1 /*
   2  * Copyright (c) 2012, 2018, 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 
  24 
  25 package org.graalvm.compiler.loop;
  26 
  27 import org.graalvm.compiler.core.common.type.Stamp;
  28 import org.graalvm.compiler.debug.GraalError;
  29 import org.graalvm.compiler.nodes.NodeView;
  30 import org.graalvm.compiler.nodes.StructuredGraph;
  31 import org.graalvm.compiler.nodes.ValueNode;
  32 
  33 /**
  34  * This class describes a value node that is an induction variable in a counted loop.
  35  */
  36 public abstract class InductionVariable {
  37 
  38     public enum Direction {
  39         Up,
  40         Down;
  41 
  42         public Direction opposite() {
  43             switch (this) {
  44                 case Up:
  45                     return Down;
  46                 case Down:
  47                     return Up;
  48                 default:
  49                     throw GraalError.shouldNotReachHere();
  50             }
  51         }
  52     }
  53 
  54     public abstract StructuredGraph graph();
  55 
  56     protected final LoopEx loop;
  57 
  58     public InductionVariable(LoopEx loop) {
  59         this.loop = loop;
  60     }
  61 
  62     public LoopEx getLoop() {
  63         return loop;
  64     }
  65 
  66     public abstract Direction direction();
  67 
  68     /**
  69      * Returns the value node that is described by this induction variable.
  70      */
  71     public abstract ValueNode valueNode();
  72 
  73     /**
  74      * Returns the node that gives the initial value of this induction variable.
  75      */
  76     public abstract ValueNode initNode();
  77 
  78     /**
  79      * Returns the stride of the induction variable. The stride is the value that is added to the
  80      * induction variable at each iteration.
  81      */
  82     public abstract ValueNode strideNode();
  83 
  84     public abstract boolean isConstantInit();
  85 
  86     public abstract boolean isConstantStride();
  87 
  88     public abstract long constantInit();
  89 
  90     public abstract long constantStride();
  91 
  92     /**
  93      * Returns the extremum value of the induction variable. The extremum value is the value of the
  94      * induction variable in the loop body of the last iteration, only taking into account the main
  95      * loop limit test. It's possible for the loop to exit before this value if
  96      * {@link CountedLoopInfo#isExactTripCount()} returns false for the containing loop.
  97      */
  98     public ValueNode extremumNode() {
  99         return extremumNode(false, valueNode().stamp(NodeView.DEFAULT));
 100     }
 101 
 102     public abstract ValueNode extremumNode(boolean assumePositiveTripCount, Stamp stamp);
 103 
 104     public abstract boolean isConstantExtremum();
 105 
 106     public abstract long constantExtremum();
 107 
 108     /**
 109      * Returns the exit value of the induction variable. The exit value is the value of the
 110      * induction variable at the loop exit.
 111      */
 112     public abstract ValueNode exitValueNode();
 113 
 114     /**
 115      * Deletes any nodes created within the scope of this object that have no usages.
 116      */
 117     public abstract void deleteUnusedNodes();
 118 }