but is this actually going to get used? if so the description should be updated with that info. otherwise I'd rather not add unused code

This extension point was inspired by #91796 where we need to run a Pass right after the vectorizers.

https://github.com/llvm/llvm-project/pull/123494