[llvm] [EarlyCSE] Fix improper icmp simplification (PR #122043)

[Yingwei Zheng via llvm-commits]

dtcxzyw wrote:

> https://godbolt.org/z/1MfndEMMs

In this case, `%4` is passed into `_ZN1A5valueEv` which has `noundef` and `nonnull/dereferenceable` parameter attributes. The optimizer will assume `%4` is nonnull in the subsequent execution path.

Without `noundef` and `nonnull/dereferenceable`, the icmp will not be optimized out: https://godbolt.org/z/chhxE3Txr




https://github.com/llvm/llvm-project/pull/122043