[llvm] [SelectionDAG] Introduce ISD::PTRADD (PR #140017)

[Owen Anderson via llvm-commits]

https://github.com/resistor commented:

Overall LGTM and matches what we have in the cheriot downstream: https://github.com/CHERIoT-Platform/llvm-project/tree/cheriot-upstream

I have noted a couple of places where I'd like to understand some optimization divergences from what we have, but I don't think those are blockers.

That said, I would like to hear from at least one other relevant reviewer before this goes in.

https://github.com/llvm/llvm-project/pull/140017