[llvm] Missed Optimization: Fold sdiv exact(((trunc x)*24 - 24), 24) into sext(trunc x - 1) (PR #201048)

[Yingwei Zheng via llvm-commits]

https://github.com/dtcxzyw requested changes to this pull request.

A correctness issue was identified by [llvm-hackme](https://github.com/dtcxzyw/llvm-hackme). Please see the [issue comment](https://github.com/llvm/llvm-project/pull/201048#issuecomment-4600262014) for details.

https://github.com/llvm/llvm-project/pull/201048