LLVM on Aarch64 Tracker

[kd-11]

LLVM doesn't work properly on aarch64. There are architectural reasons for this, particularly when used within RPCS3. There is some internal progress for all of these, so we're tracking things here to collaborate more efficiently.

• PPU LLVM
  • Breaking from guest to hypervisor (escape) is broken because of callstack unwinding being incompatible with LLVM's GHC implementation on aarch64.
    • Worked around by having a manual call stack.
  • LLVM is clobbering the link register in GHC blocks making them noreturn.
    • Worked around by modifying LLVM's reserved register list for GHC to at least leave the LR alone.
    • File a report with upstream with generated blocks.
• SPU LLVM
  • Same escape issue as PPU LLVM
  • Other undiagnosed issues (list will be added)