changeset 200:66cdb30329a6

Merge
author blacklion
date Thu, 19 Jun 2008 06:02:20 -0700
parents f139919897d2 4f91c08b3e44
children f20b3fcbb16f
files
diffstat 26 files changed, 479 insertions(+), 261 deletions(-) [+]
line wrap: on
line diff
--- a/.hgtags	Tue Jun 17 09:59:59 2008 -0700
+++ b/.hgtags	Thu Jun 19 06:02:20 2008 -0700
@@ -2,3 +2,4 @@
 7836be3e92d0a4f9ee7566f602c91f5609534e66 jdk7-b25
 ad0b851458ff9d1d490ed2d79bb84f75a9fdb753 jdk7-b26
 e3d2692f8442e2d951166dc9bd9a330684754438 jdk7-b27
+c14dab40ed9bf45ad21150bd70c9c80cdf655415 jdk7-b28
--- a/agent/src/share/classes/sun/jvm/hotspot/memory/CompactibleFreeListSpace.java	Tue Jun 17 09:59:59 2008 -0700
+++ b/agent/src/share/classes/sun/jvm/hotspot/memory/CompactibleFreeListSpace.java	Thu Jun 19 06:02:20 2008 -0700
@@ -189,7 +189,7 @@
             cur = cur.addOffsetTo(adjustObjectSizeInBytes(size));
          }
 
-         if (FreeChunk.secondWordIndicatesFreeChunk(dbg.getAddressValue(klassOop))) {
+         if (FreeChunk.indicatesFreeChunk(cur)) {
             if (! cur.equals(regionStart)) {
                res.add(new MemRegion(regionStart, cur));
             }
--- a/agent/src/share/classes/sun/jvm/hotspot/memory/FreeChunk.java	Tue Jun 17 09:59:59 2008 -0700
+++ b/agent/src/share/classes/sun/jvm/hotspot/memory/FreeChunk.java	Thu Jun 19 06:02:20 2008 -0700
@@ -28,6 +28,7 @@
 import sun.jvm.hotspot.debugger.*;
 import sun.jvm.hotspot.types.*;
 import sun.jvm.hotspot.runtime.*;
+import sun.jvm.hotspot.oops.*;
 
 public class FreeChunk extends VMObject {
    static {
@@ -42,13 +43,13 @@
       Type type = db.lookupType("FreeChunk");
       nextField = type.getAddressField("_next");
       prevField = type.getAddressField("_prev");
-      sizeField = type.getCIntegerField("_size");
+      sizeField = type.getAddressField("_size");
    }
 
    // Fields
    private static AddressField nextField;
    private static AddressField prevField;
-   private static CIntegerField sizeField;
+   private static AddressField sizeField;
 
    // Accessors
    public FreeChunk next() {
@@ -61,20 +62,34 @@
    }
 
    public long size() {
-      return sizeField.getValue(addr);
+      if (VM.getVM().isCompressedOopsEnabled()) {
+        Mark mark = new Mark(sizeField.getValue(addr));
+        return mark.getSize();
+      } else {
+        Address size = sizeField.getValue(addr);
+        Debugger dbg = VM.getVM().getDebugger();
+        return dbg.getAddressValue(size);
+      }
    }
 
    public FreeChunk(Address addr) {
       super(addr);
    }
 
-   public static boolean secondWordIndicatesFreeChunk(long word) {
-      return (word & 0x1L) == 0x1L;
+   public static boolean indicatesFreeChunk(Address cur) {
+      FreeChunk f = new FreeChunk(cur);
+      return f.isFree();
    }
 
    public boolean isFree() {
-      Debugger dbg = VM.getVM().getDebugger();
-      Address prev = prevField.getValue(addr);
-      return secondWordIndicatesFreeChunk(dbg.getAddressValue(prev));
+      if (VM.getVM().isCompressedOopsEnabled()) {
+        Mark mark = new Mark(sizeField.getValue(addr));
+        return mark.isCmsFreeChunk();
+      } else {
+        Address prev = prevField.getValue(addr);
+        Debugger dbg = VM.getVM().getDebugger();
+        long word = dbg.getAddressValue(prev);
+        return (word & 0x1L) == 0x1L;
+      }
    }
 }
--- a/agent/src/share/classes/sun/jvm/hotspot/oops/Mark.java	Tue Jun 17 09:59:59 2008 -0700
+++ b/agent/src/share/classes/sun/jvm/hotspot/oops/Mark.java	Thu Jun 19 06:02:20 2008 -0700
@@ -79,6 +79,11 @@
     noHashInPlace       = db.lookupLongConstant("markOopDesc::no_hash_in_place").longValue();
     noLockInPlace       = db.lookupLongConstant("markOopDesc::no_lock_in_place").longValue();
     maxAge              = db.lookupLongConstant("markOopDesc::max_age").longValue();
+
+    /* Constants in markOop used by CMS. */
+    cmsShift            = db.lookupLongConstant("markOopDesc::cms_shift").longValue();
+    cmsMask             = db.lookupLongConstant("markOopDesc::cms_mask").longValue();
+    sizeShift           = db.lookupLongConstant("markOopDesc::size_shift").longValue();
   }
 
   // Field accessors
@@ -120,6 +125,11 @@
 
   private static long maxAge;
 
+  /* Constants in markOop used by CMS. */
+  private static long cmsShift;
+  private static long cmsMask;
+  private static long sizeShift;
+
   public Mark(Address addr) {
     super(addr);
   }
@@ -290,4 +300,11 @@
   //
   //  // Recover address of oop from encoded form used in mark
   //  inline void* decode_pointer() { return clear_lock_bits(); }
+
+  // Copy markOop methods for CMS here.
+  public boolean isCmsFreeChunk() {
+    return isUnlocked() &&
+           (Bits.maskBitsLong(value() >> cmsShift, cmsMask) & 0x1L) == 0x1L;
+  }
+  public long getSize() { return (long)(value() >> sizeShift); }
 }
--- a/src/share/vm/classfile/vmSymbols.hpp	Tue Jun 17 09:59:59 2008 -0700
+++ b/src/share/vm/classfile/vmSymbols.hpp	Thu Jun 19 06:02:20 2008 -0700
@@ -283,6 +283,7 @@
   template(cache_field_name,                          "cache")                                    \
   template(value_name,                                "value")                                    \
   template(frontCacheEnabled_name,                    "frontCacheEnabled")                        \
+  template(stringCacheEnabled_name,                   "stringCacheEnabled")                       \
                                                                                                   \
   /* non-intrinsic name/signature pairs: */                                                       \
   template(register_method_name,                      "register")                                 \
--- a/src/share/vm/gc_implementation/concurrentMarkSweep/compactibleFreeListSpace.cpp	Tue Jun 17 09:59:59 2008 -0700
+++ b/src/share/vm/gc_implementation/concurrentMarkSweep/compactibleFreeListSpace.cpp	Thu Jun 19 06:02:20 2008 -0700
@@ -805,28 +805,30 @@
   // This must be volatile, or else there is a danger that the compiler
   // will compile the code below into a sometimes-infinite loop, by keeping
   // the value read the first time in a register.
-  oop o = (oop)p;
-  volatile oop* second_word_addr = o->klass_addr();
   while (true) {
-    klassOop k = (klassOop)(*second_word_addr);
     // We must do this until we get a consistent view of the object.
-    if (FreeChunk::secondWordIndicatesFreeChunk((intptr_t)k)) {
-      FreeChunk* fc = (FreeChunk*)p;
-      volatile size_t* sz_addr = (volatile size_t*)(fc->size_addr());
-      size_t res = (*sz_addr);
-      klassOop k2 = (klassOop)(*second_word_addr);  // Read to confirm.
-      if (k == k2) {
+    if (FreeChunk::indicatesFreeChunk(p)) {
+      volatile FreeChunk* fc = (volatile FreeChunk*)p;
+      size_t res = fc->size();
+      // If the object is still a free chunk, return the size, else it
+      // has been allocated so try again.
+      if (FreeChunk::indicatesFreeChunk(p)) {
         assert(res != 0, "Block size should not be 0");
         return res;
       }
-    } else if (k != NULL) {
-      assert(k->is_oop(true /* ignore mark word */), "Should really be klass oop.");
-      assert(o->is_parsable(), "Should be parsable");
-      assert(o->is_oop(true /* ignore mark word */), "Should be an oop.");
-      size_t res = o->size_given_klass(k->klass_part());
-      res = adjustObjectSize(res);
-      assert(res != 0, "Block size should not be 0");
-      return res;
+    } else {
+      // must read from what 'p' points to in each loop.
+      klassOop k = ((volatile oopDesc*)p)->klass_or_null();
+      if (k != NULL) {
+        assert(k->is_oop(true /* ignore mark word */), "Should really be klass oop.");
+        oop o = (oop)p;
+        assert(o->is_parsable(), "Should be parsable");
+        assert(o->is_oop(true /* ignore mark word */), "Should be an oop.");
+        size_t res = o->size_given_klass(k->klass_part());
+        res = adjustObjectSize(res);
+        assert(res != 0, "Block size should not be 0");
+        return res;
+      }
     }
   }
 }
@@ -845,31 +847,31 @@
   // This must be volatile, or else there is a danger that the compiler
   // will compile the code below into a sometimes-infinite loop, by keeping
   // the value read the first time in a register.
-  oop o = (oop)p;
-  volatile oop* second_word_addr = o->klass_addr();
   DEBUG_ONLY(uint loops = 0;)
   while (true) {
-    klassOop k = (klassOop)(*second_word_addr);
     // We must do this until we get a consistent view of the object.
-    if (FreeChunk::secondWordIndicatesFreeChunk((intptr_t)k)) {
-      FreeChunk* fc = (FreeChunk*)p;
-      volatile size_t* sz_addr = (volatile size_t*)(fc->size_addr());
-      size_t res = (*sz_addr);
-      klassOop k2 = (klassOop)(*second_word_addr);  // Read to confirm.
-      if (k == k2) {
+    if (FreeChunk::indicatesFreeChunk(p)) {
+      volatile FreeChunk* fc = (volatile FreeChunk*)p;
+      size_t res = fc->size();
+      if (FreeChunk::indicatesFreeChunk(p)) {
         assert(res != 0, "Block size should not be 0");
         assert(loops == 0, "Should be 0");
         return res;
       }
-    } else if (k != NULL && o->is_parsable()) {
-      assert(k->is_oop(), "Should really be klass oop.");
-      assert(o->is_oop(), "Should be an oop");
-      size_t res = o->size_given_klass(k->klass_part());
-      res = adjustObjectSize(res);
-      assert(res != 0, "Block size should not be 0");
-      return res;
     } else {
-      return c->block_size_if_printezis_bits(p);
+      // must read from what 'p' points to in each loop.
+      klassOop k = ((volatile oopDesc*)p)->klass_or_null();
+      if (k != NULL && ((oopDesc*)p)->is_parsable()) {
+        assert(k->is_oop(), "Should really be klass oop.");
+        oop o = (oop)p;
+        assert(o->is_oop(), "Should be an oop");
+        size_t res = o->size_given_klass(k->klass_part());
+        res = adjustObjectSize(res);
+        assert(res != 0, "Block size should not be 0");
+        return res;
+      } else {
+        return c->block_size_if_printezis_bits(p);
+      }
     }
     assert(loops == 0, "Can loop at most once");
     DEBUG_ONLY(loops++;)
@@ -907,9 +909,8 @@
   // and those objects (if garbage) may have been modified to hold
   // live range information.
   // assert(ParallelGCThreads > 0 || _bt.block_start(p) == p, "Should be a block boundary");
-  klassOop k = oop(p)->klass();
-  intptr_t ki = (intptr_t)k;
-  if (FreeChunk::secondWordIndicatesFreeChunk(ki)) return false;
+  if (FreeChunk::indicatesFreeChunk(p)) return false;
+  klassOop k = oop(p)->klass_or_null();
   if (k != NULL) {
     // Ignore mark word because it may have been used to
     // chain together promoted objects (the last one
@@ -1027,7 +1028,7 @@
     FreeChunk* fc = (FreeChunk*)res;
     fc->markNotFree();
     assert(!fc->isFree(), "shouldn't be marked free");
-    assert(oop(fc)->klass() == NULL, "should look uninitialized");
+    assert(oop(fc)->klass_or_null() == NULL, "should look uninitialized");
     // Verify that the block offset table shows this to
     // be a single block, but not one which is unallocated.
     _bt.verify_single_block(res, size);
@@ -2593,7 +2594,7 @@
   }
   res->markNotFree();
   assert(!res->isFree(), "shouldn't be marked free");
-  assert(oop(res)->klass() == NULL, "should look uninitialized");
+  assert(oop(res)->klass_or_null() == NULL, "should look uninitialized");
   // mangle a just allocated object with a distinct pattern.
   debug_only(res->mangleAllocated(word_sz));
   return (HeapWord*)res;
--- a/src/share/vm/gc_implementation/concurrentMarkSweep/concurrentMarkSweepGeneration.cpp	Tue Jun 17 09:59:59 2008 -0700
+++ b/src/share/vm/gc_implementation/concurrentMarkSweep/concurrentMarkSweepGeneration.cpp	Thu Jun 19 06:02:20 2008 -0700
@@ -190,7 +190,8 @@
   // depends on this property.
   debug_only(
     FreeChunk* junk = NULL;
-    assert(junk->prev_addr() == (void*)(oop(junk)->klass_addr()),
+    assert(UseCompressedOops ||
+           junk->prev_addr() == (void*)(oop(junk)->klass_addr()),
            "Offset of FreeChunk::_prev within FreeChunk must match"
            "  that of OopDesc::_klass within OopDesc");
   )
@@ -1039,7 +1040,7 @@
                                       // mark end of object
   }
   // check that oop looks uninitialized
-  assert(oop(start)->klass() == NULL, "_klass should be NULL");
+  assert(oop(start)->klass_or_null() == NULL, "_klass should be NULL");
 }
 
 void CMSCollector::promoted(bool par, HeapWord* start,
@@ -1309,17 +1310,25 @@
      }
   }
   oop obj = oop(obj_ptr);
-  assert(obj->klass() == NULL, "Object should be uninitialized here.");
+  assert(obj->klass_or_null() == NULL, "Object should be uninitialized here.");
   // Otherwise, copy the object.  Here we must be careful to insert the
   // klass pointer last, since this marks the block as an allocated object.
+  // Except with compressed oops it's the mark word.
   HeapWord* old_ptr = (HeapWord*)old;
   if (word_sz > (size_t)oopDesc::header_size()) {
     Copy::aligned_disjoint_words(old_ptr + oopDesc::header_size(),
                                  obj_ptr + oopDesc::header_size(),
                                  word_sz - oopDesc::header_size());
   }
+
+  if (UseCompressedOops) {
+    // Copy gap missed by (aligned) header size calculation above
+    obj->set_klass_gap(old->klass_gap());
+  }
+
   // Restore the mark word copied above.
   obj->set_mark(m);
+
   // Now we can track the promoted object, if necessary.  We take care
   // To delay the transition from uninitialized to full object
   // (i.e., insertion of klass pointer) until after, so that it
@@ -1327,7 +1336,8 @@
   if (promoInfo->tracking()) {
     promoInfo->track((PromotedObject*)obj, old->klass());
   }
-  // Finally, install the klass pointer.
+
+  // Finally, install the klass pointer (this should be volatile).
   obj->set_klass(old->klass());
 
   assert(old->is_oop(), "Will dereference klass ptr below");
@@ -6165,7 +6175,7 @@
 HeapWord* CMSCollector::next_card_start_after_block(HeapWord* addr) const {
   size_t sz = 0;
   oop p = (oop)addr;
-  if (p->klass() != NULL && p->is_parsable()) {
+  if (p->klass_or_null() != NULL && p->is_parsable()) {
     sz = CompactibleFreeListSpace::adjustObjectSize(p->size());
   } else {
     sz = block_size_using_printezis_bits(addr);
@@ -6602,7 +6612,7 @@
   }
   if (_bitMap->isMarked(addr)) {
     // it's marked; is it potentially uninitialized?
-    if (p->klass() != NULL) {
+    if (p->klass_or_null() != NULL) {
       if (CMSPermGenPrecleaningEnabled && !p->is_parsable()) {
         // Signal precleaning to redirty the card since
         // the klass pointer is already installed.
@@ -6615,11 +6625,8 @@
         if (p->is_objArray()) {
           // objArrays are precisely marked; restrict scanning
           // to dirty cards only.
-          size = p->oop_iterate(_scanningClosure, mr);
-          assert(size == CompactibleFreeListSpace::adjustObjectSize(size),
-                 "adjustObjectSize should be the identity for array sizes, "
-                 "which are necessarily larger than minimum object size of "
-                 "two heap words");
+          size = CompactibleFreeListSpace::adjustObjectSize(
+                   p->oop_iterate(_scanningClosure, mr));
         } else {
           // A non-array may have been imprecisely marked; we need
           // to scan object in its entirety.
@@ -6653,7 +6660,7 @@
     }
   } else {
     // Either a not yet marked object or an uninitialized object
-    if (p->klass() == NULL || !p->is_parsable()) {
+    if (p->klass_or_null() == NULL || !p->is_parsable()) {
       // An uninitialized object, skip to the next card, since
       // we may not be able to read its P-bits yet.
       assert(size == 0, "Initial value");
@@ -6710,7 +6717,7 @@
   HeapWord* addr = (HeapWord*)p;
   DEBUG_ONLY(_collector->verify_work_stacks_empty();)
   assert(!_span.contains(addr), "we are scanning the survivor spaces");
-  assert(p->klass() != NULL, "object should be initializd");
+  assert(p->klass_or_null() != NULL, "object should be initializd");
   assert(p->is_parsable(), "must be parsable.");
   // an initialized object; ignore mark word in verification below
   // since we are running concurrent with mutators
@@ -6868,7 +6875,7 @@
     assert(_skipBits == 0, "tautology");
     _skipBits = 2;  // skip next two marked bits ("Printezis-marks")
     oop p = oop(addr);
-    if (p->klass() == NULL || !p->is_parsable()) {
+    if (p->klass_or_null() == NULL || !p->is_parsable()) {
       DEBUG_ONLY(if (!_verifying) {)
         // We re-dirty the cards on which this object lies and increase
         // the _threshold so that we'll come back to scan this object
@@ -6890,7 +6897,7 @@
           if (_threshold < end_card_addr) {
             _threshold = end_card_addr;
           }
-          if (p->klass() != NULL) {
+          if (p->klass_or_null() != NULL) {
             // Redirty the range of cards...
             _mut->mark_range(redirty_range);
           } // ...else the setting of klass will dirty the card anyway.
@@ -7048,7 +7055,7 @@
     assert(_skip_bits == 0, "tautology");
     _skip_bits = 2;  // skip next two marked bits ("Printezis-marks")
     oop p = oop(addr);
-    if (p->klass() == NULL || !p->is_parsable()) {
+    if (p->klass_or_null() == NULL || !p->is_parsable()) {
       // in the case of Clean-on-Enter optimization, redirty card
       // and avoid clearing card by increasing  the threshold.
       return;
@@ -8023,7 +8030,7 @@
            "alignment problem");
 
     #ifdef DEBUG
-      if (oop(addr)->klass() != NULL &&
+      if (oop(addr)->klass_or_null() != NULL &&
           (   !_collector->should_unload_classes()
            || oop(addr)->is_parsable())) {
         // Ignore mark word because we are running concurrent with mutators
@@ -8036,7 +8043,7 @@
 
   } else {
     // This should be an initialized object that's alive.
-    assert(oop(addr)->klass() != NULL &&
+    assert(oop(addr)->klass_or_null() != NULL &&
            (!_collector->should_unload_classes()
             || oop(addr)->is_parsable()),
            "Should be an initialized object");
--- a/src/share/vm/gc_implementation/concurrentMarkSweep/freeBlockDictionary.hpp	Tue Jun 17 09:59:59 2008 -0700
+++ b/src/share/vm/gc_implementation/concurrentMarkSweep/freeBlockDictionary.hpp	Thu Jun 19 06:02:20 2008 -0700
@@ -22,88 +22,6 @@
  *
  */
 
-//
-// Free block maintenance for Concurrent Mark Sweep Generation
-//
-// The main data structure for free blocks are
-// . an indexed array of small free blocks, and
-// . a dictionary of large free blocks
-//
-
-// No virtuals in FreeChunk (don't want any vtables).
-
-// A FreeChunk is merely a chunk that can be in a doubly linked list
-// and has a size field. NOTE: FreeChunks are distinguished from allocated
-// objects in two ways (by the sweeper). The second word (prev) has the
-// LSB set to indicate a free chunk; allocated objects' klass() pointers
-// don't have their LSB set. The corresponding bit in the CMSBitMap is
-// set when the chunk is allocated. There are also blocks that "look free"
-// but are not part of the free list and should not be coalesced into larger
-// free blocks. These free blocks have their two LSB's set.
-
-class FreeChunk VALUE_OBJ_CLASS_SPEC {
-  friend class VMStructs;
-  FreeChunk* _next;
-  FreeChunk* _prev;
-  size_t     _size;
-
- public:
-  NOT_PRODUCT(static const size_t header_size();)
-  // Returns "true" if the "wrd", which is required to be the second word
-  // of a block, indicates that the block represents a free chunk.
-  static bool secondWordIndicatesFreeChunk(intptr_t wrd) {
-    return (wrd & 0x1) == 0x1;
-  }
-  bool isFree()       const {
-    return secondWordIndicatesFreeChunk((intptr_t)_prev);
-  }
-  bool cantCoalesce() const { return (((intptr_t)_prev) & 0x3) == 0x3; }
-  FreeChunk* next()   const { return _next; }
-  FreeChunk* prev()   const { return (FreeChunk*)(((intptr_t)_prev) & ~(0x3)); }
-  debug_only(void* prev_addr() const { return (void*)&_prev; })
-
-  void linkAfter(FreeChunk* ptr) {
-    linkNext(ptr);
-    if (ptr != NULL) ptr->linkPrev(this);
-  }
-  void linkAfterNonNull(FreeChunk* ptr) {
-    assert(ptr != NULL, "precondition violation");
-    linkNext(ptr);
-    ptr->linkPrev(this);
-  }
-  void linkNext(FreeChunk* ptr) { _next = ptr; }
-  void linkPrev(FreeChunk* ptr) { _prev = (FreeChunk*)((intptr_t)ptr | 0x1); }
-  void clearPrev()              { _prev = NULL; }
-  void clearNext()              { _next = NULL; }
-  void dontCoalesce()      {
-    // the block should be free
-    assert(isFree(), "Should look like a free block");
-    _prev = (FreeChunk*)(((intptr_t)_prev) | 0x2);
-  }
-  void markFree()    { _prev = (FreeChunk*)((intptr_t)_prev | 0x1);    }
-  void markNotFree() { _prev = NULL; }
-
-  size_t size()           const { return _size; }
-  void setSize(size_t size)     { _size = size; }
-
-  // For volatile reads:
-  size_t* size_addr()           { return &_size; }
-
-  // Return the address past the end of this chunk
-  HeapWord* end() const { return ((HeapWord*) this) + _size; }
-
-  // debugging
-  void verify()             const PRODUCT_RETURN;
-  void verifyList()         const PRODUCT_RETURN;
-  void mangleAllocated(size_t size) PRODUCT_RETURN;
-  void mangleFreed(size_t size)     PRODUCT_RETURN;
-};
-
-// Alignment helpers etc.
-#define numQuanta(x,y) ((x+y-1)/y)
-enum AlignmentConstants {
-  MinChunkSize = numQuanta(sizeof(FreeChunk), MinObjAlignmentInBytes) * MinObjAlignment
-};
 
 // A FreeBlockDictionary is an abstract superclass that will allow
 // a number of alternative implementations in the future.
--- a/src/share/vm/gc_implementation/concurrentMarkSweep/freeChunk.cpp	Tue Jun 17 09:59:59 2008 -0700
+++ b/src/share/vm/gc_implementation/concurrentMarkSweep/freeChunk.cpp	Thu Jun 19 06:02:20 2008 -0700
@@ -47,15 +47,15 @@
   Copy::fill_to_words(addr + hdr, size - hdr, baadbabeHeapWord);
 }
 
-void FreeChunk::mangleFreed(size_t size) {
+void FreeChunk::mangleFreed(size_t sz) {
   assert(baadbabeHeapWord != deadbeefHeapWord, "Need distinct patterns");
   // mangle all but the header of a just-freed block of storage
   // just prior to passing it to the storage dictionary
-  assert(size >= MinChunkSize, "smallest size of object");
-  assert(size == _size, "just checking");
+  assert(sz >= MinChunkSize, "smallest size of object");
+  assert(sz == size(), "just checking");
   HeapWord* addr = (HeapWord*)this;
   size_t hdr = header_size();
-  Copy::fill_to_words(addr + hdr, size - hdr, deadbeefHeapWord);
+  Copy::fill_to_words(addr + hdr, sz - hdr, deadbeefHeapWord);
 }
 
 void FreeChunk::verifyList() const {
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/share/vm/gc_implementation/concurrentMarkSweep/freeChunk.hpp	Thu Jun 19 06:02:20 2008 -0700
@@ -0,0 +1,137 @@
+/*
+ * Copyright 2001-2005 Sun Microsystems, Inc.  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 Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
+ * CA 95054 USA or visit www.sun.com if you need additional information or
+ * have any questions.
+ *
+ */
+
+//
+// Free block maintenance for Concurrent Mark Sweep Generation
+//
+// The main data structure for free blocks are
+// . an indexed array of small free blocks, and
+// . a dictionary of large free blocks
+//
+
+// No virtuals in FreeChunk (don't want any vtables).
+
+// A FreeChunk is merely a chunk that can be in a doubly linked list
+// and has a size field. NOTE: FreeChunks are distinguished from allocated
+// objects in two ways (by the sweeper), depending on whether the VM is 32 or
+// 64 bits.
+// In 32 bits or 64 bits without CompressedOops, the second word (prev) has the
+// LSB set to indicate a free chunk; allocated objects' klass() pointers
+// don't have their LSB set. The corresponding bit in the CMSBitMap is
+// set when the chunk is allocated. There are also blocks that "look free"
+// but are not part of the free list and should not be coalesced into larger
+// free blocks. These free blocks have their two LSB's set.
+
+class FreeChunk VALUE_OBJ_CLASS_SPEC {
+  friend class VMStructs;
+  // For 64 bit compressed oops, the markOop encodes both the size and the
+  // indication that this is a FreeChunk and not an object.
+  volatile size_t   _size;
+  FreeChunk* _prev;
+  FreeChunk* _next;
+
+  markOop mark()     const volatile { return (markOop)_size; }
+  void set_mark(markOop m)          { _size = (size_t)m; }
+
+ public:
+  NOT_PRODUCT(static const size_t header_size();)
+
+  // Returns "true" if the address indicates that the block represents
+  // a free chunk.
+  static bool indicatesFreeChunk(const HeapWord* addr) {
+    // Force volatile read from addr because value might change between
+    // calls.  We really want the read of _mark and _prev from this pointer
+    // to be volatile but making the fields volatile causes all sorts of
+    // compilation errors.
+    return ((volatile FreeChunk*)addr)->isFree();
+  }
+
+  bool isFree() const volatile {
+    LP64_ONLY(if (UseCompressedOops) return mark()->is_cms_free_chunk(); else)
+    return (((intptr_t)_prev) & 0x1) == 0x1;
+  }
+  bool cantCoalesce() const {
+    assert(isFree(), "can't get coalesce bit on not free");
+    return (((intptr_t)_prev) & 0x2) == 0x2;
+  }
+  void dontCoalesce() {
+    // the block should be free
+    assert(isFree(), "Should look like a free block");
+    _prev = (FreeChunk*)(((intptr_t)_prev) | 0x2);
+  }
+  FreeChunk* prev() const {
+    return (FreeChunk*)(((intptr_t)_prev) & ~(0x3));
+  }
+
+  debug_only(void* prev_addr() const { return (void*)&_prev; })
+
+  size_t size() const volatile {
+    LP64_ONLY(if (UseCompressedOops) return mark()->get_size(); else )
+    return _size;
+  }
+  void setSize(size_t sz) {
+    LP64_ONLY(if (UseCompressedOops) set_mark(markOopDesc::set_size_and_free(sz)); else )
+    _size = sz;
+  }
+
+  FreeChunk* next()   const { return _next; }
+
+  void linkAfter(FreeChunk* ptr) {
+    linkNext(ptr);
+    if (ptr != NULL) ptr->linkPrev(this);
+  }
+  void linkAfterNonNull(FreeChunk* ptr) {
+    assert(ptr != NULL, "precondition violation");
+    linkNext(ptr);
+    ptr->linkPrev(this);
+  }
+  void linkNext(FreeChunk* ptr) { _next = ptr; }
+  void linkPrev(FreeChunk* ptr) {
+     LP64_ONLY(if (UseCompressedOops) _prev = ptr; else)
+     _prev = (FreeChunk*)((intptr_t)ptr | 0x1);
+  }
+  void clearPrev()              { _prev = NULL; }
+  void clearNext()              { _next = NULL; }
+  void markNotFree() {
+   LP64_ONLY(if (UseCompressedOops) set_mark(markOopDesc::prototype());)
+   // Also set _prev to null
+   _prev = NULL;
+  }
+
+  // Return the address past the end of this chunk
+  HeapWord* end() const { return ((HeapWord*) this) + size(); }
+
+  // debugging
+  void verify()             const PRODUCT_RETURN;
+  void verifyList()         const PRODUCT_RETURN;
+  void mangleAllocated(size_t size) PRODUCT_RETURN;
+  void mangleFreed(size_t size)     PRODUCT_RETURN;
+};
+
+// Alignment helpers etc.
+#define numQuanta(x,y) ((x+y-1)/y)
+enum AlignmentConstants {
+  MinChunkSize = numQuanta(sizeof(FreeChunk), MinObjAlignmentInBytes) * MinObjAlignment
+};
+
--- a/src/share/vm/gc_implementation/concurrentMarkSweep/vmStructs_cms.hpp	Tue Jun 17 09:59:59 2008 -0700
+++ b/src/share/vm/gc_implementation/concurrentMarkSweep/vmStructs_cms.hpp	Thu Jun 19 06:02:20 2008 -0700
@@ -23,6 +23,7 @@
  */
 
 #define VM_STRUCTS_CMS(nonstatic_field, \
+                   volatile_nonstatic_field, \
                    static_field) \
   nonstatic_field(CompactibleFreeListSpace,    _collector,                                    CMSCollector*)                         \
   nonstatic_field(CompactibleFreeListSpace,    _bt,                                           BlockOffsetArrayNonContigSpace)        \
@@ -36,9 +37,9 @@
   nonstatic_field(CMSCollector,                _markBitMap,                                   CMSBitMap)                             \
   nonstatic_field(ConcurrentMarkSweepGeneration, _cmsSpace,                                   CompactibleFreeListSpace*)             \
      static_field(ConcurrentMarkSweepThread,   _collector,                                    CMSCollector*)                         \
+  volatile_nonstatic_field(FreeChunk,          _size,                                         size_t)                                \
   nonstatic_field(FreeChunk,                   _next,                                         FreeChunk*)                            \
   nonstatic_field(FreeChunk,                   _prev,                                         FreeChunk*)                            \
-  nonstatic_field(FreeChunk,                   _size,                                         size_t)                                \
   nonstatic_field(LinearAllocBlock,            _word_size,                                    size_t)                                \
   nonstatic_field(FreeList,                    _size,                                         size_t)                                \
   nonstatic_field(FreeList,                    _count,                                        ssize_t)                               \
--- a/src/share/vm/gc_implementation/includeDB_gc_concurrentMarkSweep	Tue Jun 17 09:59:59 2008 -0700
+++ b/src/share/vm/gc_implementation/includeDB_gc_concurrentMarkSweep	Thu Jun 19 06:02:20 2008 -0700
@@ -206,6 +206,7 @@
 
 freeBlockDictionary.hpp                 allocation.hpp
 freeBlockDictionary.hpp                 debug.hpp
+freeBlockDictionary.hpp                 freeChunk.hpp
 freeBlockDictionary.hpp                 globalDefinitions.hpp
 freeBlockDictionary.hpp                 memRegion.hpp
 freeBlockDictionary.hpp                 mutex.hpp
@@ -214,6 +215,14 @@
 freeChunk.cpp                           copy.hpp
 freeChunk.cpp                           freeBlockDictionary.hpp
 
+freeChunk.hpp                           allocation.hpp
+freeChunk.hpp                           debug.hpp
+freeChunk.hpp                           globalDefinitions.hpp
+freeChunk.hpp                           markOop.hpp
+freeChunk.hpp                           memRegion.hpp
+freeChunk.hpp                           mutex.hpp
+freeChunk.hpp                           ostream.hpp
+
 freeList.cpp                            freeBlockDictionary.hpp
 freeList.cpp                            freeList.hpp
 freeList.cpp                            globals.hpp
--- a/src/share/vm/gc_implementation/shared/immutableSpace.cpp	Tue Jun 17 09:59:59 2008 -0700
+++ b/src/share/vm/gc_implementation/shared/immutableSpace.cpp	Thu Jun 19 06:02:20 2008 -0700
@@ -66,7 +66,7 @@
 
 #endif
 
-void ImmutableSpace::verify(bool allow_dirty) const {
+void ImmutableSpace::verify(bool allow_dirty) {
   HeapWord* p = bottom();
   HeapWord* t = end();
   HeapWord* prev_p = NULL;
--- a/src/share/vm/gc_implementation/shared/immutableSpace.hpp	Tue Jun 17 09:59:59 2008 -0700
+++ b/src/share/vm/gc_implementation/shared/immutableSpace.hpp	Thu Jun 19 06:02:20 2008 -0700
@@ -59,5 +59,5 @@
   // Debugging
   virtual void print() const            PRODUCT_RETURN;
   virtual void print_short() const      PRODUCT_RETURN;
-  virtual void verify(bool allow_dirty) const;
+  virtual void verify(bool allow_dirty);
 };
--- a/src/share/vm/gc_implementation/shared/mutableNUMASpace.cpp	Tue Jun 17 09:59:59 2008 -0700
+++ b/src/share/vm/gc_implementation/shared/mutableNUMASpace.cpp	Thu Jun 19 06:02:20 2008 -0700
@@ -599,12 +599,28 @@
 // Mark the the holes in chunks below the top() as invalid.
 void MutableNUMASpace::set_top(HeapWord* value) {
   bool found_top = false;
-  for (int i = 0; i < lgrp_spaces()->length(); i++) {
+  for (int i = 0; i < lgrp_spaces()->length();) {
     LGRPSpace *ls = lgrp_spaces()->at(i);
     MutableSpace *s = ls->space();
     HeapWord *top = MAX2((HeapWord*)round_down((intptr_t)s->top(), page_size()), s->bottom());
 
     if (s->contains(value)) {
+      // Check if setting the chunk's top to a given value would create a hole less than
+      // a minimal object; assuming that's not the last chunk in which case we don't care.
+      if (i < lgrp_spaces()->length() - 1) {
+        size_t remainder = pointer_delta(s->end(), value);
+        const size_t minimal_object_size = oopDesc::header_size();
+        if (remainder < minimal_object_size && remainder > 0) {
+          // Add a filler object of a minimal size, it will cross the chunk boundary.
+          SharedHeap::fill_region_with_object(MemRegion(value, minimal_object_size));
+          value += minimal_object_size;
+          assert(!s->contains(value), "Should be in the next chunk");
+          // Restart the loop from the same chunk, since the value has moved
+          // to the next one.
+          continue;
+        }
+      }
+
       if (!os::numa_has_static_binding() && top < value && top < s->end()) {
         ls->add_invalid_region(MemRegion(top, value));
       }
@@ -620,6 +636,7 @@
           s->set_top(s->end());
         }
     }
+    i++;
   }
   MutableSpace::set_top(value);
 }
@@ -700,12 +717,14 @@
   MutableSpace *s = lgrp_spaces()->at(i)->space();
   HeapWord *p = s->cas_allocate(size);
   if (p != NULL) {
-    size_t remainder = pointer_delta(s->end(), p);
+    size_t remainder = pointer_delta(s->end(), p + size);
     if (remainder < (size_t)oopDesc::header_size() && remainder > 0) {
       if (s->cas_deallocate(p, size)) {
         // We were the last to allocate and created a fragment less than
         // a minimal object.
         p = NULL;
+      } else {
+        guarantee(false, "Deallocation should always succeed");
       }
     }
   }
@@ -761,10 +780,12 @@
   }
 }
 
-void MutableNUMASpace::verify(bool allow_dirty) const {
- for (int i = 0; i < lgrp_spaces()->length(); i++) {
-    lgrp_spaces()->at(i)->space()->verify(allow_dirty);
-  }
+void MutableNUMASpace::verify(bool allow_dirty) {
+  // This can be called after setting an arbitary value to the space's top,
+  // so an object can cross the chunk boundary. We ensure the parsablity
+  // of the space and just walk the objects in linear fashion.
+  ensure_parsability();
+  MutableSpace::verify(allow_dirty);
 }
 
 // Scan pages and gather stats about page placement and size.
--- a/src/share/vm/gc_implementation/shared/mutableNUMASpace.hpp	Tue Jun 17 09:59:59 2008 -0700
+++ b/src/share/vm/gc_implementation/shared/mutableNUMASpace.hpp	Thu Jun 19 06:02:20 2008 -0700
@@ -192,7 +192,7 @@
   // Debugging
   virtual void print_on(outputStream* st) const;
   virtual void print_short_on(outputStream* st) const;
-  virtual void verify(bool allow_dirty) const;
+  virtual void verify(bool allow_dirty);
 
   virtual void set_top(HeapWord* value);
 };
--- a/src/share/vm/gc_implementation/shared/mutableSpace.cpp	Tue Jun 17 09:59:59 2008 -0700
+++ b/src/share/vm/gc_implementation/shared/mutableSpace.cpp	Thu Jun 19 06:02:20 2008 -0700
@@ -118,7 +118,7 @@
                  bottom(), top(), end());
 }
 
-void MutableSpace::verify(bool allow_dirty) const {
+void MutableSpace::verify(bool allow_dirty) {
   HeapWord* p = bottom();
   HeapWord* t = top();
   HeapWord* prev_p = NULL;
--- a/src/share/vm/gc_implementation/shared/mutableSpace.hpp	Tue Jun 17 09:59:59 2008 -0700
+++ b/src/share/vm/gc_implementation/shared/mutableSpace.hpp	Thu Jun 19 06:02:20 2008 -0700
@@ -98,5 +98,5 @@
   virtual void print_on(outputStream* st) const;
   virtual void print_short() const;
   virtual void print_short_on(outputStream* st) const;
-  virtual void verify(bool allow_dirty) const;
+  virtual void verify(bool allow_dirty);
 };
--- a/src/share/vm/oops/markOop.hpp	Tue Jun 17 09:59:59 2008 -0700
+++ b/src/share/vm/oops/markOop.hpp	Thu Jun 19 06:02:20 2008 -0700
@@ -29,8 +29,10 @@
 //
 // Bit-format of an object header (most significant first):
 //
-//
-//  unused:0/25 hash:25/31 age:4 biased_lock:1 lock:2 = 32/64 bits
+//  32 bits: unused:0  hash:25 age:4 biased_lock:1 lock:2
+//  64 bits: unused:24 hash:31 cms:2 age:4 biased_lock:1 lock:2
+//           unused:20 size:35 cms:2 age:4 biased_lock:1 lock:2 (if cms
+//                                                               free chunk)
 //
 //  - hash contains the identity hash value: largest value is
 //    31 bits, see os::random().  Also, 64-bit vm's require
@@ -91,6 +93,7 @@
          biased_lock_bits         = 1,
          max_hash_bits            = BitsPerWord - age_bits - lock_bits - biased_lock_bits,
          hash_bits                = max_hash_bits > 31 ? 31 : max_hash_bits,
+         cms_bits                 = LP64_ONLY(1) NOT_LP64(0),
          epoch_bits               = 2
   };
 
@@ -106,7 +109,8 @@
   enum { lock_shift               = 0,
          biased_lock_shift        = lock_bits,
          age_shift                = lock_bits + biased_lock_bits,
-         hash_shift               = lock_bits + biased_lock_bits + age_bits,
+         cms_shift                = age_shift + age_bits,
+         hash_shift               = cms_shift + cms_bits,
          epoch_shift              = hash_shift
   };
 
@@ -118,7 +122,9 @@
          age_mask                 = right_n_bits(age_bits),
          age_mask_in_place        = age_mask << age_shift,
          epoch_mask               = right_n_bits(epoch_bits),
-         epoch_mask_in_place      = epoch_mask << epoch_shift
+         epoch_mask_in_place      = epoch_mask << epoch_shift,
+         cms_mask                 = right_n_bits(cms_bits),
+         cms_mask_in_place        = cms_mask << cms_shift
 #ifndef _WIN64
          ,hash_mask               = right_n_bits(hash_bits),
          hash_mask_in_place       = (address_word)hash_mask << hash_shift
@@ -360,4 +366,40 @@
 
   // see the definition in markOop.cpp for the gory details
   bool should_not_be_cached() const;
+
+  // These markOops indicate cms free chunk blocks and not objects.
+  // In 64 bit, the markOop is set to distinguish them from oops.
+  // These are defined in 32 bit mode for vmStructs.
+  const static uintptr_t cms_free_chunk_pattern  = 0x1;
+
+  // Constants for the size field.
+  enum { size_shift                = cms_shift + cms_bits,
+         size_bits                 = 35    // need for compressed oops 32G
+       };
+  // These values are too big for Win64
+  const static uintptr_t size_mask = LP64_ONLY(right_n_bits(size_bits))
+                                     NOT_LP64(0);
+  const static uintptr_t size_mask_in_place =
+                                     (address_word)size_mask << size_shift;
+
+#ifdef _LP64
+  static markOop cms_free_prototype() {
+    return markOop(((intptr_t)prototype() & ~cms_mask_in_place) |
+                   ((cms_free_chunk_pattern & cms_mask) << cms_shift));
+  }
+  uintptr_t cms_encoding() const {
+    return mask_bits(value() >> cms_shift, cms_mask);
+  }
+  bool is_cms_free_chunk() const {
+    return is_neutral() &&
+           (cms_encoding() & cms_free_chunk_pattern) == cms_free_chunk_pattern;
+  }
+
+  size_t get_size() const       { return (size_t)(value() >> size_shift); }
+  static markOop set_size_and_free(size_t size) {
+    assert((size & ~size_mask) == 0, "shouldn't overflow size field");
+    return markOop(((intptr_t)cms_free_prototype() & ~size_mask_in_place) |
+                   (((intptr_t)size & size_mask) << size_shift));
+  }
+#endif // _LP64
 };
--- a/src/share/vm/oops/methodDataOop.hpp	Tue Jun 17 09:59:59 2008 -0700
+++ b/src/share/vm/oops/methodDataOop.hpp	Thu Jun 19 06:02:20 2008 -0700
@@ -158,7 +158,6 @@
     assert(ProfileTraps, "used only under +ProfileTraps");
     uint old_flags = (_header._struct._flags & flag_mask);
     _header._struct._flags = (new_state << trap_shift) | old_flags;
-    assert(trap_state() == new_state, "sanity");
   }
 
   u1 flags() {
--- a/src/share/vm/opto/memnode.cpp	Tue Jun 17 09:59:59 2008 -0700
+++ b/src/share/vm/opto/memnode.cpp	Thu Jun 19 06:02:20 2008 -0700
@@ -253,11 +253,17 @@
   if (dom == NULL || dom->is_top() || sub == NULL || sub->is_top())
     return false; // Conservative answer for dead code
 
-  // Check 'dom'.
+  // Check 'dom'. Skip Proj and CatchProj nodes.
   dom = dom->find_exact_control(dom);
   if (dom == NULL || dom->is_top())
     return false; // Conservative answer for dead code
 
+  if (dom == sub) {
+    // For the case when, for example, 'sub' is Initialize and the original
+    // 'dom' is Proj node of the 'sub'.
+    return false;
+  }
+
   if (dom->is_Con() || dom->is_Start() || dom->is_Root() || dom == sub)
     return true;
 
@@ -271,6 +277,7 @@
          sub->is_Region(), "expecting only these nodes");
 
   // Get control edge of 'sub'.
+  Node* orig_sub = sub;
   sub = sub->find_exact_control(sub->in(0));
   if (sub == NULL || sub->is_top())
     return false; // Conservative answer for dead code
@@ -296,14 +303,16 @@
 
     for (uint next = 0; next < dom_list.size(); next++) {
       Node* n = dom_list.at(next);
+      if (n == orig_sub)
+        return false; // One of dom's inputs dominated by sub.
       if (!n->is_CFG() && n->pinned()) {
         // Check only own control edge for pinned non-control nodes.
         n = n->find_exact_control(n->in(0));
         if (n == NULL || n->is_top())
           return false; // Conservative answer for dead code
         assert(n->is_CFG(), "expecting control");
-      }
-      if (n->is_Con() || n->is_Start() || n->is_Root()) {
+        dom_list.push(n);
+      } else if (n->is_Con() || n->is_Start() || n->is_Root()) {
         only_dominating_controls = true;
       } else if (n->is_CFG()) {
         if (n->dominates(sub, nlist))
--- a/src/share/vm/opto/node.cpp	Tue Jun 17 09:59:59 2008 -0700
+++ b/src/share/vm/opto/node.cpp	Thu Jun 19 06:02:20 2008 -0700
@@ -1039,6 +1039,9 @@
 //--------------------------dominates------------------------------------------
 // Helper function for MemNode::all_controls_dominate().
 // Check if 'this' control node dominates or equal to 'sub' control node.
+// We already know that if any path back to Root or Start reaches 'this',
+// then all paths so, so this is a simple search for one example,
+// not an exhaustive search for a counterexample.
 bool Node::dominates(Node* sub, Node_List &nlist) {
   assert(this->is_CFG(), "expecting control");
   assert(sub != NULL && sub->is_CFG(), "expecting control");
@@ -1047,110 +1050,115 @@
   int iterations_without_region_limit = DominatorSearchLimit;
 
   Node* orig_sub = sub;
+  Node* dom      = this;
+  bool  met_dom  = false;
   nlist.clear();
-  bool this_dominates = false;
-  bool result = false; // Conservative answer
 
-  while (sub != NULL) {        // walk 'sub' up the chain to 'this'
-    if (sub == this) {
+  // Walk 'sub' backward up the chain to 'dom', watching for regions.
+  // After seeing 'dom', continue up to Root or Start.
+  // If we hit a region (backward split point), it may be a loop head.
+  // Keep going through one of the region's inputs.  If we reach the
+  // same region again, go through a different input.  Eventually we
+  // will either exit through the loop head, or give up.
+  // (If we get confused, break out and return a conservative 'false'.)
+  while (sub != NULL) {
+    if (sub->is_top())  break; // Conservative answer for dead code.
+    if (sub == dom) {
       if (nlist.size() == 0) {
         // No Region nodes except loops were visited before and the EntryControl
         // path was taken for loops: it did not walk in a cycle.
-        result = true;
-        break;
-      } else if (this_dominates) {
-        result = false;          // already met before: walk in a cycle
-        break;
+        return true;
+      } else if (met_dom) {
+        break;          // already met before: walk in a cycle
       } else {
         // Region nodes were visited. Continue walk up to Start or Root
         // to make sure that it did not walk in a cycle.
-        this_dominates = true; // first time meet
+        met_dom = true; // first time meet
         iterations_without_region_limit = DominatorSearchLimit; // Reset
      }
     }
     if (sub->is_Start() || sub->is_Root()) {
-      result = this_dominates;
-      break;
+      // Success if we met 'dom' along a path to Start or Root.
+      // We assume there are no alternative paths that avoid 'dom'.
+      // (This assumption is up to the caller to ensure!)
+      return met_dom;
     }
-    Node* up = sub->find_exact_control(sub->in(0));
-    if (up == NULL || up->is_top()) {
-      result = false; // Conservative answer for dead code
-      break;
-    }
-    if (sub == up && (sub->is_Loop() || sub->is_Region() && sub->req() != 3)) {
-      // Take first valid path on the way up to 'this'.
+    Node* up = sub->in(0);
+    // Normalize simple pass-through regions and projections:
+    up = sub->find_exact_control(up);
+    // If sub == up, we found a self-loop.  Try to push past it.
+    if (sub == up && sub->is_Loop()) {
+      // Take loop entry path on the way up to 'dom'.
       up = sub->in(1); // in(LoopNode::EntryControl);
+    } else if (sub == up && sub->is_Region() && sub->req() != 3) {
+      // Always take in(1) path on the way up to 'dom' for clone regions
+      // (with only one input) or regions which merge > 2 paths
+      // (usually used to merge fast/slow paths).
+      up = sub->in(1);
     } else if (sub == up && sub->is_Region()) {
-      assert(sub->req() == 3, "sanity");
+      // Try both paths for Regions with 2 input paths (it may be a loop head).
+      // It could give conservative 'false' answer without information
+      // which region's input is the entry path.
       iterations_without_region_limit = DominatorSearchLimit; // Reset
 
-      // Try both paths for such Regions.
-      // It is not accurate without regions dominating information.
-      // With such information the other path should be checked for
-      // the most dominating Region which was visited before.
       bool region_was_visited_before = false;
-      uint i = 1;
-      uint size = nlist.size();
-      if (size == 0) {
-        // No such Region nodes were visited before.
-        // Take first valid path on the way up to 'this'.
-      } else {
-        // Was this Region node visited before?
-        intptr_t ni;
-        int j = size - 1;
-        for (; j >= 0; j--) {
-          ni = (intptr_t)nlist.at(j);
-          if ((Node*)(ni & ~1) == sub) {
-            if ((ni & 1) != 0) {
-              break; // Visited 2 paths. Give up.
-            } else {
-              // The Region node was visited before only once.
-              nlist.remove(j);
-              region_was_visited_before = true;
-              for (; i < sub->req(); i++) {
-                Node* in = sub->in(i);
-                if (in != NULL && !in->is_top() && in != sub) {
-                  break;
-                }
-              }
-              i++; // Take other path.
-              break;
-            }
+      // Was this Region node visited before?
+      // If so, we have reached it because we accidentally took a
+      // loop-back edge from 'sub' back into the body of the loop,
+      // and worked our way up again to the loop header 'sub'.
+      // So, take the first unexplored path on the way up to 'dom'.
+      for (int j = nlist.size() - 1; j >= 0; j--) {
+        intptr_t ni = (intptr_t)nlist.at(j);
+        Node* visited = (Node*)(ni & ~1);
+        bool  visited_twice_already = ((ni & 1) != 0);
+        if (visited == sub) {
+          if (visited_twice_already) {
+            // Visited 2 paths, but still stuck in loop body.  Give up.
+            return false;
           }
-        }
-        if (j >= 0 && (ni & 1) != 0) {
-          result = false; // Visited 2 paths. Give up.
-          break;
-        }
-        // The Region node was not visited before.
-      }
-      for (; i < sub->req(); i++) {
-        Node* in = sub->in(i);
-        if (in != NULL && !in->is_top() && in != sub) {
+          // The Region node was visited before only once.
+          // (We will repush with the low bit set, below.)
+          nlist.remove(j);
+          // We will find a new edge and re-insert.
+          region_was_visited_before = true;
           break;
         }
       }
-      if (i < sub->req()) {
-        up = sub->in(i);
-        if (region_was_visited_before && sub != up) {
-          // Set 0 bit to indicate that both paths were taken.
-          nlist.push((Node*)((intptr_t)sub + 1));
-        } else {
-          nlist.push(sub);
+
+      // Find an incoming edge which has not been seen yet; walk through it.
+      assert(up == sub, "");
+      uint skip = region_was_visited_before ? 1 : 0;
+      for (uint i = 1; i < sub->req(); i++) {
+        Node* in = sub->in(i);
+        if (in != NULL && !in->is_top() && in != sub) {
+          if (skip == 0) {
+            up = in;
+            break;
+          }
+          --skip;               // skip this nontrivial input
         }
       }
+
+      // Set 0 bit to indicate that both paths were taken.
+      nlist.push((Node*)((intptr_t)sub + (region_was_visited_before ? 1 : 0)));
     }
-    if (sub == up) {
-      result = false;    // some kind of tight cycle
-      break;
+
+    if (up == sub) {
+      break;    // some kind of tight cycle
+    }
+    if (up == orig_sub && met_dom) {
+      // returned back after visiting 'dom'
+      break;    // some kind of cycle
     }
     if (--iterations_without_region_limit < 0) {
-      result = false;    // dead cycle
-      break;
+      break;    // dead cycle
     }
     sub = up;
   }
-  return result;
+
+  // Did not meet Root or Start node in pred. chain.
+  // Conservative answer for dead code.
+  return false;
 }
 
 //------------------------------remove_dead_region-----------------------------
--- a/src/share/vm/runtime/arguments.cpp	Tue Jun 17 09:59:59 2008 -0700
+++ b/src/share/vm/runtime/arguments.cpp	Thu Jun 19 06:02:20 2008 -0700
@@ -1174,7 +1174,7 @@
   // field offset to determine free list chunk markers.
   // Check that UseCompressedOops can be set with the max heap size allocated
   // by ergonomics.
-  if (!UseConcMarkSweepGC && MaxHeapSize <= max_heap_for_compressed_oops()) {
+  if (MaxHeapSize <= max_heap_for_compressed_oops()) {
     if (FLAG_IS_DEFAULT(UseCompressedOops)) {
       // Leave compressed oops off by default. Uncomment
       // the following line to return it to default status.
--- a/src/share/vm/runtime/globals.hpp	Tue Jun 17 09:59:59 2008 -0700
+++ b/src/share/vm/runtime/globals.hpp	Thu Jun 19 06:02:20 2008 -0700
@@ -2246,6 +2246,9 @@
   product(bool, AggressiveOpts, false,                                      \
           "Enable aggressive optimizations - see arguments.cpp")            \
                                                                             \
+  product(bool, UseStringCache, false,                                      \
+          "Enable String cache capabilities on String.java")                \
+                                                                            \
   /* statistics */                                                          \
   develop(bool, UseVTune, false,                                            \
           "enable support for Intel's VTune profiler")                      \
--- a/src/share/vm/runtime/thread.cpp	Tue Jun 17 09:59:59 2008 -0700
+++ b/src/share/vm/runtime/thread.cpp	Thu Jun 19 06:02:20 2008 -0700
@@ -2926,21 +2926,42 @@
     }
 
     if (AggressiveOpts) {
-      // Forcibly initialize java/util/HashMap and mutate the private
-      // static final "frontCacheEnabled" field before we start creating instances
+      {
+        // Forcibly initialize java/util/HashMap and mutate the private
+        // static final "frontCacheEnabled" field before we start creating instances
 #ifdef ASSERT
-      klassOop tmp_k = SystemDictionary::find(vmSymbolHandles::java_util_HashMap(), Handle(), Handle(), CHECK_0);
-      assert(tmp_k == NULL, "java/util/HashMap should not be loaded yet");
+        klassOop tmp_k = SystemDictionary::find(vmSymbolHandles::java_util_HashMap(), Handle(), Handle(), CHECK_0);
+        assert(tmp_k == NULL, "java/util/HashMap should not be loaded yet");
 #endif
-      klassOop k_o = SystemDictionary::resolve_or_null(vmSymbolHandles::java_util_HashMap(), Handle(), Handle(), CHECK_0);
-      KlassHandle k = KlassHandle(THREAD, k_o);
-      guarantee(k.not_null(), "Must find java/util/HashMap");
-      instanceKlassHandle ik = instanceKlassHandle(THREAD, k());
-      ik->initialize(CHECK_0);
-      fieldDescriptor fd;
-      // Possible we might not find this field; if so, don't break
-      if (ik->find_local_field(vmSymbols::frontCacheEnabled_name(), vmSymbols::bool_signature(), &fd)) {
-        k()->bool_field_put(fd.offset(), true);
+        klassOop k_o = SystemDictionary::resolve_or_null(vmSymbolHandles::java_util_HashMap(), Handle(), Handle(), CHECK_0);
+        KlassHandle k = KlassHandle(THREAD, k_o);
+        guarantee(k.not_null(), "Must find java/util/HashMap");
+        instanceKlassHandle ik = instanceKlassHandle(THREAD, k());
+        ik->initialize(CHECK_0);
+        fieldDescriptor fd;
+        // Possible we might not find this field; if so, don't break
+        if (ik->find_local_field(vmSymbols::frontCacheEnabled_name(), vmSymbols::bool_signature(), &fd)) {
+          k()->bool_field_put(fd.offset(), true);
+        }
+      }
+
+      if (UseStringCache) {
+        // Forcibly initialize java/lang/String and mutate the private
+        // static final "stringCacheEnabled" field before we start creating instances
+#ifdef ASSERT
+        klassOop tmp_k = SystemDictionary::find(vmSymbolHandles::java_lang_String(), Handle(), Handle(), CHECK_0);
+        assert(tmp_k == NULL, "java/lang/String should not be loaded yet");
+#endif
+        klassOop k_o = SystemDictionary::resolve_or_null(vmSymbolHandles::java_lang_String(), Handle(), Handle(), CHECK_0);
+        KlassHandle k = KlassHandle(THREAD, k_o);
+        guarantee(k.not_null(), "Must find java/lang/String");
+        instanceKlassHandle ik = instanceKlassHandle(THREAD, k());
+        ik->initialize(CHECK_0);
+        fieldDescriptor fd;
+        // Possible we might not find this field; if so, don't break
+        if (ik->find_local_field(vmSymbols::stringCacheEnabled_name(), vmSymbols::bool_signature(), &fd)) {
+          k()->bool_field_put(fd.offset(), true);
+        }
       }
     }
 
--- a/src/share/vm/runtime/vmStructs.cpp	Tue Jun 17 09:59:59 2008 -0700
+++ b/src/share/vm/runtime/vmStructs.cpp	Thu Jun 19 06:02:20 2008 -0700
@@ -1695,7 +1695,12 @@
   declare_constant(markOopDesc::no_hash)                                  \
   declare_constant(markOopDesc::no_hash_in_place)                         \
   declare_constant(markOopDesc::no_lock_in_place)                         \
-  declare_constant(markOopDesc::max_age)
+  declare_constant(markOopDesc::max_age)                                  \
+                                                                          \
+  /* Constants in markOop used by CMS. */                                 \
+  declare_constant(markOopDesc::cms_shift)                                \
+  declare_constant(markOopDesc::cms_mask)                                 \
+  declare_constant(markOopDesc::size_shift)                               \
 
   /* NOTE that we do not use the last_entry() macro here; it is used   */
   /* in vmStructs_<os>_<cpu>.hpp's VM_LONG_CONSTANTS_OS_CPU macro (and */
@@ -1959,6 +1964,7 @@
                         GENERATE_STATIC_VM_STRUCT_ENTRY)
 
   VM_STRUCTS_CMS(GENERATE_NONSTATIC_VM_STRUCT_ENTRY, \
+                 GENERATE_NONSTATIC_VM_STRUCT_ENTRY, \
                  GENERATE_STATIC_VM_STRUCT_ENTRY)
 #endif // SERIALGC
 
@@ -2100,6 +2106,7 @@
              CHECK_STATIC_VM_STRUCT_ENTRY);
 
   VM_STRUCTS_CMS(CHECK_NONSTATIC_VM_STRUCT_ENTRY,
+             CHECK_VOLATILE_NONSTATIC_VM_STRUCT_ENTRY,
              CHECK_STATIC_VM_STRUCT_ENTRY);
 #endif // SERIALGC
 
@@ -2204,6 +2211,7 @@
   debug_only(VM_STRUCTS_PARALLELGC(ENSURE_FIELD_TYPE_PRESENT, \
                                    ENSURE_FIELD_TYPE_PRESENT));
   debug_only(VM_STRUCTS_CMS(ENSURE_FIELD_TYPE_PRESENT, \
+                            ENSURE_FIELD_TYPE_PRESENT, \
                             ENSURE_FIELD_TYPE_PRESENT));
 #endif // SERIALGC
   debug_only(VM_STRUCTS_CPU(ENSURE_FIELD_TYPE_PRESENT, \