1 /*
   2  * Copyright (c) 2013, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.
   8  *
   9  * This code is distributed in the hope that it will be useful, but WITHOUT
  10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  12  * version 2 for more details (a copy is included in the LICENSE file that
  13  * accompanied this code).
  14  *
  15  * You should have received a copy of the GNU General Public License version
  16  * 2 along with this work; if not, write to the Free Software Foundation,
  17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  18  *
  19  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  20  * or visit www.oracle.com if you need additional information or have any
  21  * questions.
  22  */
  23 package org.graalvm.compiler.phases.common;
  24 
  25 import java.util.List;
  26 import java.util.Set;
  27 
  28 import org.graalvm.compiler.graph.Node;
  29 import org.graalvm.compiler.nodes.AbstractMergeNode;
  30 import org.graalvm.compiler.nodes.FixedNode;
  31 import org.graalvm.compiler.nodes.StartNode;
  32 import org.graalvm.compiler.nodes.StructuredGraph;
  33 import org.graalvm.compiler.nodes.ValueNode;
  34 import org.graalvm.compiler.nodes.extended.ValueAnchorNode;
  35 import org.graalvm.compiler.phases.Phase;
  36 import org.graalvm.compiler.phases.graph.MergeableState;
  37 import org.graalvm.compiler.phases.graph.SinglePassNodeIterator;
  38 
  39 /**
  40  * This phase performs a bit of hygiene on {@link ValueAnchorNode} by removing inputs that have
  41  * already been anchored in a dominating value anchor. Value anchors that lose their last input,
  42  * have no usages and are not marked as permanent are removed.
  43  */
  44 public class ValueAnchorCleanupPhase extends Phase {
  45 
  46     private static class State extends MergeableState<State> implements Cloneable {
  47 
  48         private final Set<Node> anchoredValues;
  49 
  50         State() {
  51             anchoredValues = Node.newSet();
  52         }
  53 
  54         State(State other) {
  55             anchoredValues = Node.newSet(other.anchoredValues);
  56         }
  57 
  58         @Override
  59         public boolean merge(AbstractMergeNode merge, List<State> withStates) {
  60             for (State other : withStates) {
  61                 anchoredValues.retainAll(other.anchoredValues);
  62             }
  63             return true;
  64         }
  65 
  66         @Override
  67         public State clone() {
  68             return new State(this);
  69         }
  70     }
  71 
  72     private static class CleanupValueAnchorsClosure extends SinglePassNodeIterator<State> {
  73 
  74         CleanupValueAnchorsClosure(StartNode start) {
  75             super(start, new State());
  76         }
  77 
  78         @Override
  79         protected void node(FixedNode node) {
  80             if (node instanceof ValueAnchorNode) {
  81                 ValueAnchorNode anchor = (ValueAnchorNode) node;
  82                 ValueNode anchored = anchor.getAnchoredNode();
  83                 if (anchored != null) {
  84                     if (state.anchoredValues.contains(anchored)) {
  85                         anchor.removeAnchoredNode();
  86                     } else {
  87                         state.anchoredValues.add(anchored);
  88                     }
  89                 }
  90                 if (anchor.getAnchoredNode() == null && anchor.hasNoUsages()) {
  91                     node.graph().removeFixed(anchor);
  92                 }
  93             }
  94         }
  95     }
  96 
  97     @Override
  98     protected void run(StructuredGraph graph) {
  99         CleanupValueAnchorsClosure closure = new CleanupValueAnchorsClosure(graph.start());
 100         closure.apply();
 101     }
 102 }