[llvm] [ElimAvailExtern] Add an option to allow to convert global variables in a specified address space to local (PR #144287)

[Shilei Tian via llvm-commits]

shiltian wrote:

> This is only safe if the function is also privatized, correct? Should the new option only take effect if the Convert bool is set (ensuring functions are also privatized)? And possibly assert if not?

At a high level (from a target-independent perspective), these are separate. We want to provide an option to privatize global variables in a specified address space, that's all. For the AMDGPU LDS variable scenario specifically, it should be the driver's responsibility to make sure the correct combination of options is used.

https://github.com/llvm/llvm-project/pull/144287