[llvm] [CGP] Reconstruct borrow chain from icmp pattern for subtract-with-carry (PR #189018)

[Paweł Bylica via llvm-commits]

chfast wrote:

@RKSimon, I created the analogous combine in DAG: https://github.com/llvm/llvm-project/pull/193707. As expected, this is better when legalization is involved (see the i128 cases).

@dtcxzyw can you able to check the impact of this one?

https://github.com/llvm/llvm-project/pull/189018