Since ldc only supports D1/Tango, you can find examples on the Tango site: http://dsource.org/projects/tango
I compile examples and look into generated *.ll but i can't find garbage collector function for LLVM like llvm_gc_allocate,llvm_gc_initialize (http://llvm.org/releases/1.9/docs/GarbageCollection.html) only variable name was %.newclass_gc_alloc