[llvm] [CodeGenPrepare] Bail out of usubo creation if sub's parent is not the same as the comparison (PR #160358)

[via llvm-commits]

AZero13 wrote:

> I'm surprised we have wholly separate implementations for these cases. The tail of the function is identical, except for the opcode. Can you refactor this so the two share the code

See https://github.com/llvm/llvm-project/pull/160327

https://github.com/llvm/llvm-project/pull/160358