[DAGCombine] Refactor common addcarry pattern.

Summary: This pattern is no very useful per se, but it exposes optimization for toehr patterns that wouldn't kick in otherwize. It's very common and worth optimizing for.

Reviewers: jyknight, nemanjai, mkuper, spatel, RKSimon, zvi, bkramer

Subscribers: llvm-commits

Differential Revision: https://reviews.llvm.org/D32756

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@304402 91177308-0d34-0410-b5e6-96231b3b80d8
2 files changed