1 /*
   2  * Copyright (c) 2012, 2014, 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.nodes.extended;
  24 
  25 import static org.graalvm.compiler.nodeinfo.NodeCycles.CYCLES_0;
  26 import static org.graalvm.compiler.nodeinfo.NodeSize.SIZE_0;
  27 
  28 import org.graalvm.compiler.core.common.calc.Condition;
  29 import org.graalvm.compiler.debug.GraalError;
  30 import org.graalvm.compiler.graph.NodeClass;
  31 import org.graalvm.compiler.graph.iterators.NodePredicates;
  32 import org.graalvm.compiler.graph.spi.Simplifiable;
  33 import org.graalvm.compiler.graph.spi.SimplifierTool;
  34 import org.graalvm.compiler.nodeinfo.NodeInfo;
  35 import org.graalvm.compiler.nodes.FixedGuardNode;
  36 import org.graalvm.compiler.nodes.IfNode;
  37 import org.graalvm.compiler.nodes.ReturnNode;
  38 import org.graalvm.compiler.nodes.ValueNode;
  39 import org.graalvm.compiler.nodes.calc.ConditionalNode;
  40 import org.graalvm.compiler.nodes.calc.FloatingNode;
  41 import org.graalvm.compiler.nodes.calc.IntegerEqualsNode;
  42 import org.graalvm.compiler.nodes.spi.Lowerable;
  43 import org.graalvm.compiler.nodes.spi.LoweringTool;
  44 
  45 /**
  46  * Instances of this node class will look for a preceding if node and put the given probability into
  47  * the if node's taken probability. Then the branch probability node will be removed. This node is
  48  * intended primarily for snippets, so that they can define their fast and slow paths.
  49  */
  50 @NodeInfo(cycles = CYCLES_0, cyclesRationale = "Artificial Node", size = SIZE_0)
  51 public final class BranchProbabilityNode extends FloatingNode implements Simplifiable, Lowerable {
  52 
  53     public static final NodeClass<BranchProbabilityNode> TYPE = NodeClass.create(BranchProbabilityNode.class);
  54     public static final double LIKELY_PROBABILITY = 0.6;
  55     public static final double NOT_LIKELY_PROBABILITY = 1 - LIKELY_PROBABILITY;
  56 
  57     public static final double FREQUENT_PROBABILITY = 0.9;
  58     public static final double NOT_FREQUENT_PROBABILITY = 1 - FREQUENT_PROBABILITY;
  59 
  60     public static final double FAST_PATH_PROBABILITY = 0.99;
  61     public static final double SLOW_PATH_PROBABILITY = 1 - FAST_PATH_PROBABILITY;
  62 
  63     public static final double VERY_FAST_PATH_PROBABILITY = 0.999;
  64     public static final double VERY_SLOW_PATH_PROBABILITY = 1 - VERY_FAST_PATH_PROBABILITY;
  65 
  66     @Input ValueNode probability;
  67     @Input ValueNode condition;
  68 
  69     public BranchProbabilityNode(ValueNode probability, ValueNode condition) {
  70         super(TYPE, condition.stamp());
  71         this.probability = probability;
  72         this.condition = condition;
  73     }
  74 
  75     public ValueNode getProbability() {
  76         return probability;
  77     }
  78 
  79     public ValueNode getCondition() {
  80         return condition;
  81     }
  82 
  83     @Override
  84     public void simplify(SimplifierTool tool) {
  85         if (probability.isConstant()) {
  86             double probabilityValue = probability.asJavaConstant().asDouble();
  87             if (probabilityValue < 0.0) {
  88                 throw new GraalError("A negative probability of " + probabilityValue + " is not allowed!");
  89             } else if (probabilityValue > 1.0) {
  90                 throw new GraalError("A probability of more than 1.0 (" + probabilityValue + ") is not allowed!");
  91             } else if (Double.isNaN(probabilityValue)) {
  92                 /*
  93                  * We allow NaN if the node is in unreachable code that will eventually fall away,
  94                  * or else an error will be thrown during lowering since we keep the node around.
  95                  */
  96                 return;
  97             }
  98             boolean usageFound = false;
  99             for (IntegerEqualsNode node : this.usages().filter(IntegerEqualsNode.class)) {
 100                 assert node.condition() == Condition.EQ;
 101                 ValueNode other = node.getX();
 102                 if (node.getX() == this) {
 103                     other = node.getY();
 104                 }
 105                 if (other.isConstant()) {
 106                     double probabilityToSet = probabilityValue;
 107                     if (other.asJavaConstant().asInt() == 0) {
 108                         probabilityToSet = 1.0 - probabilityToSet;
 109                     }
 110                     for (IfNode ifNodeUsages : node.usages().filter(IfNode.class)) {
 111                         usageFound = true;
 112                         ifNodeUsages.setTrueSuccessorProbability(probabilityToSet);
 113                     }
 114                     if (!usageFound) {
 115                         usageFound = node.usages().filter(NodePredicates.isA(FixedGuardNode.class).or(ConditionalNode.class)).isNotEmpty();
 116                     }
 117                 }
 118             }
 119             if (usageFound) {
 120                 ValueNode currentCondition = condition;
 121                 replaceAndDelete(currentCondition);
 122                 if (tool != null) {
 123                     tool.addToWorkList(currentCondition.usages());
 124                 }
 125             } else {
 126                 if (!isSubstitutionGraph()) {
 127                     throw new GraalError("Wrong usage of branch probability injection!");
 128                 }
 129             }
 130         }
 131     }
 132 
 133     private boolean isSubstitutionGraph() {
 134         return hasExactlyOneUsage() && usages().first() instanceof ReturnNode;
 135     }
 136 
 137     /**
 138      * This intrinsic should only be used for the condition of an if statement. The parameter
 139      * condition should also only denote a simple condition and not a combined condition involving
 140      * &amp;&amp; or || operators. It injects the probability of the condition into the if
 141      * statement.
 142      *
 143      * @param probability the probability that the given condition is true as a double value between
 144      *            0.0 and 1.0.
 145      * @param condition the simple condition without any &amp;&amp; or || operators
 146      * @return the condition
 147      */
 148     @NodeIntrinsic
 149     public static native boolean probability(double probability, boolean condition);
 150 
 151     @Override
 152     public void lower(LoweringTool tool) {
 153         throw new GraalError("Branch probability could not be injected, because the probability value did not reduce to a constant value.");
 154     }
 155 }