src/share/vm/gc/g1/heapRegion.cpp

rev 12937 : imported patch 8071280-specialize-heapregion-oops-on-card-seq-iterate
rev 12939 : imported patch 8162928-micro-optimizations-in-remembered-set-scan
rev 12943 : imported patch 8177044-remove-scan-top

*** 825,835 ****
  // G1OffsetTableContigSpace code; copied from space.cpp.  Hope this can go
  // away eventually.
  
  void G1ContiguousSpace::clear(bool mangle_space) {
    set_top(bottom());
-   _scan_top = bottom();
    CompactibleSpace::clear(mangle_space);
    reset_bot();
  }
  
  #ifndef PRODUCT
--- 825,834 ----
*** 857,902 ****
                                                      HeapWord* end) {
    _bot_part.alloc_block(start, end);
    return _bot_part.threshold();
  }
  
- HeapWord* G1ContiguousSpace::scan_top() const {
-   G1CollectedHeap* g1h = G1CollectedHeap::heap();
-   HeapWord* local_top = top();
-   OrderAccess::loadload();
-   const unsigned local_time_stamp = _gc_time_stamp;
-   assert(local_time_stamp <= g1h->get_gc_time_stamp(), "invariant");
-   if (local_time_stamp < g1h->get_gc_time_stamp()) {
-     return local_top;
-   } else {
-     return _scan_top;
-   }
- }
- 
  void G1ContiguousSpace::record_timestamp() {
    G1CollectedHeap* g1h = G1CollectedHeap::heap();
    uint curr_gc_time_stamp = g1h->get_gc_time_stamp();
  
    if (_gc_time_stamp < curr_gc_time_stamp) {
-     // Setting the time stamp here tells concurrent readers to look at
-     // scan_top to know the maximum allowed address to look at.
- 
-     // scan_top should be bottom for all regions except for the
-     // retained old alloc region which should have scan_top == top
-     HeapWord* st = _scan_top;
-     guarantee(st == _bottom || st == _top, "invariant");
- 
      _gc_time_stamp = curr_gc_time_stamp;
    }
  }
  
- void G1ContiguousSpace::record_retained_region() {
-   // scan_top is the maximum address where it's safe for the next gc to
-   // scan this region.
-   _scan_top = top();
- }
- 
  void G1ContiguousSpace::safe_object_iterate(ObjectClosure* blk) {
    object_iterate(blk);
  }
  
  void G1ContiguousSpace::object_iterate(ObjectClosure* blk) {
--- 856,874 ----
*** 917,926 ****
  }
  
  void G1ContiguousSpace::initialize(MemRegion mr, bool clear_space, bool mangle_space) {
    CompactibleSpace::initialize(mr, clear_space, mangle_space);
    _top = bottom();
-   _scan_top = bottom();
    set_saved_mark_word(NULL);
    reset_bot();
  }
  
--- 889,897 ----