[clang] [llvm] [BasicAA] Do not decompose past casts with different index width (PR #119365)

[Ulrich Weigand via llvm-commits]

uweigand wrote:

@redstar looks like this disables an optimization on z/OS with mixed pointer widths.  Please have a look whether this is relevant.

https://github.com/llvm/llvm-project/pull/119365