[llvm] [SimplifyCFG] Fix Missing Case Computation for Arbitrary Width Integers (PR #77831)

[Qiongsi Wu via llvm-commits]

qiongsiwu wrote:

>     * `switch i128` is rare in real code.
> 
>     * It is impossible to convert it into jump table.

Sounds good! The PR is revised. I kept the test case to "document" the behaviour, but I can take it out if it is not necessary. 



https://github.com/llvm/llvm-project/pull/77831