(* high-to-mid.sml
 *
 * COPYRIGHT (c) 2010 The Diderot Project (http://diderot.cs.uchicago.edu)
 * All rights reserved.
 *
 * Translation from HighIL to MidIL representations.
 *)

structure HighToMid : sig

    val translate : HighIL.program -> MidIL.program

  end = struct

    structure SrcIL = HighIL
    structure SrcOp = SrcIL.Op
    structure DstIL = MidIL
    structure DstOp = DstIL.Op
    structure VMap = SrcIL.Var.Map

  (* expand the field Inside operator into a image-space test *)
    fun expandInside (env, result, pos, fld) = let
	  val pos' = lookupVar (env, pos)
	  val fld = (case valueOf fld
		 of SrcIL.OP(SrcOp.Field fld, []) => fld
		  | _ => raise Fail "bogus field binding"
		(* end case *))
	  fun expand (FieldDef.CONV(_, img, _)) => let
		val imgPos = newVar ??
		in [
		  (imgPos, DstIL.OP(DstOp.Transform img, [pos'])),
		  (result, DstIL.OP(DstOp.Inside img, [imgPos]))
		] end
	    | expand (FieldDef.NEG fld) => expand fld
	    | expand (FieldDef.SUM(fld1, dlf2)) => raise Fail "expandInside: SUM"
	  in
	    expand fld
	  end

  (* generate a new variable indexed by dimension *)
    local
      val dimNames = Vector.fromList[ "x", "y", "z" ];
    in
    fun newVar_dim (prefix, d) =
	  DstIL.Var.new (prefix ^ Vector.sub(dimNames, d))

    fun assign (x, rator, args) = (x, DstIL.OP(rator, args))
    fun intLit (x, i) = (x, DstIL.LIT(Literal.Int(IntInf.fromInt i)))

    fun generate (n, f) = List.concat(List.tabulate(n, f))

  (* generate code for probing the field (D^k (v * h)) at pos *)
    fun probe (result, (k, v, h), pos) = let
	  val ImageInfo.ImgInfo{dim, ty=([], ty), ...} = v
	  val dimTy = DstOp.VecTy dim
	  val s = Kernel.support h
	  val sTy = DstOp.VecTy(2*s)
	(* generate the transform code *)
	  val x = DstIL.Var.new "x"	(* image-space position *)
	  val f = DstIL.Var.new "f"
	  val nd = DstIL.Var.new "nd"
	  val n = DstIL.Var.new "n"
	  val transformCode = [
		  assign(x, DstIL.Transform v, [pos]),
		  assign(nd, DstIL.Floor dim, [x]),
		  assign(f, DstIL.Sub dimTy, [x, nd]),
		  assign(n, DstOp.TruncToInt dim, [nd])
		]
	(* generate code to load the voxel data *)
	  fun forAxis (axis, suffix, offsets) = if (axis > 0)
		then generate (2*s, fn i => let
		    val suffix = suffix ^ Int.toString i
		    val offsets = i - (s - 1) :: offsets
		    in
		      forAxis (axis-1, suffix, offsets)
		    end)
		else let
		  fun computeIndices (_, []) = ([], [])
		    | computeIndices (i, offset::offsets) = let
			val index = newVar_dim("i", i)
			val t1 = newVar "t1"
			val t2 = newVar "t2"
			val (indices, code) = computeIndices (i+1, offsets)
			val code = intLit(t1, offset) ::
			      assign(t2, DstOp.Select i, [n]) ::
			      assign(index, DstOp.Add(DstOp.IntTy), [t1, t2]) ::
			      code
			val indices = index::indices
			in
			  (indices, code)
			end
		  val (indices, indicesCode) = computeIndices (0, ~(s-1) :: offsets)
		  val a = DstIL.Var.new "a"
		  val vox = DstIL.Var.new("v" ^ suffix)
		  in
		    indicesCode :: [
			assign(a, VoxelAddress v, indices),
			assign(vox, LoadVoxels(ty, 2*s))
		      ]
		  end
(* FIXME: we need a way to get out the voxel-vector variables too! *)
	  val loadCode = forAxis (dim-1, "", [])
	  in
	    ??
	  end

    end

    fun expandProbe (env, result, fld, pos) = let
	  val pos' = lookupVar (env, pos)
	  val fld = (case valueOf fld
		 of SrcIL.OP(SrcOp.Field fld, []) => fld
		  | _ => raise Fail "bogus field binding"
		(* end case *))
	  fun expand (result, FieldDef.CONV(0, img, h)) => let
		val imgPos = newVar ??
		val xformStm = (imgPos, DstIL.OP(DstOp.Transform img, [pos']))
(* generate samples based on kernel support and dimensionality of image *)
		in
		  xformStm :: probeStms
		end
	    | expand (FieldDef.CONV(k, img, h)) => ??
	    | expand (FieldDef.NEG fld) => let
		val r = newVar ??
		val stms = expand (r, fld)
		in
		  (r, DstIL.OP(DstOp.Neg ty, [r])) :: stms
		end
	    | expand (FieldDef.SUM(fld1, dlf2)) => raise Fail "expandInside: SUM"
	  in
	    List.rev (expand (result, fld))
	  end

  end

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	  in
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