[llvm] [DA] Fix symbolic RDIV and Strong SIV with impossible assumptions (PR149501) (PR #157761)

[Sebastian Pop via llvm-commits]

sebpop wrote:

> Consider using [Stacked Pull Requests](https://llvm.org/docs/GitHub.html#stacked-pull-requests).

Thanks for the pointer: a very helpful read.

Is there a way to stack PRs already created?
The docs only show how to create stacked PRs. 

https://github.com/llvm/llvm-project/pull/157761