6939027: G1: assertion failure during the concurrent phase of cleanup

Summary: The outgoing region map is not maintained properly and it's causing an assert failure. Given that we don't actually use it, I'm removing it. I'm piggy-backing a small change on this which removes a message that it's printed before a Full GC when DisableExplicitGC is set.
Reviewed-by: apetrusenko, ysr

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

@@ -913,7 +913,6 @@ void G1CollectedHeap::do_collection(bool full, bool clear_all_soft_refs,
   }
 
   if (full && DisableExplicitGC) {
-    gclog_or_tty->print("\n\n\nDisabling Explicit GC\n\n\n");
     return;
   }
 

hotspot/src/share/vm/gc_implementation/g1/heapRegionRemSet.cpp

@@ -662,8 +662,6 @@ void OtherRegionsTable::add_reference(OopOrNarrowOopStar from, int tid) {
         prt = PosParPRT::alloc(from_hr);
       }
       prt->init(from_hr);
-      // Record the outgoing pointer in the from_region's outgoing bitmap.
-      from_hr->rem_set()->add_outgoing_reference(hr());
 
       PosParPRT* first_prt = _fine_grain_regions[ind];
       prt->set_next(first_prt);  // XXX Maybe move to init?
@@ -1073,11 +1071,7 @@ int HeapRegionRemSet::num_par_rem_sets() {
 
 HeapRegionRemSet::HeapRegionRemSet(G1BlockOffsetSharedArray* bosa,
                                    HeapRegion* hr)
-    : _bosa(bosa), _other_regions(hr),
-      _outgoing_region_map(G1CollectedHeap::heap()->max_regions(),
-                           false /* in-resource-area */),
-      _iter_state(Unclaimed)
-{}
+  : _bosa(bosa), _other_regions(hr), _iter_state(Unclaimed) { }
 
 
 void HeapRegionRemSet::setup_remset_size() {
@@ -1148,30 +1142,11 @@ void HeapRegionRemSet::par_cleanup() {
   PosParPRT::par_contract_all();
 }
 
-void HeapRegionRemSet::add_outgoing_reference(HeapRegion* to_hr) {
-  _outgoing_region_map.par_at_put(to_hr->hrs_index(), 1);
-}
-
 void HeapRegionRemSet::clear() {
-  clear_outgoing_entries();
-  _outgoing_region_map.clear();
   _other_regions.clear();
   assert(occupied() == 0, "Should be clear.");
 }
 
-void HeapRegionRemSet::clear_outgoing_entries() {
-  G1CollectedHeap* g1h = G1CollectedHeap::heap();
-  size_t i = _outgoing_region_map.get_next_one_offset(0);
-  while (i < _outgoing_region_map.size()) {
-    HeapRegion* to_region = g1h->region_at(i);
-    if (!to_region->in_collection_set()) {
-      to_region->rem_set()->clear_incoming_entry(hr());
-    }
-    i = _outgoing_region_map.get_next_one_offset(i+1);
-  }
-}
-
-
 void HeapRegionRemSet::scrub(CardTableModRefBS* ctbs,
                              BitMap* region_bm, BitMap* card_bm) {
   _other_regions.scrub(ctbs, region_bm, card_bm);

hotspot/src/share/vm/gc_implementation/g1/heapRegionRemSet.hpp

@@ -179,13 +179,6 @@ private:
 
   OtherRegionsTable _other_regions;
 
-  // One set bit for every region that has an entry for this one.
-  BitMap _outgoing_region_map;
-
-  // Clear entries for the current region in any rem sets named in
-  // the _outgoing_region_map.
-  void clear_outgoing_entries();
-
   enum ParIterState { Unclaimed, Claimed, Complete };
   volatile ParIterState _iter_state;
   volatile jlong _iter_claimed;
@@ -243,10 +236,6 @@ public:
     _other_regions.add_reference(from, tid);
   }
 
-  // Records the fact that the current region contains an outgoing
-  // reference into "to_hr".
-  void add_outgoing_reference(HeapRegion* to_hr);
-
   // Removes any entries shown by the given bitmaps to contain only dead
   // objects.
   void scrub(CardTableModRefBS* ctbs, BitMap* region_bm, BitMap* card_bm);