/*
* 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.objectmodel;
import org.jikesrvm.VM;
import org.jikesrvm.Constants;
import org.jikesrvm.mm.mminterface.MemoryManagerConstants;
import org.jikesrvm.runtime.Magic;
import org.vmmagic.pragma.Entrypoint;
import org.vmmagic.pragma.Interruptible;
import org.vmmagic.pragma.Uninterruptible;
import org.vmmagic.unboxed.Address;
import org.vmmagic.unboxed.ObjectReference;
import org.vmmagic.unboxed.Offset;
import org.vmmagic.unboxed.Word;
/**
* Defines other header words not used for
* core Java language support of memory allocation.
* Typically these are extra header words used for various
* kinds of instrumentation or profiling.
*
* @see ObjectModel
*/
@Uninterruptible
public final class MiscHeader implements Constants, MiscHeaderConstants {
private static final Offset MISC_HEADER_START = JavaHeaderConstants.MISC_HEADER_OFFSET;
/* offset from object ref to .oid field, in bytes */
static final Offset OBJECT_OID_OFFSET = MISC_HEADER_START;
/* offset from object ref to OBJECT_DEATH field, in bytes */
static final Offset OBJECT_DEATH_OFFSET = OBJECT_OID_OFFSET.plus(BYTES_IN_ADDRESS);
/* offset from object ref to .link field, in bytes */
static final Offset OBJECT_LINK_OFFSET = OBJECT_DEATH_OFFSET.plus(BYTES_IN_ADDRESS);
/////////////////////////
// Support for YYY (an example of how to add a word to all objects)
/////////////////////////
// offset from object ref to yet-to-be-defined instrumentation word
// static final int YYY_DATA_OFFSET_1 = (VM.YYY ? MISC_HEADER_START + GC_TRACING_HEADER_WORDS : 0);
// static final int YYY_DATA_OFFSET_2 = (VM.YYY ? MISC_HEADER_START + GC_TRACING_HEADER_WORDS + 4 : 0);
// static final int YYY_HEADER_BYTES = (VM.YYY ? 8 : 0);
/**
* How many available bits does the misc header want to use?
*/
static final int REQUESTED_BITS = 0;
/**
* The next object ID to be used.
*/
@Entrypoint
private static Word oid;
/**
* The current "time" for the trace being generated.
*/
private static Word time;
/**
* The address of the last object allocated into the header.
*/
@Entrypoint
private static Word prevAddress;
static {
oid = Word.fromIntSignExtend(4);
time = Word.fromIntSignExtend(4);
prevAddress = Word.zero();
}
/**
* Perform any required initialization of the MISC portion of the header.
* @param obj the object ref to the storage to be initialized
* @param tib the TIB of the instance being created
* @param size the number of bytes allocated by the GC system for this object.
* @param isScalar are we initializing a scalar (true) or array (false) object?
*/
@Uninterruptible
public static void initializeHeader(Object obj, TIB tib, int size, boolean isScalar) {
/* Only perform initialization when it is required */
if (MemoryManagerConstants.GENERATE_GC_TRACE) {
Address ref = Magic.objectAsAddress(obj);
ref.store(oid, OBJECT_OID_OFFSET);
ref.store(time, OBJECT_DEATH_OFFSET);
oid = oid.plus(Word.fromIntSignExtend((size - GC_TRACING_HEADER_BYTES) >> LOG_BYTES_IN_ADDRESS));
}
}
/**
* Perform any required initialization of the MISC portion of the header.
* @param bootImage the bootimage being written
* @param ref the object ref to the storage to be initialized
* @param tib the TIB of the instance being created
* @param size the number of bytes allocated by the GC system for this object.
* @param isScalar are we initializing a scalar (true) or array (false) object?
*/
@Interruptible("Only called during boot iamge creation")
public static void initializeHeader(BootImageInterface bootImage, Address ref, TIB tib, int size,
boolean isScalar) {
/* Only perform initialization when it is required */
if (MemoryManagerConstants.GENERATE_GC_TRACE) {
bootImage.setAddressWord(ref.plus(OBJECT_OID_OFFSET), oid, false, false);
bootImage.setAddressWord(ref.plus(OBJECT_DEATH_OFFSET), time, false, false);
bootImage.setAddressWord(ref.plus(OBJECT_LINK_OFFSET), prevAddress, false, false);
prevAddress = ref.toWord();
oid = oid.plus(Word.fromIntSignExtend((size - GC_TRACING_HEADER_BYTES) >> LOG_BYTES_IN_ADDRESS));
}
}
public static void updateDeathTime(Object object) {
if (VM.VerifyAssertions) VM._assert(MemoryManagerConstants.GENERATE_GC_TRACE);
if (MemoryManagerConstants.GENERATE_GC_TRACE) {
Magic.objectAsAddress(object).store(time, OBJECT_DEATH_OFFSET);
}
}
public static void setDeathTime(Object object, Word time_) {
if (VM.VerifyAssertions) VM._assert(MemoryManagerConstants.GENERATE_GC_TRACE);
if (MemoryManagerConstants.GENERATE_GC_TRACE) {
Magic.objectAsAddress(object).store(time_, OBJECT_DEATH_OFFSET);
}
}
public static void setLink(Object object, ObjectReference link) {
if (VM.VerifyAssertions) VM._assert(MemoryManagerConstants.GENERATE_GC_TRACE);
if (MemoryManagerConstants.GENERATE_GC_TRACE) {
Magic.objectAsAddress(object).store(link, OBJECT_LINK_OFFSET);
}
}
public static void updateTime(Word time_) {
if (VM.VerifyAssertions) VM._assert(MemoryManagerConstants.GENERATE_GC_TRACE);
time = time_;
}
public static Word getOID(Object object) {
if (VM.VerifyAssertions) VM._assert(MemoryManagerConstants.GENERATE_GC_TRACE);
if (MemoryManagerConstants.GENERATE_GC_TRACE) {
return Magic.objectAsAddress(object).plus(OBJECT_OID_OFFSET).loadWord();
} else {
return Word.zero();
}
}
public static Word getDeathTime(Object object) {
if (VM.VerifyAssertions) VM._assert(MemoryManagerConstants.GENERATE_GC_TRACE);
if (MemoryManagerConstants.GENERATE_GC_TRACE) {
return Magic.objectAsAddress(object).plus(OBJECT_DEATH_OFFSET).loadWord();
} else {
return Word.zero();
}
}
public static ObjectReference getLink(Object ref) {
if (VM.VerifyAssertions) VM._assert(MemoryManagerConstants.GENERATE_GC_TRACE);
if (MemoryManagerConstants.GENERATE_GC_TRACE) {
return ObjectReference.fromObject(Magic.getObjectAtOffset(ref, OBJECT_LINK_OFFSET));
} else {
return ObjectReference.nullReference();
}
}
public static Address getBootImageLink() {
if (VM.VerifyAssertions) VM._assert(MemoryManagerConstants.GENERATE_GC_TRACE);
if (MemoryManagerConstants.GENERATE_GC_TRACE) {
return prevAddress.toAddress();
} else {
return Address.zero();
}
}
public static Word getOID() {
if (VM.VerifyAssertions) VM._assert(MemoryManagerConstants.GENERATE_GC_TRACE);
if (MemoryManagerConstants.GENERATE_GC_TRACE) {
return oid;
} else {
return Word.zero();
}
}
public static void setOID(Word oid_) {
if (VM.VerifyAssertions) VM._assert(MemoryManagerConstants.GENERATE_GC_TRACE);
if (MemoryManagerConstants.GENERATE_GC_TRACE) {
oid = oid_;
}
}
public static int getHeaderSize() {
return NUM_BYTES_HEADER;
}
/**
* For low level debugging of GC subsystem.
* Dump the header word(s) of the given object reference.
* @param ref the object reference whose header should be dumped
*/
public static void dumpHeader(Object ref) {
// by default nothing to do, unless the misc header is required
if (MemoryManagerConstants.GENERATE_GC_TRACE) {
VM.sysWrite(" OID=", getOID(ref));
VM.sysWrite(" LINK=", getLink(ref));
VM.sysWrite(" DEATH=", getDeathTime(ref));
}
}
}