[llvm] [GVN] Invalidate ICF cache when clearing the instructions (PR #68145)

[Wael Yehia via llvm-commits]

w2yehia wrote:

> Thanks, @w2yehia, Can you also share how you got this test case for future purposes, I mean how do you run llvm-reduce for lto issue?

I used -save-temps to dump intermediate IR, picked the `*.0.2.internalize.bc` file, and tried it with `opt "-passes=lto<O3>"` and was able to reproduce the failure. After that I ran a bugpoint, which took few hours but was slowly making progress, so took the reduced IR, and fed into llvm-reduce which finished in few minutes.

https://github.com/llvm/llvm-project/pull/68145