[snipe.git] / trans / temp.sml

(* L3 Compiler
 * Temporaries
 * Author: Kaustuv Chaudhuri <kaustuv+@cs.cmu.edu>
 * Modified: Alex Vaynberg <alv@andrew.cmu.edu>
 * Modified: Frank Pfenning <fp@cs.cmu.edu>
 *)

signature TEMP = 
sig
  type temp
  datatype size = Byte | Word | Long | Quad

  val reset : unit -> unit           (* resets temp numbering *)
  val new : string -> size -> temp   (* returns a unique new temp *)
  val name : temp -> string          (* returns the name of a temp *)
  val size : temp -> size            (* returns the size of a temp *)
  val compare : temp * temp -> order (* comparison function *)
  val eq : temp * temp -> bool
  val cmpsize : size * size -> order
  val sfx : size -> string
  val sts : int -> size
end

structure Temp :> TEMP = 
struct
  datatype size = Byte | Word | Long | Quad
  type temp = int * string * size

  local
    val counter = ref 1
  in
    (* warning: calling reset() may jeopardize uniqueness of temps! *)
    fun reset () = ( counter := 1 )
    fun new str size = (!counter, str, size) before ( counter := !counter + 1 )
  end

  fun sfx Byte = "b"
    | sfx Word = "w"
    | sfx Long = "l"
    | sfx Quad = "q"

  fun name (t,s, sz) = "+t" ^ Int.toString t ^ "[" ^ s ^ "]" ^ sfx sz
  fun size (t, s, sz) = sz
  fun compare ((t1,_,_),(t2,_,_)) = Int.compare (t1,t2)

  fun eq ((t1,_,_), (t2,_,_)) = t1 = t2

  fun cmpsize (Quad,Quad) = EQUAL
    | cmpsize (Quad,_) = GREATER
    | cmpsize (_,Quad) = LESS
    | cmpsize (Long,Long) = EQUAL
    | cmpsize (Long,_) = GREATER
    | cmpsize (_,Long) = LESS
    | cmpsize (Word,Word) = EQUAL
    | cmpsize (Word,_) = GREATER
    | cmpsize (_,Word) = LESS
    | cmpsize (Byte,Byte) = EQUAL

  fun sts 8 = Quad
    | sts 4 = Long
    | sts 2 = Word
    | sts 1 = Byte
    | sts _ = raise ErrorMsg.InternalError "Temp.sts: invalid size"

end