/*
 *  This file is part of the Jikes RVM project (http://jikesrvm.org).
 *
 *  This file is licensed to You under the Eclipse Public License (EPL);
 *  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/eclipse-1.0.php
 *
 *  See the COPYRIGHT.txt file distributed with this work for information
 *  regarding copyright ownership.
 */
package org.jikesrvm.ppc;

import org.jikesrvm.mm.mminterface.MemoryManager;
import org.jikesrvm.runtime.ArchEntrypoints;
import org.jikesrvm.runtime.Magic;
import org.jikesrvm.scheduler.RVMThread;
import org.jikesrvm.VM;
import org.vmmagic.pragma.Uninterruptible;
import org.vmmagic.pragma.Untraced;
import org.vmmagic.unboxed.Address;
import org.vmmagic.unboxed.Offset;
import org.vmmagic.unboxed.WordArray;
import org.vmmagic.unboxed.Word;

/**
 * The machine state comprising a thread's execution context.
 */
@Uninterruptible
public abstract class Registers implements ArchConstants {
  // The following are used both for thread context switching
  // and for hardware exception reporting/delivery.
  //
  @Untraced
  public final WordArray gprs; // word size general purpose registers (either 32 or 64 bit)
  @Untraced
  public final double[] fprs; // 64-bit floating point registers
  public final WordArray gprsShadow;
  public final double[] fprsShadow;
  public Address ip; // instruction address register

  // The following are used by exception delivery.
  // They are set by either Runtime.athrow or the C hardware exception
  // handler and restored by "Magic.restoreHardwareExceptionState".
  // They are not used for context switching.
  //
  public Address lr;     // link register
  public boolean inuse; // do exception registers currently contain live values?

  private static final Address invalidIP = Address.max();

  public Registers() {
    gprs = gprsShadow = MemoryManager.newNonMovingWordArray(NUM_GPRS);
    fprs = fprsShadow = MemoryManager.newNonMovingDoubleArray(NUM_FPRS);
    ip = invalidIP;
  }

  public final void clear() {
    for (int i=0;i<NUM_GPRS;++i) {
      gprs.set(i,Word.zero());
    }
    for (int i=0;i<NUM_FPRS;++i) {
      fprs[i]=0.;
    }
    ip=Address.zero();
    lr=Address.zero();
  }

  public final void copyFrom(Registers other) {
    for (int i=0;i<NUM_GPRS;++i) {
      gprs.set(i,other.gprs.get(i));
    }
    for (int i=0;i<NUM_FPRS;++i) {
      fprs[i]=other.fprs[i];
    }
    ip=other.ip;
    lr=other.lr;
  }

  public final void assertSame(Registers other) {
    boolean fail=false;
    for (int i=0;i<NUM_GPRS;++i) {
      if (gprs.get(i).NE(other.gprs.get(i))) {
        VM.sysWriteln("Registers not equal: GPR #",i);
        fail=true;
      }
    }
    for (int i=0;i<NUM_FPRS;++i) {
      if (fprs[i]!=other.fprs[i]) {
        VM.sysWriteln("Registers not equal: FPR #",i);
        fail=true;
      }
    }
    if (ip.NE(other.ip)) {
      VM.sysWriteln("Registers not equal: IP");
      fail=true;
    }
    if (lr.NE(other.lr)) {
      VM.sysWriteln("Registers not equal: LR");
      fail=true;
    }
    if (fail) {
      RVMThread.dumpStack();
      VM.sysFail("Registers.assertSame() failed");
    }
  }

  /** @return framepointer for the deepest stackframe */
  public final Address getInnermostFramePointer() {
    return gprs.get(FRAME_POINTER).toAddress();
  }

  /** @return next instruction address for the deepest stackframe */
  public final Address getInnermostInstructionAddress() {
    if (ip.NE(invalidIP)) return ip; // ip set by hardware exception handler or Magic.threadSwitch
    return Magic.getNextInstructionAddress(getInnermostFramePointer()); // ip set to -1 because we're unwinding
  }

  /** Update the machine state to unwind the deepest stackframe. */
  public final void unwindStackFrame() {
    ip = invalidIP; // if there was a valid value in ip, it ain't valid anymore
    gprs.set(FRAME_POINTER, Magic.getCallerFramePointer(getInnermostFramePointer()).toWord());
  }

  /**
   * 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(Address newip, Address newfp) {
    ip = newip;
    gprs.set(FRAME_POINTER, newfp.toWord());
  }

  /**
   * 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() {
    Address fp = Magic.getFramePointer();
    ip = Magic.getReturnAddress(fp);
    gprs.set(FRAME_POINTER, Magic.getCallerFramePointer(fp).toWord());
  }

  public final Address getIPLocation() {
    Offset ipOffset = ArchEntrypoints.registersIPField.getOffset();
    return Magic.objectAsAddress(this).plus(ipOffset);
  }

}