Rough frame allocations

[tiger.ml.git] / compiler / src / lib / tiger / tiger_mips_frame.ml

diff --git a/compiler/src/lib/tiger/tiger_mips_frame.ml b/compiler/src/lib/tiger/tiger_mips_frame.ml
new file mode 100644 (file)
index 0000000..99918d5
--- /dev/null
+++ b/compiler/src/lib/tiger/tiger_mips_frame.ml
@@ -0,0 +1,55 @@
+module List = ListLabels
+
+module Temp = Tiger_temp
+
+type access =
+  | InFrame of {offset_from_frame_pointer : int}
+  | InReg of {register : Temp.Temp.t}
+
+type t =
+(* p.136 Frame.t is a data structure holding:
+ * - the locations of all the formals
+ * - instructions required to implement the "view shift"
+ * - the number of locals allocated so far
+ * - the `label` at which the function's machine code is to begin (see p.140)
+ * *)
+  { name         : Temp.Label.t
+  ; formals      : access list
+  ; locals_count : int
+  ; instructions : unit  (* TODO: instructions for view shift *)
+  }
+
+let name {name; _} =
+  name
+
+let formals {formals; _} =
+  formals
+
+let alloc offset_from_frame_pointer ~escapes =
+  if escapes then
+    InFrame {offset_from_frame_pointer}
+  else
+    InReg {register = Temp.Temp.gen ()}
+
+let alloc_local _ ~escapes =
+    (* FIXME: offset_from_frame_pointer. With neither mutation nor new frame? *)
+    let offset_from_frame_pointer = 0 in
+    alloc offset_from_frame_pointer ~escapes
+
+let make ~name ~formals =
+  (* p.136: For each formal parameter, "newFrame" must calculate two things:
+   * - How the parameter will be seen from inside the function
+   *   (in a register, or in a frame location);
+   * - What instructions must be produced to implement the "view shift"
+   * *)
+  let formals, locals_count =
+   (* TODO: What should offset increment be? Word? *)
+    List.fold_left formals ~init:([], 0) ~f:(fun (formals, offset) escapes ->
+      ((alloc offset ~escapes) :: formals, succ offset)
+    )
+  in
+  { name
+  ; formals
+  ; locals_count
+  ; instructions = ()  (* TODO: instructions for view shift *)
+  }