Can I debug llvm source code by iMac Xcode?

Hi,

I can build llvm3.1 source code by CMAKE first, which generate LLVM.xcodeproj. And then open it by iMac Xcode and build llvm project execution files, clang, llc, llvm-as, ... . But I don't know how to debug it on Xcode IDE since the menu "Product -- Test" is grey color (not enabled). I am writing a llvm backend for fun and used to debug it on linux by gdb -args llc ... . I really hope to run IDE debug for llvm backend. Could someone please let me know your debug tool in llvm development. Should I do debug in linux or Xcode?

Best regards

Jonathan