[llvm] [SimplifyCfg] Add nneg to zext for switch to table conversion (PR #147180)

[Yingwei Zheng via llvm-commits]

dtcxzyw wrote:

> Seems like there need to be some backend change also to remove the zext instruction see https://godbolt.org/z/Kc3MhxPdo

Might be related https://github.com/llvm/llvm-project/commit/b7d0c9b9d8e2b5c5d6677e368e3cdaf438df294e

https://github.com/llvm/llvm-project/pull/147180