[llvm] [SimplifyCFG] Avoid sinking loads/stores that impact vectorization (PR #222587)

[Ashutosh Nema via llvm-commits]

nema-ashutosh wrote:

> Why is it not possible to handle this in the vectorizer?
> 
> I think that trying to avoid transforms to keep code in a shape the current vectorizer likes is a losing proposition, and I believe that pretty much all previous attempts to do this ultimately ended up making the vectorizer more powerful instead.

Thanks for sharing your perspective. I explored the possibility of handling this in the vectorizer, and it looks feasible. I'll prepare a change to address this in the vectorizer and share it soon. 

I hope @fhahn should also be fine with this, since we keep the sink in SimplifyCFG and only change the cases the vectorizer can actually vectorize.

https://github.com/llvm/llvm-project/pull/222587