The existing Windows Itanium patches for dllimport/export behaviour w.r.t vtables/rtti can't be adopted for PS4 due to backwards compatibility reasons (see comments on https://reviews.llvm.org/D90299).
This review is for adding our PS4 scheme for this to Clang.
This is somewhat of a WIP. I am aware that some of these patches seem a bit awkwardly placed. Any assistance in how to refactor these patches would be extremely helpful.