[llvm] [ConstraintElim] Fold sadd.with.overflow with a constant op. (PR #223239)

[Yingwei Zheng via llvm-commits]

dtcxzyw wrote:

> No improvements in llvm-opt-benchmarks-nightly. It improves end-to-end
optimizations for Swift (which emits a lot of checked arithmetic) and
also Clang + UBsan.

https://huggingface.co/buckets/llvm-opt-benchmark/llvm-opt-benchmark/tree/box3d_ubsan
https://huggingface.co/buckets/llvm-opt-benchmark/llvm-opt-benchmark/tree/zlib-ng_ubsan

I am fine with adding more cases :)


https://github.com/llvm/llvm-project/pull/223239