[llvm] [InstCombine] Fold selection between less than zero and one (PR #69961)

[via llvm-commits]

XChy wrote:

> Then the optimization in this patch is handled somewhere?

Yes. What we need to do is just making `A pred C ? (A << BW - 1) : 1` -> `ZExt(A pred C ? A < 0 : 1)`. This form is easier to fold in other optimization.

https://github.com/llvm/llvm-project/pull/69961