[llvm] [InstCombine] Remove Store when its Ptr is removable (PR #79565)

[Matt Arsenault via llvm-commits]

arsenm wrote:

> Possibly the error message just needs to be improved to make it clear that this is not necessary a problem?

I think the message definitely should be improved. Downgrade the message to warning?

> > Put up a WIP https://github.com/arsenm/llvm-project/tree/issue68120-worklist-issue
> 
> This will miscompile cases if there are multiple uses along the stripped chain, I think?

I started guarding against these, but so far I haven't had much luck avoiding the second iteration in the mixed multiple use cases. 

https://github.com/llvm/llvm-project/pull/79565