[clang] [Clang][CodeGen] Use ptrtoaddr for pointer diff (PR #210729)

[Nikita Popov via cfe-commits]

nikic wrote:

I think we still need https://github.com/llvm/llvm-project/pull/180244 first. @fhahn What's the status on that?

https://github.com/llvm/llvm-project/pull/210729