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      1 /*
      2  * Copyright (C) 2007 The Android Open Source Project
      3  *
      4  * Licensed under the Apache License, Version 2.0 (the "License");
      5  * you may not use this file except in compliance with the License.
      6  * You may obtain a copy of the License at
      7  *
      8  *      http://www.apache.org/licenses/LICENSE-2.0
      9  *
     10  * Unless required by applicable law or agreed to in writing, software
     11  * distributed under the License is distributed on an "AS IS" BASIS,
     12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
     13  * See the License for the specific language governing permissions and
     14  * limitations under the License.
     15  */
     16 
     17 package com.android.dx.ssa.back;
     18 
     19 import com.android.dx.ssa.SetFactory;
     20 import com.android.dx.util.IntSet;
     21 import java.util.ArrayList;
     22 
     23 /**
     24  * A register interference graph
     25  */
     26 public class InterferenceGraph {
     27     /**
     28      * {@code non-null;} interference graph, indexed by register in
     29      * both dimensions
     30      */
     31     private final ArrayList<IntSet> interference;
     32 
     33     /**
     34      * Creates a new graph.
     35      *
     36      * @param countRegs {@code >= 0;} the start count of registers in
     37      * the namespace. New registers can be added subsequently.
     38      */
     39     public InterferenceGraph(int countRegs) {
     40         interference = new ArrayList<IntSet>(countRegs);
     41 
     42         for (int i = 0; i < countRegs; i++) {
     43             interference.add(SetFactory.makeInterferenceSet(countRegs));
     44         }
     45     }
     46 
     47     /**
     48      * Adds a register pair to the interference/liveness graph. Parameter
     49      * order is insignificant.
     50      *
     51      * @param regV one register index
     52      * @param regW another register index
     53      */
     54     public void add(int regV, int regW) {
     55         ensureCapacity(Math.max(regV, regW) + 1);
     56 
     57         interference.get(regV).add(regW);
     58         interference.get(regW).add(regV);
     59     }
     60 
     61     /**
     62      * Dumps interference graph to stdout for debugging.
     63      */
     64     public void dumpToStdout() {
     65         int oldRegCount = interference.size();
     66 
     67         for (int i = 0; i < oldRegCount; i++) {
     68             StringBuilder sb = new StringBuilder();
     69 
     70             sb.append("Reg " + i + ":" + interference.get(i).toString());
     71 
     72             System.out.println(sb.toString());
     73         }
     74     }
     75 
     76     /**
     77      * Merges the interference set for a register into a given bit set
     78      *
     79      * @param reg {@code >= 0;} register
     80      * @param set {@code non-null;} interference set; will be merged
     81      * with set for given register
     82      */
     83     public void mergeInterferenceSet(int reg, IntSet set) {
     84         if (reg < interference.size()) {
     85             set.merge(interference.get(reg));
     86         }
     87     }
     88 
     89     /**
     90      * Ensures that the interference graph is appropriately sized.
     91      *
     92      * @param size requested minumum size
     93      */
     94     private void ensureCapacity(int size) {
     95         int countRegs = interference.size();
     96 
     97         interference.ensureCapacity(size);
     98 
     99         for (int i = countRegs; i < size; i++) {
    100             interference.add(SetFactory.makeInterferenceSet(size));
    101         }
    102     }
    103 }
    104