1 /*
   2  * Copyright (c) 2011, 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 Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
  20  * CA 95054 USA or visit www.sun.com if you need additional information or
  21  * have any questions.
  22  *
  23  */
  24 
  25 package sun.jvm.hotspot.oops;
  26 
  27 import java.io.*;
  28 import java.util.*;
  29 import sun.jvm.hotspot.debugger.*;
  30 import sun.jvm.hotspot.runtime.*;
  31 import sun.jvm.hotspot.types.*;
  32 import sun.jvm.hotspot.utilities.*;
  33 
  34 // BitData
  35 //
  36 // A BitData holds a flag or two in its header.
  37 public class BitData extends ProfileData {
  38 
  39   // nullSeen:
  40   //  saw a null operand (cast/aastore/instanceof)
  41   static final int nullSeenFlag              = DataLayout.firstFlag + 0;
  42   static final int bitCellCount = 0;
  43 
  44   public BitData(DataLayout layout) {
  45     super(layout);
  46   }
  47 
  48   static int staticCellCount() {
  49     return bitCellCount;
  50   }
  51 
  52   public int cellCount() {
  53     return staticCellCount();
  54   }
  55 
  56   // Accessor
  57 
  58   // The nullSeen flag bit is specially known to the interpreter.
  59   // Consulting it allows the compiler to avoid setting up nullCheck traps.
  60   boolean nullSeen()     { return flagAt(nullSeenFlag); }
  61 
  62   // Code generation support
  63   // static int nullSeenByteConstant() {
  64   //   return flagNumberToByteConstant(nullSeenFlag);
  65   // }
  66 
  67   static int bitDataSize() {
  68     return cellOffset(bitCellCount);
  69   }
  70 
  71   public void printDataOn(PrintStream st) {
  72     printShared(st, "BitData");
  73   }
  74 }