7106024: CMS: Removed unused code for precleaning in remark phase

Summary: Remove dead code.
Reviewed-by: stefank, ysr

src/share/vm/gc_implementation/concurrentMarkSweep/concurrentMarkSweepGeneration.cpp

@@ -3582,16 +3582,6 @@ void CMSCollector::checkpointRootsInitialWork(bool asynch) {
        " or no bits are set in the gc_prologue before the start of the next "
        "subsequent marking phase.");
 
-  // Temporarily disabled, since pre/post-consumption closures don't
-  // care about precleaned cards
-  #if 0
-  {
-    MemRegion mr = MemRegion((HeapWord*)_virtual_space.low(),
-                             (HeapWord*)_virtual_space.high());
-    _ct->ct_bs()->preclean_dirty_cards(mr);
-  }
-  #endif
-
   // Save the end of the used_region of the constituent generations
   // to be used to limit the extent of sweep in each generation.
   save_sweep_limits();

src/share/vm/memory/cardTableModRefBS.cpp

@@ -662,23 +662,6 @@ MemRegion CardTableModRefBS::dirty_card_range_after_reset(MemRegion mr,
   return MemRegion(mr.end(), mr.end());
 }
 
-// Set all the dirty cards in the given region to "precleaned" state.
-void CardTableModRefBS::preclean_dirty_cards(MemRegion mr) {
-  for (int i = 0; i < _cur_covered_regions; i++) {
-    MemRegion mri = mr.intersection(_covered[i]);
-    if (!mri.is_empty()) {
-      jbyte *cur_entry, *limit;
-      for (cur_entry = byte_for(mri.start()), limit = byte_for(mri.last());
-           cur_entry <= limit;
-           cur_entry++) {
-        if (*cur_entry == dirty_card) {
-          *cur_entry = precleaned_card;
-        }
-      }
-    }
-  }
-}
-
 uintx CardTableModRefBS::ct_max_alignment_constraint() {
   return card_size * os::vm_page_size();
 }

src/share/vm/memory/cardTableModRefBS.hpp

@@ -435,9 +435,6 @@ public:
   MemRegion dirty_card_range_after_reset(MemRegion mr, bool reset,
                                          int reset_val);
 
-  // Set all the dirty cards in the given region to precleaned state.
-  void preclean_dirty_cards(MemRegion mr);
-
   // Provide read-only access to the card table array.
   const jbyte* byte_for_const(const void* p) const {
     return byte_for(p);