VM_Registers.java

/*
 *  This file is part of the Jikes RVM project (http://jikesrvm.org).
 *
 *  This file is licensed to You under the Common Public License (CPL);
 *  You may not use this file except in compliance with the License. You
 *  may obtain a copy of the License at
 *
 *      http://www.opensource.org/licenses/cpl1.0.php
 *
 *  See the COPYRIGHT.txt file distributed with this work for information
 *  regarding copyright ownership.
 */
package org.jikesrvm.ia32;

import org.jikesrvm.runtime.VM_ArchEntrypoints;
import org.jikesrvm.runtime.VM_Magic;
import org.vmmagic.pragma.Uninterruptible;
import org.vmmagic.unboxed.Address;
import org.vmmagic.unboxed.LocalAddress;
import org.vmmagic.unboxed.Offset;
import org.vmmagic.unboxed.WordArray;

/**
 * The machine state comprising a thread's execution context.
 */
@Uninterruptible
public abstract class VM_Registers extends org.jikesrvm.VM_Registers implements VM_RegisterConstants {

  public LocalAddress fp;     // frame pointer


  public VM_Registers() {
    gprs = WordArray.create(NUM_GPRS);
    fprs = new double[NUM_FPRS];
  }

  /**
   * Return framepointer for the deepest stackframe
   */
  public final LocalAddress getInnermostFramePointer() {
    return fp;
  }

  /**
   * Return next instruction address for the deepest stackframe
   */
  public final LocalAddress getInnermostInstructionAddress() {
    return ip;
  }

  /**
   * update the machine state as if the stackframe were unwound.
   */
  public final void unwindStackFrame() {
    ip = VM_Magic.getReturnAddress(fp);
    fp = VM_Magic.getCallerFramePointer(fp);
  }

  /**
   * set ip & fp. used to control the stack frame at which a scan of
   * the stack during GC will start, for ex., the top java frame for
   * a thread that is blocked in native code during GC.
   */
  public final void setInnermost(LocalAddress newip, LocalAddress newfp) {
    ip = newip;
    fp = newfp;
  }

  /**
   * set ip and fp values to those of the caller. used just prior to entering
   * sigwait to set fp & ip so that GC will scan the threads stack
   * starting at the frame of the method that called sigwait.
   */
  public final void setInnermost() {
    LocalAddress current_fp = VM_Magic.getFramePointer();
    ip = VM_Magic.getReturnAddress(current_fp);
    fp = VM_Magic.getCallerFramePointer(current_fp);
  }

  public final LocalAddress getIPLocation() {
    Offset ipOffset = VM_ArchEntrypoints.registersIPField.getOffset();
    return VM_Magic.objectAsLocalAddress(this).plus(ipOffset);
  }
}