[llvm] [llubi] Add support for constant inttoptr/ptrtoint expressions (PR #207028)

[Ralf Jung via llvm-commits]

RalfJung wrote:

Sorry for the slow response, I had a big deadline in $job so fell behind on notifications.

I agree that ptrtoint in a const expression makes no sense at all. That operation has a side-effect (exposing the provenance), which isn't valid for a const expression.  ptrtoaddr might make sense as a const expression though it is tricky since the actual address isn't known at compile time... but then I don't know much about const expressions in LLVM so maybe that is not a problem.

inttoptr is "fine" is the sense that the resulting pointer will have a provenance that can only access allocations that are "pre-exposed at program startup" (e.g. memory regions set up at fixed addresses by the hardware or loader).

> This patch treats constant inttoptr/ptrtoint expressions as if they are executed just before the user.

So llubi already has support for inttoptr/ptrtoint in regular code? How do those behave? That's the much more interesting  question IMO.^^

https://github.com/llvm/llvm-project/pull/207028