title: Changing calling convention in gcc/g++ abi
body: <p>How could I enforce gcc/g++ to not use registers but only stack in x86_64
  to pass arguments to functions,
  like it was in 32-bit version
  (and possibly take the function result this way).
  I know it breaks official ABI and both the caller side and the called side
  must be compiled this way so it works. I don't care if push/pop or mov/sub way
  is used. I expect there should be a flag to compiler that could enforce it
  but I couldn't find it.</p>