[llvm] [Attributor] Teach HeapToStack about conservative GC allocators (PR #113299)

[Elias Naur via llvm-commits]

eliasnaur wrote:

> I'm not sure. If the memory can be free at background, a pointer could be potentially not dereferenceable. That contradicts to the `IsAssumedNoFree` here, because this `nofree` means the pointer is still dereferenceable after the function call.

Are you saying that the background freeing could happen while pointers to the memory are reachable? This is explicitly not the case for GC systems that arrange for every pointer to be unreachable before freeing the memory.

https://github.com/llvm/llvm-project/pull/113299