[llvm] [WIP] [GlobalIsel] Add combine for select with constants (PR #121088)

[Christudasan Devadasan via llvm-commits]

cdevadas wrote:

> But, here we add the latter missing combine for select in globalIsel.

This description is ambiguous. Does GlobalISel currently support only the latter?

https://github.com/llvm/llvm-project/pull/121088