7095243: Disambiguate ReferenceProcessor::_discoveredSoftRefs

Summary: Add a new, separate, pointer to the base of the array of discovered reference lists and use this new pointer in places where we iterate over the entire array.
Reviewed-by: ysr, brutisso

src/share/vm/gc_implementation/g1/g1CollectedHeap.cpp

@@ -5068,7 +5068,7 @@ public:
 
     // Select discovered lists [i, i+stride, i+2*stride,...,limit)
     for (int idx = i; idx < limit; idx += stride) {
-      DiscoveredList& ref_list = rp->discovered_soft_refs()[idx];
+      DiscoveredList& ref_list = rp->discovered_refs()[idx];
 
       DiscoveredListIterator iter(ref_list, &keep_alive, &always_alive);
       while (iter.has_next()) {

src/share/vm/memory/referenceProcessor.cpp

@@ -105,19 +105,22 @@ ReferenceProcessor::ReferenceProcessor(MemRegion span,
   _discovery_is_mt     = mt_discovery;
   _num_q               = MAX2(1, mt_processing_degree);
   _max_num_q           = MAX2(_num_q, mt_discovery_degree);
-  _discoveredSoftRefs  = NEW_C_HEAP_ARRAY(DiscoveredList,
+  _discovered_refs     = NEW_C_HEAP_ARRAY(DiscoveredList,
                                           _max_num_q * number_of_subclasses_of_ref());
-  if (_discoveredSoftRefs == NULL) {
+  if (_discovered_refs == NULL) {
     vm_exit_during_initialization("Could not allocated RefProc Array");
   }
+  _discoveredSoftRefs    = &_discovered_refs[0];
   _discoveredWeakRefs    = &_discoveredSoftRefs[_max_num_q];
   _discoveredFinalRefs   = &_discoveredWeakRefs[_max_num_q];
   _discoveredPhantomRefs = &_discoveredFinalRefs[_max_num_q];
-  // Initialized all entries to NULL
+
+  // Initialize all entries to NULL
   for (int i = 0; i < _max_num_q * number_of_subclasses_of_ref(); i++) {
-    _discoveredSoftRefs[i].set_head(NULL);
-    _discoveredSoftRefs[i].set_length(0);
+    _discovered_refs[i].set_head(NULL);
+    _discovered_refs[i].set_length(0);
   }
+
   // If we do barriers, cache a copy of the barrier set.
   if (discovered_list_needs_barrier) {
     _bs = Universe::heap()->barrier_set();
@@ -129,7 +132,7 @@ ReferenceProcessor::ReferenceProcessor(MemRegion span,
 void ReferenceProcessor::verify_no_references_recorded() {
   guarantee(!_discovering_refs, "Discovering refs?");
   for (int i = 0; i < _max_num_q * number_of_subclasses_of_ref(); i++) {
-    guarantee(_discoveredSoftRefs[i].is_empty(),
+    guarantee(_discovered_refs[i].is_empty(),
               "Found non-empty discovered list");
   }
 }
@@ -138,9 +141,9 @@ void ReferenceProcessor::verify_no_references_recorded() {
 void ReferenceProcessor::weak_oops_do(OopClosure* f) {
   for (int i = 0; i < _max_num_q * number_of_subclasses_of_ref(); i++) {
     if (UseCompressedOops) {
-      f->do_oop((narrowOop*)_discoveredSoftRefs[i].adr_head());
+      f->do_oop((narrowOop*)_discovered_refs[i].adr_head());
     } else {
-      f->do_oop((oop*)_discoveredSoftRefs[i].adr_head());
+      f->do_oop((oop*)_discovered_refs[i].adr_head());
     }
   }
 }
@@ -423,15 +426,15 @@ void ReferenceProcessor::enqueue_discovered_reflists(HeapWord* pending_list_addr
   AbstractRefProcTaskExecutor* task_executor) {
   if (_processing_is_mt && task_executor != NULL) {
     // Parallel code
-    RefProcEnqueueTask tsk(*this, _discoveredSoftRefs,
+    RefProcEnqueueTask tsk(*this, _discovered_refs,
                            pending_list_addr, _max_num_q);
     task_executor->execute(tsk);
   } else {
     // Serial code: call the parent class's implementation
     for (int i = 0; i < _max_num_q * number_of_subclasses_of_ref(); i++) {
-      enqueue_discovered_reflist(_discoveredSoftRefs[i], pending_list_addr);
-      _discoveredSoftRefs[i].set_head(NULL);
-      _discoveredSoftRefs[i].set_length(0);
+      enqueue_discovered_reflist(_discovered_refs[i], pending_list_addr);
+      _discovered_refs[i].set_head(NULL);
+      _discovered_refs[i].set_length(0);
     }
   }
 }
@@ -691,7 +694,7 @@ void ReferenceProcessor::abandon_partial_discovery() {
     if (TraceReferenceGC && PrintGCDetails && ((i % _max_num_q) == 0)) {
       gclog_or_tty->print_cr("\nAbandoning %s discovered list", list_name(i));
     }
-    abandon_partial_discovered_list(_discoveredSoftRefs[i]);
+    abandon_partial_discovered_list(_discovered_refs[i]);
   }
 }
 
@@ -952,7 +955,7 @@ void ReferenceProcessor::clean_up_discovered_references() {
         "\nScrubbing %s discovered list of Null referents",
         list_name(i));
     }
-    clean_up_discovered_reflist(_discoveredSoftRefs[i]);
+    clean_up_discovered_reflist(_discovered_refs[i]);
   }
 }
 
@@ -1402,7 +1405,7 @@ void ReferenceProcessor::verify_ok_to_handle_reflists() {
 void ReferenceProcessor::clear_discovered_references() {
   guarantee(!_discovering_refs, "Discovering refs?");
   for (int i = 0; i < _max_num_q * number_of_subclasses_of_ref(); i++) {
-    clear_discovered_references(_discoveredSoftRefs[i]);
+    clear_discovered_references(_discovered_refs[i]);
   }
 }
 

src/share/vm/memory/referenceProcessor.hpp

@@ -255,7 +255,11 @@ class ReferenceProcessor : public CHeapObj {
   int             _num_q;
   // The maximum MT'ness degree of the queues below
   int             _max_num_q;
-  // Arrays of lists of oops, one per thread
+
+  // Master array of discovered oops
+  DiscoveredList* _discovered_refs;
+
+  // Arrays of lists of oops, one per thread (pointers into master array above)
   DiscoveredList* _discoveredSoftRefs;
   DiscoveredList* _discoveredWeakRefs;
   DiscoveredList* _discoveredFinalRefs;
@@ -267,7 +271,8 @@ class ReferenceProcessor : public CHeapObj {
   int num_q()                              { return _num_q; }
   int max_num_q()                          { return _max_num_q; }
   void set_active_mt_degree(int v)         { _num_q = v; }
-  DiscoveredList* discovered_soft_refs()   { return _discoveredSoftRefs; }
+
+  DiscoveredList* discovered_refs()        { return _discovered_refs; }
 
   ReferencePolicy* setup_policy(bool always_clear) {
     _current_soft_ref_policy = always_clear ?
@@ -411,6 +416,7 @@ class ReferenceProcessor : public CHeapObj {
   // constructor
   ReferenceProcessor():
     _span((HeapWord*)NULL, (HeapWord*)NULL),
+    _discovered_refs(NULL),
     _discoveredSoftRefs(NULL),  _discoveredWeakRefs(NULL),
     _discoveredFinalRefs(NULL), _discoveredPhantomRefs(NULL),
     _discovering_refs(false),