1 /*
   2  * Copyright (c) 2014, 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 
  24 
  25 package org.graalvm.compiler.core.common.cfg;
  26 
  27 import java.util.Collection;
  28 
  29 public interface AbstractControlFlowGraph<T extends AbstractBlockBase<T>> {
  30 
  31     int BLOCK_ID_INITIAL = -1;
  32     int BLOCK_ID_VISITED = -2;
  33 
  34     /**
  35      * Returns the list blocks contained in this control flow graph.
  36      *
  37      * It is {@linkplain CFGVerifier guaranteed} that the blocks are numbered and ordered according
  38      * to a reverse post order traversal of the control flow graph.
  39      *
  40      * @see CFGVerifier
  41      */
  42     T[] getBlocks();
  43 
  44     Collection<Loop<T>> getLoops();
  45 
  46     T getStartBlock();
  47 
  48     /**
  49      * True if block {@code a} is dominated by block {@code b}.
  50      */
  51     static boolean isDominatedBy(AbstractBlockBase<?> a, AbstractBlockBase<?> b) {
  52         int domNumberA = a.getDominatorNumber();
  53         int domNumberB = b.getDominatorNumber();
  54         return domNumberA >= domNumberB && domNumberA <= b.getMaxChildDominatorNumber();
  55     }
  56 
  57     /**
  58      * True if block {@code a} dominates block {@code b} and {@code a} is not identical block to
  59      * {@code b}.
  60      */
  61     static boolean strictlyDominates(AbstractBlockBase<?> a, AbstractBlockBase<?> b) {
  62         return a != b && dominates(a, b);
  63     }
  64 
  65     /**
  66      * True if block {@code a} dominates block {@code b}.
  67      */
  68     static boolean dominates(AbstractBlockBase<?> a, AbstractBlockBase<?> b) {
  69         assert a != null && b != null;
  70         return isDominatedBy(b, a);
  71     }
  72 
  73     /**
  74      * Calculates the common dominator of two blocks.
  75      *
  76      * Note that this algorithm makes use of special properties regarding the numbering of blocks.
  77      *
  78      * @see #getBlocks()
  79      * @see CFGVerifier
  80      */
  81     static AbstractBlockBase<?> commonDominator(AbstractBlockBase<?> a, AbstractBlockBase<?> b) {
  82         if (a == null) {
  83             return b;
  84         } else if (b == null) {
  85             return a;
  86         } else if (a == b) {
  87             return a;
  88         } else {
  89             int aDomDepth = a.getDominatorDepth();
  90             int bDomDepth = b.getDominatorDepth();
  91             AbstractBlockBase<?> aTemp;
  92             AbstractBlockBase<?> bTemp;
  93             if (aDomDepth > bDomDepth) {
  94                 aTemp = a;
  95                 bTemp = b;
  96             } else {
  97                 aTemp = b;
  98                 bTemp = a;
  99             }
 100             return commonDominatorHelper(aTemp, bTemp);
 101         }
 102     }
 103 
 104     static AbstractBlockBase<?> commonDominatorHelper(AbstractBlockBase<?> a, AbstractBlockBase<?> b) {
 105         int domNumberA = a.getDominatorNumber();
 106         AbstractBlockBase<?> result = b;
 107         while (domNumberA < result.getDominatorNumber()) {
 108             result = result.getDominator();
 109         }
 110         while (domNumberA > result.getMaxChildDominatorNumber()) {
 111             result = result.getDominator();
 112         }
 113         return result;
 114     }
 115 
 116     /**
 117      * @see AbstractControlFlowGraph#commonDominator(AbstractBlockBase, AbstractBlockBase)
 118      */
 119     @SuppressWarnings("unchecked")
 120     static <T extends AbstractBlockBase<T>> T commonDominatorTyped(T a, T b) {
 121         return (T) commonDominator(a, b);
 122     }
 123 }