Has the jit3 been ported to any 64 bit architectures yet? I might have found something nasty: When prologue(Method* meth) in jit3/icode.c is called it calls _slot_const_const(0, (jword)l, (jword)meth, HAVE_prologue, Tnull); (via the slot_const_const macro) where l is a label pointer (64 bit in my case)