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

[Nikita Popov via cfe-commits]

nikic wrote:

Thanks. I can repro now.

I believe this is a representative reduction: https://llvm.godbolt.org/z/eTrcEjf91

The relevant fold is: https://github.com/llvm/llvm-project/blob/fa3c2e9f49471a15ff9314503f9922e287a63908/llvm/lib/Analysis/InstructionSimplify.cpp#L5682-L5689

Folding this to ptrtoaddr is incorrect because we lose the provenance escape.

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