[llvm] Reland [SimplifyCFG] Delete the unnecessary range check for small mask operation (PR #70542)

[via llvm-commits]

https://github.com/zmodem commented:

I think we misunderstood each other. I meant we should have a test where the default case is reasonable, but does not yield a constant value. For example because it calls a function and feeds the return value to the phi node.

https://github.com/llvm/llvm-project/pull/70542