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

[Shivam Gupta via llvm-commits]

xgupta wrote:

Thanks, @nikic for the fix. How do you get the bc/ll file for llvm-reduce i.e. which flag is used when building python?

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