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Java example source code file (OopMapCacheEntry.java)

This example Java source code file (OopMapCacheEntry.java) is included in the alvinalexander.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" TM.

Learn more about this Java project at its project page.

Java - Java tags/keywords

bitmap, celltypestatelist, maskfillerfornative, method, offsetclosure, oopmapcacheentry, oopmapforcacheentry, verifyclosure

The OopMapCacheEntry.java Java example source code

/*
 * Copyright (c) 2001, Oracle and/or its affiliates. All rights reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.
 *
 * This code is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
 * or visit www.oracle.com if you need additional information or have any
 * questions.
 *
 */

package sun.jvm.hotspot.interpreter;

import sun.jvm.hotspot.oops.*;
import sun.jvm.hotspot.utilities.*;

public class OopMapCacheEntry {
  // Iteration
  public boolean isValue(int offset) { return !entryAt(offset); }
  public boolean isOop  (int offset) { return entryAt(offset);  }
  public void    iterateOop(OffsetClosure oopClosure) {
    int n = numberOfEntries();
    for (int i = 0; i < n; i++) {
      if (entryAt(i)) {
        oopClosure.offsetDo(i);
      }
    }
  }

  // Initialization
  public void fill(Method method, int bci) {
    this.method = method;
    this.bci = bci;
    if (method.isNative()) {
      // Native method activations have oops only among the parameters and one
      // extra oop following the parameters (the mirror for static native methods).
      fillForNative();
    } else {
      OopMapForCacheEntry gen = new OopMapForCacheEntry(method, bci, this);
      gen.computeMap();
    }
  }

  public void setMask(CellTypeStateList vars,
                      CellTypeStateList stack,
                      int stackTop) {
    // compute bit mask size
    int maxLocals = (int) method.getMaxLocals();
    int nEntries  = maxLocals + stackTop;
    maskSize      = nEntries;
    allocateBitMask();

    CellTypeStateList curList = vars;
    int listIdx = 0;

    for (int entryIdx = 0; entryIdx < nEntries; entryIdx++, listIdx++) {
      // switch to stack when done with locals
      if (entryIdx == maxLocals) {
        curList = stack;
        listIdx = 0;
      }

      CellTypeState cell = curList.get(listIdx);
      // set oop bit
      if ( cell.isReference()) {
        mask.atPut(entryIdx, true);
      }
    }

    // verify bit mask
    if (Assert.ASSERTS_ENABLED) {
      Assert.that(verifyMask(vars, stack, maxLocals, stackTop), "mask could not be verified");
    }
  }

  //----------------------------------------------------------------------
  // Internals only below this point
  //
  private Method method;    // the method for which the mask is valid
  private int    bci;       // the bci    for which the mask is valid
  private int    maskSize;  // the required mask size in bits
  private BitMap mask;      // may be null if mask is empty

  Method method()        { return method; }
  int bci()              { return bci; }
  int numberOfEntries()  { return maskSize; }
  boolean entryAt(int offset) {
    return mask.at(offset);
  }

  void setEmptyMask()    { mask = null; }
  void allocateBitMask() {
    if (maskSize > 0) {
      mask = new BitMap(maskSize);
    }
  }

  // fills the bit mask for native calls
  void fillForNative() {
    if (Assert.ASSERTS_ENABLED) {
      Assert.that(method.isNative(), "method must be native method");
    }
    maskSize = (int) method.getSizeOfParameters();
    allocateBitMask();
    // fill mask for parameters
    MaskFillerForNative mf = new MaskFillerForNative(method, mask, maskSize);
    mf.generate();
  }

  static class VerifyClosure implements OffsetClosure {
    private OopMapCacheEntry entry;
    private boolean          failed;

    VerifyClosure(OopMapCacheEntry entry)          { this.entry = entry; }
    public void offsetDo(int offset)               { if (!entry.isOop(offset)) failed = true; }
    boolean failed()                               { return failed; }
  }

  boolean verifyMask(CellTypeStateList vars, CellTypeStateList stack, int maxLocals, int stackTop) {
    // Check mask includes map
    VerifyClosure blk = new VerifyClosure(this);
    iterateOop(blk);
    if (blk.failed()) return false;

    // Check if map is generated correctly
    for(int i = 0; i < maxLocals; i++) {
      boolean v1 = isOop(i);
      boolean v2 = vars.get(i).isReference();
      if (Assert.ASSERTS_ENABLED) {
        Assert.that(v1 == v2, "locals oop mask generation error");
      }
    }

    for(int j = 0; j < stackTop; j++) {
      boolean v1 = isOop(maxLocals + j);
      boolean v2 = stack.get(j).isReference();
      if (Assert.ASSERTS_ENABLED) {
        Assert.that(v1 == v2, "stack oop mask generation error");
      }
    }
    return true;
  }
}

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