--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/core_untangle.sml	Sat Nov 01 21:24:43 2008 -0400
@@ -0,0 +1,215 @@
+(* Copyright (c) 2008, Adam Chlipala
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * - Redistributions of source code must retain the above copyright notice,
+ *   this list of conditions and the following disclaimer.
+ * - Redistributions in binary form must reproduce the above copyright notice,
+ *   this list of conditions and the following disclaimer in the documentation
+ *   and/or other materials provided with the distribution.
+ * - The names of contributors may not be used to endorse or promote products
+ *   derived from this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
+ * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR 
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ *)
+
+structure CoreUntangle :> CORE_UNTANGLE = struct
+
+open Core
+
+structure U = CoreUtil
+structure E = CoreEnv
+
+structure IS = IntBinarySet
+structure IM = IntBinaryMap
+
+fun default (k, s) = s
+
+fun exp (e, s) =
+    case e of
+        ENamed n => IS.add (s, n)
+
+      | _ => s
+
+fun untangle file =
+    let
+        fun decl (dAll as (d, loc)) =
+            case d of
+                DValRec vis =>
+                let
+                    val thisGroup = foldl (fn ((_, n, _, _, _), thisGroup) =>
+                                              IS.add (thisGroup, n)) IS.empty vis
+
+                    val used = foldl (fn ((_, n, _, e, _), used) =>
+                                       let
+                                           val usedHere = U.Exp.fold {con = default,
+                                                                      kind = default,
+                                                                      exp = exp} IS.empty e
+                                       in
+                                           IM.insert (used, n, IS.intersection (usedHere, thisGroup))
+                                       end)
+                               IM.empty vis
+
+                    fun p_graph reachable =
+                        IM.appi (fn (n, reachableHere) =>
+                                    (print (Int.toString n);
+                                     print ":";
+                                     IS.app (fn n' => (print " ";
+                                                       print (Int.toString n'))) reachableHere;
+                                     print "\n")) reachable
+
+                    (*val () = print "used:\n"
+                    val () = p_graph used*)
+
+                    fun expand reachable =
+                        let
+                            val changed = ref false
+
+                            val reachable =
+                                IM.mapi (fn (n, reachableHere) =>
+                                            IS.foldl (fn (n', reachableHere) =>
+                                                         let
+                                                             val more = valOf (IM.find (reachable, n'))
+                                                         in
+                                                             if IS.isEmpty (IS.difference (more, reachableHere)) then
+                                                                 reachableHere
+                                                             else
+                                                                 (changed := true;
+                                                                  IS.union (more, reachableHere))
+                                                         end)
+                                                     reachableHere reachableHere) reachable
+                        in
+                            (reachable, !changed)
+                        end
+
+                    fun iterate reachable =
+                        let
+                            val (reachable, changed) = expand reachable
+                        in
+                            if changed then
+                                iterate reachable
+                            else
+                                reachable
+                        end
+
+                    val reachable = iterate used
+
+                    (*val () = print "reachable:\n"
+                    val () = p_graph reachable*)
+
+                    fun sccs (nodes, acc) =
+                        case IS.find (fn _ => true) nodes of
+                            NONE => acc
+                          | SOME rep =>
+                            let
+                                val reachableHere = valOf (IM.find (reachable, rep))
+
+                                val (nodes, scc) = IS.foldl (fn (node, (nodes, scc)) =>
+                                                                if node = rep then
+                                                                    (nodes, scc)
+                                                                else
+                                                                    let
+                                                                        val reachableThere =
+                                                                            valOf (IM.find (reachable, node))
+                                                                    in
+                                                                        if IS.member (reachableThere, rep) then
+                                                                            (IS.delete (nodes, node),
+                                                                             IS.add (scc, node))
+                                                                        else
+                                                                            (nodes, scc)
+                                                                    end)
+                                                   (IS.delete (nodes, rep), IS.singleton rep) reachableHere
+                            in
+                                sccs (nodes, scc :: acc)
+                            end
+
+                    val sccs = sccs (thisGroup, [])
+                    (*val () = app (fn nodes => (print "SCC:";
+                                               IS.app (fn i => (print " ";
+                                                                print (Int.toString i))) nodes;
+                                               print "\n")) sccs*)
+
+                    fun depends nodes1 nodes2 =
+                        let
+                            val node1 = valOf (IS.find (fn _ => true) nodes1)
+                            val node2 = valOf (IS.find (fn _ => true) nodes2)
+                            val reachable1 = valOf (IM.find (reachable, node1))
+                        in
+                            IS.member (reachable1, node2)
+                        end
+
+                    fun findReady (sccs, passed) =
+                        case sccs of
+                            [] => raise Fail "Untangle: Unable to topologically sort 'val rec'"
+                          | nodes :: sccs =>
+                            if List.exists (depends nodes) passed
+                               orelse List.exists (depends nodes) sccs then
+                                findReady (sccs, nodes :: passed)
+                            else
+                                (nodes, List.revAppend (passed, sccs))
+
+                    fun topo (sccs, acc) =
+                        case sccs of
+                            [] => rev acc
+                          | _ =>
+                            let
+                                val (node, sccs) = findReady (sccs, [])
+                            in
+                                topo (sccs, node :: acc)
+                            end
+
+                    val sccs = topo (sccs, [])
+                    (*val () = app (fn nodes => (print "SCC':";
+                                               IS.app (fn i => (print " ";
+                                                                print (Int.toString i))) nodes;
+                                               print "\n")) sccs*)
+
+                    fun isNonrec nodes =
+                        case IS.find (fn _ => true) nodes of
+                            NONE => NONE
+                          | SOME node =>
+                            let
+                                val nodes = IS.delete (nodes, node)
+                                val reachableHere = valOf (IM.find (reachable, node))
+                            in
+                                if IS.isEmpty nodes then
+                                    if IS.member (reachableHere, node) then
+                                        NONE
+                                    else
+                                        SOME node
+                                else
+                                    NONE
+                            end
+
+                    val ds = map (fn nodes =>
+                                     case isNonrec nodes of
+                                         SOME node =>
+                                         let
+                                             val vi = valOf (List.find (fn (_, n, _, _, _) => n = node) vis)
+                                         in
+                                             (DVal vi, loc)
+                                         end
+                                       | NONE =>
+                                         (DValRec (List.filter (fn (_, n, _, _, _) => IS.member (nodes, n)) vis), loc))
+                                 sccs
+                in
+                    ds
+                end
+              | _ => [dAll]
+    in
+        ListUtil.mapConcat decl file
+    end
+
+end