[rvm-commits] SF.net SVN: jikesrvm:[15780] rvmroot/trunk

[<ste...@us...>]

Revision: 15780
          http://jikesrvm.svn.sourceforge.net/jikesrvm/?rev=15780&view=rev
Author:   steveb-oss
Date:     2009-09-16 12:13:01 +0000 (Wed, 16 Sep 2009)

Log Message:
-----------
Another step towards RVM-845

Modified Paths:
--------------
    rvmroot/trunk/MMTk/ext/vm/jikesrvm/org/jikesrvm/mm/mmtk/Barriers.java
    rvmroot/trunk/MMTk/harness/src/org/mmtk/harness/Mutator.java
    rvmroot/trunk/MMTk/src/org/mmtk/plan/PlanConstraints.java
    rvmroot/trunk/MMTk/src/org/mmtk/plan/generational/GenConstraints.java
    rvmroot/trunk/MMTk/src/org/mmtk/plan/poisoned/PoisonedConstraints.java
    rvmroot/trunk/MMTk/src/org/mmtk/plan/refcount/RCBaseConstraints.java
    rvmroot/trunk/MMTk/src/org/mmtk/plan/semispace/gctrace/GCTraceConstraints.java
    rvmroot/trunk/MMTk/src/org/mmtk/plan/stickyimmix/StickyImmixConstraints.java
    rvmroot/trunk/MMTk/src/org/mmtk/plan/stickyms/StickyMSConstraints.java
    rvmroot/trunk/rvm/src/org/jikesrvm/mm/mminterface/Barriers.java
    rvmroot/trunk/rvm/src/org/jikesrvm/mm/mminterface/MemoryManager.java

Modified: rvmroot/trunk/MMTk/ext/vm/jikesrvm/org/jikesrvm/mm/mmtk/Barriers.java
===================================================================
--- rvmroot/trunk/MMTk/ext/vm/jikesrvm/org/jikesrvm/mm/mmtk/Barriers.java	2009-09-09 16:10:08 UTC (rev 15779)
+++ rvmroot/trunk/MMTk/ext/vm/jikesrvm/org/jikesrvm/mm/mmtk/Barriers.java	2009-09-16 12:13:01 UTC (rev 15780)
@@ -24,16 +24,15 @@
   /**
    * Perform the actual write of the write barrier.
    *
-   * @param ref The object that has the reference field
+   * @param objref The object that has the reference field
    * @param target The value that the slot will be updated to
    * @param offset The offset from the ref
    * @param location The index of the FieldReference
    * @param mode The context in which the write is occurring
    */
   @Inline
-  public final void referenceWrite(ObjectReference ref, ObjectReference target,
-      Word offset, Word location, int mode) {
-    Magic.setObjectAtOffset(ref.toObject(), offset.toOffset(), target.toObject(), location.toInt());
+  public final void referenceWrite(ObjectReference objref, ObjectReference target, Word offset, Word location, int mode) {
+    Magic.setObjectAtOffset(objref.toObject(), offset.toOffset(), target.toObject(), location.toInt());
   }
 
   /**
@@ -46,16 +45,50 @@
    * @param ref The object that has the reference field
    */
   @Inline
-  public final void referenceWrite(Address slot, ObjectReference target,
-      Word unusedA, Word unusedB) {
+  public final void referenceWrite(Address slot, ObjectReference target, Word unusedA, Word unusedB) {
     slot.store(target);
   }
 
   /**
+   * Perform the actual read of the read barrier.
+   *
+   * @param objref The object that has the reference field
+   * @param offset The offset from the ref
+   * @param location The index of the FieldReference
+   * @param mode The context in which the write is occurring
+   * @return the read value
+   */
+  @Inline
+  public final ObjectReference referenceRead(ObjectReference objref, Word offset, Word location, int mode) {
+    return ObjectReference.fromObject(Magic.getObjectAtOffset(objref.toObject(), offset.toOffset(), location.toInt()));
+  }
+
+  /**
+   * Sets an element of an object array without invoking any write
+   * barrier.  This method is called by the Map class to ensure
+   * potentially-allocation-triggering write barriers do not occur in
+   * allocation slow path code.
+   *
+   * @param dst the destination array
+   * @param index the index of the element to set
+   * @param value the new value for the element
+   */
+  @UninterruptibleNoWarn
+  public final void referenceArrayStoreNoGCBarrier(Object[] dst, int index, Object value) {
+    if (org.jikesrvm.VM.runningVM) {
+      Address base = ObjectReference.fromObject(dst).toAddress();
+      Address slot = base.plus(Offset.fromIntZeroExtend(index << LOG_BYTES_IN_ADDRESS));
+      VM.activePlan.global().storeObjectReference(slot, ObjectReference.fromObject(value));
+    } else {
+      dst[index] = value;
+    }
+  }
+
+  /**
    * Atomically write a reference field of an object or array and return
    * the old value of the reference field.
    *
-   * @param ref The object that has the reference field
+   * @param objref The object that has the reference field
    * @param target The value that the slot will be updated to
    * @param offset The offset from the ref
    * @param unused Unused
@@ -63,9 +96,8 @@
    * @return The value that was replaced by the write.
    */
   @Inline
-  public final ObjectReference referenceAtomicWrite(ObjectReference ref, ObjectReference target,
-      Word offset, Word unused, int mode) {
-    Object obj = ref.toObject();
+  public final ObjectReference referenceAtomicWrite(ObjectReference objref, ObjectReference target, Word offset, Word unused, int mode) {
+    Object obj = objref.toObject();
     Object newObject = target.toObject();
     Object oldObject;
     do {
@@ -77,7 +109,7 @@
   /**
    * Attempt an atomic compare and exchange in a write barrier sequence.
    *
-   * @param ref The object that has the reference field
+   * @param objref The object that has the reference field
    * @param old The old reference to be swapped out
    * @param target The value that the slot will be updated to
    * @param offset The offset from the ref
@@ -86,32 +118,16 @@
    * @return True if the compare and swap was successful
    */
   @Inline
-  public final boolean referenceTryCompareAndSwap(ObjectReference ref, ObjectReference old, ObjectReference target,
-      Word offset, Word unused, int mode) {
+  public final boolean referenceTryCompareAndSwap(ObjectReference objref, ObjectReference old, ObjectReference target, Word offset, Word unused, int mode) {
     Object oldValue;
     do {
-      oldValue = Magic.prepareObject(ref, offset.toOffset());
+      oldValue = Magic.prepareObject(objref, offset.toOffset());
       if (oldValue != old) return false;
-    } while (!Magic.attemptObject(ref, offset.toOffset(), oldValue, target));
+    } while (!Magic.attemptObject(objref, offset.toOffset(), oldValue, target));
     return true;
   }
 
   /**
-   * Perform the actual read of the read barrier.
-   *
-   * @param ref The object that has the reference field
-   * @param offset The offset from the ref
-   * @param location The index of the FieldReference
-   * @param mode The context in which the write is occurring
-   * @return the read value
-   */
-  @Inline
-  public final ObjectReference referenceRead(ObjectReference ref,
-      Word offset, Word location, int mode) {
-    return ObjectReference.fromObject(Magic.getObjectAtOffset(ref.toObject(), offset.toOffset(), location.toInt()));
-  }
-
-  /**
    * Perform the actual write of the write barrier, writing the value as a raw word.
    *
    * @param ref The object that has the reference field
@@ -183,24 +199,4 @@
     return Magic.getWordAtOffset(ref.toObject(), offset.toOffset(), location.toInt());
   }
 
-  /**
-   * Sets an element of an object array without invoking any write
-   * barrier.  This method is called by the Map class to ensure
-   * potentially-allocation-triggering write barriers do not occur in
-   * allocation slow path code.
-   *
-   * @param dst the destination array
-   * @param index the index of the element to set
-   * @param value the new value for the element
-   */
-  @UninterruptibleNoWarn
-  public final void referenceArrayStoreNoGCBarrier(Object[] dst, int index, Object value) {
-    if (org.jikesrvm.VM.runningVM) {
-      Address base = ObjectReference.fromObject(dst).toAddress();
-      Address slot = base.plus(Offset.fromIntZeroExtend(index << LOG_BYTES_IN_ADDRESS));
-      VM.activePlan.global().storeObjectReference(slot, ObjectReference.fromObject(value));
-    } else {
-      dst[index] = value;
-    }
-  }
 }

Modified: rvmroot/trunk/MMTk/harness/src/org/mmtk/harness/Mutator.java
===================================================================
--- rvmroot/trunk/MMTk/harness/src/org/mmtk/harness/Mutator.java	2009-09-09 16:10:08 UTC (rev 15779)
+++ rvmroot/trunk/MMTk/harness/src/org/mmtk/harness/Mutator.java	2009-09-16 12:13:01 UTC (rev 15780)
@@ -302,7 +302,7 @@
     check(index < limit, "Index "+index+" out of bounds "+limit);
 
     Address referenceSlot = ObjectModel.getRefSlot(object, index);
-    if (ActivePlan.constraints.needsWriteBarrier()) {
+    if (ActivePlan.constraints.needsReferenceWriteBarrier()) {
       context.referenceWrite(object, referenceSlot, value, referenceSlot.toWord(), null, Plan.ARRAY_ELEMENT);
       if (gcEveryWB) {
         gc();
@@ -346,7 +346,7 @@
 
     Address referenceSlot = ObjectModel.getRefSlot(object, index);
     ObjectReference result;
-    if (ActivePlan.constraints.needsReadBarrier()) {
+    if (ActivePlan.constraints.needsReferenceReadBarrier()) {
       result = context.referenceRead(object, referenceSlot, null, null, Plan.INSTANCE_FIELD);
     } else {
       result = referenceSlot.loadObjectReference();

Modified: rvmroot/trunk/MMTk/src/org/mmtk/plan/PlanConstraints.java
===================================================================
--- rvmroot/trunk/MMTk/src/org/mmtk/plan/PlanConstraints.java	2009-09-09 16:10:08 UTC (rev 15779)
+++ rvmroot/trunk/MMTk/src/org/mmtk/plan/PlanConstraints.java	2009-09-16 12:13:01 UTC (rev 15780)
@@ -22,21 +22,21 @@
  * issues with ordering of static initialization.
  */
 @Uninterruptible public abstract class PlanConstraints {
-  /** @return True if this Plan requires write barriers. */
-  public boolean needsWriteBarrier() { return false; }
+  /** @return True of this Plan requires read barriers on java.lang.reference types. */
+  public boolean needsJavaLangReferenceReadBarrier() { return false; }
 
+  /** @return True if this Plan requires write barriers on reference types. */
+  public boolean needsReferenceWriteBarrier() { return false; }
+
   /** @return True of this Plan requires read barriers on reference types. */
-  public boolean needsJavaLangReferenceReadBarrier() { return false; }
+  public boolean needsReferenceReadBarrier() { return false; }
 
-  /** @return True of this Plan requires read barriers. */
-  public boolean needsReadBarrier() { return false; }
+  /** @return True if this Plan requires static write barriers on reference types. */
+  public boolean needsReferenceStaticWriteBarrier() { return false;}
 
-  /** @return True if this Plan requires static write barriers. */
-  public boolean needsStaticWriteBarrier() { return false;}
+  /** @return True if this Plan requires static read barriers on reference types. */
+  public boolean needsReferenceStaticReadBarrier() { return false; }
 
-  /** @return True if this Plan requires static read barriers. */
-  public boolean needsStaticReadBarrier() { return false; }
-
   /** @return True if this Plan requires linear scanning. */
   public boolean needsLinearScan() { return org.mmtk.utility.Constants.SUPPORT_CARD_SCANNING;}
 

Modified: rvmroot/trunk/MMTk/src/org/mmtk/plan/generational/GenConstraints.java
===================================================================
--- rvmroot/trunk/MMTk/src/org/mmtk/plan/generational/GenConstraints.java	2009-09-09 16:10:08 UTC (rev 15779)
+++ rvmroot/trunk/MMTk/src/org/mmtk/plan/generational/GenConstraints.java	2009-09-16 12:13:01 UTC (rev 15780)
@@ -46,11 +46,11 @@
 
   /** @return True if this plan requires a write barrier */
   @Override
-  public boolean needsWriteBarrier() { return true; }
+  public boolean needsReferenceWriteBarrier() { return true; }
 
   /** @return True if this plan requires a static barrier */
   @Override
-  public boolean needsStaticWriteBarrier() { return Gen.USE_STATIC_WRITE_BARRIER; }
+  public boolean needsReferenceStaticWriteBarrier() { return Gen.USE_STATIC_WRITE_BARRIER; }
 
   /** @return The specialized scan methods required */
   @Override

Modified: rvmroot/trunk/MMTk/src/org/mmtk/plan/poisoned/PoisonedConstraints.java
===================================================================
--- rvmroot/trunk/MMTk/src/org/mmtk/plan/poisoned/PoisonedConstraints.java	2009-09-09 16:10:08 UTC (rev 15779)
+++ rvmroot/trunk/MMTk/src/org/mmtk/plan/poisoned/PoisonedConstraints.java	2009-09-16 12:13:01 UTC (rev 15780)
@@ -24,11 +24,11 @@
 @Uninterruptible
 public class PoisonedConstraints extends MSConstraints {
   @Override
-  public boolean needsWriteBarrier() { return true; }
+  public boolean needsReferenceWriteBarrier() { return true; }
   @Override
-  public boolean needsReadBarrier() { return true; }
+  public boolean needsReferenceReadBarrier() { return true; }
   @Override
-  public boolean needsStaticWriteBarrier() { return false; }
+  public boolean needsReferenceStaticWriteBarrier() { return false; }
   @Override
-  public boolean needsStaticReadBarrier() { return false; }
+  public boolean needsReferenceStaticReadBarrier() { return false; }
 }

Modified: rvmroot/trunk/MMTk/src/org/mmtk/plan/refcount/RCBaseConstraints.java
===================================================================
--- rvmroot/trunk/MMTk/src/org/mmtk/plan/refcount/RCBaseConstraints.java	2009-09-09 16:10:08 UTC (rev 15779)
+++ rvmroot/trunk/MMTk/src/org/mmtk/plan/refcount/RCBaseConstraints.java	2009-09-16 12:13:01 UTC (rev 15780)
@@ -30,7 +30,7 @@
   @Override
   public int gcHeaderWords() { return RCHeader.GC_HEADER_WORDS_REQUIRED; }
   @Override
-  public boolean needsWriteBarrier() { return true; }
+  public boolean needsReferenceWriteBarrier() { return true; }
   @Override
   public int maxNonLOSDefaultAllocBytes() { return MAX_FREELIST_OBJECT_BYTES; }
 }

Modified: rvmroot/trunk/MMTk/src/org/mmtk/plan/semispace/gctrace/GCTraceConstraints.java
===================================================================
--- rvmroot/trunk/MMTk/src/org/mmtk/plan/semispace/gctrace/GCTraceConstraints.java	2009-09-09 16:10:08 UTC (rev 15779)
+++ rvmroot/trunk/MMTk/src/org/mmtk/plan/semispace/gctrace/GCTraceConstraints.java	2009-09-16 12:13:01 UTC (rev 15780)
@@ -22,7 +22,7 @@
 @Uninterruptible
 public class GCTraceConstraints extends SSConstraints {
   @Override
-  public boolean needsWriteBarrier() { return true; }
+  public boolean needsReferenceWriteBarrier() { return true; }
   @Override
   public boolean generateGCTrace() { return true; }
 }

Modified: rvmroot/trunk/MMTk/src/org/mmtk/plan/stickyimmix/StickyImmixConstraints.java
===================================================================
--- rvmroot/trunk/MMTk/src/org/mmtk/plan/stickyimmix/StickyImmixConstraints.java	2009-09-09 16:10:08 UTC (rev 15779)
+++ rvmroot/trunk/MMTk/src/org/mmtk/plan/stickyimmix/StickyImmixConstraints.java	2009-09-16 12:13:01 UTC (rev 15780)
@@ -32,7 +32,7 @@
 
   /** @return True if this plan requires a write barrier */
   @Override
-  public boolean needsWriteBarrier() { return true; }
+  public boolean needsReferenceWriteBarrier() { return true; }
 
   /** @return True if this Plan requires a header bit for object logging */
   @Override

Modified: rvmroot/trunk/MMTk/src/org/mmtk/plan/stickyms/StickyMSConstraints.java
===================================================================
--- rvmroot/trunk/MMTk/src/org/mmtk/plan/stickyms/StickyMSConstraints.java	2009-09-09 16:10:08 UTC (rev 15779)
+++ rvmroot/trunk/MMTk/src/org/mmtk/plan/stickyms/StickyMSConstraints.java	2009-09-16 12:13:01 UTC (rev 15780)
@@ -32,7 +32,7 @@
 
   /** @return True if this plan requires a write barrier */
   @Override
-  public boolean needsWriteBarrier() { return true; }
+  public boolean needsReferenceWriteBarrier() { return true; }
 
   /** @return True if this Plan requires a header bit for object logging */
   @Override

Modified: rvmroot/trunk/rvm/src/org/jikesrvm/mm/mminterface/Barriers.java
===================================================================
--- rvmroot/trunk/rvm/src/org/jikesrvm/mm/mminterface/Barriers.java	2009-09-09 16:10:08 UTC (rev 15779)
+++ rvmroot/trunk/rvm/src/org/jikesrvm/mm/mminterface/Barriers.java	2009-09-16 12:13:01 UTC (rev 15780)
@@ -44,23 +44,24 @@
   }
 
   /** True if the garbage collector requires write barriers on reference putfield, arraystore or modifycheck */
-  private static final boolean NEEDS_REFERENCE_GC_WRITE_BARRIER     = Selected.Constraints.get().needsWriteBarrier();
+  private static final boolean NEEDS_REFERENCE_GC_WRITE_BARRIER     = Selected.Constraints.get().needsReferenceWriteBarrier();
   /** True if the VM requires write barriers on reference putfield */
   public static final boolean  NEEDS_REFERENCE_PUTFIELD_BARRIER     = NEEDS_REFERENCE_GC_WRITE_BARRIER;
   /** True if the VM requires write barriers on reference arraystore */
   public static final boolean  NEEDS_REFERENCE_ASTORE_BARRIER       = NEEDS_REFERENCE_GC_WRITE_BARRIER;
   /** True if the garbage collector requires read barriers on reference getfield or arrayload */
-  private static final boolean NEEDS_REFERENCE_GC_READ_BARRIER      = Selected.Constraints.get().needsReadBarrier();
+  private static final boolean NEEDS_REFERENCE_GC_READ_BARRIER      = Selected.Constraints.get().needsReferenceReadBarrier();
   /** True if the VM requires read barriers on reference getfield */
   public static final boolean  NEEDS_REFERENCE_GETFIELD_BARRIER     = NEEDS_REFERENCE_GC_READ_BARRIER;
   /** True if the VM requires read barriers on reference arrayload */
   public static final boolean  NEEDS_REFERENCE_ALOAD_BARRIER        = NEEDS_REFERENCE_GC_READ_BARRIER;
+
   /** True if the selected plan requires write barriers on reference putstatic */
-  private static final boolean NEEDS_REFERENCE_GC_PUTSTATIC_BARRIER = Selected.Constraints.get().needsStaticWriteBarrier();
+  private static final boolean NEEDS_REFERENCE_GC_PUTSTATIC_BARRIER = Selected.Constraints.get().needsReferenceStaticWriteBarrier();
   /** True if the selected plan requires write barriers on reference putstatic */
   public static final boolean  NEEDS_REFERENCE_PUTSTATIC_BARRIER    = NEEDS_REFERENCE_GC_PUTSTATIC_BARRIER;
   /** True if the selected plan requires read barriers on reference getstatic */
-  private static final boolean NEEDS_REFERENCE_GC_GETSTATIC_BARRIER = Selected.Constraints.get().needsStaticReadBarrier();
+  private static final boolean NEEDS_REFERENCE_GC_GETSTATIC_BARRIER = Selected.Constraints.get().needsReferenceStaticReadBarrier();
   /** True if the selected plan requires read barriers on reference getstatic */
   public static final boolean  NEEDS_REFERENCE_GETSTATIC_BARRIER    = NEEDS_REFERENCE_GC_GETSTATIC_BARRIER;
 
@@ -114,47 +115,49 @@
   }
 
   /**
-   * Barrier for writes of references to non-heap locations (eg statics)
+   * Barrier for loads of references from fields of instances (ie getfield).
    *
-   * @param value the new value to be stored
-   * @param offset the offset of the field to be modified
-   * @param locationMetadata an int that encodes the source location being modified
+   * @param ref the object which is the subject of the getfield
+   * @param offset the offset of the field to be read
+   * @param locationMetadata an int that encodes the source location being read
+   * @return The value read from the field.
    */
   @Inline
   @Entrypoint
-  public static void referenceNonHeapWrite(Object value, Offset offset, int locationMetadata) {
-    if (NEEDS_REFERENCE_GC_PUTSTATIC_BARRIER) {
-      ObjectReference src = ObjectReference.fromObject(Magic.getJTOC());
-      Selected.Mutator.get().referenceNonHeapWrite(src.toAddress().plus(offset),
-          ObjectReference.fromObject(value),
+  public static Object referenceFieldRead(Object ref, Offset offset, int locationMetadata) {
+    if (NEEDS_REFERENCE_GC_READ_BARRIER) {
+      ObjectReference src = ObjectReference.fromObject(ref);
+      return Selected.Mutator.get().referenceRead(src,
+          src.toAddress().plus(offset),
           offset.toWord(),
-          Word.fromIntZeroExtend(locationMetadata));
+          Word.fromIntZeroExtend(locationMetadata),
+          INSTANCE_FIELD).toObject();
     } else if (VM.VERIFY_ASSERTIONS)
       VM.assertions._assert(false);
+    return null;
   }
 
   /**
-   * Barrier for conditional compare and exchange of reference fields.
+   * Barrier for loads of references from fields of arrays (ie aload).
    *
-   * @param ref the object which is the subject of the compare and exchanges
-   * @param offset the offset of the field to be modified
-   * @param old the old value to swap out
-   * @param value the new value for the field
+   * @param ref the array containing the reference.
+   * @param index the index into the array were the reference resides.
+   * @return the value read from the array
    */
   @Inline
-  public static boolean referenceTryCompareAndSwap(Object ref, Offset offset, Object old, Object value) {
-    if (NEEDS_REFERENCE_GC_WRITE_BARRIER || NEEDS_REFERENCE_GC_READ_BARRIER) {
-      ObjectReference src = ObjectReference.fromObject(ref);
-      return Selected.Mutator.get().referenceTryCompareAndSwap(src,
-          src.toAddress().plus(offset),
-          ObjectReference.fromObject(old),
-          ObjectReference.fromObject(value),
+  @Entrypoint
+  public static Object referenceArrayRead(Object ref, int index) {
+    if (NEEDS_REFERENCE_GC_READ_BARRIER) {
+      ObjectReference array = ObjectReference.fromObject(ref);
+      Offset offset = Offset.fromIntZeroExtend(index << MemoryManagerConstants.LOG_BYTES_IN_ADDRESS);
+      return Selected.Mutator.get().referenceRead(array,
+          array.toAddress().plus(offset),
           offset.toWord(),
-          Word.zero(), // do not have location metadata
-          INSTANCE_FIELD);
+          Word.zero(), // don't know metadata
+          ARRAY_ELEMENT).toObject();
     } else if (VM.VERIFY_ASSERTIONS)
       VM.assertions._assert(false);
-    return false;
+    return null;
   }
 
   /**
@@ -186,70 +189,68 @@
   }
 
   /**
-   * Barrier for loads of references from fields of instances (ie getfield).
+   * Barrier for loads of references from non-heap locations (ie getstatic)
    *
-   * @param ref the object which is the subject of the getfield
-   * @param offset the offset of the field to be read
+   * @param offset the offset of the field to be modified
    * @param locationMetadata an int that encodes the source location being read
-   * @return The value read from the field.
+   * @return the value read from the field
    */
   @Inline
   @Entrypoint
-  public static Object referenceFieldRead(Object ref, Offset offset, int locationMetadata) {
-    if (NEEDS_REFERENCE_GC_READ_BARRIER) {
-      ObjectReference src = ObjectReference.fromObject(ref);
-      return Selected.Mutator.get().referenceRead(src,
+  public static Object referenceNonHeapRead(Offset offset, int locationMetadata) {
+    if (NEEDS_REFERENCE_GC_GETSTATIC_BARRIER) {
+      ObjectReference src = ObjectReference.fromObject(Magic.getJTOC());
+      return Selected.Mutator.get().referenceNonHeapRead(
           src.toAddress().plus(offset),
           offset.toWord(),
-          Word.fromIntZeroExtend(locationMetadata),
-          INSTANCE_FIELD).toObject();
+          Word.fromIntZeroExtend(locationMetadata)).toObject();
     } else if (VM.VERIFY_ASSERTIONS)
       VM.assertions._assert(false);
     return null;
   }
 
+
   /**
-   * Barrier for loads of references from fields of arrays (ie aload).
+   * Barrier for writes of references to non-heap locations (eg statics)
    *
-   * @param ref the array containing the reference.
-   * @param index the index into the array were the reference resides.
-   * @return the value read from the array
+   * @param value the new value to be stored
+   * @param offset the offset of the field to be modified
+   * @param locationMetadata an int that encodes the source location being modified
    */
   @Inline
   @Entrypoint
-  public static Object referenceArrayRead(Object ref, int index) {
-    if (NEEDS_REFERENCE_GC_READ_BARRIER) {
-      ObjectReference array = ObjectReference.fromObject(ref);
-      Offset offset = Offset.fromIntZeroExtend(index << MemoryManagerConstants.LOG_BYTES_IN_ADDRESS);
-      return Selected.Mutator.get().referenceRead(array,
-          array.toAddress().plus(offset),
+  public static void referenceNonHeapWrite(Object value, Offset offset, int locationMetadata) {
+    if (NEEDS_REFERENCE_GC_PUTSTATIC_BARRIER) {
+      ObjectReference src = ObjectReference.fromObject(Magic.getJTOC());
+      Selected.Mutator.get().referenceNonHeapWrite(src.toAddress().plus(offset),
+          ObjectReference.fromObject(value),
           offset.toWord(),
-          Word.zero(), // don't know metadata
-          ARRAY_ELEMENT).toObject();
+          Word.fromIntZeroExtend(locationMetadata));
     } else if (VM.VERIFY_ASSERTIONS)
       VM.assertions._assert(false);
-    return null;
   }
 
   /**
-   * Barrier for loads of references from non-heap locations (ie getstatic)
+   * Barrier for conditional compare and exchange of reference fields.
    *
+   * @param ref the object which is the subject of the compare and exchanges
    * @param offset the offset of the field to be modified
-   * @param locationMetadata an int that encodes the source location being read
-   * @return the value read from the field
+   * @param old the old value to swap out
+   * @param value the new value for the field
    */
   @Inline
-  @Entrypoint
-  public static Object referenceNonHeapRead(Offset offset, int locationMetadata) {
-    if (NEEDS_REFERENCE_GC_GETSTATIC_BARRIER) {
-      ObjectReference src = ObjectReference.fromObject(Magic.getJTOC());
-      return Selected.Mutator.get().referenceNonHeapRead(
+  public static boolean referenceTryCompareAndSwap(Object ref, Offset offset, Object old, Object value) {
+    if (NEEDS_REFERENCE_GC_WRITE_BARRIER || NEEDS_REFERENCE_GC_READ_BARRIER) {
+      ObjectReference src = ObjectReference.fromObject(ref);
+      return Selected.Mutator.get().referenceTryCompareAndSwap(src,
           src.toAddress().plus(offset),
+          ObjectReference.fromObject(old),
+          ObjectReference.fromObject(value),
           offset.toWord(),
-          Word.fromIntZeroExtend(locationMetadata)).toObject();
+          Word.zero(), // do not have location metadata
+          INSTANCE_FIELD);
     } else if (VM.VERIFY_ASSERTIONS)
       VM.assertions._assert(false);
-    return null;
+    return false;
   }
-
 }

Modified: rvmroot/trunk/rvm/src/org/jikesrvm/mm/mminterface/MemoryManager.java
===================================================================
--- rvmroot/trunk/rvm/src/org/jikesrvm/mm/mminterface/MemoryManager.java	2009-09-09 16:10:08 UTC (rev 15779)
+++ rvmroot/trunk/rvm/src/org/jikesrvm/mm/mminterface/MemoryManager.java	2009-09-16 12:13:01 UTC (rev 15780)
@@ -106,7 +106,7 @@
    */
   @Interruptible
   public static void init() {
-    if (VM.VerifyAssertions) VM._assert(!Selected.Constraints.get().needsStaticReadBarrier());
+    if (VM.VerifyAssertions) VM._assert(!Selected.Constraints.get().needsReferenceStaticReadBarrier());
     CollectorThread.init();
     org.jikesrvm.mm.mmtk.Collection.init();
   }


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