Chris@82: (*
Chris@82:  * Copyright (c) 1997-1999 Massachusetts Institute of Technology
Chris@82:  * Copyright (c) 2003, 2007-14 Matteo Frigo
Chris@82:  * Copyright (c) 2003, 2007-14 Massachusetts Institute of Technology
Chris@82:  *
Chris@82:  * This program is free software; you can redistribute it and/or modify
Chris@82:  * it under the terms of the GNU General Public License as published by
Chris@82:  * the Free Software Foundation; either version 2 of the License, or
Chris@82:  * (at your option) any later version.
Chris@82:  *
Chris@82:  * This program is distributed in the hope that it will be useful,
Chris@82:  * but WITHOUT ANY WARRANTY; without even the implied warranty of
Chris@82:  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
Chris@82:  * GNU General Public License for more details.
Chris@82:  *
Chris@82:  * You should have received a copy of the GNU General Public License
Chris@82:  * along with this program; if not, write to the Free Software
Chris@82:  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
Chris@82:  *
Chris@82:  *)
Chris@82: 
Chris@82: open Util
Chris@82: 
Chris@82: (* Here, we have functions to transform a sequence of assignments
Chris@82:    (variable = expression) into a DAG (a directed, acyclic graph).
Chris@82:    The nodes of the DAG are the assignments, and the edges indicate
Chris@82:    dependencies.  (The DAG is analyzed in the scheduler to find an
Chris@82:    efficient ordering of the assignments.)
Chris@82: 
Chris@82:    This file also contains utilities to manipulate the DAG in various
Chris@82:    ways. *)
Chris@82: 
Chris@82: (********************************************
Chris@82:  *  Dag structure
Chris@82:  ********************************************)
Chris@82: type color = RED | BLUE | BLACK | YELLOW
Chris@82: 
Chris@82: type dagnode = 
Chris@82:     { assigned: Variable.variable;
Chris@82:       mutable expression: Expr.expr;
Chris@82:       input_variables: Variable.variable list;
Chris@82:       mutable successors: dagnode list;
Chris@82:       mutable predecessors: dagnode list;
Chris@82:       mutable label: int;
Chris@82:       mutable color: color}
Chris@82: 
Chris@82: type dag = Dag of (dagnode list)
Chris@82: 
Chris@82: (* true if node uses v *)
Chris@82: let node_uses v node = 
Chris@82:   List.exists (Variable.same v) node.input_variables
Chris@82: 
Chris@82: (* true if assignment of v clobbers any input of node *)
Chris@82: let node_clobbers node v = 
Chris@82:   List.exists (Variable.same_location v) node.input_variables
Chris@82: 
Chris@82: (* true if nodeb depends on nodea *)
Chris@82: let depends_on nodea nodeb =
Chris@82:   node_uses nodea.assigned nodeb ||
Chris@82:   node_clobbers nodea nodeb.assigned
Chris@82: 
Chris@82: (* transform an assignment list into a dag *)
Chris@82: let makedag alist =
Chris@82:   let dag = List.map
Chris@82:       (fun assignment ->
Chris@82: 	let (v, x) = assignment in
Chris@82: 	{ assigned = v;
Chris@82: 	  expression = x;
Chris@82: 	  input_variables = Expr.find_vars x;
Chris@82: 	  successors = [];
Chris@82: 	  predecessors = [];
Chris@82: 	  label = 0;
Chris@82: 	  color = BLACK })
Chris@82:       alist
Chris@82:   in begin
Chris@82:     for_list dag (fun i ->
Chris@82: 	for_list dag (fun j ->
Chris@82: 	  if depends_on i j then begin
Chris@82: 	    i.successors <- j :: i.successors;
Chris@82: 	    j.predecessors <- i :: j.predecessors;
Chris@82: 	  end));
Chris@82:     Dag dag;
Chris@82:   end
Chris@82: 
Chris@82: let map f (Dag dag) = Dag (List.map f dag)
Chris@82: let for_all (Dag dag) f = 
Chris@82:   (* type system loophole *)
Chris@82:   let make_unit _ = () in
Chris@82:   make_unit (List.map f dag)
Chris@82: let to_list (Dag dag) = dag
Chris@82: 
Chris@82: let find_node f (Dag dag) = Util.find_elem f dag
Chris@82: 
Chris@82: (* breadth-first search *)
Chris@82: let rec bfs (Dag dag) node init_label =
Chris@82:   let _ =  node.label <- init_label in
Chris@82:   let rec loop = function
Chris@82:       [] -> ()
Chris@82:     | node :: rest ->
Chris@82: 	let neighbors = node.predecessors @ node.successors in
Chris@82: 	let m = min_list (List.map (fun node -> node.label) neighbors) in
Chris@82: 	if (node.label > m + 1) then begin
Chris@82: 	  node.label <- m + 1;
Chris@82: 	  loop (rest @ neighbors);
Chris@82: 	end else
Chris@82: 	  loop rest
Chris@82:   in let neighbors = node.predecessors @ node.successors in
Chris@82:   loop neighbors
Chris@82: