[llvm] [DA] Add a testcase for GCD test (PR #190261)

[Ehsan Amiri via llvm-commits]

amehsan wrote:

> Since it's already past Wednesday, I'll take this over.

go ahead. I disagree with your assessment on priority of this testcase, but I am fine if you want to take it over. 

https://github.com/llvm/llvm-project/pull/190261