[llvm] [DAG] Generalize fold (not (neg x)) -> (add X, -1) (PR #154348)

[guan jian via llvm-commits]

rez5427 wrote:

Well, I reverted the earlier changes and rebased the branch with the latest modifications to llvm/test/CodeGen/X86/shift-i128.ll. This test case had one fewer line due to this fold.

https://github.com/llvm/llvm-project/pull/154348