Implement stack layout (Unfinished)

Signed-off-by: Mariano Uvalle <u.g.a.mariano@gmail.com>

hw3/bin/backend.ml

@@ -87,6 +87,10 @@ let lookup m x = List.assoc x m
 
    TODO: The section below still reads like giberish,
    mabye reading the rest of the code/tests will help.
+   Update: This makes sense now, whenever you're adding two numbers together
+   or performing any operations on them, you need them to be in registers.
+   All locals in this compilation strategy are in the stack, so when
+   operating on them we need to move them to registers...
 
    One strategy for compiling instruction operands is to use a
    designated register (or registers) for holding the values being
@@ -309,7 +313,25 @@ let arg_loc (n : int) : operand =
    - see the discussion about locals
 *)
 let stack_layout (args : uid list) ((block, lbled_blocks) : cfg) : layout =
-  failwith "stack_layout not implemented"
+  (* offset is in quad unitsf.
+     We start at 0, but rbp already contains a values (rbp of the calling
+     function) so we don't count it as a valid slot, consumers should decrement
+     it before using it.
+  *)
+  let open Int64 in
+  let next_offset =
+    let offset = ref 0 in
+    let next_offset' _ =
+      offset := !offset - 1;
+      !offset
+    in
+    next_offset'
+  in
+  let op_from_offset o = Ind3 (Lit (mul 8L (of_int o)), Rbp) in
+  let layout_args =
+    List.fold_left (fun acc arg -> (arg, op_from_offset (next_offset ())) :: acc) [] args
+  in
+  layout_args
 ;;
 
 (* The code for the entry-point of a function must do several things: