--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/graal/GraalCompiler/src/com/sun/c1x/gen/PhiResolver.java	Wed Apr 27 11:50:44 2011 +0200
@@ -0,0 +1,238 @@
+/*
+ * Copyright (c) 2009, 2010, Oracle and/or its affiliates. All rights reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+package com.sun.c1x.gen;
+
+import static com.sun.cri.ci.CiValue.*;
+
+import java.util.*;
+
+import com.sun.c1x.ir.*;
+import com.sun.cri.ci.*;
+
+/**
+ * Converts {@link Phi} instructions into moves.
+ *
+ * Resolves cycles:
+ * <pre>
+ *
+ *  r1 := r2  becomes  temp := r1
+ *  r2 := r1           r1 := r2
+ *                     r2 := temp
+ * </pre>
+ *
+ * and orders moves:
+ *
+ * <pre>
+ *  r2 := r3  becomes  r1 := r2
+ *  r1 := r2           r2 := r3
+ * </pre>
+ *
+ * @author Marcelo Cintra
+ * @author Thomas Wuerthinger
+ * @author Doug Simon
+ */
+public class PhiResolver {
+
+    /**
+     * Tracks a data flow dependency between a source operand and any number of the destination operands.
+     */
+    static class Node {
+
+        /**
+         * A source operand whose value flows into the {@linkplain #destinations destination} operands.
+         */
+        final CiValue operand;
+
+        /**
+         * The operands whose values are defined by the {@linkplain #operand source} operand.
+         */
+        final ArrayList<Node> destinations;
+
+        /**
+         * Denotes if a move instruction has already been emitted to initialize the value of {@link #operand}.
+         */
+        boolean assigned;
+
+        /**
+         * Specifies if this operand been visited for the purpose of emitting a move instruction.
+         */
+        boolean visited;
+
+        /**
+         * Specifies if this is the initial definition in data flow path for a given value.
+         */
+        boolean startNode;
+
+        Node(CiValue operand) {
+            this.operand = operand;
+            destinations = new ArrayList<Node>(4);
+        }
+
+        @Override
+        public String toString() {
+            StringBuilder buf = new StringBuilder(operand.toString());
+            if (!destinations.isEmpty()) {
+                buf.append(" ->");
+                for (Node node : destinations) {
+                    buf.append(' ').append(node.operand);
+                }
+            }
+            return buf.toString();
+        }
+    }
+
+    private final LIRGenerator gen;
+
+    /**
+     * The operand loop header phi for the operand currently being process in {@link #dispose()}.
+     */
+    private Node loop;
+
+    private CiValue temp;
+
+    private final ArrayList<Node> variableOperands = new ArrayList<Node>(3);
+    private final ArrayList<Node> otherOperands = new ArrayList<Node>(3);
+
+    /**
+     * Maps operands to nodes.
+     */
+    private final HashMap<CiValue, Node> operandToNodeMap = new HashMap<CiValue, Node>();
+
+    public PhiResolver(LIRGenerator gen) {
+        this.gen = gen;
+        temp = IllegalValue;
+    }
+
+    public void dispose() {
+        // resolve any cycles in moves from and to variables
+        for (int i = variableOperands.size() - 1; i >= 0; i--) {
+            Node node = variableOperands.get(i);
+            if (!node.visited) {
+                loop = null;
+                move(null, node);
+                node.startNode = true;
+                assert temp.isIllegal() : "moveTempTo() call missing";
+            }
+        }
+
+        // generate move for move from non variable to arbitrary destination
+        for (int i = otherOperands.size() - 1; i >= 0; i--) {
+            Node node = otherOperands.get(i);
+            for (int j = node.destinations.size() - 1; j >= 0; j--) {
+                emitMove(node.operand, node.destinations.get(j).operand);
+            }
+        }
+    }
+
+    public void move(CiValue src, CiValue dest) {
+        assert dest.isVariable() : "destination must be virtual";
+        // tty.print("move "); src.print(); tty.print(" to "); dest.print(); tty.cr();
+        assert src.isLegal() : "source for phi move is illegal";
+        assert dest.isLegal() : "destination for phi move is illegal";
+        Node srcNode = sourceNode(src);
+        Node destNode = destinationNode(dest);
+        srcNode.destinations.add(destNode);
+      }
+
+    private Node createNode(CiValue operand, boolean source) {
+        Node node;
+        if (operand.isVariable()) {
+            node = operandToNodeMap.get(operand);
+            assert node == null || node.operand.equals(operand);
+            if (node == null) {
+                node = new Node(operand);
+                operandToNodeMap.put(operand, node);
+            }
+            // Make sure that all variables show up in the list when
+            // they are used as the source of a move.
+            if (source) {
+                if (!variableOperands.contains(node)) {
+                    variableOperands.add(node);
+                }
+            }
+        } else {
+            assert source;
+            node = new Node(operand);
+            otherOperands.add(node);
+        }
+        return node;
+    }
+
+    private Node destinationNode(CiValue opr) {
+        return createNode(opr, false);
+    }
+
+    private void emitMove(CiValue src, CiValue dest) {
+        assert src.isLegal();
+        assert dest.isLegal();
+        gen.lir.move(src, dest);
+    }
+
+    // Traverse assignment graph in depth first order and generate moves in post order
+    // ie. two assignments: b := c, a := b start with node c:
+    // Call graph: move(NULL, c) -> move(c, b) -> move(b, a)
+    // Generates moves in this order: move b to a and move c to b
+    // ie. cycle a := b, b := a start with node a
+    // Call graph: move(NULL, a) -> move(a, b) -> move(b, a)
+    // Generates moves in this order: move b to temp, move a to b, move temp to a
+    private void move(Node src, Node dest) {
+        if (!dest.visited) {
+            dest.visited = true;
+            for (int i = dest.destinations.size() - 1; i >= 0; i--) {
+                move(dest, dest.destinations.get(i));
+            }
+        } else if (!dest.startNode) {
+            // cycle in graph detected
+            assert loop == null : "only one loop valid!";
+            loop = dest;
+            moveToTemp(src.operand);
+            return;
+        } // else dest is a start node
+
+        if (!dest.assigned) {
+            if (loop == dest) {
+                moveTempTo(dest.operand);
+                dest.assigned = true;
+            } else if (src != null) {
+                emitMove(src.operand, dest.operand);
+                dest.assigned = true;
+            }
+        }
+    }
+
+    private void moveTempTo(CiValue dest) {
+        assert temp.isLegal();
+        emitMove(temp, dest);
+        temp = IllegalValue;
+    }
+
+    private void moveToTemp(CiValue src) {
+        assert temp.isIllegal();
+        temp = gen.newVariable(src.kind);
+        emitMove(src, temp);
+    }
+
+    private Node sourceNode(CiValue opr) {
+        return createNode(opr, true);
+    }
+}