[llvm] [InstCombine] Fold `(x < 2^32) & (trunc(x to i32) == 0)` into `x == 0` (PR #171195)

[Tirthankar Mazumder via llvm-commits]

wermos wrote:

I've redone the entire implementation. I removed my previous changes and modified `decomposeBitTestICmp` to convert the `trunc X` into a `X & Mask`.

https://github.com/llvm/llvm-project/pull/171195