cannam@127: (*
cannam@127:  * Copyright (c) 1997-1999 Massachusetts Institute of Technology
cannam@127:  * Copyright (c) 2003, 2007-14 Matteo Frigo
cannam@127:  * Copyright (c) 2003, 2007-14 Massachusetts Institute of Technology
cannam@127:  *
cannam@127:  * This program is free software; you can redistribute it and/or modify
cannam@127:  * it under the terms of the GNU General Public License as published by
cannam@127:  * the Free Software Foundation; either version 2 of the License, or
cannam@127:  * (at your option) any later version.
cannam@127:  *
cannam@127:  * This program is distributed in the hope that it will be useful,
cannam@127:  * but WITHOUT ANY WARRANTY; without even the implied warranty of
cannam@127:  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
cannam@127:  * GNU General Public License for more details.
cannam@127:  *
cannam@127:  * You should have received a copy of the GNU General Public License
cannam@127:  * along with this program; if not, write to the Free Software
cannam@127:  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
cannam@127:  *
cannam@127:  *)
cannam@127: 
cannam@127: open Util
cannam@127: 
cannam@127: (* Here, we have functions to transform a sequence of assignments
cannam@127:    (variable = expression) into a DAG (a directed, acyclic graph).
cannam@127:    The nodes of the DAG are the assignments, and the edges indicate
cannam@127:    dependencies.  (The DAG is analyzed in the scheduler to find an
cannam@127:    efficient ordering of the assignments.)
cannam@127: 
cannam@127:    This file also contains utilities to manipulate the DAG in various
cannam@127:    ways. *)
cannam@127: 
cannam@127: (********************************************
cannam@127:  *  Dag structure
cannam@127:  ********************************************)
cannam@127: type color = RED | BLUE | BLACK | YELLOW
cannam@127: 
cannam@127: type dagnode = 
cannam@127:     { assigned: Variable.variable;
cannam@127:       mutable expression: Expr.expr;
cannam@127:       input_variables: Variable.variable list;
cannam@127:       mutable successors: dagnode list;
cannam@127:       mutable predecessors: dagnode list;
cannam@127:       mutable label: int;
cannam@127:       mutable color: color}
cannam@127: 
cannam@127: type dag = Dag of (dagnode list)
cannam@127: 
cannam@127: (* true if node uses v *)
cannam@127: let node_uses v node = 
cannam@127:   List.exists (Variable.same v) node.input_variables
cannam@127: 
cannam@127: (* true if assignment of v clobbers any input of node *)
cannam@127: let node_clobbers node v = 
cannam@127:   List.exists (Variable.same_location v) node.input_variables
cannam@127: 
cannam@127: (* true if nodeb depends on nodea *)
cannam@127: let depends_on nodea nodeb =
cannam@127:   node_uses nodea.assigned nodeb ||
cannam@127:   node_clobbers nodea nodeb.assigned
cannam@127: 
cannam@127: (* transform an assignment list into a dag *)
cannam@127: let makedag alist =
cannam@127:   let dag = List.map
cannam@127:       (fun assignment ->
cannam@127: 	let (v, x) = assignment in
cannam@127: 	{ assigned = v;
cannam@127: 	  expression = x;
cannam@127: 	  input_variables = Expr.find_vars x;
cannam@127: 	  successors = [];
cannam@127: 	  predecessors = [];
cannam@127: 	  label = 0;
cannam@127: 	  color = BLACK })
cannam@127:       alist
cannam@127:   in begin
cannam@127:     for_list dag (fun i ->
cannam@127: 	for_list dag (fun j ->
cannam@127: 	  if depends_on i j then begin
cannam@127: 	    i.successors <- j :: i.successors;
cannam@127: 	    j.predecessors <- i :: j.predecessors;
cannam@127: 	  end));
cannam@127:     Dag dag;
cannam@127:   end
cannam@127: 
cannam@127: let map f (Dag dag) = Dag (List.map f dag)
cannam@127: let for_all (Dag dag) f = 
cannam@127:   (* type system loophole *)
cannam@127:   let make_unit _ = () in
cannam@127:   make_unit (List.map f dag)
cannam@127: let to_list (Dag dag) = dag
cannam@127: 
cannam@127: let find_node f (Dag dag) = Util.find_elem f dag
cannam@127: 
cannam@127: (* breadth-first search *)
cannam@127: let rec bfs (Dag dag) node init_label =
cannam@127:   let _ =  node.label <- init_label in
cannam@127:   let rec loop = function
cannam@127:       [] -> ()
cannam@127:     | node :: rest ->
cannam@127: 	let neighbors = node.predecessors @ node.successors in
cannam@127: 	let m = min_list (List.map (fun node -> node.label) neighbors) in
cannam@127: 	if (node.label > m + 1) then begin
cannam@127: 	  node.label <- m + 1;
cannam@127: 	  loop (rest @ neighbors);
cannam@127: 	end else
cannam@127: 	  loop rest
cannam@127:   in let neighbors = node.predecessors @ node.successors in
cannam@127:   loop neighbors
cannam@127: